invertebrates

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Invertebrates

deutrosomes - radial cleavage, endomesoderm forming, all coelemate coelem form from fusion of enterocoelos pouches, **** forms at or near blastopore, mouth new formation, included echinodermata, hemichordata, chardata and brachiopoda. protostomes - spiral cleavage, primative gut mesoderm, endomesoderm usually from a particaular blastomere, embryology mostly determinate (mosaic), mouth from at or near blastophore **** new formation. includes platyhelminths, annelida, molluscs and arthropoda. 

echinodermata - thick, spiney skin, 5 sided symmetry, tube feet, skeleton like structure. coelomate meaning - gut, ectoderm, mesoderm, eipderm, peritoneum.e.g starfish (subcalls asteroidea), sea lillies, class stelleroida, sea urchin (class echinoidea), sea cucumber.

protochordates (still deutrostomes) - 3 groups hemichordates, urochordates and cephalochordates. share vertebrate and non-vertebrate features - notochord,  dorsal nerve chord and gills but lack proper vertebral column.

2 classes in hemichordata - pterobracnhia and enteropneusta - notochord is diff from a chordate notochord which puts them is seperate phylum. pterobranchia - colonial grow inside disguarded mollusc shells, 2 tentacled arm. Enteropneusta - acorn shaped proboscis, fleshy collar, worm like- trunk perforated by many pharyngeal slits which open out into atria called pharynx  e.g acorn worm.

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protochordates

urochordata - the tunicates. ascidiacea (sea squirts), thaliacea and larvacea. larval form shows important chordate features. sea squirt - adults loose notochord and hollow dorsal nerve cord and pharynx with gill slits.. entire body enclosed by a cellulose tunic, filter feed by cilary action. sac shaped body filled with perforated cilia covered pharynx, gut and gonad lie free in atrium. ciona - most chordate features lost as pharynx develops into enormous filter feeding mechanism at adult stage.

thaliacea - salpa, has opaque bands of muscle and internal organs, muscle pump water through body. larvacea - e.g of neotony where juvenille becomes sexually mature, larva becomes mature without losing tail or notochord.

cephalochordates - one genus branchiostoma small and have all chordate features including postanal tail and thyroid gland.

summary - hemichordates posses some chordate features. Urochordates and cephalochordates posses all of them, even if not present in all life stages.

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flatworms: platyhelminths

deutrostomes - starfish, ciona, salpa, oikopleura. starfish phylum: echinodermata class: asteroidea - 5 pointed radial symmetry, complex series of fluid filled canals derived from pair of coelomic compartments. sea anemone - phylum: cnidaria (hydra, jellyfish and coral) class: anthozoa. Sea urchin phylum: echinodermata class: echinoidea, 5 fold radial symmetry and tube feet. 

acoelomate body plan - gut endoderm mesoderm and ectoderm. have circular muscle layer, longitudinal muscle layer and parenchyma and dorsoventral muscles. bilateral symmetry, cephalization and single openning to gut with pharynx. 4 classes - cestoda, monogena, trematoda and turbellaria. flat so allow diffusion, move using cillia, mucus and muscles. hermaphrodites - both sex organs.

cestoda - tape worm thick and leathery so wont be digested. parasitic lives in digestive tract, lays lots of eggs needs lots of mitochondria, not segments but 3 parts scolex, neck and strobilla, scolex has pincers to attach to intestine. 

trematoda - liverfluke has hooks and suckers, parasitic feed on blood, usually on molluscs, parasitic life cycle - eggs in feces, sporocycst in snail, leaves snail as carcaria into fish, raw fish eaten by final host. 

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platyhelminths

parasitic flatworms have free swimming larvae to find next host, some have resting stage and reactiviated by some stimulus, some are chemically attracted, some mimic prey of next host.

monogena parasite with very sharp teeth like hooks. 

phylum nemertea, ribon worm - rhynchocoel, muscle, circulatory system, through gut, move w/ muscle and cilia, cuticle, very muscular. flat and acoelomate. 

rotifera - projections called toes on foot, ciliar to draw in foot, longitudinal muscles working against number of transverse rings, no males - genetic exchange.

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round worms: nematoda

superphylum: ecdysozoa (arthropods and nematodes). pseudocoelomates lumen, pseudocoel and cuticle. through gut, no circular muscles, ventral nerve chord, dorsal nerve cord, longitudinal muscles arragnement (thrashes around), lack cilia, triradiate pharynx, 4 areas of muscle antagonisitic, tubular digestive systems openings at both ends, bilaterally symmetrical body, radial symmetry head. molts culticle, gas exchange across body, pseudocoel fluid contains haemoglobin, usually parasitic. 

hook worms - parasitic latch onto invertebrate intestines. ascaroid nematodes - gut parasite of many vertebrates. nematomophora - 3 part piercing stilletos, poisen glands, spines. vinegar worms - thrash around as no circular muscles. loricifera - swimming appendages in larva, neck, stylets, introvert, sensory hair cells.

lophophorates - animals that have a lophophore or tuft. a ring of ciliated tentacles used for filter feeding all protostomes. 4 groups - brachiopoda, byrozoa, phoronida and entoprocta. within protostomia group which includes lophophorate e.g molluscs and annelids, ecdysozoa e.g arthropods and nematodes and platyzoa e.g plathyhelmnths and rotifers. 

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segmented worms: annelida

protostomes, bilaterally symmetrical, coelomate, longitudinal and circular muscles, parapodia for locomotion, segmented so muscles act on each segment, reptition of internal organs, brain and sense organs, septa between segments, collagen as cuticle, coellom body cavity, chaetea hairs, mucus secreting glands, member of lophotrochozoa. 

polychaeta - ragworm - pincers, epidermis, cuticle, circular muscles, mesoderm tissue, through gut, parapodia use to walk and swim needed for gass exchange as lots of capilleries, dorsal and ventral blood vessels, tentacles, eyes, pharynx. have trochophore larvae - have sensory tuft of cilia, mouth, ****, pygidium.

oligochaeta - earthworm , clitellum segment, peristomium and prostomium, very muscular, setae bristlles on underside, chaetea hairs, circular, longitudinal and gut muscles, all hemaphrodites, through gut. crop, gizzard, intestine. contractile vessels around gut. 

hirudinea - leech. posterior and anterior suckers, 34 segments, no chaetae, bilaterally symmetrical, muscles act against sinuses. 

echiura - adults arent segmented larvae are, hueg probosis (tail), brain in tail, trocophore larvae with cilary bands and apical tuft of sensory cilia. 

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tardigrada and onychophora

tardigrada - water bear. superphylum: ecdysozoa. bilaterally symmetric, 4 pairs of clawed appendages not jointed. arthropod-like striated muscles, no specialised respiratory oragans, like arthropods they lack cilia. paired ventral nerve cord like arthropods, claws (totpods), chitinous cuticle. 

onychophora - velvet worms superphylum: ecdysozoa. thin waxy cuticles, nocternal carnivores, shoot proteinaceous glue at prey from slime glands. annelid charactoristics - single feeding appendages, hydrostatic skeleton, longitudinal and circular muscles for movement, segmented. arthropod like - jaw musculature is striated, chitin cuticle, main body cavity is heeamocoel not true coelom, gas exchange through spiriciles, mouth appendages mandible like. however has unjointed walking legs and pair of antennae jaws and oral papillae. 

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molluscs

superphylum: lophotrochozea. cephalopod : squid, cuttlefish and octopus, Gastropod - snails and slugs. foot, mantle and radulla. mantle for breathing, excretion and where shell is secreted. Foot for movement (slime glands) and radulla - tongue covered in silicon teeth in oesophagus. Long gut as herbivors, gill in mantle.

trochophre larvae like annelids. - apical tuft, prototroch, metatroch and blastophore. annelida, echiura, molluscs and arthropods all evolved from/have throcophore larva.

aplacophora - ventral nerve cord, dorsal blood vessel, gonad, cuticle, big radulla no foot. monoplacophoran - radulla behind mouth, big foot for movement. chitons - class polyplacophora - 8 plates, ancient, no eyes, shell plates. 

gastropods with shells. snail - huge foot, gills in mantle, tenticles, all organs twisted 180 so shell is at back, pneumostome. gastropods without shells e.g slugs due to mutation in larvae. 

seabutterfly uses foot as wings to fly. prosobranchs - oldest gastropod with shell. bivalves - freshwater mussels, radulla not necessary, draw in water and excrete through siphon, large foot for movement, gills. scaphopoda - captacula tentacles for searching, long tubes of thin shells stick in mud to get worms. 

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molluscs: cephalopoda

nautilus - shell on inside, usually one arm is different and used for reproduction. nautilus has external shell for bouyancy can be controlle dby pumping water in and out. radula, mantle and tentacles

squid - loligo - squirts out ink, mantle and mantle artery, radula next to ****, tentacles, feet, siphon, gonad and cecum, internal shell.

cuttlefish - order: sepida. change colour, chunky body, internal cuttlebone for buoyancy, radulla, shorter arms, 8 arms 2 tentacles. suckers. 

octopus - small beak, tiny shell inside, bilateral symmetry, suckers, no skeleton so can fit in tiny places, 4 pairs of arms. 

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arthropods

appendages enclosed in cuticle, range of muscles, head appendages specialise in sensory operations and feeding, thorax/abdomen appendages specialise in locomotion, reproduction etc. one branch - uniramus, 2 branches - biramus. segmentation like annelids. body cavity bundled in hemocoel, circulatory system, heart, sinuses, some have gills and lungs, insects have trachea with spiracles tracheoles and trachea, exoskeleton! cuticle secretated by epidermis. 

internal fertilization - spermatophores e.g crickets, velvet worm, scorpion can use penis to guide female to spermatophore. indirect development egg - larva- pupa (metamorphosis) - adult. e.g caterpillar - grub - maggot.

3 diff subphyla - trilobitomorpha, chelicerata and mandibulata. trilobitomorpha - all extinct. 

chelicercata - no antena, no appendages on 1st segment 2nd has claws. class: merostomata. extinct. horshoe crabs look like crustaceans, 8 legs. class : arachnida has spiders, mites and scorpians. spider - prosoma and opisthosoma 8 legs, 4 pairs of eyes, book lung and spinnerete. pycnogonida - sea spiders, dominated by thorax. 

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arthropods

mandibuata - uniramous and biramous appendages  and mandables (jaws) . insects millipedes and crustacians. class myriapoda - millipedes and centapeds, 1 pair of legs per segment, single pair of antenae, simple eyes, pairs of madibles inside mouth, spiracles attached to tracheoles.

insecta - success due to small size, wings and metamorphosis. All have head, thorax and abdomen with 3 pairs of walking legs on thorax. organs for hearing, huge range of mouth parts, tracheal system, cross striated muscles. class apterogota e.g silver fish no wings, thin tanslucent no metamophosis, spermatophores.

pterygota - 2 pairs of wings and waxy cuticle. suborders: exopterygota - cockroaches, earwigs, grasshoppers and lice. Endopterygota - ants, bees, beetles, fleas and butterflys. lepidoptera - butterflys and moths, scales cover body and wings, undergo complete metamorphosis. Odonata - dragonflies, teeth on madibles, 2 pairs transparent wings. Coleoptera - beetles and ladybirds 'sheathed' wings under elythea. orthoptera - grasshopers, crickets and locusts - can fold wings, hind legs for jumping. diptera - fly/maggots cruicial for soil waste. hymenoptera - bees, ants and wasps, hindwings connected to form wings, ovipositor often modified stinger. 

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arthropods : crustacea

crustacea - 2 pairs of antennae, a pair of mandibles ad 2 pairs of maxillae. subclasses: cirrepeda - barncales 6 plates, suspension feeders. naupilus - cyprid - adult. copepoda - plankton, most numberous. branchiopoda - daphnia water fleas, and shrimp, gills on all parts. Branchiura - fish lice.

malacostraca - class with over 20,000 species including krill. isopoda - woodlice 7 pairs of legs. amphipoda - no carapace look like prawns. decopoda - hard skeleton, crabs, lobster, prawns and shrimp. 10 legs, front 3 pairs act as mouthparts, remainder peripods, one pair enlarged pincers. 

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cnidaria

screte cnidae (nematocysts). planula larvae in the life cycle. sea anemones, hydra, jelly fish, coral. bodies consist of mesoglia sandwhiched between 2 layers of epithelium one cell thick. tentacles that bear cnidocytes. 

class scyphozoa - jelly fish. four or eight oral arms form mouth. radial symmetry. ring of muscle fibres around ring of dome. 98% water. mouth opens in cenral stomach. medusa body form, 2 layers living tissue/epidermis + gastrodermis, mesogleu gelatinour layer.

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