biology_finalcl1.txt

A. regulation B. reproduction C. respiration D. synthesis (Answers - C )

A. fine adjustment knobs B. coarse adjustment knobs C. nosepiece D. diaphragm (Answers - A )

A. 20µm B. 80µm C. 200µm D. 800µm (Answers -A )

A. a microtome B. microdissection tools C. an electron microscope D. gene sequencers (Answers - B )

A. independent variable B. dependent variable C. hypothesis D. control (Answers - D )

A. the heterotroph hypothesis B. the cell theory C. the theory of natural selection D. cellular respiration (Answers - B )

A. cytoplasm B. vacuoles C. a cell membrane D. a cell wall (Answers - D )

A. Golgi apparatus B. lysosome C. mitochondrion D. ribosome (Answers - C )

A. diffusion B. osmosis C. endocytosis D. active transport (Answers - B )

A. similarity of structure B. similarity of function C. evolutionary development D. phylogeny (Answers - B )

A. kingdom B. phylum C. genus D. species (Answers - C )

A. virus B. bacterium C. paramecium D. slime mold (Answers - A )

A. have a nuclear membrane B. lack a nuclear membrane C. lack genetic material D. are multicellular (Answers - B )

A. bacteria and blue-green algae B. euglena and green algae C. amoeba and paramecium D. slime molds and fungi (Answers - C )

A. algae B. fungi C. animal-like protists D. bryophytes (Answers - B )

A. Fungi B. Protista C. Anamalia D. Plantae (Answers - D )

A. arthropoda B. mollusca C. fishes D. echinodermata (Answers - A )

A. osteichthyes B. amphibia C. reptilia D. aves (Answers - D )

A. hydrolysis B. dehydration synthesis C. photosynthesis D. cellular respiration (Answers - B )

A. glucose and maltose B. glycerol and fatty acids C. amino acids and polypeptides D. carboxylic acid and glycogen (Answers - B )

A. hydrogen B. oxygen C. nitrogen D. carbon (Answers - C )

A. 3 B. 6 C. 7 D. 8 (Answers - A )

A. scientific method B. theory of natural selection C. fluid mosaic model D. lock-and-key model (Answers - D )

A. oxygen concentration B. substrate concentration C. enzyme concentration D. pH (Answers - A )

A. guard cells B. stomates C. phloem cells D. palisade cells (Answers - B )

A. PGAL B. ATP C. DNA D. CO2 (Answers - A )

A. phloem B. xylem C. cambium D. meristem (Answers - B )

A. phloem cells B. root hair cells C. cortex cells D. root cap (Answers - B )

A. large intestine B. small intestine C. blood D. liver (Answers - C )

A. capillaries B. arteries C. veins D. alveoli (Answers -B )

A. alveoli B. bronchioles C. bronchi D. stomates (Answers - A )

A. vacuoles B. chloroplasts C. ribosomes D. mitochondria (Answers - D )

A. nephridia B. nephrons C. Malpighian tubules D. tracheal tubes (Answers - B )

A. evaporation B. condensation C. precipitation D. transpiration (Answers - A )

A. muscles and setae B. muscles and glands C. muscles and chitin D. muscles and bones (Answers - D )

A. ingestion B. excretion C. circulation D. regulation (Answers - D )

A. axon B. cyton C. synapse D. terminal branch (Answers - B )

A. cerebrum B. cerebellum C. medulla D. hypothalamus (Answers - A )

A. fast and of short duration B. slow and widespread, often targeting several organs C. fast and of long duration D. slow and limited, always targeting only one organ (Answers - B )

A. pituitary B. thyroid C. hypothalamus D. adrenal (Answers - A )

A. food B. oxygen C. hormones D. enzymes (Answers - C )

A. ganglia B. spinal cord C. brain D. nerve net (Answers - D )

A. skin B. lungs C. tracheal tubes D. mouth (Answers - A )

A. circulation B. excretion C. digestion D. respiration (Answers - D )

A. metamorphosis B. parthenogenesis C. mitosis D. meiosis (Answers - C )

A. interphase B. prophase C. anaphase D. telophase (Answers - A )

A. budding B. binary fission C. regeneration D. vegetative propagation (Answers - B )

A. 4 B. 8 C. 16 D. 32 (Answers - D )

A. spore formation B. cleavage C. mitosis D. meiosis (Answers - D )

A. excretion only B. reproduction only C. excretion and reproduction D. fertilization and development (Answers - C )

A. ovary B. fallopian tube C. vagina D. uterus (Answers - B )

A. uterus and ovaries B. vagina and cervix C. fallopian tubes and follicles D. pituitary gland and ovaries (Answers - D )

A. cleavage B. meiosis C. budding D. oogenesis (Answers - A )

A. umbilical cord B. placenta C. amnion D. fallopian tube (Answers - B )

A. the formation of a new plant from seeds B. a method of producing vegetables C. a form of sexual reproduction D. the formation of a new plant from part of an already existing plant (Answers - D )

A. stem cutting B. grafting C. layering D. natural attachment (Answers - B )

A. ovule B. pistil C. pollen grain D. seed (Answers - C )

A. no fertilization B. single fertilization C. double fertilization D. triple fertilization (Answers - C )

A. parts of a flower B. food for a developing embryo C. the embryo of a seed D. the male reproductive parts of a plant (Answers - C )

A. be dispersed B. develop C. be dormant D. have the same niche (Answers - A )

A. sperm cell B. egg cell C. gene D. zygote (Answers - C )

A. phenotype B. genotype C. gametes D. DNA (Answers - A )

A. homozygous dominant B. heterozygous C. recessive D. not determinable (Answers - B)

A. TT ◊ TT B. tt ◊ tt C. Tt ◊ Tt D. Tt ◊ tt (Answers - C )

A. YyRr ◊ YyRr B. YYRR ◊ YYRR C. YYRR ◊ yyrr D. yyrr ◊ yyrr (Answers - A )

A. 75% white, 25% red B. 75% red, 25% white C. 100% pink D. 25% red, 50% pink, 25% white (Answers - D )

A. 1 B. 22 C. 23 D. 46 (Answers - B )

A. IBi ◊ ii B. IBi ◊ IAIA C. IAIA ◊ IBIB D. IAIA ◊ ii (Answers - D )

A. sex linked B. dominant C. multiple alleles D. homozygous (Answers - A )

A. that a mutation probably occurred, preventing chlorophyll production B. natural selection C. the influence of the environment on gene expression D. the need for light in chlorophyll production (Answers - C )

A. RNA B. a nucleotide C. a codon D. an amino acid (Answers - B )

A. mitosis B. translation C. semiconservative replication D. asexual reproduction (Answers - C )

A. translocation and transpiration B. evaporation and condensation C. DNA replication and ATP production D. transcription and translation (Answers - D )

A. peptide B. nitrogen bond C. codon D. nucleotide (Answers - C )

A. carry an amino acid on one end, while having an anticodon on the other end B. manufacture mRNA C. make DNA molecules D. carry ribosomal RNA (Answers - A )

A. chromosome mutation B. gene mutation C. translocation D. deletion (Answers - B )

A. 2n B. n + 1 C. 2n + 1 D. 2n - 1 (Answers - B )

A. a defective dominant allele B. a defective recessive allele C. nondisjunction of chromosome pair number 21 D. a missing enzyme (Answers - A )

A. addition B. genomics C. genetic engineering D. parthenogenesis (Answers - C )

A. genetics B. evolution C. ecology D. biotechnology (Answers - B )

A. codons B. fossils C. alleles D. Archeae (Answers - B )

A. determine the occurrence of genetic mutations B. create a common ancestor C. create variations in a species D. determine the age of a fossil (Answers - D )

A. vestigial B. homologous C. analogous D. complementary (Answers - B )

A. the use or lack of use of organs B. the need to adapt to a changing environment C. mutations D. the inheritance of acquired characteristics (Answers - C )

A. mutations B. a large gene pool C. no migration D. no natural selection (Answers - A )

A. attitude B. longitude C. altitude D. latitude (Answers - D )

A. mice living in a field B. mice and owls living in a field C. animals in a field and their surrounding environment D. animals in a field and their food (Answers - A )

A. intraspecific competition B. symbiosis C. the predator-prey relationship D. abiotic interaction (Answers - B )

A. more energy becomes available B. number of organisms increases C. number of plants increases D. less energy is available (Answers - D )

A. evaporation and precipitation B. osmosis and dehydration synthesis C. protein synthesis and nitrogen fixation D. photosynthesis and respiration (Answers - A )

A. a food chain B. ecological succession C. the flow of energy through the ecosystem D. population growth (Answers - B )

A. ecosystem B. habitat C. biome D. continent (Answers - C )

A. population growth B. disease C. global warming D. forest fires (Answers - A )

A. biodiversity B. rich soil that can be used for growing crops C. ability to remove carbon dioxide from the atmosphere D. ability to produce large amounts of oxygen (Answers - A )

A. hydrogen fuel B. wind energy C. solar energy D. natural gas (Answers - )

A. digestion B. ingestion C. assimilation D. reproduction (Answers - B )

A. homeostasis B. regulation C. synthesis D. metabolism (Answers - D )

A. homeostasis B. metabolism C. reproduction D. regulation (Answers - C )

A. assimilation B. homeostasis C. transport D. respiration (Answers - B )

A. receive stimuli from the external environment B. bring materials from the external environment into contact with all the cells of the organism C. break down nutrients so that the cells can use them D. remove solid waste materials from the digestive system (Answers - B )

A. ingestion B. digestion C. absorption D. assimilation (Answers - D )

A. ingestion B. synthesis C. respiration D. digestion (Answers - C )

A. synthesis B. digestion C. assimilation D. respiration (Answers - A )

A. transport B. regulation C. respiration D. synthesis (Answers - B )

A. excretion B. repair C. transport D. synthesis (Answers - A )

A. simple microscope B. compound microscope C. ultracentrifuge D. electron microscope (Answers - D )

A. dissecting microscope B. ultracentrifuge C. microdissection tools D. electron microscope (Answers - C )

A. a dissecting microscope B. an ultracentrifuge C. microdissection tools D. an electron microscope (Answers - A )

A. simple microscope B. compound microscope C. ultracentrifuge D. electron microscope (Answers - A )

A. the microscope is not properly focused B. the microscope is too powerful C. the microscope is not powerful enough D. the studentís finger is too thick (Answers - D )

A. 50X B. 70X C. 600X D. 6000X (Answers - C )

A. diaphragm B. ocular C. fine adjustment knob D. coarse adjustment knob (Answers - A )

A. 25µm B. 100µm C. 400µm D. 4,000µm (Answers - B )

A. 0.675mm B. 6.75mm C. .000675mm D. 675mm (Answers - A )

A. 20µm B. 200µm C. 500µm D. 5,000µm (Answers - B )

Answer: Anton van Leeuwenhoek was the first to see living things such as bacteria and animal-like protists. Although Zacharias Janssen preceded Leeuwenhoek and made a compound microscope, he did not use it to study living things.

Answer: Robert Hooke used a compound microscope to observe cork from the bark of the cork oak tree and saw small box-like structures that he named cells.

Answer: Robert Brown discovered the nucleus while working with plant cells.

1. A microscope is needed to see cells because they are too small to be seen by the naked eye.The tools most often used to magnify cells are the compound and electron microscopes.

2. The cell theory states that the cell is the basic unit of structure and function in all living things. Also, new cells arise only from previously existing cells.

3. All organisms are composed of cells, function as a result of their cells, and produce new offspring by cell reproduction. These concepts of the cell theory serve to unite all living things.

4. The structural hierarchy that is found in all organisms builds on the concept that the cell isthe basic unit of structure in all living things. Similar cells combine to form tissues, similar tissues combine to form organs, organs work together to form organ systems, and all the different organ systems combine to form the organism.

5. Viruses do not have the cell structures common to most cells. Most biologists do not consider them living things.

The outer boundary of the cell protects the cell, controls what goes in and out of the cell (selective permeability), and holds the cell together.

• Contains chromosomes, which have DNA and control the heredity of the cell. Controls the reproduction of the cell. A nuclear membrane surrounds the
• chromosomes.
• 3. Nucleolus Found inside the nucleus; associated with the production of ribosomes.

inside the cytoplasm.

Centrioles are cylindrical in shape and function in the reproduction of the cell.

Small oval-shaped structures containing the green pigment, chlorophyll. They produce glucose during photosynthesis.

Found in plant cells outside the cell membrane. The cell wall is made of cellulose, which is rigid and nonliving. This organelle gives the plant cell support and shape.

Answer: Organelles are the parts that make up a cell.

Answer: The organelles that are found in most cells are cell membrane, nucleus, nucleolus, vacuoles, and cytoplasm. Note: Mature red blood cells do not have a nucleus and are an exception.

Answer: The nucleus contains chromosomes, which have DNA and control the heredity and reproduction of the cell.

Answer: The cytoplasm is the liquid within the cell membrane in which all parts of the cell float.

1. Animal cells have two centrioles and many small vacuoles. Plant cells do not have centrioles, but they have chloroplasts and one or two large vacuoles.

2. Selective (or semi) permeability is the ability of a cell membrane to control the movement of materials into and out of the cell. Materials that enter the cell are water, food, and oxygen, which are needed by the cell to perform its life functions. Materials that leave through the cell membrane are wastes such as carbon dioxide. Also, the cell membrane prevents harmful organisms and substances such as poisons, viruses, and bacteria from entering the cell.

3. The cell membrane is a living part of the cell and is found in all cells. The cell wall is nonliving and made of cellulose. It is found only in plant cells.

4. Chloroplasts contain the green pigment, chlorophyll, and function in photosynthesis for the production of food.

Answer: The cell membrane is the outer boundary of the cell; the nuclear membrane surrounds and protects the chromosomes of the cell.

Answer: Ribosomes are sites for protein synthesis. Proteins are needed for growth, repair, and reproduction of new cells.

Answer: Mitochondria are the energy factories of a cell and are associated with cellular respiration. In the mitochondria, oxygen is used to chemically release energy that is stored in food. During this process, the waste products carbon dioxide and water are produced.

Answer:1. According to the fluid mosaic model, the cell membrane consists of two layers of lipid with proteins spread throughout the layers and in between the layers.

Answer: 2. The Golgi body has flattened membranes that look like plates stacked on top of each other, and their function is to package proteins. The membranes of the endoplasmic reticulum form a canal-like network within the cell that functions in the transport of materials. Some endoplasmic reticulum membranes have ribosomes attached to them and are referred to as rough endoplasmic reticulum. Ribosomes are never attached to the Golgi body.

Answer: 3. Lysosomes contain digestive enzymes for the breakdown of food. If the lysosome membrane breaks, the enzymes it contains leak into the cytoplasm and digest the organelles of the cell. This results in the death of the cell. Thus, lysosomes are sometimes called the “suicide sacs” of the cell.

Answer: 4. Endocytosis is a process by which the cell membrane forms a small pocket or pouch that surrounds and engulfs food particles that are too large to pass through the membrane; this pocket is called the endocytotic or pinocytotic vesicle.

The movement of any molecule (except water) from an area of high concentration to an area of low concentration.

The movement of the water molecule only from an area of high concentration to an area of low concentration.

Answer: Molecular transport is the movement of molecules across a membrane.

Answer: Passive transport is the movement of molecules from areas of high concentration to areas of low concentration. No energy is required.

Answer: Active transport is the movement of molecules from areas of low concentration to areas of high concentration. Energy is required.

Answer: 1. Circulation is concerned with the movement of materials such as food, oxygen, and water from the environment to all cells of the organism. Molecular transport explains how these materials get into the cell.

Answer: 2. Small molecules can pass through a cell membrane; large molecules cannot.

Answer: 3. Diffusion is the movement of any molecule (except water) from areas of high concentration to areas of low concentration. Osmosis is the movement of water molecules from areas of high concentration to areas of low concentration.

A. The cell is the basic unit of structure in all living things. B. The cell is the basic unit of function in all living things. C. New cells arise only from previously existing cells. D. All living things have chloroplasts. Answer: D

A. metabolism B. the cell theory C. organ systems D. fluid mosaic model Answer: B

A. organism → organ systems → organs → tissues → cells B. cells → tissues → organs → organ systems → organism C. cells → organs → tissues → organ systems → organism D. organ systems → organism → organs → tissues → cells Answer: B

A. chloroplasts B. centrioles C. a cell membrane D. vacuoles Answer: B

microscope? A. ribosomes B. cell membrane C. nucleus D. vacuoles Answer: A

A. mitochondria B. ribosomes C. Golgi body D. lysosomes Answer: A

A. cell wall B. cell membrane C. endoplasmic reticulum D. nucleus Answer: A

A. Golgi body B. mitochondrion C. vacuole D. centriole Answer: C

A. Golgi body B. endoplasmic reticulum C. lysosome D. endocytotic vesicle or pinocytotic vesicle Answer: D

• 10. Select the description that best illustrates the structure of the cell membrane.
• A. three layers: protein/lipid/protein B. three layers: lipid/protein/lipid C. two layers of protein D. two layers of lipid with proteins spread throughout the layers and in between the layers Answer: D

A. growth and repair B. energy C. transport D. respiration Answer: A

A. transport materials from one location to another within the cell B. control the movement of materials into and out of the cell C. actively manufacture vacuoles and lysosomes D. hold the cell together Answer: B

A. virus B. bacteria C. plant cell D. animal cell Answer: D

A. passive transport B. active transport C. diffusion D. osmosis Answer: B

concentration is characteristic of: A. passive transport B. active transport C. diffusion D. osmosis Answer: B

A. diffusion B. active transport C. endocytosis D. osmosis Answer: D

Answer: Living things are classified into logical groupings to make it easier for biologists to study them.

Answer: Diversity refers to the millions of different kinds of living things that exist on earth.

Answer: Phylogeny refers to the evolutionary development and history of a species of organism.

Answer: The three-domain system of classification includes Bacteria, Archaea, and Eukarya. Domain Eukarya is subdivided into the following four kingdoms: Protista, Fungi, Plantae, and Animalia. The six-kingdom system of classification includes Eubacteria, Archaeabacteria, Protista, Fungi, Plantae, and Animalia.

Answer: domain → kingdom → phylum → class → order → family → genus → species

Answer: Viruses are not classified into a domain because many biologists do not consider them living things. Outside a cell, viruses do not perform life functions such as respiration, ingestion, transport, excretion, and locomotion.

Answer: A virus is capable of reproduction only when inside a host cell.

Answer: A virus consists mostly of genetic material (DNA or RNA) surrounded by one or two protein coats.

Answer: 1. A virus invades a cell’s nucleus destroying the cell’s DNA. The virus then inserts its own genetic material and takes over the life functions of the cell. The virus begins to replicate within the cell. Eventually, the cell bursts and dies—releasing the newly formed viruses, and the process can begin again.

Answer: 2. A human cannot catch a cold from a dog because the virus that causes a cold in dogs is unable to insert itself into human cells.

Answer: Single-celled organisms (unicellular), primitive cells dating back at least 350 million years, with prokaryotic cells.

Answer: Prokaryotic cells lack a nuclear membrane surrounding their genetic material.

Answer: Heterotrophs are organisms that obtain food for energy, growth, repair, and reproduction of new cells. Autotrophs are usually green plants that make their own food by the process of photosynthesis.

Answer: 1. Bacteria have cell walls that contain peptidoglycan, and they respond to antibiotics. Archaea have cell walls that lack peptidoglycan, and they do not respond to antibiotics.

Answer: 2. Bacteria are considered primitive organisms because the current-day Bacteria are similar to those that lived 350 million years ago. These organisms are prokaryotic, which is a primitive cellular characteristic.

Answer: 3. These organisms should be classified in the domain Archaea. The lack of a nuclear membrane indicates that the organisms are prokaryotic. Archaea is the only domain with organisms that are prokaryotic, lack peptidoglycan, and are found in salt lakes.

Answer: 4. Bacteria evolved before viruses. At first it might seem that viruses evolved before Bacteria because they are not cells and do not perform life functions except for reproduction. However, this is not the case. To reproduce, a virus must have a host cell to invade. The host cells must be there first for viruses to reproduce.

Answer: Protista are mostly unicellular organisms with animal-like, plant-like, or fungus- like characteristics. Protists can be heterotrophic or autotrophic. All protists are eukaryotic.

Answer: Amoeba move with the help of pseudopods, false feet that are cellular extensions of the organism and constantly change shape. As a result, the amoeba is an organism that does not have a definite shape. The paramecium is covered with tiny hair-like structures called cilia that are used to propel the organism back and forth in the water. Trypanosoma has a tail called a flagellum that it whips back and forth to propel itself.

Answer: Slime molds are unicellular organisms. Some have only one nucleus (cellular slime molds); others have many nuclei (acellular slime molds). In many ways slime molds resemble a huge amoeba. All slime molds are nongreen and heterotrophic.

Answer: 1. Prokaryotic cells do not have a nuclear membrane and are characteristic of organisms in the domains Bacteria and Archaea. Eukaryotic cells have a nuclear membrane and are characteristic of organisms in the domain Eukarya.

Answer: 2. Euglenophyta and Chlorophyta are phyla, containing organisms that have plant-like characteristics. They are green, autotrophic, and are capable of photosynthesis. The animal-like protists are nongreen and heterotrophic.

Answer: 3. Green algae are in the kingdom Protista, and they are eukaryotic with cell walls that have cellulose. Archaea are prokaryotic and have cell walls lacking cellulose.

Answer: Fungi are eukaryotic, have cell walls made of chitin and their cells lack chloroplasts. They are heterotrophic, decomposers, and unicellular and multicellular organisms. Fungi are broken down into several phyla, with organisms classified according to methods of reproduction.

Answer: Many fungi are heterotrophic and obtain their food by absorption from decaying vegetation.

Answer: Fungi are composed of thread-like filaments called hyphae that are attached to rhizoids on the bottom end. Rhizoids anchor the organism to its food source. The top of the organism often forms a reproductive structure called a sporangium.

Answer: A parasite is an organism that lives off another organism called the host. The parasite often harms or kills its host. Examples of fungi that are parasitic in humans are those that cause ringworm and athlete’s foot.

Answer: Symbiosis is a relationship between two organisms that live together where at least one of the organisms benefits from the association. An example of symbiosis can be seen in lichen.

Answer: 1. Fungi cells lack chloroplasts; as a result, fungi are heterotrophs. The plant-like protists are green, have chloroplasts and are autotrophic (making their own food by photosynthesis).

Answer: 2. Fungi are important to soil health and maintenance because they decompose dead plant material, returning important nutrients to the soil.

Answer: 3. Lichen is a combination of a green alga (or blue-green bacteria) living inside a fungus. The alga or bacteria provide the fungus with food produced by photosynthesis. The fungus provides the alga or bacteria with a place to live and the moisture necessary for photosynthesis.

Answer: 4. Fungi can’t make their own food because they are nongreen, lacking the photosynthetic pigment chlorophyll.

Answer: Plantae are autotrophic and make their own food by photosynthesis. They have the green pigment chlorophyll. Green plants are multicellular and eukaryotic and can be classified into several phyla or divisions.

Answer: Green plants have chlorophyll and can make their own food by photosynthesis. During photosynthesis, plants take in carbon dioxide and water from their environment, producing a sugar called glucose. Glucose serves as food for the plant.

Answer: Bryophytes are low-growing green plants that do not have vascular tissue for the transport of materials. Also, they do not have true roots, stems or leaves. Examples of Bryophytes are liverworts and mosses.

Answer: Vascular plants have vascular tissue (for the transport of materials), true roots, stems, and leaves. As a result, they can grow tall. Examples of vascular plants are trees and shrubs.

Answer: Most conifers have needle-like leaves, are evergreen, and reproduce from seeds found in cones.

Answer: 1. Green plants have chlorophyll, are autotrophic, and make their own food by photosynthesis. Fungi cells lack chloroplasts, are heterotrophic, and obtain their food from decaying vegetation.

Answer: 2. Bryophytes do not have the vascular tissue needed to transport materials upward in a plant. As a result, they can’t grow as tall as vascular plants.

Answer: 3. Coniferophyta reproduce from seeds found in cones. Anthophyta reproduce from seeds found inside fruit.

Answer: 4. Monocots have one seed part (cotyledon) that cannot be split. Dicots have two seed parts (cotyledons) that can be split into two halves.

Answer: Animals are multicellular, heterotrophic organisms. Animals use locomotion to find food. Animal cells are eukaryotic. Some animals are classified as invertebrates; others are vertebrates.

Answer: Porifera are sponges; they do not have a mouth but have pores that draw in water for cells to filter and absorb food. Sponges have two cell layers, and most are marine and sessile. Cnidaria are the coelenterates and include hydra, jellyfish, coral, and sea anemones. Cnidaria have two cell layers, a mouth for ingestion, and a hollow body cavity for digestion. They also have stinging cells, tentacles, and many are motile.

Answer: In bilateral symmetry, the right and left sides of the organism are similar.

Answer: Platyhelminthes are flatworms. Examples are planaria and tapeworms. Nematodes are roundworms. Examples are trichinella and hookworm. Annelida are segmented worms. Examples are the earthworm and sandworm.

Answer: Annelida are segmented worms and have a tube-within-a-tube body construction.

Answer: 1. Animals are heterotrophic organisms that depend on locomotion to find food. Green plants have chlorophyll and can make their own food by photosynthesis. During photosynthesis, plants take in carbon dioxide and water from their environment—producing a sugar called glucose. Glucose serves as food for the plant.

Answer: 2. Mollusks have soft bodies and a hard shell. In the case of the octopus, the shell is inside a soft body.

Answer: 3. Insects are members of the class Insecta. Insects have three body parts: head, thorax, and abdomen. Insects also have three pairs of legs. Most have two pairs of wings, and many are capable of metamorphosis. Spiders are members of the class Arachnida. Spiders have two body parts (cephalothorax and abdomen), eight legs, and no wings.

Answer: 4. Metamorphosis is a complete change in the body structure of an organism from young to adult. The transformation of a caterpillar into a butterfly is an example of metamorphosis.

Answer: 5. Crustaceans use gills for breathing, and insects use tracheal tubes.

Answer: In a cold-blooded animal, the body temperature of the organism is the same as that of the environment. Fishes are cold blooded. As the temperature of the water that a fish is swimming in changes, the body temperature of the fish changes accordingly. Other vertebrate classes that are cold blooded are amphibians and reptiles.

Answer: Invertebrates are animals without backbones; vertebrates are animals with backbones.

Answer: Although many turtles spend much of their lives in water, they have lungs for breathing and they return to land to reproduce. Fishes breathe through gills and are basically marine or fresh water organisms.

Answer: 1. A bat is classified as a mammal because it has hair, and the females have mammary glands that can feed milk to their young. Although a bat can fly, it does not have feathers, which is a characteristic that is exclusive to birds.

Answer: 2. Fishes have scales, fins, and gills for breathing. Amphibians have lungs as adults and lack fins and scales. Amphibians have the ability to perform metamorphosis, but fishes do not.

Answer: 3. Osteichthyes are bony fishes; sharks are boneless fishes containing cartilage.

Answer: 4. Humans are mammals (in the class Mammalia) because we have mammary glands and body hair.

Answer: 5. Insects are invertebrates that have the ability to perform metamorphosis. Amphibians are vertebrates that can perform metamorphosis.

A. development B. size C. structure and evolutionary development D. function Answer: C

A. Leeuwenhoek B. Linnaeus C. Hooke D. Brown Answer: B

A. genus and specific epithet B. class and genus C. genus and phylum D. phylum and specific epithet Answer: A

A. kingdom B. species C. phylum D. class Answer: B

A. phylum B. genus C. class D. species Answer: D

A. the same genus but different species B. the same species but different genus C. the same species but different phyla D. the same genus but different kingdoms Answer: A

A. Acer B. rubrum C. Acer rubrum D. plants Answer: C

A. species → genus → phylum → class B. phylum → class → genus → species C. genus → species → phylum → class D. phylum → genus → class → species Answer: B

A. genus B. species C. kingdom D. phylum Answer: C

A. Crenulta acetabularia B. Mediterrania acetabularia C. Acetabularia crenulta D. Mediterrania crassa Answer: C

A. Archaea B. Bacteria C. Eukarya D. Protista Answer: D

A. Bacteria B. Protista C. slime molds D. Fungi Answer: A

A. lack a nuclear membrane B. have a nuclear membrane C. lack chromosomes D. lack DNA Answer: B

A. animal-like protists B. plants C. fungi D. Archaea Answer: A

to perform: A. photosynthesis B. reproduction C. digestion D. excretion Answer: A

A. Protista B. Fungi C. Plantae D. Animalia Answer: A

A. green plants B. eukaryotic C. heterotrophic D. decomposers of dead plants Answer: A

A. Eubacteria and Fungi B. algae and blue-green algae C. Coniferophyta and Anthophyta D. protozoa and slime molds Answer: C

A. Cnidaria B. Fungi C. Anthophyta D. Porifera Answer: C

A. slime molds and green algae B. amoeba and paramecia C. hydra and jellyfish D. ferns and grasses Answer: C

A. leech B. earthworm C. planarian D. sandworm Answer: C

A. planarian and leech B. hydra and coral C. starfish and sea urchin D. insect and spider Answer: D

A. tentacles B. a soft body and a hard interior shell C. an exoskeleton D. jointed appendages Answer: B

A. Cnidaria B. Annelida C. Arthropoda D. Echinodermata Answer: D

A. shark B. tuna C. eel D. cat Answer: D

A. Invertebrates B. Chordata C. Cnidaria D. Animalia Answer: B

A. an exoskeleton B. a dorsal nerve cord C. chloroplasts D. a two-cell layered body wall Answer: B

A. Osteichthyes B. Aves C. Amphibia D. Reptilia Answer: C

as a: A. bird B. mammal C. reptile D. amphibian Answer: B

A. Most biologists do not consider them living things. B. They are primitive cells. C. They can reproduce. D. Many cause disease in plants and animals. Answer: A

Answer: An element is a substance that contains only one kind of atom. The element sulfur contains only sulfur atoms, iron contains only iron atoms and so on. The atom is the smallest part of an element that still retains all the properties of the element.

Answer: A compound is a chemical combination of two or more kinds of atoms. In a compound, atoms of elements lose their original properties and take on the properties of the compound. Examples of compounds are water, salt, and methane.

Answer: A symbol is an abbreviation for an element, and a formula is an abbreviation for a compound.

Answer: A chemical bond is the electron arrangement (or force) that holds atoms together. The two kinds of chemical bonds are the ionic bond and the covalent bond.

Answer: Stearic acid is an organic compound. Stearic acid contains carbon and hydrogen together; compounds of carbon and hydrogen are usually organic.

Answer: The elements that are found in all living things are hydrogen, oxygen, nitrogen, and carbon. Remember the pneumonic device HONC.

Answer: Carbon forms four bonds when creating a compound.

Answer: Ethane and propane are organic compounds. Their structural formulas show that they contain carbon and hydrogen.

1. A chemical formula shows the elements and the number of atoms for each element in a compound. A structural formula adds to this the arrangement of the atoms in the compound.

2. In a structural formula, the line between the carbon and hydrogen atoms represents a covalent bond, which is a pair of shared electrons.

Answer: Water, which is inorganic, is the most abundant compound found in all living things. Without water, life on earth could not exist because the cytoplasm of a cell contains mostly water. Most organisms are composed of 70%–95% water.

Answer: The elements found in carbohydrates are carbon, hydrogen, and oxygen. The suffix -ate indicates the presence of oxygen.

Answer: The ratio of hydrogen atoms to oxygen atoms in a carbohydrate is 2:1.

Answer: Carbohydrates are an important source of energy for organisms.

Answer: Monosaccharides are simple (or single) sugars. When two monosaccharides are combined, we get a double sugar called a disaccharide.

1. Dehydration synthesis is the formation of a large molecule from two smaller molecules by the removal of water.

2. Maltose is a disaccharide that is formed by combining two glucose molecules via dehydration synthesis.

3. The maltose molecule can be broken down into two glucose molecules by adding water. This type of chemical reaction is called hydrolysis. Hydrolysis is the opposite of dehydration synthesis.

4. A polysaccharide consists of many glucose molecules combined. Polysaccharides can be formed by dehydration synthesis.

5. Starch is a storage form of sugar in plants, and glycogen is a storage form of sugar in animals. It is much more efficient to store one molecule of starch than hundreds of glucose molecules. When a plant needs sugar for energy production, starch molecules can be broken down by hydrolysis.

Answer: Glycerol is an alcohol that has a three-carbon chain. Each carbon has a hydroxyl group (OH-) attached to it.

Answer: A fatty acid is an organic molecule with a long carbon chain that ends with a carboxyl group (COOH).

Answer: Lipids are organic molecules that include fats, oils, and waxes.

• Answer: Lipids are used for energy and, along with proteins, help form the membranes
• of cells.

1. Lipids are formed by dehydration synthesis. One glycerol molecule is combined with three fatty acid molecules.

2. Lipids are broken down by hydrolysis. One lipid molecule + three water molecules yield one glycerol molecule + three fatty acid molecules.

• can you discover which molecule is capable of providing the most energy?
• 3. A molecule of lipid can release more energy than a molecule of sugar. A careful examination of the structural formulas of the two molecules shows that the lipid molecule is larger than the sugar molecule. When broken down, the lipid releases the most energy.

Answer: Carbon, hydrogen, oxygen, and nitrogen are the elements found in all proteins. Only proteins have the element nitrogen.

Answer: Amino acids are the building blocks of proteins.

Answer: Hemoglobin—Aids in the transport of oxygen to the cells of an organism. Antibodies—Proteins in the blood that can help fight disease. Nucleoproteins—The DNA molecule is important for heredity and reproduction. RNA aids in protein synthesis. Hormones—Chemical messengers that aid in the life function of regulation. Enzymes—Organic catalysts that speed up the rate of chemical reactions.

Answer: A peptide bond is a carbon-nitrogen bond that holds two amino acid molecules together. The peptide bond is formed by dehydration synthesis.

. Proteins are formed by the dehydration synthesis of 40 or more amino acids. Many proteins are complex molecules containing millions of amino acids.

2. Protein synthesis takes place at the ribosome.

3. A dipeptide is a compound of two amino acids combined by one peptide bond. A protein is the combination of 40 or more amino acids.

4. Proteins are broken down into amino acids by hydrolysis.

5.The number of different proteins that can be made is infinite. Think of each of the 20 different amino acids in the human body as a letter of the alphabet. The smallest word these letters form can have any combination of 40 letters, and many words can be millions of letters long. An infinite number of words can be produced. Now just imagine that each word is a protein! Of the infinite number of proteins possible, the human body has approximately 50,000 different proteins.

4. pH 3 is the stronger acid because it is further away from neutral on the acid side of the pH scale. The lower the acid pH number, the stronger the acid.

5. pH 10 is a stronger base because it is further away from neutral on the base side of the pH scale. The higher the base pH number, the stronger the base.

6. NaCl is not an acid because it does not produce the hydrogen ion (H+).

Answer: Enzymes speed up the rate of chemical reactions. Without enzymes, the chemical reactions that take place in an organism do not work, and the organism dies.

Answer: The substrate is the substance that an enzyme works on. For example, in the formation of a lipid, the substrate is glycerol and three fatty acids.

Answer: An enzyme-substrate complex forms when an enzyme combines with a substrate.

Answer: Only one kind of enzyme can be used for each type of chemical reaction. For example, maltase can be used to make or break down maltose; lipase can be used to make or break down a lipid. However, maltase cannot be used to make or break down a lipid, and lipase cannot be used to make or break down maltose.

Answer: Kinase is an enzyme. All enzymes end in the suffix -ase. The ending on the name of a compound can be used to identify the type of compound. Compounds with names ending in -ose are sugars, compounds with names ending in -ol are alcohols, and most compounds with names ending in -ine are amino acids. Note that some amino acids have names that do not end in -ine, such as aspartic acid.

1. The lock-and-key model of enzyme action is used to show that only one kind of enzyme can be used to speed up each type of chemical reaction, just as only one key can fit into a lock. An enzyme can be used to help make or break down a compound, and an enzyme is never used up. A key can be used to open or close a lock again and again. In organisms, the enzyme is the key, and the substrate is the lock.

Protease cannot speed up the formation of maltose from glucose because the active site of protease is not compatible with the shape of the glucose molecules, and therefore an enzyme-substrate complex cannot form. However, maltase can be used to make maltose, and protease can be used to make a protein. Enzyme action is specific: One enzyme is used for each type of chemical reaction, and it must be the correct enzyme!

3. Very high and low temperatures distort the active site of an enzyme. As a result, the rate of enzyme action decreases. Very low or very high pH has a similar effect on the rate of enzyme action.

4. As more enzymes are added, enzyme action increases and eventually levels off when all the substrate is being worked on. As more substrate is added, enzyme action increases and eventually levels off when all the enzymes are being used.

5. When a person has a fever, the higher temperature distorts the active sites of enzymes in the body. As a result, the rate of many chemical reactions decreases, making a person feel sick.

Answer: The cuticle is a thin, waxy layer that covers the upper epidermis of a leaf and prevents the loss of water. The cuticle must be transparent so that light can pass through to the photosynthetic cell layers of the leaf.

Answer: The palisade and spongy mesophyll layers are capable of photosynthesis.

Answer: The upper epidermis of many leaves has a waxy cuticle that the lower epidermis does not. The lower epidermis has guard cells and stomates, which are lacking in the upper epidermis.

Answer: The vascular bundles form the transportation network of the leaf, stem, and root. The phloem cells carry sugar and starch down to the roots for storage. The xylem cells carry water and minerals up from the roots.

Answer: Guard cells control the opening and closing of the stomates. During the day the guard cells produce sugar by photosynthesis, causing their walls to curve inward and away from each other and creating a space between the cells called a stomate. At night the process is reversed, and the stomate closes.

1. The leaves of plants are important because they are the sites for photosynthesis in plants. During photosynthesis, plants produce glucose that they and other organisms depend on for food. Many organisms use oxygen produced during photosynthesis in the life process of respiration.

The palisade layer performs the most photosynthesis. Look at the diagram of the cross section of the leaf:The palisade layer cells are closer to the sun. Many palisade layer cells are packed tightly together. Palisade cells are large cells and contain many chloroplasts. Spongy mesophyll layer cells don’t perform as much photosynthesis as palisade layer cells. Spongy mesophyll cells are further from the sun, fewer in number, smaller, and don’t have as many chloroplasts.

Desert plants must have a thick, waxy cuticle to prevent the loss of water.

4. The stomates of a leaf function in photosynthesis, respiration, transpiration, excretion, and evaporation. Photosynthesis—The stomates allow carbon dioxide into the leaf. Carbon dioxide and water combine to form glucose and oxygen. Respiration—The stomates allow oxygen into the leaf. Oxygen is used to release the energy stored in glucose.Transpiration—Water is lost through the stomates. Excretion—Oxygen is a waste product of photosynthesis that can exit the leaf through the stomate. Carbon dioxide is a waste product of respiration that also exits the leaf through the stomate. Evaporation—The change of a liquid into a gas.

Plants require carbon dioxide for photosynthesis and oxygen for respiration. Plants are capable of both processes. Animals perform only respiration.

Answer: Chlorophyll traps light energy that is used to split water molecules.

Answer: Green is the worst wavelength of light for photosynthesis because the leaf reflects rather than absorbs this wavelength, making it unavailable to the plant as a source of energy.

Answer: A coenzyme is a molecule that can transfer hydrogen and electrons from one reaction to another. In photosynthesis, the coenzyme NADP transfers hydrogen and electrons from light to dark reactions. In humans, many vitamins function as coenzymes.

Answer: The stem supports the leaves of the plant while serving as a pathway for the transport of water and minerals up from the roots and sugars and starches down from the leaves.

Answer: Monocots are nonwoody (herbaceous) plants with vascular bundles that are scattered throughout the stem. Monocot vascular bundles lack cambium cells, and most are annuals, living for only one growing season. Dicots are woody plants with vascular bundles found directly behind the bark. The vascular bundles of dicots contain phloem, cambium, and xylem. Dicots are perennial plants.

Answer: In the winter, cold temperatures kill phloem and xylem cells, producing a ring of dead cells called an annual ring.

Answer: Translocation is the movement of food through a plant.

1. Phloem cells are specialized for downward transport, carrying sugars and starches to the roots. Xylem cells are specialized for upward transport, carrying water and minerals up to the leaves.

2. Cambium cells are important because they are meristematic cells and are capable of producing phloem and xylem.

3. A stem must have lenticels for respiration. These small openings in the stem allow oxygen in and carbon dioxide out. The living cells of the vascular bundle use the oxygen for energy production.

4. Girdling breaks the continuity of the vascular bundles. Water is not able to move up the stem, and food is not able to move down. As a result, the plant eventually dies.

Answer: The root anchors the plant to the ground and supports the stem. Roots absorb water and minerals, sending these materials up through the stem to the leaves. Also, roots serve as a major storage site of starch.

Answer: The cortex cells of the root are used for storage.

Answer: Osmosis is the process by which water can enter a root hair cell. In osmosis, water moves from areas of high concentration to areas of low concentration. If you missed this question, review molecular transport in Chapter 2.

1. Epidermis cells are the outer layer of cells in a root. Epidermis cells are small and round and function in the absorption of water and minerals from the soil. Root hair cells are elongated cells on the outside of the root with a large surface area that is specialized for the absorption of water and minerals. The large surface area of root hair cells allows them to absorb more water than the epidermis cells.

2. Starch is a polysaccharide formed from many molecules of glucose combined. It is more efficient to store one molecule of starch as opposed to several hundred molecules of glucose.

3. Chloroplasts contain the chlorophyll molecule, which is used to trap light energy needed for photosynthesis. Because roots are underground and not exposed to light, it is pointless for them to have chloroplasts.

4. Meristematic cells are reproductive cells. The meristematic cells of the root are responsible for root growth deeper into the soil.

Answer: Starch digestion begins in the mouth, protein digestion begins in the stomach, and lipid digestion begins in the small intestines. All digestion is completed in the small intestines.

Answer: Peristalsis is a series of involuntary muscle contractions of the esophagus that forces food into the stomach.

Answer: Most digestion takes place in the small intestines, and all digestion is completed there.

Answer: The appendix is a vestigial organ and does nothing for human digestion. At some point in human evolutionary history, it probably did have a digestive function.

Answer: Mechanical digestion is a physical process that breaks food down into smaller particles, but the type of food remains the same. Chemical digestion breaks down carbohydrates into sugars, proteins into amino acids, and lipids into glycerol and fatty acids.

1. The liver produces bile, which emulsifies fats. The pancreas produces pancreatic fluid that contains several enzymes, which help break down carbohydrates, proteins, and lipids. The pancreatic fluid also contains bicarbonate, which neutralizes the acid from the stomach.

2. Mechanical digestion is important because it increases the surface area of food, making chemical digestion more efficient.

3. Hydrochloric acid is important because it activates pepsinogen, forming pepsin (a gastric protease), which begins the breakdown of proteins into small polypeptides and amino acids. Pepsin requires acidic conditions to function.

4. The end products of digestion are sugars, amino acids, glycerol, and fatty acids.

5. The end products of digestion enter the blood from the villi of the small intestines.The circulatory system transports these food molecules to all cells of the body.

Answer: The heart pumps blood and helps maintain blood pressure. Actually, the heart is a dual pump with two sides. The right atrium receives blood from the body, and the right ventricle pumps blood to the lungs. The left atrium receives blood from the lungs, and the left ventricle pumps blood out to the organs of the body.

Answer: In humans, blood flows clockwise in a circle beginning and ending with the heart. It is a closed circulatory system because blood never leaves the blood vessels.

Answer: The human blood vessels are arteries, veins, and capillaries. Arteries have thick muscular walls that pulse and carry blood away from the heart to the organs. Veins have thin muscular walls that contain valves and carry blood back to the heart. Capillaries are one cell in diameter and connect arteries to veins.

Answer: Plasma is the straw-colored liquid part of the blood and makes up about 55% of the blood. Plasma consists mostly of water and proteins. Plasma carries the end products of digestion to the cells, transports urea wastes from the cells, and transports antibodies, hormones, and other proteins. Red blood cells have the iron-containing hemoglobin molecule that helps transport oxygen to the cells and carbon dioxide from the cells. White blood cells help the body fight disease by destroying bacteria and other foreign substances. Platelets are cell fragments that interact with fibrinogen and help the blood to clot.

1. The two pulmonary arteries carry the most deoxygenated blood from the right ventricle to the lungs. Deoxygenated blood is low in oxygen but high in carbon dioxide. In the lungs, an exchange of gases takes place; the red blood cells lose carbon dioxide and pick up oxygen. Oxygenated blood returns to the heart via the four pulmonary veins. The left ventricle pumps the oxygenated blood to all parts of the body. In general, arteries carry oxygenated blood, and veins carry deoxygenated blood. The pulmonary arteries and pulmonary veins are the exceptions.

2. In the lungs, oxygen enters the red blood cells by diffusion. The concentration of oxygen in the lungs is much higher than in the red blood cells, and the oxygen molecules move from areas of high concentration to areas of low concentration.

3. The backward flow of blood in the circulatory system is prevented by the pumping action of the heart, which helps to keep the blood flowing in a forward direction. Valves in the heart prevent the backward flow of blood in the heart, and valves in the veins prevent the backward flow of blood in those blood vessels.

4. The left ventricle has the thickest walls of the heart because it must pump blood throughout the entire body.

5. Capillaries in the right toe → small veins in the toe → large vein in the right leg → inferior vena cava → right atrium → right ventricle → pulmonary arteries → lungs → left atrium → left ventricle → aorta → large artery in the right leg → small arteries in the right toe → capillaries in the toe.

Answer: Oxygen enters the body through the nose or the mouth.

Answer: The rings of cartilage in the trachea are needed to keep the trachea constantly open. If the trachea collapses, air containing oxygen is not able to enter the body, and this could cause death.

Answer: When a person swallows, a small flap called the epiglottis covers the trachea and prevents food from entering, keeping the person from choking to death.

1. Nose/mouth → trachea → bronchi → bronchioles → alveoli → capillaries → red blood cell.

• 2. The alveoli are air sacs found in the lungs and surrounded by capillaries. Oxygen from the
• alveoli diffuses into the capillaries.

3. Oxygen enters a red blood cell by the process of diffusion. Diffusion is the movement of molecules from areas of high concentration to areas of low concentration. In the lungs, capillaries that surround the alveoli have a high concentration of oxygen, and red blood cells have a low concentration of oxygen. As a result, oxygen diffuses across the moist membranes of red blood cells to enter these cells.

4. The diaphragm forces air into and out of the lungs. The diaphragm is a muscle located under the lungs. As the diaphragm moves up, air is pushed out of the lungs. As the diaphragm moves down, air is pulled into the lungs.

5. The level of CO2 in the blood determines the rate of respiration. The higher the CO2 level in the blood, the faster the rate of respiration.

Answer: The kidneys remove urea, water, and salt from the blood. The resulting mixture is known as urine.

Answer: The ureter is a tube that carries urine from the renal pelvis to the urinary bladder. The urinary bladder is a temporary storage site for urine. The urethra is a tube that carries urine from the urinary bladder to the outside of the body.

Answer: Heart → aorta → renal artery → small artery → glomerulus → small vein → renal vein → inferior vena cava → heart.

Answer: The glomerulus is a ball of capillaries inside Bowman’s capsule in the nephron. The glomerulus is part of the circulatory system.

1. Filtration in the kidneys takes place when wastes leave the blood of the glomerulus and enter Bowman’s capsule in the nephron.

2. Glomerulus → Bowman’s capsule in the nephron → nephron tube → collecting tubule → renal pelvis.

3. The loop of Henle is important for the reabsorption of glucose, amino acids and water into the blood of the capillaries that surround the loop.

4. Renal pelvis of the kidney → ureter → urinary bladder → urethra → outside the body.

5. Blood that enters the kidneys is high in urea and salts; blood that leaves the kidneys is low in urea and salts.

Answer: The liver produces the waste product urea from dead red blood cells and excess amino acids.

Answer: The waste products removed by the lungs are carbon dioxide and water.

Answer: Dead red blood cells are broken down into urea by the liver.

1. Blood in capillaries → alveoli → bronchioles → bronchi → trachea → nose/mouth → outside the body.

2. Urea is formed in the liver by the process of deamination. Amino acids lose their amino group to form ammonia, which is converted chemically into urea.

3. Carbon dioxide enters the alveoli by diffusion, and water enters by osmosis. Both of these molecules are moving from an area of high concentration in the capillaries that surround the alveoli to an area of low concentration inside the alveoli. Passive transport is the movement of molecules from areas of high concentration to areas of low concentration. Diffusion is the movement of any molecule except water. Osmosis is the movement of the water molecule.

4. Cellular respiration produces the carbon dioxide and water that is removed by the lungs.

Answer: The skin can function as an organ of excretion by removing sweat (water, urea, and salt) from the body. The skin also removes heat. The skin is the body’s first line of defense against disease. As long as the skin is intact, it acts as a barrier against harmful organisms such as bacteria.

Answer: Sweat glands are coiled tubes with a duct that extends to the surface forming an opening called a pore through which water, urea, and salt wastes can exit.

1. Heat is lost by radiation to the atmosphere when blood flows through dilated (widened) capillaries near the skin’s surface. In cold weather, the capillaries constrict (narrow) and less blood flows through the skin, conserving heat. Humans are warm blooded and must maintain a constant body temperature of approximately 37°C.

2. If excess heat is not removed, body temperature goes up. The active sites of enzymes become distorted, and important chemical reactions in the body slow down and stop. This can cause sickness and possibly death.

3. Both the skin and the kidneys remove urea, water, and salt. However, unlike the kidneys, the skin removes very little urea. Sweat removed by the skin is about 99% water. The skin plays a major role in regulating the body’s temperature by either removing or conserving heat. Almost no heat is lost by the removal of wastes from the kidneys.

Answer: Locomotion is the ability of an organism to move from one place to another to obtain food, find a mate, and avoid predators.

Answer: An endoskeleton is one where the bones and cartilage are found inside the body. An exoskeleton is found outside the body and is made of a hard, shell-like substance called chitin.

Answer: A joint is where two bones meet.

Answer: Ligaments connect bones to each other.

1. Skeletal muscle is made of cells that have combined to form fibers called striations. The function of these muscles is to move the bones during locomotion.

2. Skeletal muscles are connected to bones by tendons.

3. Muscles of the endoskeleton work together in pairs called flexors and extensors. Flexors move bones toward the body, and extensors move bones away from the body. As the bones move, so does the person.

4. Voluntary muscles are muscles that are consciously controlled. Skeletal muscles are an example of voluntary muscles; decisions can be made about when to use them. Involuntary muscles are muscles that are not consciously controlled. Smooth muscle and cardiac muscle are examples of involuntary muscles.

Answer: The nervous system and the endocrine system, working together, carry out the life function of regulation.

Answer: A stimulus is a change in the environment of an organism. A response is the reaction of an organism to a stimulus.

Answer: Receptors are organs in the body capable of detecting a stimulus. The effectors are the organs that carry out the response. The receptors are the five sensory organs of the body: eyes, ears, nose, tongue, and skin. The effectors are the muscles and glands of the body. The skeletal muscles help with locomotion, and the endocrine glands help regulate various organ systems.

1. The life function of regulation helps a person adapt to changes in the environment. The reaction of the person is the response. The ability to respond to environmental change enables the individual to maintain homeostasis and survive. For example, a person walking down a street sees a large box and walks around it. The box was the stimulus, and walking around the box was the response. However, if the person didn’t see the box and tripped over it, he might be injured or break his neck and die.

2. Nervous system responses are fast, have a short duration and are limited in scope. For example, if a person touches a hot object, his hand is removed in a fraction of a second. The response is over quickly and is limited to just the person’s hand.

3. The nerve cells are the basic unit of structure and function in the nervous system. The nerve cells act as lines of communication between the various parts of the body. Nerve cells act as a link between the receptors and the brain or spinal cord. Nerve cells keep the brain and spinal cord in contact with the effectors of the body. Also, the brain is made of millions of nerve cells.

4. The brain is the processing center of the body. The brain receives information from the receptors, interprets this information, and signals an effector to carry out an appropriate response. The brain is not a receptor organ. Without receiving information from a receptor, the brain doesn’t know anything.

5. If the nerve cells from the spinal cord to the effectors are damaged, a person might be paralyzed in part of his body. The nerve cells from the spinal cord signal the effectors to carry out an appropriate response. Damaged nerve cells break the line of communication to the effectors, preventing them from responding.

Answer: Neurons and nerve cells are different names for the same structure. A nerve is a bundle of axons surrounded by connective tissue.

Answer: The parts of the cyton are: Nucleus: Controls the nerve cell and functions in reproduction Cytoplasm: The site of the organelles and chemical reactions Dendrites: Detect stimuli

Answer: The axon connects the cyton to the terminal branches and carries the nerve impulse from the cyton to the terminal branches.

1. The synapse is a space between the terminal branches of one neuron and the dendrites of the next neuron.

2. Neurotransmitters such as acetylcholine are chemicals produced by the terminal branches of a neuron that are secreted into the synapse. When they contact the dendrites of the next nerve cell, a nerve impulse begins in that nerve cell.

3. A nerve impulse is electrical and chemical, electrical in the nerve cell and chemical in the synapse between nerve cells. Inside the nerve cell, the nerve impulse is a depolarization wave. The axon of a resting nerve cell is positively charged on the outside and negatively charged on the inside; as an impulse goes down the axon, the outside becomes positively charged, and the inside becomes negatively charged. Between nerve cells, chemicals called neurotransmitters transmit the nerve impulse to the next nerve cell.

4. Nerve impulses always travel from the cyton through the axon to the terminal branches.

5. Cholinesterase is important because it is the enzyme that breaks down acetylcholine in the synapse so that the same message does not keep repeating itself. If acetylcholine remains in the synapse, the dendrites of the next neuron are continuously stimulated. Cholinesterase breaks down acetylcholine to prevent this from happening. After cholinesterase does its work, it breaks down so that in the future, acetylcholine can again be produced in the synapse.

Answer: The sensory neuron in a receptor detects the stimulus and transmits the nerve impulse to the interneuron. The interneuron is located in the spinal cord and receives the nerve impulse from the sensory neuron and relays the impulse to the motor neuron. The motor neuron transmits the impulse to an effector to carry out the response.

Answer: A reflex is an automatic, involuntary, unlearned response to a stimulus. The reflex arc is a great way to respond to a potentially harmful situation such as coming into contact with a sharp object or a flame, where a fast response is necessary to avoid injury.

Answer: The brain has three major parts. The cerebrum is responsible for interpreting information received from the receptors. This is the conscious part of the brain and controls voluntary activities, judgment, and memory. The cerebellum controls coordination and balance. The medulla controls involuntary body activities such as breathing, heartbeat, digestion, blinking, and sneezing.

1. A simple reflex must be a fast, immediate, and automatic response to a stimulus for a person to avoid injury. The brain takes too long to evaluate information by thinking and processing. By the time the brain has finished doing its job, the person is probably injured. Consider the following example: A person accidentally touches a hot object. If the sensory neuron transmitted this information to the brain, the brain might start thinking along these lines, “The object is hot. How hot is it? Is it so hot that the hand must be removed now? Can the hand be removed later? How quickly should the hand be removed?” By this time the person’s hand might be severely burned. The simple reflex takes the thinking out of the response and gives a fast result!

2. The cerebrum is the largest part of the brain and controls the five senses, judgment, memory, voluntary activities, and much more.

3. The spinal cord plays a central role in the reflex arc, helping to control simple reflex actions when fast responses are needed.

4. A squirrel has the ability to walk on the branch of a tree and to jump from limb to limb without falling. Squirrels have a terrific sense of balance and coordination as a result of a large cerebellum in comparison to the size of their cerebrum. However, squirrels are not known for their thinking abilities.

5. Respiration is an activity that goes on all the time in humans. If the cerebrum controlled the process of respiration, little time would be left over for thinking. The cerebrum would be too concerned with when to breathe in, when to exhale, and so on. This is why the medulla controls activities that there isn’t time to think about, such as respiration and digestion.

Answer: Endocrine glands are ductless glands whose secretions (hormones) reach their target by traveling through the blood. Exocrine glands have ducts through which their secretions travel to reach their target.

Answer: Hormones are chemical messengers produced by endocrine glands. Hormones signal other organs of the body to perform a variety of functions.

Answer: Hormones reach their target by traveling through the blood. Endocrine glands do not have ducts that connect them to their target.

1. The pituitary gland produces a stimulating hormone (SH) that travels through the blood to an endocrine gland. The endocrine gland detects the SH and produces its own hormone to reach a target. When the pituitary gland detects the endocrine gland’s hormone, the production of SH is stopped.

2. In the endocrine system feedback is important because it shuts down an endocrine pathway after the target organ has been signaled.

3. The nervous system and the endocrine system are similar in that they both play a major role in maintaining homeostasis, and both secrete chemical messengers. The nervous system produces neurotransmitters, and the endocrine system produces hormones.

4. Three differences exist between the nervous system and the endocrine system: Nerve impulses travel through neurons; hormones travel through the blood. Nerve responses are faster than endocrine responses. Nerve responses are of shorter duration than endocrine responses.

Answer: The pituitary gland is called the master gland because it produces hormones that control the other endocrine glands. For example, stimulating hormones (SHs) target other endocrine glands to produce their hormones.

Answer: The hypothalamus of the brain produces hormones that control the pituitary gland and has nerve fibers that extend into this gland. The hypothalamus is the organ that ties the nervous system to the endocrine system.

Answer: The thyroid gland produces the hormone thyroxin. Thyroxin controls the rate of metabolism in most cells of the body, along with physical and mental development.

Answer: Adrenalin is called the body’s emergency hormone because, in an emergency, adrenalin can signal the liver to release sugar into the blood for use by the muscles to produce energy. Adrenalin can increase the breathing rate, heartbeat, blood pressure, and blood clotting, preparing a person for fight or flight.

Answer: The ovaries of a female produce the hormones estrogen and progesterone. Estrogen is responsible for female secondary sex characteristics. Progesterone is a hormone that helps maintain the lining of the uterus. Estrogen and progesterone function

1. Insulin and glucagon regulate blood-sugar levels. Insulin targets the liver and instructs it to remove sugar from the blood and to produce glycogen (animal starch). Glucagon targets the liver, causing it to break down glycogen into sugar, which is released into the blood.

2. The parathyroid glands regulate the level of calcium in the blood by producing the parathyroid hormone, which targets the bones to release calcium. Bones are mostly calcium and can act like a bank for this mineral.

3. Cortisone, cortisol, and aldosterone are produced by the adrenal cortex. Cortisone and cortisol are anti-inflammatories and have antiallergic effects. Cortisone can treat skin diseases and help manage stress. Aldosterone regulates the level of salt in the blood and helps maintain the body’s electrolyte balance.

4. The pancreas produces pancreatic fluid, which enters the small intestines through a duct, acting as an exocrine gland. The pancreas contains the Islets of Langerhans cells that produce the hormones insulin and glucagon, which reach their targets by traveling through the blood. In this way, the pancreas functions as an endocrine gland (or ductless gland).

5. A person with hypoglycemia has a low blood-sugar level. It might be tempting to treat this condition by simply telling the person to eat foods with sugar. This is a mistake that could result in death. The mere symptoms of a disease should not be treated; the cause of a disease should be. When an individual with hypoglycemia eats foods with sugar, the Islets of Langerhans respond by oversecreting insulin, lowering the sugar level further. A person with hypoglycemia should be put on a low-carbohydrate diet to prevent the oversecretion of insulin and the lowering of sugar levels that follow.

Answer: Extracellular digestion takes place outside the cells of an organism in an organ or organ system specialized for this purpose. Intracellular digestion takes place inside cells in organelles called food vacuoles. Most organisms have both extra- and intracellular digestion. The exception is unicellular organisms, which have only intracellular digestion.

Answer: Animal-like protists have food vacuoles for digestion.

1. Animal-like protists are one-celled organisms that carry out their life functions in a manner typical of individual cells. They give us a better understanding of the functioning of individual cells in humans. For example, the life functions of human white blood cells called phagocytes are similar to those of amoeba.1. Animal-like protists are one-celled organisms that carry out their life functions in a manner typical of individual cells. They give us a better understanding of the functioning of individual cells in humans. For example, the life functions of human white blood cells called phagocytes are similar to those of amoeba.

2. The pseudopods of amoeba are false feet, which are used for locomotion and to capture food. The amoeba is like a blob that is constantly changing shape as its pseudopods move about. The amoeba uses its pseudopods to engulf food by a process called phagocytosis.

3. Animal-like protists live in water. As a result, water is constantly entering by osmosis. If water is not removed, the organism would swell and eventually explode. The contractile vacuoles of animal-like protists are organelles that squeeze excess water out by active transport.

4. Proteins are the only nutrients in food that contain the element nitrogen. Ammonia is a nitrogenous waste that is produced as a result of protein digestion.

5. The amoeba and paramecium do not need a transport system because they are unicellular and in direct contact with their environment. Materials circulate within these organisms by the movement of the cytoplasm.

Answer: The hydra has a two-way digestive system. Food enters through the mouth, and undigested food can exit from the mouth.

Answer: A hydra can produce carbon dioxide and ammonia as waste products.

Answer: Carbon dioxide and ammonia are excreted by diffusion through the cell membrane of the hydra’s ectoderm cells into the surrounding water. The endoderm cells excrete these wastes into the water of the digestive cavity.

1. The hydra has extracellular digestion that takes place in the digestive cavity and intracellular digestion that takes place in the food vacuoles of the ectoderm and endoderm cells.

2. A hydra does not need a transport system because all its cells are in contact with its watery environment. The endoderm cells are in contact with water in the digestive cavity, and the ectoderm cells are in contact with the surrounding water.

3. A hydra is basically sessile. However, it can glide on its base and somersault. A hydra can move long distances by allowing water currents to carry it to a new location.

4. The hydra has a nerve net but does not have a brain or nerve cord to control its responses.

Answer: The earthworm has a one-way digestive system. The pharynx sucks in food from the mouth to the esophagus, where peristalsis forces the food into the crop. Food is stored in the crop and pushed into the gizzard for mechanical digestion. From the gizzard, food enters the intestines where chemical digestion occurs. From the intestines, digested food enters the blood, and waste leaves through the anus.

Answer: In earthworms, digested food enters the blood from the intestines. The capillaries from dorsal and ventral blood vessels distribute the digested food to the cells.

Answer: Earthworms produce carbon dioxide and water as waste products from respiration. They produce ammonia and urea as nitrogen wastes.

1. The earthworm has extracellular digestion that takes place in the digestive system and intracellular digestion that takes place in the cells of the organs.

2. The earthworm has a closed circulatory system, dorsal and ventral blood vessels surrounded by five aortic arches (hearts) that pump blood. Capillaries from the major blood vessels to the organs supply food and oxygen.

3. The segments of the earthworm have muscles and four pairs of bristles (called setae) that grab the soil and allow the worm to dig.

4. The earthworm has a primitive brain that is composed of two ganglia connected to a ventral nerve cord. Together, the ganglia and the nerve cord coordinate the activities of the worm.

5. Oxygen in the air diffuses through the moist skin of the earthworm into capillaries, which carry the oxygen to the two major blood vessels.

Answer: The grasshopper has a one-way digestive system. The grasshopper has a mouth for the mechanical digestion of food. From the mouth, food enters the esophagus and moves into the crop for storage. Food in the crop enters the gizzard (where mechanical digestion takes place) and then moves into the stomach (where chemical digestion occurs). From the stomach, digested food enters the blood, and waste enters the large intestines, moves to the small intestines, and exits through the anus.

Answer: From the stomach, digested food enters the blood, and the dorsal blood vessel sprays the blood over the organs.

Answer: Carbon dioxide from the cells diffuses into the tracheal tubes and exits through the spiracles. Uric acid is a solid, nitrogenous waste that exits through the anus.

1. The grasshopper has extracellular digestion that takes place in the digestive system and intracellular digestion that takes place in the cells of the organs.

2. The grasshopper has an open circulatory system with a dorsal blood vessel that can pump blood. The blood sprays out of the dorsal blood vessel to bathe the organs, supplying food to the cells.

3. Grasshoppers can walk and jump because they have three pairs of legs. Grasshoppers can fly because they have two pairs of wings.

4. The grasshopper has a brain that consists of two large, combined ganglia that are attached to two ventral nerve cords. The brain and nerve cords coordinate the activities of the grasshopper.

5. The crop and gizzard are digestive organs found in insects but not in humans.

Answer: Asexual reproduction is the formation of a new individual from one parent. Sexual reproduction is the formation of a new individual from two parents.

Answer: Unicellular organisms such as amoeba, paramecia and yeast reproduce asexually. Some multicellular organisms such as molds and green plants reproduce asexually to form new individuals.

Answer: When the parent cell reproduces asexually, it does not exist anymore. Two daughter cells form from the parent, and they are identical to each other.

Answer: The advantages of asexual reproduction are that only one parent is required, and all the offspring are identical to the parent. The disadvantage is that no variety exists among the offspring.

1. Multicellular organisms perform asexual reproduction to produce new cells for growth and to replace cells in the organism that have died.

2. During asexual reproduction, the cytoplasm divides equally; the chromosomes replicate and are distributed equally to each daughter cell.

3. During asexual reproduction, each chromosome replicates. If the parent cell has 10 chromosomes, after replication it has 20. When the cytoplasm divides, these 20 chromosomes are distributed equally so that each daughter cell has 10 chromosomes.

4. Each daughter cell has 46 chromosomes. The species number of chromosomes remains the same from one generation to the next.

5. Chromosomes contain the hereditary information of a cell. If a daughter cell was produced with missing chromosomes, this error could result in the death of the cell because the functions controlled by that chromosome would not be available. For example, suppose the chromosome with the information needed to produce digestive enzymes was missing; the cell would not have the enzymes needed to digest food and would die.

Answer: An organism that reproduces by binary fission has equal division of the cytoplasm and equal distribution of the nuclear material to form two identical daughter cells.

Answer: Plants can use their roots, stems or leaves to produce a new plant.

Answer: A missing part makes it difficult for an organism to find food or defend itself. The ability to replace the missing part makes the organism whole and competitive once again.

1. When yeast cells reproduce by budding, the division of the cytoplasm is unequal. The larger cell is the parent, and the smaller cell is the bud. In binary fission, the division of the cytoplasm is equal.

2. Spores have a protective outer wall that lets them survive unfavorable conditions. However, as soon as food and water are available, the spore can form a new organism.

3. Regeneration is considered an example of asexual reproduction because when an organism loses a part, cells in the organism reproduce to replace the missing part. Some organisms can be cut in half and still grow back the missing part, resulting in the formation of two organisms.

Answer: During its life cycle, most of a cell’s time is spent in interphase performing its life functions. The only thing the cell is resting from is mitosis.

Answer: Replication of the chromosomes signals the end of interphase and the start of mitosis, or cell division. At this point the cell enters a stage of mitosis known as prophase.

Answer: During prophase the nuclear membrane and nucleolus disappear, and the centrioles begin to move to opposite sides of the cell. For the first time we can see astral rays, spindle fibers and chromatids.

Answer: In metaphase the chromatids are lined up on the spindle fibers in the middle of the cell.

Answer: In this stage of mitosis, the chromatids separate and move toward opposite sides of the cell.

1. This is the stage of mitosis that results in daughter-cell formation. Each cell has a nucleus with a nucleolus and a pair of centrioles.

2. A chromatid is a chromosome and its duplicate held together by a centromere.

• 3. Equal division of the cytoplasm is important because each daughter cell must end up with
• enough cell organelles to carry out the life functions.

4. The end result of mitosis is two identical daughter cells, each approximately the same size and containing the same number of chromosomes.

5. In animal-cell mitosis, centrioles and astral rays are present. Plant-cell mitosis does not have these structures.

Answer: Gametes are the male sex cells (sperm) and the female sex cells (ova).

Answer: Fertilization is the union (combination) of sperm and egg cells during sexual reproduction.

Answer: Somatic cells are any cells in the body that are not gametes.

Answer: The gonads (sex organs) produce gametes. The testes produce sperm, and the ovaries produce ova.

Answer: The advantage of sexual reproduction is variety among the offspring, which inherit some characteristics from each parent. The disadvantage is that two parents are required, so each must find a mate.

1. Organisms that reproduce sexually form gametes that have half the species number of chromosomes. When gametes combine during fertilization (n + n), the species number of chromosomes (2n) is restored.

2. Haploid cells are gametes with n chromosomes. Diploid cells are somatic cells with 2n chromosomes.

• chromosomes?
• 3. The stomach cells of the gorilla have 48 chromosomes. Stomach cells and pancreas cells are somatic cells, and all somatic cells in an organism have the same number of chromosomes.

4. A gamete in this organism has 15 chromosomes. Gametes (n) have half the number of chromosomes found in somatic cells (2n). 2n = 30 n = 15

5. The diploid number for this cell is 48. If the haploid number is n = 24, the diploid number is 2n (2 × 24 = 48).

Answer: The end result of meiosis is the formation of gametes with n chromosomes.

Answer: During synapsis each pair of homologous chromosomes and their replicas come together to form a set of four chromosomes called a tetrad. Disjunction is the breaking up of the tetrad. Two chromosomes go into one cell, and the other two go into another cell.

Answer: If synapsis and tetrad formation take place during prophase, the cell goes through the process of meiosis. However, if a tetrad is not formed and chromatids begin to line up on the spindle fiber, the cell enters mitosis.

1. Meiosis is reduction division; somatic cells that have 2n chromosomes produce gametes that have n chromosomes. After fertilization is complete, the number of chromosomes is restored (n + n = 2n). Without meiosis, gametes would have 2n chromosomes; after fertilization there would be 4n (2n + 2n = 4n). After each generation, the chromosome number for the species would double, and soon there would be no room for anything but chromosomes in the cell.

2. During spermatogenesis, four sperm cells are produced from each primary spermatocyte. In oogenesis, one ovum is produced along with three polar bodies.

3. The polar bodies produced during oogenesis die and disintegrate because they have very little cytoplasm and not enough organelles to carry out the life functions of the cell.

4. The major difference between meiosis and mitosis is that meiosis has two cell divisions, and mitosis has only one. The second cell division in meiosis reduces the number of chromosomes from 2n to n. Meiosis results in the production of four gametes, and mitosis produces two daughter cells.

Answer: Sperm cells are produced in the testes by the process of gametogenesis. During meiosis one primary spermatocyte produces four sperm cells.

Answer: Sperm cells are stored in the epididymis, where they mature before entering the vas deferens.

Answer: The seminal vesicles produce one of the three fluids that make up semen. Prior to combining with seminal fluid, sperm cells are not motile. Seminal fluid activates sperm cells and gives them motility.

Answer: The prostate gland produces the second of the three fluids that make up semen. The fluid from the prostate gland contains a substance that neutralizes the acid pH of the vagina, which would otherwise kill sperm cells.

Answer: Bulbourethral glands produce the third fluid found in semen, which contains a substance that neutralizes the acid conditions found in the male’s urethra.

1. The scrotum is a sac located outside the body cavity. The temperature in the scrotum is a few degrees lower than normal body temperature, which is necessary for proper sperm- cell production and development.

2. The testes produce sperm cells for reproduction and the sex hormone testosterone, which regulates male secondary sex characteristics.

3. The urethra has two jobs; it carries sperm cells out of the body for reproduction, and during excretion it helps remove urine from the body.

4. Semen contains sperm cells and fluid from the seminal vesicles, prostate gland and bulbourethral glands.

5. Sperm are produced in the testes, stored in the epididymis and then move into the ejaculatory duct. The ejaculatory duct connects to the urethra, which takes the sperm out of the body.

Answer: Egg cells are produced in the ovaries by the process of oogenesis. During meiosis one primary oocyte produces one egg cell and three polar bodies. This process takes place before a baby girl is born. The purpose of the menstrual cycle is to mature and release an egg for fertilization.

Answer: In humans fertilization takes place in a fallopian tube.

Answer: If an egg cell is not fertilized, it disintegrates and dies.

1. The ovaries produce egg cells for reproduction and hormones for regulation. The hormone estrogen regulates female secondary sex characteristics and stimulates the uterus to start producing its capillary lining. Progesterone maintains the uterine lining during the menstrual cycle.

2. Shortly after fertilization a zygote begins to divide, and the several cells that form implant themselves into the wall of the uterus where an embryo eventually develops. In the uterus, the embryo develops into a fetus.

3. The penis deposits sperm cells into the vagina, and if an egg cell is present, the sperm swim through the cervix, into the uterus and finally into the fallopian tube that contains the egg. Fertilization takes place in the fallopian tube.

4. After a zygote is produced, a fertilization membrane forms around the zygote, preventing other sperm cells from entering the egg. The head of a sperm cell contains enzymes that can break down the membrane that surrounds the egg. However, these enzymes cannot break down the fertilization membrane because it is made of different proteins, and enzyme action is specific.

Answer: FSH produced by the anterior pituitary gland starts the menstrual cycle by stimulating follicles to mature an egg and by stimulating the ovary to begin the production of estrogen.

• Answer: Follicles are cavities located in the ovaries where egg cells are matured during
• the menstrual cycle.

Answer: Ovulation is the release of an egg cell from the ovary.

Answer: After ovulation, the follicle is repaired by the growth of a mass of hormone- producing cells called the corpus luteum.

Answer: Estrogen is a hormone that travels through the blood to reach its target.

1. The follicular stage is the first stage of the menstrual cycle. This stage is dominated by the presence of the follicle. The follicle begins to mature an egg and produce the hormone estrogen.

2. Estrogen begins the development of the uterine lining. Progesterone is responsible for maintaining the uterine lining.

3. When the level of progesterone is low, the uterine lining begins to break down.

• 4. Progesterone produced by the developing embryo during pregnancy maintains the
• uterine lining.

5. For a woman to ovulate, an egg must be present and then released. Giving a woman FSH stimulates her follicles to mature an egg; giving her LH results in the release of the egg. FSH and LH are the two hormones found in fertility pills.

Answer: Cleavage is a special series of mitotic cell divisions, where each time the cells divide they get smaller and smaller. The size of the morula is about the same size as the zygote, yet the morula is a solid ball composed of many cells.

Answer: Embryological development begins in the fallopian tube with the first cleavage division. By the fifth day the blastocyst is implanted into the wall of the uterus, where embryological development continues until the eighth week, when the embryo is called a fetus.

Answer: Differentiation occurs at some point between the blastocyst stage and the gastrula stage and results in the cells of the developing embryo becoming different from each other. Certain cells form the eye, others the brain and so on.

1. Sometimes when a woman ovulates, two egg cells are released (each from its own follicle). If each egg cell is fertilized by a different sperm cell, fraternal twins result. Fraternal twins are different from each other genetically.

2. The cells of the gastrula are different from each other. Each cell is programmed to become a specific type of tissue or organ in the body. The cells of the blastocyst are undifferentiated and can form any type of tissue or organ in the body.

3. Stem cells are important because they have the potential of being removed from the blastocyst and used to create tissue and organs that can serve as replacement parts for damaged human organs.

4. The three layers of the gastrula are the ectoderm, mesoderm and endoderm. The ectoderm layer forms the skin and nervous system. The mesoderm layer forms the skeletal, circulatory and reproductive systems. The endoderm produces the organs of the digestive and respiratory systems.

5. Sexual reproduction takes place at fertilization, when a sperm cell and an egg cell combine to form a zygote. After fertilization, human development takes place asexually by mitosis.

Answer: A fetus is the name given to an embryo after the eighth week of development.

Answer: The amnion is a sac that contains a fluid called amniotic fluid. The sac and its fluid protect the fetus from shock.

Answer: The umbilical cord connects the fetus to the placenta and is the fetus’s lifeline. The fetus gets its food, oxygen and water from the placenta through the umbilical cord. Wastes from the fetus pass through the umbilical cord to the placenta.

1. Cells in the placenta produce progesterone, which maintains the uterine lining during pregnancy.

2. The placenta is a combination of tissue from the mother’s uterine wall and from the developing fetus.

3. The fetus has its own circulatory system, heart and blood cells for the transport of materials. The baby’s blood and the mother’s blood never mix with each other during development.

4. Gestation is the period of time from fertilization to birth and lasts approximately nine months.

Answer: Vegetative propagation is a form of asexual reproduction by plants. New plants are produced from the root, stem or leaf of an already existing plant.

Answer: A sweet potato placed in water develops many young plants called shoots from the enlarged root. Each of these can produce a new sweet potato plant.

Answer: The eyes of a white potato are actually buds. When one of these buds is removed along with a section of the potato and put into the ground, a new potato plant forms. The starch in the potato serves as food for the developing plant until leaves form and the process of photosynthesis begins, enabling the young plant to produce its own food.

Answer: Bulbs have a short underground stem with thick, fleshy leaves; corms do not have thick, fleshy leaves.

1. Vegetative propagation is considered asexual reproduction because new plants are produced from part of an existing plant. Gamete production and seed formation do not take place in vegetative propagation.

2. A runner is an aboveground stem that grows horizontally along the surface when the stem touches the ground; buds from the stem produce a new plant. A rhizome is an underground stem that grows horizontally along the surface; shoots from buds in the stem develop into new plants.

3. A bulb can produce several smaller bulbs at the base of its short stem. Each of these small bulbs can develop into a new plant.

4. When a Bryophyllum leaf falls on moist soil, new “baby” plants can form from the edges of the leaf.

Answer: A cutting is a root, stem or leaf that is cut off an existing plant and put into water, moist sand or soil to produce a new plant.

Answer: Roses have long branches that can be bent into the ground and covered with a layer of soil so that a small part of the branch is left sticking out. Roots and stems form from the bent branch. When the bent branch is cut, two separate rose plants are obtained.

Answer: In grafting, a stem (scion) is cut off a plant and attached to the stem of a plant that is rooted in the ground (stock). The fruit produced by this combination is the fruit of the scion.

1. In natural vegetative propagation, a plant reproduces asexually on its own from a part of itself. In artificial vegetative propagation, humans take roots, stems or leaves from existing plants to produce new plants.

2. Seedless grapes are propagated vegetatively by grafting. A scion from a seedless grape vine is grafted onto a stock from a seeded grape vine to produce only seedless grapes.

3. Farmers always use apple trees or other fruit trees produced by grafting because the fruit of the scion is genetically the same as the plant the scion was taken from. If the tree the scion is taken from produces great-tasting apples, the grafted apple tree produces exactly the same quality of apple. Also, grafted trees mature and produce fruit sooner than those started from seed.

4. A disadvantage of vegetative propagation is the lack of variation among the offspring. The offspring can never be better than the parent.

Answer: The flower is the reproductive part of an anthophyte plant.

Answer: The male part of the flower is the stamen. Remember the men in stamen to help you recall that this is the male part of the flower. The female part of the flower is the pistil.

Answer: The ovules of a flower are produced in the ovary.

Answer: Pollen grains are produced in the anther of the stamen.

1. Flowers are produced by plants in the phylum Anthophyta.

2. The petals of a flower are often colored to attract insects, birds and other animals that help in the process of pollination.

3. The stigma is sticky so that when a pollen grain falls on it, the pollen grain doesn’t fall off.

4. Pollen grains contain the male gametophytes of the flower that fertilize the female gametophytes. Many pollen grains contain three monoploid nuclei, a tube nucleus and two sperm nuclei. Some pollen grains have a tube nucleus and a generative nucleus that divides to produce two sperm nuclei when a pollen tube is formed. A protective outer wall surrounds all pollen grains.

5. An ovule is an embryo sac that contains seven cells. One of these is the monoploid (n) egg cell, and another is a cell with two monoploid nuclei that help form the seed. An ovary can contain one or more ovules.

Answer: Pollination is the transfer of pollen from an anther to a stigma.

Answer: The three kinds of pollination are self-pollination, cross-pollination and artificial pollination. Self-pollination is the transfer of pollen from an anther to a stigma within the same flower. Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower. Artificial pollination occurs when humans transfer the pollen.

Answer: After fertilization takes place, the petals of the flower fall off and the ovary begins to enlarge, eventually becoming a fruit.

1. After a pollen grain lands on a stigma, its protective wall breaks down and a pollen tube forms. The pollen tube grows through the style to the ovary. The two sperm nuclei enter the ovule through an opening called the micropyle to fertilize the egg and the cell that contains the two monoploid nuclei.

2. Two fertilizations take place in the ovule. One sperm nucleus fertilizes the egg cell to produce a diploid zygote (2n). The other sperm nucleus combines with a cell that has two monoploid nuclei to form a cell (3n).

3. This 3n cell becomes the endosperm of the seed. The endosperm contains starch and provides food for an embryo during germination.

4. After fertilization, the zygote becomes the embryo of the seed.

5. The parts of a plant that are not fruits are the roots, leaves and stems. In some plants these structures can produce new plants by vegetative propagation. Also, all parts of a flower except the ripened ovary are not fruits.

Answer: Seeds are important in plant reproduction because they contain the embryo that becomes a new plant. Seeds are important sources of food for humans and animals.

Answer: The epicotyl becomes the upper part of the stem and the leaves of the plant.

Answer: The hypocotyl develops into the roots and the lower part of the stem.

1. A dicot seed has two cotyledons, or seed parts, that can be separated from each other. A monocot seed has only one cotyledon.

2. The endosperm of the cotyledon supplies the embryo with food during germination.

3. The seed coat protects the seed and its embryo prior to germination.

4. The micropyle is a tiny opening in the seed through which the sperm nuclei enter to fertilize the ovule.

Answer: Seed dispersal is necessary to reduce competition between the parent and new plant for scarce resources such as light, soil and water.

Answer: The agents of seed dispersal are wind, water, insects and other animals. The agents for seed dispersal are the same as those for pollination.

Answer: Germination is the breaking of dormancy and the development of a seed into a new plant.

1. Fruit helps disperse the seeds of a plant by attracting animals that eat the fruit and then deposit the seeds at a new location.

2. The first part of a seed to germinate is the hypocotyl, which forms the roots needed to anchor the new plant in the soil.

3. The endosperm provides the embryo with food during germination. After all the endosperm has been used up, the cotyledons that contain the endosperm fall off the stem.

4. Dormancy is a period of inactivity for a seed, where life functions have been slowed down or temporarily suspended.

Answer: Homologous chromosomes are pairs of similar chromosomes found in diploid cells.

Answer: In a hybrid or heterozygous individual, where we have two different kinds of alleles for a trait, the characteristic of the trait that we see is called dominant.

Answer: The gene is the hereditary unit or factor that is passed down from one generation to the next. Genes are composed of DNA molecules and determine the characteristics of traits in an organism.

Answer: An allele is different forms of genes for a trait. Alleles occupy corresponding positions on homologous chromosomes. Two alleles determine a trait.

1. A trait is some distinguishing feature or property of an organism. A characteristic refers to the different versions or expressions of the trait. For example, height is a trait in pea plants; tall or short stems are characteristics.

2. The homozygous or pure genotype has two of the same kinds of alleles for a trait (for example, TT, two alleles for the tall characteristic of height). The heterozygous or hybrid genotype has two different kinds of alleles for a trait (for example, Tt, an allele for tall and an allele for short).

3. The only way to get the recessive characteristic of a trait is to have two of the recessive alleles (for example, tt, or homozygous short).

Answer: When an organism has two different alleles for a trait, the characteristic we see is the dominant one.

Answer: When two hybrids are crossed, each allele segregates (separates) during gamete formation so that new allele combinations (genotypes) can be formed at fertilization.

Answer: The Punnett square is used to show different allelic combinations of gametes and to predict the probability of offspring ratios.

1. The result of a hybrid cross by genotype is always 1:2:1, one homozygous dominant to two heterozygous to one homozygous recessive. As a percentage, this ratio is expressed as 25% homozygous dominant to 50% heterozygous to 25% homozygous recessive.

2. The Punnett square can be used as a mathematical tool to predict the possible results that can be obtained from a genetic cross. To get actual results, the genetic cross has to be per- formed. Real-world results are always different from predicted results. However, the larger the sample used, the closer the actual result is to the predicted result. In his experiments, Mendel used large numbers of pea plants.

Answer: In a dihybrid cross, alleles for the different traits separate and are inherited independently of each other.

Answer: A dihybrid has the hybrid (heterozygous) genotype for two different traits. For example, YyRr is a dihybrid. This individual is hybrid for seed color and seed texture.

Answer: Yellow and wrinkled. Yy is hybrid yellow, and rr is homozygous wrinkled.

1. A dihybrid individual can produce four kinds of gametes.

2. To solve a dihybrid cross, a Punnett square must have 16 boxes. The 4 boxes on each side represent the four possible gametes that can be produced by each dihybrid parent.

3. The dihybrid cross produces a phenotype ratio of 9:3:3:1. If you memorize this ratio, you will not have to spend the time needed to solve dihybrid cross problems by the Punnett square method.

Answer: To determine the genotype of an organism, we do a test cross. We cross the organism having the unknown genotype with a homozygous recessive. If any of the off- spring have the recessive characteristic of the trait, the unknown organism is heterozygous. If all the offspring have the dominant characteristic, the unknown organism is most likely homozygous.

Answer: 25% red, 50% pink and 25% white. This is a 1:2:1 ratio. If you remember the ratio produced when two individuals with the new characteristic are crossed, you do not need to work out the solution with a Punnett square. If you wish to check your answer with a Punnett square, you can use R for the red allele and W for the white allele. The genetic cross that gives the solution is RW × RW.

Answer: 50% pink and 50% white. The genetic cross that gives the answer is RW × WW. Use a Punnett square to find the solution.

1. The homozygous recessive is always used in a test cross because this organism has a known genotype, two recessive alleles for a trait. An organism with the dominant characteristic cannot be used because we don’t know if it is homozygous or heterozygous. We would not know the genotype of the test organism or the genotype of the organism it is being crossed with. The results obtained from crossing two unknown genotypes cannot lead to any conclusions as to their allele combinations.

2. In incomplete dominance, we have two different alleles for a trait and neither is dominant. In codominance, both alleles are dominant.

3. The genotype ratio produced is 25% red, 50% roan and 25% white. To solve this problem, use CR for the red allele and CW for the white allele. The genetic cross that gives the answer is CR CW × CR CW. Use a Punnett square to find the solution.

Answer: Human somatic cells have 23 pairs of chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes).

Answer: Gametogenesis produces sperm cells and egg cells that are haploid.

Answer: The chance of producing a male or female child is one in two or 50:50.

Answer: Sex chromosomes determine whether an individual is male (XY) or female (XX). Autosomes have no role in sex determination; however, they carry alleles for many other traits.

1. A karyotype is an arrangement of chromosomes that were removed from a nucleus and arranged in decreasing size order.

2. Human somatic cells have 44 autosomes (22 pairs) and two sex chromosomes (1 pair).

3. All gametes have one sex chromosome. A sperm cell can have an X or Y sex chromosome.Egg cells contain only X sex chromosomes.

4. The male parent determines the sex of the child.

5. The sex of a new individual is determined at the instant of fertilization when the sperm and egg cells combine.

Answer: The four different blood types are A, B, AB, and O. The type of antigen present on the surface of the red blood cell determines the blood type of the individual.

Answer: People with type A blood have antigen A on the red blood cell. Individuals with type B blood have antigen B. Those with type AB blood have antigens A and B. Finally, people with type O blood do not have any antigens on their red blood cells.

Answer: People with type A blood have antibody B in their plasma. Individuals with type B blood have antibody A. Those with type AB blood do not have antibodies A or B in their plasma. People with type O blood have antibodies A and B.

Answer: Three alleles control human blood types. Six different genotypes are possible for the four blood types. Look at the preceding table for the different genotype combinations.

1. A person with type O blood can donate to anyone in an emergency because type O blood does not contain antigens on the red bloods cell that can cause agglutination or clumping of the blood.

2. A person with blood type A cannot donate blood to a person with blood type B. The type A individual has anti-B antibodies that cause agglutination with antigen B in a person with blood type B.

Answer: Sex-linked traits are traits that have an allele located on the X chromosome and sometimes on the Y chromosome. Two examples of sex-linked traits are hemophilia and color blindness.

Answer: A carrier is a female that has an allele for a sex-linked disease but does not have the disease.

Answer: A person with hemophilia who gets a cut or bruise does not stop bleeding because the individual is missing a clotting factor in the blood.

Answer: The genotype of a color blind woman is XnXn, or homozygous recessive.

Answer: A son inherits a sex-linked allele from his mother. If a woman is heterozygous, her son has a 50% chance of having a sex-linked disease. A daughter can inherit a sex-linked allele from her mother or father.

Answer: In genetics a pedigree chart is used to keep track of a trait in a family from one generation to the next.

Answer: On a pedigree chart, different generations are indicated by the use of Roman numerals. The parent generation is generation I, and their offspring are in generation II.

Answer: To indicate that a couple is married or has mated, a horizontal line is drawn between a circle (female) and a square (male).

Answer: The phenotype of an organism is determined by its genotype and any environmental factors that can influence the expression of certain alleles.

Answer: Some organisms have darker extremities because they have an allele that produces a heat-sensitive enzyme, which promotes melanin production. In warm areas, the enzyme is less active; less melanin is produced, and the fur of the animal is lighter. In the cooler extremities, the enzyme is more active; more melanin is produced, and the fur in these areas is darker.

1. Identical twins are used in studies that investigate the influence of environment on heredity because they have the same heredity (genes). Thus, the only variable in the study is the specific environmental influence that is being investigated.

2. The difference in the color of the bacteria can be explained by the effect of temperature on the expression of the allele that controls color.

3. The white fur color in winter allows the fox to blend in with the snow in its environment. This helps the fox be a more efficient predator and, at the same time, enables the fox to avoid animals that might consider it prey.

Answer: The DNA molecule is a double helix. Watson and Crick discovered this in 1953.

Answer: The DNA molecule is composed of thousands to millions of repeating nucleotides.

Answer: A nucleotide contains deoxyribose, a phosphate group and one of four possible nitrogen bases.

Answer: The four possible nitrogen bases in a nucleotide are adenine (A), guanine (G), cytosine (C), and thymine (T).

Answer: The DNA molecule replicates when the chromosome that it is in replicates. During mitosis, replication takes place at the very end of interphase.

1. The paired nucleotides of the DNA molecule are held together by weak hydrogen bonds. The weak hydrogen bonds allow the molecule to easily separate or unzip during replication and to recombine when replication is complete.

2. The deoxyribose molecules in DNA are held together by phosphate groups.

3. The complementary strand to A-C-T-G-T-C is T-G-A-C-A-G. In a DNA molecule, adenine pairs with thymine, and cytosine pairs with guanine.

4. A DNA molecule replicates when its two strands unzip, and nucleotides in the cell pair up with their complements on each original strand. At the completion of replication, two molecules of DNA are formed. Each molecule is composed of one old (original) strand and one new strand.

5. In semiconservative replication, each molecule that is formed has one old (original) strand and one new strand.

Answer: Protein synthesis takes place at the ribosome. Ribosomes can be found attached to the endoplasmic reticulum or floating free in the cytoplasm.

Answer: Proteins are used for growth, repair and reproduction of new cells. DNA and RNA are important nucleoproteins. The kinds of proteins that we have determine our traits.

Answer: A codon is genetic code, a set of three nitrogen bases in DNA or mRNA.

1. DNA is a double helix, contains deoxyribose, and one of its nitrogen bases is thymine. RNA is a single helix, contains ribose, and has uracil instead of the nitrogen base thymine. DNA is found in the nucleus, and RNA is found in the cytoplasm.

2. Transcription is a process that produces RNA nucleoproteins. Transcription begins when a segment of DNA unzips, and one strand acts as a template for the formation of single- stranded mRNA. Complementary nitrogen bases pair up with bases on DNA to form mRNA. When the mRNA molecule is complete, it separates from the DNA and leaves the nucleus. At this point, each DNA strand recombines with its complement.

3. Translation is the process by which the ribosome combines amino acids to produce proteins. The function of transfer RNA (tRNA) molecules is to bring amino acids to mRNA at the ribosome. The ribosome moves down the mRNA molecule, and the amino acids are attached to each other by peptide bonds that form by dehydration synthesis. When the protein has been formed, the tRNA molecules separate from the ribosome (as does the newly formed protein).

4. mRNAand tRNA differ in both structure and function. mRNA is a long, single-stranded nucleoprotein with many codons that have the information needed to direct the order of amino acids in a protein. tRNA molecules have two sides. One side of a tRNA molecule attaches to an amino acid; the other side has an anticodon that is complementary to a codon on mRNA. tRNA molecules bring amino acids to the correct location on an mRNA molecule.

5. The sequence of nitrogen bases on the tRNA anticodon is U-A-C. This answer is obtained by first finding the complementary nitrogen base sequence of the mRNA molecule, which is A-U-G. The complement of T is A, the complement of A is U (RNA has the nitrogen base uracil instead of thymine), and the complement of C is G. The tRNA anticodon is the complement of mRNA. mRNA is A-U-G. The complement of A is U, the complement of U is A, and the complement of G is C. This gives us the answer U-A-C.

Answer: A mutation is a change or error in a gene or chromosome.

Answer: The different types of mutations are gene mutations and chromosomal mutations. Gene mutations can be point or frameshift mutations. Chromosomal mutations that result from nondisjunction change the chromosome number of the organism. Structural mutations can occur because of deletions, additions, translocations, or inversions.

Answer: Mutations can be caused by environmental factors such as ultraviolet rays and cosmic rays. Another cause of mutations results from mutagenic agents such as X-rays, gamma rays, nuclear radiation, and carcinogens.

Answer: Mutations can be passed down from one generation to the next if a gamete containing a mutated allele or chromosome takes part in the fertilization process.

Answer: Carcinogens are chemicals that cause gene mutations, which can result in cancer. Some examples of carcinogens are asbestos, benzene, some food dyes, and PCBs.

1. When a point mutation occurs, one nitrogen base in a codon is replaced by another nitrogen base. The number of bases in the codon remains the same (three), and only one codon is affected. The changed codon results in a different amino acid in the polypeptide that is being synthesized.

2. In a frameshift mutation, one nitrogen base is added or deleted from a codon on an mRNA molecule. In a deletion, a nitrogen base is removed; all the remaining nitrogen bases shift to the left, and every codon after the deletion has a new set of three nitrogen bases. In an addition, a nitrogen base is inserted. This forces the nitrogen bases to shift to the right, and each codon then has a new set of three nitrogen bases.

3. When nondisjunction occurs during meiosis, chromosomes fail to separate, and a change in chromosome number results. One gamete has an extra chromosome, and the other gamete is missing one chromosome. After fertilization a zygote is produced that has 2n + 1 or 2n – 1 chromosomes.

4. In an addition, a segment of chromosome breaks off and is added to its homologous chromosome. However, in translocation, a segment of chromosome breaks off and is added to a different (nonhomologous) chromosome.

5. Mutagenic agents are environmental or man-made factors that can cause mutations. Examples of some mutagenic agents are ultraviolet rays, cosmic rays, X-rays, gamma rays, nuclear radiation, and carcinogens.

Answer: Mutations result in the production of defective alleles that can be inherited. These defective alleles are responsible for many genetic diseases in humans.

Answer: The chance of this child having cystic fibrosis is 25%. This is a hybrid cross, and the ratio produced by a hybrid cross is always 3:1. The chance of having a child with cystic fibrosis is one in four (25%). A person must have two recessive alleles to have this genetic disease. If N represents the normal allele, and n represents the defective recessive allele, the cross that gives the result is Nn × Nn. Use a Punnett square to solve this problem.

Answer: A child that tests positive for PKU disease is put on a special diet that is low in phenylalanine to control this disease. High levels of phenylalanine lead to nervous system problems, mental retardation and decreased body growth. Preventing high levels of phenylalanine avoids these complications.

Answer: Tay-Sachs disease results when an individual has two recessive alleles that are defective for the production of the enzyme called Hex-A. A heterozygous individual has one normal allele for the production of this enzyme. As long as one allele is working to produce Hex-A, the individual does not have the disease.

Answer: Normal red blood cells are round, and sickle-cell red blood cells are crescent shaped. The sickle cells tend to block the flow of blood in small blood vessels.

1. Huntington’s disease is caused by one defective dominant allele. Most other human genetic diseases are caused by the presence of two recessive alleles. In Huntington’s disease, the presence of a protein damages nerve cells in the brain. In some recessive genetic diseases, the absence of a protein (usually an enzyme) causes the disease. Examples of this can be seen with Tay-Sachs disease and PKU.

2. Their chances of having a child that will develop Huntington’s disease is 50%. To have Huntington’s disease a person needs to have only one defective dominant allele for the disease. If H represents the allele for Huntington’s disease, and h represents the normal allele, the genotype for the man is Hh and for the woman is hh. The cross that gives the result is Hh × hh. Use a Punnett square to find the solution.

3. The probability that this child will have sickle-cell anemia is 25%. This is the hybrid cross again. The ratio produced by a hybrid cross is always 3:1. The chance is one in four (25%) of this child having sickle-cell anemia. A person must have two recessive alleles to have this genetic disease. The key used to represent the alleles in this problem is different from others that we have seen. HbA represents the normal allele, and HbS represents the defective recessive allele. The letters Hb represent the hemoglobin molecule. Actually, any letter combination can be used that makes sense to you when solving genetic problems. The cross that gives the result is HbAHbS × HbAHbS. Use a Punnett square to solve this problem.

4. No. This child of these parents has a 0% chance of having Tay-Sachs disease. The child must have two defective recessive alleles to have the disease. This cannot occur given the genotypes of the parents. If N represents the normal allele, and n represents the defective recessive allele, the cross that gives the result is Nn × NN. Use a Punnett square to find the solution.

5. A simple blood test can be done to determine whether either of the prospective parents carries an allele for a genetic disease. Genetic counseling of the parents can help them determine the risk factors they face when having children.

Answer: Biotechnology involves the use of engineering and technology to advance biological research. Some applications of biotechnology are in the areas of gene sequencing, genetic engineering, cloning, and stem cell research.

Answer: The three key goals of the Human Genome Project were to determine the sequences of the 3 billion nitrogen base pairs in DNA, identify the 30,000 genes in human DNA, and create a database to store this information that would be available to researchers.

Answer: The Human Genome Project is important because it will enhance our knowledge of gene function and lead to the discovery of new methods of diagnosing and treating disease.

Answer: Genetic engineering is a technique used to transfer genes from the chromosomes of one species into the chromosomes of another species.

Answer: A vector is a carrier used to bring DNA into other cells. Viruses and bacterial plasmids are examples of commonly used vectors.

1. The restriction enzyme endonuclease can be used to cut a gene out of the DNA from one chromosome, and the enzyme DNA ligase can be used to splice the inserted gene into another chromosome. This technique results in the production of a recombinant DNA molecule.

2. Plasmids are pieces of circular DNA in bacteria that are often used in gene splicing. A spliced plasmid can be inserted into other cells.

3. One method of cloning involves removal of the nucleus from a somatic cell and its insertion into an unfertilized egg cell that has had its nucleus removed. An embryo develops that becomes a new individual, identical to the one that donated the nucleus.

4. Stem cells are obtained from the blastocyst stage of embryological development. To harvest stem cells, the embryo is destroyed. Many people feel human life begins at conception and the destruction of an embryo prevents the formation of a new individual. Others feel that an embryo is not a human and that the benefits to be derived from stem cell research are of primary importance.

5. The traditional method of embryo production involves the union of egg and sperm cells at fertilization to produce a zygote. This zygote becomes an embryo as a result of cleavage. Cloning and parthenogenesis are two biotechnological methods of embryo production.

Answer: Evolution is the change that has occurred in a species of organism with the passage of time.

Answer: A fossil is the remains of an organism that lived in the past.

Answer: The soft parts of organisms are rarely fossilized because they decay rapidly after the death of the organism. The hard parts of the organism decay slowly and can form fossils.

Answer: Amber is a form of fossilized resin from trees that can contain trapped insects or plant material.

Answer: Refrigeration results in fossil formation because cold temperatures can dramatically slow down the process of decay.

1. Evolution shows how organisms have changed over time. Evolution accounts for the huge diversity of living things that exist on earth.

2. Fossils are strong evidence in support of evolution because they are the tangible remains of organisms that have lived in the past. Fossils can be compared to current organisms so that any changes that have taken place can be determined.

3. An imprint is an impression of a part of an organism. Examples of imprints are leaf prints and footprints. A mold is an outline of the organism that is left behind after the organism dies, becomes covered with sand or mud, and then decays.

4. Tar pits contain asphalt that surrounds the bones of the organism preventing the bacteria of decay from breaking down the bones. These preserved bones eventually become fossils.

5. Petrifaction occurs when minerals in water diffuse into the cells of a dead organism, forming rock.

Answer: Fossils are found in sedimentary rock.

Answer: Fossils are dated to determine when the organism that formed the fossil was alive.

Answer: Igneous rock is formed by volcanic activity and lava flow. The high temperatures associated with this type of rock formation destroy any organisms, preventing the for- mation of fossils.

Answer: The half-life of carbon-14 is short (5,730 years), so after 50,000–70,000 years not enough carbon-14 is left in a fossil to be measured.

1. In relative dating, the age of a fossil is not determined. However, the age of one fossil relative to another can be determined. For example, fossils in layers near the top of a rock formation are younger than fossils near the bottom.

2. An index fossil represents a species of organism that was found all over the world but lived for a short period of time. If the age of an index fossil is known, it can be used to determine the age of other fossils in the same layer. In addition, fossils in layers above the index fossil are younger. Fossils in layers below the index fossil are older.

3. Absolute dating gives an approximate date of when the organism represented by a fossil died. Absolute dating relies on the radioactivity of certain elements and their half-life. The older the fossil, the more the radioactive element has decayed.

4. Carbon-14 dating is a form of absolute dating. Carbon-14 has a half-life of 5,730 years. The carbon-14 in a fossil sample decays into half its original amount every 5,730 years. A sample that has one-eighth the original amount of carbon-14 has gone through three half- lives and is 3 × 5,730 (or 17,190) years old.

5. Rocks generally don’t contain carbon, so trying to use carbon-14 to date a rock is meaningless. Carbon-14 dating can be used to date fossils that contain carbon, such as bones and teeth (hard parts). To date rocks that might contain fossils, uranium 238 and the potassium-argon method can be used.

Answer: Homologous structures are similar in construction and evolutionary development but dissimilar in function. Homologous structures are often used to show evolutionary relationships between organisms. Examples of homologous structures are the forelimb of a human and the wing of a bat.

Answer: Analogous structures are similar in function but dissimilar in construction and evolutionary development. Examples of analogous structures are the wing of a bird and the wing of an insect.

Answer: A vestigial structure at one time had a function but no longer has a function. The change from functionality to nonfunctionality demonstrates evolution. For example, at one time the human appendix had a digestive function but now does not. This change shows that humans have evolved.

1. A common ancestor is an individual from which two or more related species could have evolved.

2. Comparative anatomy is a technique used to compare homologous body structures of organisms. The more the structures are similar to each other, the closer the evolutionary relationship is between the organisms.

3. If fossilized camel skeletons from different points in history are compared, the differences between them shows a pattern of change that proves evolution occurred.

4. The similarity between embryos during the early stages of development supports the concept of the common ancestor.

5. Comparative biochemistry provides strong evidence for evolution. The close similarity in complex molecules found between different species argues in favor of a common ancestor from which organisms could have evolved (changed). For example, human insulin differs from cow insulin in only 3 out of 51 amino acids. Cow insulin is close enough to human insulin that it can be given to diabetics.

Answer: The result of overproduction is competition for scarce resources such as food, water, and territory.

Answer: Variation refers to the different and diverse forms of a trait.

Answer: According to Darwin, the best variations are selected by nature. The modern approach to evolution states that nature selects the organisms with alleles for the fittest variations; these organisms are the ones most likely to reproduce and pass on the alleles for these variations to the next generation.

Answer: Darwin’s theory of natural selection is best described by gradualism, which states that evolution is a gradual, slow and continuous process that proceeds in numerous small steps over many generations.

1. According to the concept of acquired characteristics, the more an organism uses a structure, the better and more highly developed the structure becomes. The acquired improvement can be inherited by the offspring.

2. To Darwin, survival of the fittest meant that those individuals that had the most-fit variations got the opportunity to reproduce and to pass these variations on to the next generation.

3. Darwin believed that with the passage of time, the most-fit variations became the norm within a population, eventually giving rise to a new species of organism.

4. The concept of mutations is used to explain how variations can occur in a species of organism.

5. The punctuated equilibrium explanation of evolution states that change occurs in sudden spurts during which many species are formed, followed by long periods of stability with no speciation.

Answer: Within a population, the frequency of an allele remains constant from generation to generation, as long as certain conditions are met.

Answer: The two mathematical equations used to express the Hardy-Weinberg law are p+q=1 and p2 +2pq+q2 =1.

Answer: An increase in the size of the gene pool creates an increase in statistical accuracy.

Answer: Migrations of individuals into or out of a population changes the frequency of alleles in a population.

Answer: Twenty percent of the fruit flies have the recessive allele for white eyes. The equation p + q = 1 can be used to solve the problem. Here, p is the percentage of individuals with the dominant allele (0.8 or 80%), and q is the percentage of individuals with the recessive allele. p+q=1 0.8 + q = 1 q = 0.2 or 20%

1. Geographic isolation is the physical separation of individuals within a population and is caused by geographical barriers such as mountains, deserts, oceans, and rivers.

2. Geographic isolation upsets the Hardy-Weinberg law by reducing the size of the gene pool and interfering with random mating.

3. Environmental factors upset the Hardy-Weinberg law by selecting one variation within a population over another.

4. The Hardy-Weinberg law states that within a population the frequency of an allele remains constant. Any change in the frequency of an allele in a population might indicate that evolution is taking place.

Answer: The gases that were probably present in this atmosphere were: water vapor, nitrogen, carbon monoxide, carbon dioxide, and some hydrogen.

Answer: Some of the first organic molecules to form on earth were simple sugars, amino acids, fatty acids, glycerol, and nucleotides.

Answer: According to the heterotroph hypothesis, the first cells to originate on earth were primitive prokaryotic heterotrophs.

1. Carbon dioxide was added to the earth’s atmosphere by anaerobic respiration of the first heterotrophs.

2. The first heterotrophs were prokaryotic, reproduced by binary fission, and produced energy by fermentation (anaerobic respiration). Modern-day heterotrophs are eukaryotic, reproduce by mitosis, have mitochondria, and produce energy by aerobic respiration.

3. The endosymbiotic theory states that eukaryotic cells incorporated primitive prokaryotic cells that eventually evolved to become mitochondria and chloroplasts.

Answer: Ecology is the branch of biology that studies living things, their interrelationships with each other and their interrelationship with the environment. Two interrelationships exist. The first is between living things. The second is between living things and their environment.

Answer: Abiotic factors are all the nonliving things in the environment such as climate, light, temperature, water, and soil. Biotic factors are all the living things that are found in the environment.

Answer: Humus is the part of soil that is formed from decayed plant and animal material. Humus provides nutrients and minerals for plants and increases the capability of soil to retain water.

1. Generally the further a location is north or south of the equator, the colder the climate. Geographical features such as mountains, proximity to water, and elevation affect climate. One side of a mountain range can have lots of rainfall, while the other side is a desert. Locations close to water tend to be cooler in summer and warmer in winter. Higher elevations tend to have colder climates.

2. The greater the duration and intensity of light in a given location, the higher the temperature. High temperatures in an area increase evaporation from bodies of water and increase transpiration, which is the loss of water from the leaves of a plant.

3. The abiotic conditions of the northern United States and Canada are very different from those found in desert regions where cactus plants grow. The cold winters, excess precipitation, different soil conditions, reduced duration of light, and reduced intensity of light are factors that prevent cactus plants from surviving in the northern United States and Canada.

Answer: A population contains members of the same species that live together in a specific location, while a community has several different populations that live together in a specific location.

Answer: An ecosystem consists of a community and the abiotic factors in its environment.

Answer: Habitat is where an organism lives in its environment. Niche is the role or job that the organism has.

1. The carrying capacity of the land refers to the land’s capability to supply enough food to feed a population. When the number of individuals in a population exceeds the carrying capacity of the land, some members of the population must migrate to a new location or some will die of starvation.

2. Intraspecific competition is competition between members of the same species. Interspecific competition is competition between members of different species. Organisms compete for territory, food and water. In the case of intraspecific competition, organisms also compete for a mate.

3. A predator is an animal that hunts and kills for food; the prey is the animal that is hunted. When the prey population increases, the predator population also increases. As the prey population decreases, the predator population decreases. Predators are important because they keep the prey population from increasing to the point where it exceeds the carrying capacity of the land.

Answer: Symbiosis is a relationship between two organisms that live together where at least one of the organisms benefits from the association.

Answer: Commensalism is a relationship where one organism benefits from the association, and the other is neither helped nor harmed.

Answer: Coevolution is a process by which species adapt to changes in one another.

1. Mutualism is a symbiotic relationship that is beneficial to both organisms.

2. Mutualism is the type of symbiosis described here. The insects benefit by gathering pollen for food. The plants benefit by having their flowers pollinated so that they can reproduce.

3. The parasite uses the host for a place to live and a source of food. The host is an unwilling participant in this relationship and is injured or killed by the parasite.

Answer: The sun is the source of energy that flows through the ecosystem.

Answer: A food chain shows how energy is transferred from one organism to another in an ecosystem.

Answer: A predator is a heterotroph that hunts and kills its prey to obtain food for energy. Predators are carnivores and are primary, secondary or tertiary consumers. A scavenger is a carnivore that eats food left over by predators. Scavengers do not kill the animals they eat.

1. The flow of energy through an ecosystem is considered unidirectional because energy is never recycled. Energy never returns to the sun.

2. As energy flows through the food chain from one group of organisms to the next, less energy is available because each group uses up energy for life functions such as locomotion, respiration, digestion, and reproduction.

3. Organisms in food webs have the opportunity to eat other foods if one food becomes unavailable. However, an organism in a food chain has only one choice of food. If that food is not available, the organism in the food chain dies.

Answer: In ecology, recycling refers to the reuse of important abiotic factors such as water, oxygen, carbon dioxide, and nitrogen.

Answer: Light energy from the sun is never recycled. The flow of energy through an ecosystem is unidirectional.

Answer: Water can enter the atmosphere by evaporation from oceans, lakes, and rivers. Water also enters the atmosphere by transpiration from plants.

1. The sun provides the energy needed for the evaporation of water from oceans, lakes, and rivers. This water condenses to form clouds, and precipitation returns the water to the oceans, lakes, and rivers for collection so that the process can begin again.

2. The two biological processes involved in the oxygen/carbon dioxide cycle are photosyn- thesis and respiration. Photosynthesis is a process that puts oxygen into the atmosphere and removes carbon dioxide. Respiration uses oxygen and puts carbon dioxide into the atmosphere. See Chapter 6 for a comparison of respiration and photosynthesis.

3. The amount of carbon dioxide that is introduced into the atmosphere exceeds the amount of oxygen used during aerobic respiration because additional carbon dioxide is added by decomposers, the burning of fossil fuels and the burning of forests.

4. Four different kinds of bacteria are involved in the nitrogen cycle:❑ Nitrogen-fixing bacteria take free nitrogen from the atmosphere and produce nitrates. ❑ Bacteria of decay are responsible for breaking down dead plants and animals into ammonia. ❑ Denitrifying bacteria convert ammonia into free nitrogen. ❑ Nitrifying bacteria convert ammonia into nitrites.

Answer: Succession is a process by which one biotic community is replaced by another until a climax community of plants and animals develops.

Answer: The current community in an area often changes the physical conditions of its environment so that it is no longer favorable for it to continue living there. When this happens, it is replaced (succeeded) by a community that can survive under the altered conditions. A change in the climate of an area often makes conditions unfavorable for one community and more favorable for another.

Answer: A pioneer organism is the first organism to occupy an area. Lichens are an example of pioneer organisms.

1. Primary succession begins in an area that never had life. Secondary succession occurs in areas where life has previously existed. Secondary succession often follows a catastrophe that destroys an existing community.

2. A climax community is the last community to occupy an area. A climax community is stable and self-perpetuating.

3. A climax community can be destroyed by fires, volcanic eruptions, hurricanes, changes in climate, or human activities.

Answer: A biome is a large geographical area having one kind of climate and a climax community of unique plants and animals.

Answer: Trees cannot grow in the tundra because of permafrost, a condition where the ground is permanently frozen. The root system of trees cannot grow in frozen soil.

Answer: The most stable and least changing biome is the marine biome. Climate has very little effect on this biome. The temperature of the water at any given depth in the ocean varies within narrow limits. The salinity of water remains relatively constant at 3.5%.

1. The abiotic factors of the environment limit the kinds of plants and animals that are in a biome. As a result, each biome has its own unique plant and animal life. The trees of the taiga and the temperate deciduous forest cannot survive in the tundra because of permafrost. Tropical rain forest plants cannot survive in the desert because of insufficient rainfall. Rain forest plants can’t grow in a marine biome.

2. Desert plants have adapted several ingenious methods for survival in a dry climate. Some plants have a thick, waxy cuticle that helps prevent the loss of water. Others have small or needle-like leaves with few stomates. Many desert plants have extensive underground root systems that help absorb any precipitation that might fall. Others have thick stems that are adapted for the storage of water.

3. The tropical rain forests are ecologically important because of their tremendous biodiversity. More than 50% of the earth’s plant and animal life is found in this biome.

Answer: Increased population growth creates added demands for the earth’s limited resources of energy, food, water, and living space. Furthermore, more people results in an increase in pollution and a decrease in biodiversity.

Answer: Nonrenewable resources are resources that cannot be replaced. Examples of nonrenewable resources are fossil fuels. Renewable resources are replaceable. Examples of renewable resources are trees, wildlife, food crops, cattle, fish, and land.

Answer: The major sources of man-made pollution are the burning of fossil fuels, industrial waste, pesticides, insecticides, fertilizer, and biological waste. Volcanic eruptions that emit ash and other particles are an example of a source of natural pollution.

lung cancer. Pollutants in water and soil can cause cancer in humans.

1. Exponential population growth refers to the doubling of the population every few years.

2. Scarce resources can be preserved by decreasing population growth, reducing the use of fossil fuels and through conservation of the environment. In addition, currently available resources can be reused and recycled.

3. Global warming has the potential of causing major disruptions in the world’s ecosystems. An increase in temperature can result in melting glaciers and rising sea levels. Changes in climate might occur that produce droughts in some areas and flooding in others. Additional threats are wildfires, reduced water supplies, reduced biodiversity, and crop failures.

Answer: Conservation is concerned with the protection and maintenance of an ecosystem and its biological communities.

Answer: The most important steps that can be taken to help conserve and protect the environment are reducing the rate of human population growth and striving toward negative population growth. In addition, reducing pollution and the use of fossil fuels, along with protecting open spaces and wildlife, helps to conserve resources.

Answer: Biological pest control is the control of a pest population by nonchemical means (predators, parasites, animal-like protists, bacteria, and diseases) to destroy or control a pest population.

1. Water conservation can be achieved by reducing pollution from agriculture. Runoff from fertilizers, pesticides, and animal wastes are the main causes of water pollution. Control of point source pollution from factories, sewage treatment plants, and home septic tanks can also help preserve the water supply.

2. The soil in rain forests is acidic, low in nutrients, and needs to be heavily fertilized to grow crops. However, fertilizer is expensive and not often used by farmers in land that was once rain forest. As a result, the farmers get a low yield on their crop production. In the mean- time, this valuable resource (along with its diverse plant and animal life) is destroyed.

3. Biological pest controls do not pollute the environment and do not kill helpful insects and birds because they target a specific pest population. Biological controls are harmless to humans. The disadvantage of biological pest controls is that they are expensive and often require repeated applications. In addition, biological controls generally target only one type of pest, unlike chemical controls whose action is more widespread.

4.Some alternative sources of energy are solar energy, wind energy, hydrogen fuel, and nuclear energy.