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"Parazoa" : Phylum Porifera
- sponges; only extant parazoa group
- Classes:
- Calcarea (calcium carbonate spicules)
- Silicea (glass spicules)
- Demospongia (glass spicules and/or spongin fibers)
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Phylum Cnidaria
- Classes:
- Hydrozoa (Hydra)
- Scyphozoa (true jellies; Aurelia)
- Anthozoa (anemenies/corals; Metridium)
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Phylum Platyhelminthes
- flatworms
- Classes:
- Turbellaria (planaria)
- Trematoda (flukes)
- Cestoda (tapeworms)
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Phylum Nematoda
roundworms
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Kingdom Animalia derived characteristics
- multicellular
- descended from a hypothetical flagellated protist ancestor
- artificial taxons include parazoa and eumetazoa
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eumetazoa
- all other animal phyla besides porifera
- differentiated cells
- true tissues derived from germ layers
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diploblastic
- 2 germ layers - endoderm and ectoderm
- cnidarians
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ectoderm
- outermost primary germ layer in animal embryos
- gives rise to outer covering, skin, and its accessory organs; nervous system
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endoderm
- innermost primary germ layer
- gives rise to digestive tract lining and its accessory organs; lungs
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mesoderm
- germ layer between ectoderm and endoderm
- mesodermally-derived cells include the coelom lining and organs
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triploblastic
consists of 3 germ layers - ectoderm, mesoderm, endoderm
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radial symmetry
- cnidarians, echinoderms
- divided by many planes through the central axis of its body
- top (oral side with mouth) and bottom (aboral side)
- no distinct head
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bilateral symmetry
- divided into mirror halves through one longitudinal plane (medial)
- right and left sides (lateral)
- distinct head (anterior) and tail (posterior)
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cephalization
an evolutionary trend towards concentrating sensory and nervous system at the anterior end of the organism
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no possession of a coelom
- lack mesoderm
- includes porifera and diploblastic animals (cnidarians)
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coelom
- body cavity
- usually deveoped from mesoderm layers
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acoelomates
- do not possess a coelom
- possess mesoderm
- platyhelminthes
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pseudocoelomates
- possess an internal fluid-filled cavity, but the cavity is incompletely lines with mesoderm-derived tissue
- nematoda
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coelomates
- include most animal phyla
- coelom forms during embryonic development
- fluid-filled cavity completely lined with mesodermally-derived cells
- organs are suspended by double layers (mesenteries)
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a coelom is important because it provides:
- room for organs to grow and develop
- an increased surface area for gas exchange and nutrient transport into/out of organs
- a hydrostatic skeleton for support and movement
- a place to store materials
- a route to pass wastes and gametes to the outside
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internal skeleton (sponges)
- composed of spicules
- Calcarea (calcareous spicules)
- Silicea (glass spicules)
- Demospongiae (protinaceous spicules, spongin)
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body specialization (sponges)
- no cephalization
- no segmentation
- every cell exchanges gases and eliminates wastes through diffusion
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adaptations for a sessile lifestyle (sponges)
no distinct nervous, muscular, or endocrine systems
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cellular level of organization (sponges)
- no tissues, organs, organ systems
- no obvious body symmetry
- somatic regeneration - isolated cells can aggregate and form a new sponge
- totipotent - each cell can potentially give rise to any other cell type
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digestive system (sponges)
- none; no germ layers, digestive tract, or coelom
- pores and canals lead to the central spongocoel, through which water moves
- digestion occurs in the choanocytes and amebocytes
- intracellular digestion
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choanocytes (sponges)
- flagellated cells that are involved in many activities
- important in intracellular digestion
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amebocytes (sponges)
- amoeboid cells involved in intracellular digestion (receive food vacuoles from choanoctyes) and food transport
- involved in spicule production, reproduction, contraction
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ostia and water flow (sponges)
- small; lead to small incurrent canals
- -- in the spongocoel
- -- water exits through a large, single osculum (outcurrent pore)
- water currents formed by teh beating of choanocyte flagella lining the radial canals
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pinacocytes (sponges)
think, plate-like cells lining the outside of the sponge, the spongocoel, and canals
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mesohyl (sponges)
- thin, gel-like matrix
- amebocytes scattered here throughout
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reproduction (sponges)
- cell clusters are sponge larvae, called amphiblastulas (formed by the zygote undergoing mitosis)
- eggs retained in the mesohyl, sperm captured by choanocytes; fertilization considered internal
- amphiblastulas break through the spongocoel and exit out the osculum
- reproduce asexually by fragmenting and budding
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body plan (cnidarians)
- diploblastic
- acoelomate
- mesoglea - an acellular gelatinous layer between the two dermal layers
- radial symmetry
- unsegmented
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body forms (cnidarians)
- sessile polyp - hydrozoans and anthozoans
- free-swimming medusa - scyphozoa
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integumentary systems (cnidarians)
- no specialized integument
- some colonial species have a protective outer covering composed of proteins, polysaccharides, and chitin (collectively called the perisarc) that surrounded all of the polyps
- epidermis contains cnidocytes
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cnidocytes
- stinging cells
- possess a spiked, harpoon-like organelle (nematocyst) that can be discharged
- pierce, entangle, paralyze prey; self-defense
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digestive systems (cnidarians)
- occurs extracellularly in the gastrovascular cavity
- fluids move through due to body wall contractions and ciliated actions in the gastrodermis
- mostly carnivorous diet
- some have symbiotic algae living inside of them (eg, coral)
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respiratory/circulatory systems (cnidarians)
- no specialized circulatory, respiratory systems
- simple diffusion of gases across body wall
- ciliary action can move contents in the gastrovascular cavity
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osmoregulatory/excretory systems (cnidarians)
no specialized systems
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nervous systems (cnidarians)
- simple nerve net
- no brain/cephalization
- bidirectional synapses - nerve potentials can go both ways across a synapse (unique)
- neurosensory cells that can respond to light, touch, balance
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reproductive systems (cnidarians)
- reproduce asexually by budding
- sexually; either medusa or polyps produce both the eggs and sperm
- external fertilization
- generally dioecious
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skeletal systems (cnidarians)
- no major support structures
- coral species form an exoskeleton made of calcium carbonate
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muscular systems (cnidarians)
cells found in both the epidermis (epitheliomuscular cells) and in the gastrodermis (nutritive-muscular cells) are capable of contraction
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Aurelia life cycle (cnidarian)
- ciliated larval stage (the planula) settles on the bottom, forming a polyp (the scyphistoma)
- the scyphistoma eventually becomes the strobila
- the strobila forms many medusae asexually, by budding
- the ephyra is a young medusa that matures into a dioecious adult
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Obelia life cycle (colonial hydrozoan cnidarian)
- is a thecate - the polyp is mostly coverd in a sheath
- entire colony encased in a transparent protective tube (perisarc)
- colonies grow by asexually budding polyps
- form multiple medusae by budding; medusae grow into dioecious, sexually mature adults, which externally fertilize a zygote; grows into planula larva, which settles and develops into a polyp; young polyp grows by reproducing asexually through budding
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gastrozooids (polyp type in sessile hydrozoan colonies)
feeding polyp with tentacles
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gonozooids (polyp type in sessile hydrozoan colonies)
- reproductive polyps
- -- see "Obelia life cycle"
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hydrorhiza (hydrozoan colony)
- a stolon attached to the substrate
- gives rise to stalks, called hydrocauli
- the living part of the hydrocauli is called the coenosarc, which surrounds a common gastrovascular cavity
- individual polyps (zooids) are attached to the hydrocaulus
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anthozoans (cnidarians)
- all are marine
- only have polyp stage
- includes corals
- secrete a protective outer skeleton of calcium carbonate
- make up the larges class of cnidarians
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body plan (platyhelminthes)
- dorsoventrally flattened body
- triploblastic
- acoelomate
- unsegmented (tapeworms produce structures called protoglottids, which make them appear segmented)
- bilateral symmetry
- organ system level of organization - distinct tissues and organs including epithelial, muscular, and nervous tissues
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osmoregulatory/excretory systems (platyhelminthes)
- protonephridium - closed tubular systems that open to the outside along the length of the body at various points called nephridiopores
- nitrogenous wastes (ammonia) diffuse out of each cell into the environment
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respiratory/circulatory systems (platyhelminthes)
- no specialized systems
- parasitic flatworms typically use anaerobic respiration
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digestive systems (platyhelminthes)
- incomplete digestive tract consisting of a gastrovascular cavity
- initially extracellular digestion, followed by intracellular digestion inside cells lining the gastrovascular cavity
- in some parasitic species, the digestive tract is much reduced or absent; obtains its food in predigested form (by the host)
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nervous systems (platyhelminthes)
- cephalization
- cerebral ganglia in the anterior end and several pairs of lateral nerve cords running along the length of the body
- nerve cells are unidirectional
- parasitic flatworms often exhibit reduced cephalization and lack sensory organs
- distinct sensory neurons and motor neurons
- receptor organs that respond to light, tough, chemicals, gravity, and currents
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diet and living situation (platyhelminthes)
- free-living carnivores
- parasites within the digestive, respiratory, circulatory systems
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reproductive systems (platyhelminthes)
- typically monoecious
- cross-fertilize (exchange sperm with another organism)
- parasitic tapeworms may self-fertilize
- internal fertilization
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integumentary systems (platyhelminthes)
- distinct integument that protects their body from the host's digestive enzymes
- move by muscular action and by ciliary action - mucus serves as a lubricating slime as the animal moves
- can regenerate lost body parts; cells are not totipotent
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muscular systems (platyhelminthes)
- ciliary motion
- circular and longitudinal muscles are present in the body wall
- thrash about
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Clonorchis life cycle (platyhelminthes fluke: Class Trematoda)
- larval stages (miracidia) that hatch from eggs
- infect intermediate hosts (aquatic snails); a single miracidium forms a single mother sporocyst within the snail hemocoel; asexually forms daughter parasites; germ cells within the sporocyst may develop into redia, larvae with mouths and gastrovascular cavities; within redia, germ balls develop into cercariae, another distinct larval stage
- cercaridae burrow through the snail's body wall; with a muscular tail, they infect a second intermediate host (fish) where the larva encyst as metacercariae
- a human eats the fish (plus encysted metacercariae); inside the human's digestive tract, the adult flukes leave the metacercariae cysts; mature and produce eggs; eggs are passed through the feces and into water again, where miracidia hatch from them
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Schistosoma life cycle (platyhelminthes fluke: Class Trematoda)
- adults live in veins; eggs leave through feces and into water
- miracidium excysts from an egg; burrows into an intermediate host (snail) and becomes a mother sporocyst, which asexually produces daughter sporocysts which mature in the snail's digestive tract
- each daughter sporocyst produces many cercariae, which burrow out of the snail and into the exposed skin of a human host; then loses its tail and becomes a young schistosomule, traveling through the circulatory system and maturing into adults
- no metacercaria stages
- males have split bodies with females inside (called the gynocophoral canal)
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Taenia life cycle (platyhelminthes tapeworm: Class Cestoda)
- generally lack a digestive system, developed the ability to absorb nutrients across their body wall (from the contents of their host); sensory systems are much reduced or absent
- the scolex (head) often contains suckers/hooks that allow the tapeworm to attach to the intestinal wall
- remainder of the body consists of segments called protoglottids, each of which contains both testes and ovaries (produced asexually by budding); eggs (within protoglottids or relased from) exis with the host's feces; picked up by an intermediate host, where they eggs hatch into larvae and encyst in muscles
- the human (final/definitive host) eats the intermediate host
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body plan (nematodes)
- roundish, cylindrical
- unsegmented
- tapered ends
- pseudocoelom
- triploblastic
- bilaterally symmetrical
- cephalization
- exhibit eutely - each individual consists of exactly the same number of cells (unique)
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muscular systems (nematodes)
- only longitudinal muscles in the body wall (no circular or diagonal muscles)
- no muscles surround the roundworm's digestive tract
- pressure is exerted on the contents of the gut by hydrostatic pressure
- muscles send processes to the nerves for innervation, not vice versa (unique)
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digestive systems (nemetodes)
- complete digestive tract
- unidirectional
- pharynx present
- extracellular digestion within the gut, followed by intracellular digestion
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integumentary systems (nematodes)
- cuticle (containing chitin) produced by the epidermis
- typically have four molts and four larval stages
- the cuticle maintains turgor pressure, prevents the worm from drying out quickly, provides mechanical protection, and is resistant to digestion by the host's digestive tract (for parasites)
- cuticle is similar to cuticle of arthropods
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diet and living situation (nematodes)
- free-living carnivores
- free-living detrivores (feed on dead plant and animal tissue)
- parasites
- sound in marine, freshwater systems, moise soils, and in the tissues and fluids of nearly all plants and animals
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respiratory/circulatory systems (nematodes)
- no specialized systems
- gases diffuse across body wall
- parasitic forms may use anaerobic respiration
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osmoregulatory/excretory systems (nematodes)
- series of excretory canals
- no flame bulbs
- renette cells - special excretory cells that absorb nitrogenous wastes, which can be passed through a pore outside
- eliminate ammonia via the gut (similar to arthropods)
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reproductive systems (nematodes)
- dioecious
- internal fertilization
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skeletal systems (nematodes)
use a hydrostatic skeleton (from the pseudocoelom) and the cuticle to provide structure
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nervous systems (nematodes)
- simple
- cephalization
- nerve cords run posteriorly
- several sense organs for touch; a few can detect light
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Ascaris life cycle (nematodes)
- intestinal
- eggs deposited in the host's feces; development occurs inside the egg, two larval molts occur inside the egg; after ingestion, they hatch or cyst in the host's intestines, then find their way to the lungs; work its way to being swallowed again, back down to the small intestine
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