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Genetic Drift
- Random changes in the allele frequency of a population between generations; genetic drift tends to have more dramatic effects in smaller populations than in larger ones
- decreases genetic diversity
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Founder Effect
- A type of genetic drift in which a small number of individuals leaves one population and establishes a new population
- decreased genetic variation
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Bottleneck Effect
- A type of genetic drift that occurs when a population is suddenly reduced to a small number of individuals and alleles are lost from the population as a result
- decreases genetic variation
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What processes can lead to alternations in a gene pool?
- mutation introducing new alleles into the population
- natural selection favoring some alleles over others
- genetic drift
- influx of alleles from neighboring population (gene flow)
- no random mating of individuals
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Gene Flow
- the movement of alleles from one population to another, which may increase the genetic diversity of a population
- does not lead to adaptation
- increases genetic diversity by introducing alleles from its neighbors
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Inbreeding
- mating between closely related individuals
- does not change the allele frequency within a population
- increases the proportion of homozygous individuals to heterozygotes
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Why is inbreeding typically harmful to a population?
the accumulation of harmful recessive phenotypes can lower fitness (and thus fertality)
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Hardy-Weinberg Equilibrium
- non-evolving
- both allele and genotype frequencies remain constant from one generation to the next
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The Biological Species Concept
The definition of a species as a ppopulation of individuals whose members can interbreed and produce offspring
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Ecological Isolation
different environments
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Temporal Isolation
mating behavior or fertility at different times
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Behavioral Isolation
Different mating activities
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Mechanical Isolation
mating organs are incompatible
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Gametic Isolation
Cametes cannot unite
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Hybrid Inviability
Gametes unite but viable offspring cannot form
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Hybrid Infertility
Viable hybrid offspring cannot reproduce.
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What is the difference between genetic drift and natural selection?
genetic drift is random
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Evolution
Change in allele frequencies in a population over time
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Why is Tiktaalik considered a transitiional species?
splits the difference between something we think of as a fish and something we think of as a limbed animal
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What does a paleontologist study?
ancient life by means of the fossil record
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Why do scientists believe the fossil record supports Darwin's idea?
- not all organisms are preserved but it is extensive enough to show the overall arc of life
- all organisms have decended from a single common ancestor billions of years ago, and the fossil record shows an ordered succession of evolutionary stages as organisms evolved and diversified
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How are rocks and in some cases fossils dated?
by looking at the relative amount of carbon 14 remaing
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Direct dating
Fossils are at least as old as the rocks that incase them. Since some types of rocks can be dated directly by a method known as radiometric dating it is possible to determine the age of fossils embedded within them.
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Relative Dating
- if fossils are found sandwiched in rock layers that cannot be directly dated, they can be dated indirectly by their position with repect to rocks or fossils of known age.
- determining the age of a fossil from its position relative to layers of rock or fossils of known age
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Homology
anatomical, genetic, or developmental similarity among organisms due to common ancestry
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What do scientists believe these structures tell us about hte relationship between organisms that share homologous structures?
that organisms all shared a common ancestor at sometime in the distant past
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What do scientists believe the homologous structures observed during the development of many orgainsms tell us about the relationship between these organisms?
- its strong evidence that all vertebrate animals are related by common ancestry
- genetic changes over time have introduced modifications in later stages that give rise to distinct species with vast physical differences
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Vestigial Structures
a structure inherited from an ancestor that no longer serves a clear function in the organism that possesses it
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What do scientists believe vestigial structures tell us about the orgainism that posses them?
- they are strong evidence for evolution
- these "useless" features are inherited from an ancestor in whom they did serve a function
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What aspect of DNA is believed by scientists to be an indication of the existence of a common ancestor?
Every molecule of DNA is made of the same four nucleotides, and all organisms use the information encoded by those nucleotides to make proteins in the same basic way, using the universal genetic code
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How can DNA be used to determine the relatedness of organisms?
related organisms share DNA sequences inherited from a common ancestor. Over time, the sequence in each species acquires indepenent mutations.
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What are the differences between a prokaryotic and eukaryotic organism?
- dna floats freely in the cytoplasm instead of being housed in a nucleus
- usually unicellular instead of muticellular
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How does the size of a prokaryotic organism differ from the size of a eukaryotic organism?
microscopic, on the order of 1-10 microns which is about 1/10 the thickness of human hair
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Bacteria examples
- Spriochetes
- Gram Positive
- Green filamentous bacteria
- Proteobacteria
- Cyanobacteria
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Archaea examples
- T. celer
- thermoproteus
- methanococcus
- methanobacterium
- halophiles
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Eukarya examples
- slime molds
- animals
- fungi
- plants
- ciliates
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Archaea
- Archaea are similar to bacteria but they are genetically very different from bacteria.
- Archaea are sometimes known as “extremophiles” because they often live in very harsh conditions.
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Bacteria
- Bacteria are prokaryotic cells with a diverse array of lifestyles.
- Most possess a cell wall, but their genetic diversity leads to a wide variety of differences in nutrition, metabolism, structure, and lifestyle.
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Which domains are prokaryotic and which are eukaryotic?
- Archaea and bacteria are prokaryotic
- eukarya is eukaryotic
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Which domain (or domains) contain orgainsms that are found in a tremendous variety of habitats?
bacteria and archaea
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Which domain contains organisms found in extreme environments?
archaea
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Which domain is most likely to cause an infection, say in a cut on a human body?
Bacteria
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How are prokaryotes indentified, particularly if they cannot be grown in a culture?
- biologists rely on DNA to identify prokaryotic organisms
- finding a unique dna sequence in a sample means the researchers have discovered a new organism
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Autotrophic bacteria
are able to make their own food directly, using material from the nonliving environment
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heterotrophic bacteria
must rely on other living organisms to provide them with food
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How do prokaryotic organisms reproduce?
binary fission
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Prokaryotes found in salty environments such as the Dead Sea or Great Salt Lake are referred to as
halophiles
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Prokaryotes found in hot springs are referred to as
thermoproteus
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What types of environments are prokaryotes found?
just about any
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Photosynthetic bacteria would fall into which category?
autotrophic
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What structures do some prokaryotes posses that allow them to be mobile?
flagella
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What structures do some prokaryotes posses that both allow them to attach to substrates as well as other prokaryotes while trading DNA?
pili
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How does the chromosome of a prokaryotic organism differ from that of an eukaryotic organism?
bacteria has one single looped chromosome
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