vertebrates

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vertebrates

vertbrates - notochord (flexible rod that extends through length of body), hollow nerve chord along the dorsal side which develops into brain and spinal chord, pharyngeal slits -  gills evolved into hinged jaw, post anal tail and bilateral symmetry

fish - kingdom: Animalia, Phylum: Chordata sub-phylum: Vertebrata. 

jawless fish: cartilaginous skeleton, no paired fins, most primative. Super class Agnatha e.g hagfish - tentacle and mucous glands very slimey, has skull but no vertebral column, and lampreys - parasite with suckers and good eyes. Ostracoderms earlies known fossil vertebrate. 

jawed fish: super class Gnathostomata, paired fins and jaws which developed from gill arches. Placoderms earliest jawed vertebrates. cartilaginous fish (class chondrichthyes) elasmobranches - sharks, rays and skates. Holocephalans - chimaeras. have hinged jaw, exposed gill slits, skin covered in placoid scales, poisition of claspers.

Bony fish (class osteichthyes) ray finned fish - teleosts, sturgeon, gars, bowfin. Lobe finned fish = ancestors of tetrapods, lungfish and coelacanths. smooth skin, cartilage skeleton, lack replaceable teeth, have claspers like sharks and rays.

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fish

sharks vs rays and skates. sharks - fusiform body, gills on side of head, eyes at side of head, swim with thrusts of tail, heterocercal tail provides lift, often highly specialized predators have good vision, smell, vibration and electromagnetic senses, replaceable rows of teeth made from modified placoid scales, lateral line system sense vibration, ampullae of lorenzini sense bioelectric fields, small spiracles behind eyes.

Rays and skates - dorso-ventrally flatterened, gills underneath, eyes at top of head, wing like pectoral fins, tail sometimes modified as sting, bottom feeders, large spiracles on top of head used for respiration. both have large liver containing oil called squalene to keep buoyant and streamlined body - placoid scales and heterocercal tail. 

Osteichthyes: bony fish. Lobe finned or ray finned. both - lateral line, skin covered in scales, swim bladder, paired fins, operculum covering gills, hinged jaw. ray finned - 95% of fish. fins are webs of skin supported by bony spines. 3 types - chondrosteans e.g sturgeon, Holosteans e.g bowfin and gar and Teleosts - most species. teleosts - buoyancy - swim bladder is gas filled sack, ancestral lung adapted for buoyancy, volume can be altered to change buoyancy. air in - gas gland air enters swim bladder, rete mirable, network of parrallel blood vessel concentrates o2. Air out - gas diffuses into blood through ovale.

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fish 2

lobe finned - sarcopterygians. Coelacanths and lungfish. bony skeleton, fleshy lobed paired fins, and use swim bladder for respiration. rhipidistians - extinct group had lungs as well as gills, ancestors of first tetrapods : amphibians.

differences between chondrichythes and osteichythyes. Chondrichythes - cartilage, placoid scales, dorso-ventral flattening or fusiform, lift from heterocercal tail and squalene in liver, usually internal fertilization and males have claspers, several uncovered gill slits. 

Osteichythyes - bone skeleton, bony scales, lateral flattening, swim-bladder, usually external fertilization, operculum.

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amphibians

mudskippers, lungfish, blennies - amphibious teleosts can move about on land and breath air. co-opted existing structures for resp and movement. requirements for living on land - breathing air - lung and swim bladder both air filled cavity just with different purposes, gas exchnage requires moist enviroments, air is dry so lungs are folded inside body and open to the outside by narrow passages to reduce water loss. Support and locomotion - limbs and skeleton must support weight, lobe finned fish had an evolutionary advantage due to movement capability of boney elements of paired fins. Mechanism of regulating water loss. Reproduction and temp regulation. 

tetrapod - four footed, four limbs in 2 pairs. some have no visible limbs but evolved from limbed ancestor. 2 major branches amniotes (mammals, reptiles and birds) and amphibians (caecillians, salamanders and newts, forgs and toads). 

evolution of amphibians - 300mya abundance of insects, less predators, warm humid, swampy enviro. caecilians - snake like. salamanders and newts (order: caudata) with tail. Frogs and toads (order: anura) no tail. charactorisitcs: ectothermic, dependant on moist enviro, senses shift from lateral line to smell and hearing, strengthened body skeleton, reduced skull bone, anurans unique pelvis for leaping, moist permeable glandular skin no scales for resp, hydration, absorb water and salts, mucus glands helps prevent desiccation

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amphibians

charactoristics contd. - defense, camouflage and protection, some have poison glands. 3 chambered heart, aquatic reproduction and metamorphis. 

typical life cycle - aquatic eggs and larvae - no legs, gills, lateral line, long finned tail like fish then undergo metamorphosis. formation of 4 legs, lose gills, skin develops glands, eyes develop eyelids, eardrum developed, in anurans tail disappears. 

caecilians, order: gymnophiona : elongate, many vertebrae, long ribs, poor eyes, no legs, terminal ****, small calcite scales, males have protrusible penis. mostly burrowing living underground, internal fertilizers. 75% vivaparus young, 25% oviparous. 

salamanders and newts: order caudata: long slender body, four limbs, long tail, back feet has 5 toes, carnivorous, can regenerate, front feet 4 toes, eyes reduced. respiration - have gills, lungs or both, gills usually external, some have simple sac-like lungs, some lack both and exchange o2 and co2 through skin and mouth lining - valarian resp. neoteny - males release spermatophore which is picked up by female to fertlise eggs, some larvae metamophose into adults while some become sexually mature and remain in larval form (neotones). 

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amphibians 2

frogs and toads, order: Anura: specialised for leaping, moist skin, no tail, strong hind legs, webbed feet, pair of external eardrums called typanum. most are herbivorous, striking metamorphosis, never permanent larval stage as in salamaders, need nearby water source for reproduction. Frogs have smooth skin and adapted to jump, toads more terrestrial, dry warty skin and walk. defense - leaping, camoflagyem inflation, teeth, colour/behaviour, poison gland e.g poison dart frogs. 

respiration- external fertlilisation, breif courtship males grip females in amplexus and release sperm over eggs, midwife toad, darwins frog, often no parental care, high egg mortality. tailed frog - internal fert use tail to insert sperm into female, eggs depositited under rocks and tadpoles have mouths to latch onto rocks. parental care - darwin frog, males carry tadpoles in mouth, marsupial frog - carry young in pouches on mothers back, surinam toad - eggs and tadpoles incubate under mothers skin, strawberry poison dart frog - rear young in small pools of water, tree frogs - build a foam nest in trees. 

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reptiles

furless amniotes. first truly terrestrial vertebrates. 3 key adaptations - amniotic egg, internal fert and water tight skin. amniotic egg - broke ties to aquatic reproduction, most important for terrestrial evolution. waterproof egg with shell, amnion surrounds a fluid filled cavity that protects embryo from dying out. Other membranes function in gas exchange, waste removal and supplying nutrients. 

intenral fert - occurs through cloaca, copulatory organs inside body. snakes and lizards - pair of hemipenes. turtles and crocodilians have single penis. Tuatara lack copulatory organs and press cloacas together. most are oviparous (lay eggs), young harch as lung breathers not aquatic larvae. Some squamates are viviparous, or ovoviviparous. temperature dependant sex determination. water tight skin - enriched with keratin. also dermal and epidermal scales. chromatophores- dermal colour bearing cells.

better body support - paired limbs with 5 toes, adapted for running swimming jumping etc. gecko feet have elastic hairs called setae. 3 chambered heart with partially divided ventricles, cros have 4. better lungs no cutaneous resp, **** in air by expanding rib cage. also have jaws better adapted for biting/tearing, larger longer jaw muscle, teeth set in bony sockets. water conservation - nitrogenous waste secreted as dry paste -uric acid. salts removed by salt gland. more complex brain and nervous system, still ectothermic.

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reptiles 2

amniotes 3 groups - anapsides (solid skull) all extinct. Synapsids have one hole in skull mammal like reptiles, gave rise to mammals. Diapsids: pair of holes behind each eye = gave rise to all other reptilian groups and birds. diapsid reptiles split into lepidosaurs which gave rise to snakes lizards and tuatras. and Archosaurs - dinosaurs, crocs and birds. 

subclass diapdisa. order squamata: lizards, snakes and worm lizards. Order Sphenodonta: tuataras. Order crocodillia: crocs and aligators. Order testudines: turtles. 

testudines: turtles, tortoises and terrapins. enclosed in keratin scale shells. dorsal carapace and ventral plastron. shell fused to thoasic vertebrae and ribs. cant expand ribs for resp so uses muscles. lack teeth have horned plate, slow metabolism, slow maturity, oviparous with internal fert and no parental care.

spendodontia: tuatara. most unspecialised. only in new zealand. lives in burrows parietal third eye part of pineal gland thought to be involved in circadian rythms and thermoreg, slow growing.

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reptiles 3

squamata: snakes and lizards. modified kinetic skull, quadrate bones allow wide gape, dry scaly skin shed, only vertebrates with hemipenes. lizards - most 4 limbs short body and tail. movable eye lids. chameleons - zygodactylous feet, stereoscopic eyes, highly midified tongue (bone, muscle and sinew), no ears, prehensile tail, head ornamentation and colour change. snakes - entirely limbless, numerous vertebrae, highly kinetic skull, chemical sense - jacobson's organ and forked tongue. smell to track prey, vibration sensitive, infrared sensitive receptors between nostril and eyes.

order: crocodilia. clawed/webbed toes, flat head, elonfate reinforced skull, wide gap massive jaw, cloesest to dinos, oviparous TCSD - low temp = females. high temp = males.

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birds class: aves

first fossil bird - archaeopteryx. Had teeth and bony tail like dinos but feathers like bird.evolved from theropods - bipedal dinos with long neck e.g t-rex. both have 3-toed foot, furcula, air filled bones and feathers. birds - feathers!, lay eggs, hind limbs for walking, forelimbs modified to wings, keratinized beak. diff to reptiles - endothermic, 4 chambered heart, nearly hollow bones, forelimbs form wings, feathers. similarities - feathers are modified scales and have scales on legs and feet, also produce uric acid and have cloaca.

feathers - modified scales made of keratin, contour - cover and stremline, rachis covered in barbs branched to form barbules that have hooks. Down feathers - lie under, no interlocking barbules, provide insulation.

adaption for flight - no bone marrow, hollow bones with criss-crossing struts (pneumatized). No large jaw or teeth, most vertebrae fused for ridged frame, sternum with large keel to anchor flight muscles. endothermic and insulated with feathers and fat, wings for lift and propulsion, lots of energy and o2 from efficient resp and digestion, weight reduction.

resp - lungs no alveoli, tube like parabronchi - continuous airflow. air sacs, interconnected, connected to lungs, extend into bones. 2 resp cycles for breath to pass through system. digestion - no teeth, gizzards, thick muscular walls used to grind food. 

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birds 2

lack internal organs, no urinary bladder females only one ovary, wings concave, lift generated by flow of air over wings. flightless birds - smaller wing bones, absent of reduced keel, more feathers, usually large. 

class aves: paleognathae (ancient jaw) mostly flightless, large flat sternum with poor pectoral muscles, induces flying tinamous. Neognathae (new jaw) - flying. migration - increase amount of space for breeding reduces comp. food availability. stimulus - reproductive cyles, lengthneing of day stimulates fat accumulation and development of gonads and pituitary gland in brain releases gonatotropichormones. navigation - use landmarks, experience of older birds, internal nav system, earths magnetic field, sun and stars, combination of enviro and innate cues, natural selection.

beak and feeding specialisations - fishing, nector feeder, filter feeder, surface prober, carnivore, insectivore etc. toucan bill - biggest beak-body ratio. laced with blood vessels used for thermoregulation.

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mammals

synapsids. characterisitics of mammals - hair, produce milk, warm blooded, placenta, advanced nervous system, strong jaw and teeth, diaphragm. skin - dermis and epidermis, hair horns, hooves, glands. hair - key feature. grows from hair follicle sunk into dermis, can be shedd, made of keratin. 2 kinds soft under hair for insulation and course long guard hair for protection and colouration. snowshoe hare had 2 annual molts to camoflauge. hairs can be modified e.g bristles, spines, whiskers or vibrassae sensory hairs. order: pholidota. only mammal with scales - overlapping made of fused hairs, insectivores with no teeth and long tongue. 

horns - true horns made of bone not shed. antlers made of bone shed each year. rhino horn hair filaments cemented together not attached to skull. tusks evolved from teeth usually enlarged canines but incisors for elephants. glands - sweat, scent, sebaceous (oil) and mammary. teeth - heterodont: different forms for diff functions. incisors - snipping or biting. canines - for piercing. premolars - shearing and slicing. molars - crushing and grinding. 

insectivores - small mammals feed on small invertebrates have sharp pointed teeth. herbivores - 2 groups browsers and grazer e.g cows (ungulates) and gnawers e.g rabbits and rodents. most have absent of reduced canines. rodents have continuously growing incisors. 

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mammals

synapsids. characterisitics of mammals - hair, produce milk, warm blooded, placenta, advanced nervous system, strong jaw and teeth, diaphragm. skin - dermis and epidermis, hair horns, hooves, glands. hair - key feature. grows from hair follicle sunk into dermis, can be shedd, made of keratin. 2 kinds soft under hair for insulation and course long guard hair for protection and colouration. snowshoe hare had 2 annual molts to camoflauge. hairs can be modified e.g bristles, spines, whiskers or vibrassae sensory hairs. order: pholidota. only mammal with scales - overlapping made of fused hairs, insectivores with no teeth and long tongue. 

horns - true horns made of bone not shed. antlers made of bone shed each year. rhino horn hair filaments cemented together not attached to skull. tusks evolved from teeth usually enlarged canines but incisors for elephants. glands - sweat, scent, sebaceous (oil) and mammary. teeth - heterodont: different forms for diff functions. incisors - snipping or biting. canines - for piercing. premolars - shearing and slicing. molars - crushing and grinding. 

insectivores - small mammals feed on small invertebrates have sharp pointed teeth. herbivores - 2 groups browsers and grazer e.g cows (ungulates) and gnawers e.g rabbits and rodents. most have absent of reduced canines. rodents have continuously growing incisors. 

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mammals 2

herb digestion - cellulose hard to break down so long digestive tract, continuous eating, fermentation using anaerobic bacteria and protozoa in gut. hindgut fermentation (cecal) - simple stomach, enormous cecum, anaerobic ferm in large cecum, included odd-toed ungulates e.g horse, rhino, elephant. hares rabbits and rodents - coprophagy - some eat faeces to digest food twice. rumination - huge 4 chambered stomachs, chew cud which is then regurgitated and chewed again. incucles even toed ungulates (cattle, sheep, deer, pig, goat). carnivores - cecum reduced or absent, large feed periodically. omnivores - eat both. 

reproduction - monotemes, marsupials and placental mammals. young always dependant on one or both parents, lactation. monotremes - lay eggs, mammary glands but no ****** feed through openning in skin. e.g duckbilled platypus and echidna. marsupials - pouch, young born early and live and feed in females pouch, short gestation long lactation. placental - dominant, connects foetus to uterine wall, high surface area for uptake of o2 nutrients and elimination of waste, long gestation period. hormones produced to stop egg production and reject genetically diff foetus. 

whales and dolphins order cetacea: long gestation, breath through blowhole, fusiform, flippers modified forelimbs, vestigial hind limbs, fused neck vertebrae, insulated with blubber not hair. lots of myoglobin, larger body = larger muscle mass bigger o2 storage.

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mammals 2

herb digestion - cellulose hard to break down so long digestive tract, continuous eating, fermentation using anaerobic bacteria and protozoa in gut. hindgut fermentation (cecal) - simple stomach, enormous cecum, anaerobic ferm in large cecum, included odd-toed ungulates e.g horse, rhino, elephant. hares rabbits and rodents - coprophagy - some eat faeces to digest food twice. rumination - huge 4 chambered stomachs, chew cud which is then regurgitated and chewed again. incucles even toed ungulates (cattle, sheep, deer, pig, goat). carnivores - cecum reduced or absent, large feed periodically. omnivores - eat both. 

reproduction - monotemes, marsupials and placental mammals. young always dependant on one or both parents, lactation. monotremes - lay eggs, mammary glands but no ****** feed through openning in skin. e.g duckbilled platypus and echidna. marsupials - pouch, young born early and live and feed in females pouch, short gestation long lactation. placental - dominant, connects foetus to uterine wall, high surface area for uptake of o2 nutrients and elimination of waste, long gestation period. hormones produced to stop egg production and reject genetically diff foetus. 

whales and dolphins order cetacea: long gestation, breath through blowhole, fusiform, flippers modified forelimbs, vestigial hind limbs, fused neck vertebrae, insulated with blubber not hair. lots of myoglobin, larger body = larger muscle mass bigger o2 storage.

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mammals final

mysticetes: baleen whales - no teeth, long horny plates edges with bristles instead, fitler feed, 2 blowholes. odontocetes : toothed whales - feed on fish and squid, dolphins, orcas and sperm whales, most use advanced echolocation for hunting and navigation.

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