24 Pages

Biological Sciences
Course Code
BISC 316
Tammy Mc Mullan

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Paired fins and limbs 6. Improve locomotion; strut to prevent body -homology between crossopterygian and from tipping on side isthyostegid limbs not due to direct evolution of limbs, but to a common pattern of development -Ordovician and Silurian -extensive shallow seas Fin to limb -ostracoderms, placoderm, acanthodii 1. Formation of stylopod and zeugopod -Osteichthyes (Devonian) –radiation of fish (sarcopterygion) 2. Form of autopod region (wrists, fingers) Tetrapods 3. Determination of number of bones/digits -First skeletal evidence of tetrapods appear in (sarcopterygion) early Devonian 4. Loss of fin rays (tetrapods) -continents moving closer together -losing shallow seas Tetrapods – late activation of hox d 12 -fewer epicontinental seas -formation of large continents -sarcopterygion fish shape some characteristics -Laurasia/Gondwanaland separated by the with early tetrapods Tethys Sea -earlier tetrapods are more fish like than once -land is productive, moist, vascular plants thought Carboniferous Why did the fish limbs evolve? -Pangea present throughout the Permian and -some environment with fluctuating water Triassic levels, decreasing oxygen supply -160 million years -covered 36% earth surface Selection pressure favored the evolution of -fewer epicontinental seas lungs/limbs -Pangea colonized by vertebrates - Limbs evolved from fins with axial skeleton Devonian -fin rays allowed the fins to be flexible -large horsetail/giant club mosses -axial skeleton gave support -First fossil seeds appeared late Devonian Selective pressure that favored limbs Carboniferous 1. Exploit unoccupied habitats -increased diversity of terrestrial -shallow water, more abundant prey, less invertebrates/plants predators -cockroach, large dragonflies 2. Explot abundant food in shallow water Herbivores and predators 3. Escape unfavorable environment Land offered novel foods and habitats -leaves a drying out pond Higher oxygen levels 4. Avoidance of predators in shallow water 5. Improve locomotion; anchor points as body Class amphibian nonamniotic tetrapods undulates forward -early tetrapods “labryrinthodont” -4 groups 1.”stem tetrapods” or labyrinthodontia -Dorsally flattened with eyes on top of head – -Acanthostega/Icthyostega means spend time on top of water to look for 2.Batracomorphia prey items -lepospondyli/temnospondyli ancestor to -lungs modern amphibians -fins used to prop up body in order to gulp air 3. Reptiliomorpha –ancestral reptiles 4. Lissamphibia –living amphibians Elpistostegidae and tetrapods have 1. Limbs skeletons similar Origins of tetrapods 2. Bones of skull in similar positions -sarcopterygii (lobe finned fish) -frontal bone distinct 1. Osteolepiformes 3. Lungs 2. Elpistostegidae (Panderichthyes) 4. Ribs project ventrally Tiktaalik rosaea 5. Labryinthodont teeth -complex folded tooth 1. Osteolepiformes -“the gap between fishes and tetrapods has Tiktaalik rosaea narrowed” -ancestral characteristics -cylindrical body 1. Body scales -thick scales 2. Fin rays -Variable caudal structures –different tail shape 3. Lower jaw and palette – some bones indicates different habitats tetrapod like -paired crescent shaped vertebrae 4. Well developed gills -very similar to earliest tetrapods -ribs project dorsally from vertebrae -derived characteristics -probably didn’t spend much time in 1. Flattened skull with eyes dorsal shallow water, bad bottom support 2. Wide spiracular notch -labryrinthodont teeth 3. Loss of opercular, subopercular and extrascapular -long snout and teeth stalked or ambushed  Mobile neck prey maybe similar to frogfish, ambush Move neck independently from body predator 4. No dorsal fin 5. Pectoral girdle and fin capable of complex -similar behavior to extant frogfish movement and support (functional wrist/ankle -can walk and slow gallop on ocean floor and digit joints) 6. Overlapping ribs with unicate process 2. Elpistostegidae 7. Bony connections between vertebrae -resemble the early tetrapods -dorsal fins New fossil tetrapod tracks -reduced tail -18 my before first skeletal fossil of tetrapod -large fish >1m long -10 my before elpistostegadian fishes -long snout -0.5-2.5 m long -marine, not stream/forest habitat Tetrapod group Stem tetrapods 1. Stem tetrapod -Combination of fish-like and terrestrial -paraphyletic assemblage of late Devonian characteristics genera 1. Groove in ceratobranchial indicates afferent -Acanthostega branchail arteries in gills. -Icthyostega 2. Flange on cleithrum (part of pectoral girdle) supports the posterior wall of operculum Acanthostega –older of the 2 3. Sensory canal of lateral line embodied in -Mainly aquatic – gills/lungs dermal bone of skull -Forelimb is more fin-like than Icthyostega (Same pattern as sarcopterygii) -small articulation surface on vertebrae 4. Caudal fin broadened dorsally/ventral  -neural arches, weakly ossified aquatic -ribs short and strain 5. Opercular bone lost, but pre opercular bone present Icthyostega -skeleton had basic structural features of Terrestrial characteristics terrestrial vertebrates 1. Scales – v shaped row of ventral armor across -“suspension bridge” abdomen -Vertebral/column must resist collapsing 2. bent forelimbs used as a prop (same as -girdle and limbs must be firmly attached to the elephant seals) vertebral column 3. Pelvic limbs used as paddle for steering Osteolepidiformes – 2 sets of bones from -capable of locomotion on land Centrum (intercentrum and pleurocentrum) -we developed limbs etc Icthyostega – similar but articulation between -Why did they retain gills which can only neural arches transfer force to adjacent function in water? vertebrae -living amphibious fish have retained their gills -counters twisting movement of spinal column -excrete CO2 and nitrogenous wastes when moving on land -broad overlap of ribs Origins of tetrapods -origins of tetrapods and that of terrestrial -large interclavicles brace ventral muscles for lifestyle must have been two separate events pectoral girdle -Late Devonian to early carboniferous – stem -forelimbs bent at elbows tetrapods -pelvic girdle bony plates in the fishes enlarged (“Labryrinthodont”) radiated into 2 lineages to form a skid like structure attached to (clades) vertebral column by sucrial tip Batracomorpha Reptilomorpha 2. Batrachomorpha 2. Long stout ribs for muscle attachment -broad flat skull -contraction and relaxation of muscle changes -more aquatic than anthraosaurus volume of thoracic cavity -Includes temnospondyles –largest and longest 3. Head becomes flatter/longer lasting group of primitive non-amniotes -possibly related to development of stronger tetrapods buccal pump -some living amphibians (frogs) are derived 4. Cutaneous respiration from the group 2. Gravity 3. Reptilomorph -fish body supported by water -diverse array of animals Need strong support fore and aft to prevent -dome shaped skulls buckling of body -anthracosaur predominant group -on land gravity pulls body down -largely terrestrial  Weight on ventral surface -ancestor of amniotes appear in the late  Spine must support limbs and resist bending carboniferous in some places and have increased mobility in others 4. Lissamphibia (modern species) -amphibian -requirements on land are: -modern species 1. Vertebrates with firm centra 1.urodela –tailed amphibians –salamanders 2. Interveterbral joint that could move or resist 2. Anura – tailless amphibians – frogs and toads motion 3. Gymnophionans – legless amphibian 3. Vertebral column and girdles closely associated First vertebrate on land -advantages -pectoral and pelvic girdle -new food sources virtually competitor free -large and stronger -disadvantageous -fish 1. Respiration Girdles don’t support body; act as pivot or 2. Gravity anchor points 3. Desiccation Pelvic girdle is not attached to vertebral girdle 1. Respiration Amphibian -lung used to acquire oxygen from air Appendages attached to girdle -crossopterygii and dipnoi -limbs and girdle attachment to vertebral -tetrapod lungs greatly increased in complexity column especially when associated with endothermy -limbs and girdle attached to vertebral column Problem -pectoral girdle fused to sternum in later -how do you get the air into your lungs tetrapods and all modern amphibians 1. Limbs to assist in raising the body off the -orientation of the limbs ground Reduces contact with ground -head movement -osteichthyes -later “labryrinthodont” -pectoral girdle attached indirectly to vertebral Trend toward expulsion of either column 1. The pleurocentrum or Head and body move as one unit 2. The intercentrum -articular surface at back of the skull is a single  More solid Centrum flattened surface -stem reptiles, modern reptiles, birds, mammals -tetrapods  Enlargement of pleurocentrum -occipital condyles divided into a rounded pair Eventual loss of the intercentrum -One articular surface at back of skull is a single flattened surface -3 conditions evolved 1. Intercentrum develops – extinct line -tetrapods 2. Intercentrum and pleurocentrum develops -occipital condyles divided into a rounded pair two centra formed – extinct line -One articular surface on each side 3. Pleurocentrum expanded and fused to form a -allows the head to move up and down complete ring – reptiles, birds, mammals -independently of the body -Lissamphibia -simple discs and rings -no clear story -interlocking vertebrae -Centrum – no evidence of intercentrum and -more efficient pleurocentrum -maintains flexibility -no cartilaginous preformation -enhance strength -adjacent vertebrae articulate by their centra -some may also articulate by process carried on Structure of vertebrae the neural arch -Centrum – principle component -zygapohyses Below spinal cord -consists of one or two elements Types of centra articulation -If two – intercentrum and pleurocentrum -shape of the articulatory surfaces at the end of -if one the centra is important both functionally and -it may be the intercentrum (some extinct evolutionarily tetrapods) -or the pleurocentrum (amniotes) -5 conditions 1. Amphicoelus – both surfaces are concave Evolution of vertebrae structure  Limited movements in many directions -sarcopterygion, Elpistostegidae and some stem 2. Procoelus – centra concave anteriorly and tetrapods convex posteriorly -2 sets of ossification in centra region 3. Opistocoelus – centra concave posteriorly -posterior end below neural arch and convex anteriorly =pleurocentrum Procoelus and opishocoelus permit motion in Icthyostega and other early tetrapods any direction and resist dislocation 4. Acoelus – centra has flat end withstand 6. Increasing cornification of the skin compression and limit motion LECTURE 11 5. Heterocoelus – saddle shaped ends Amniotes Allowed vertical and lateral flexing Classification in amniotes Prevent rotation around the axis of the spine Adaptations -modification to skull, vertebral joint, limbs, Non-amniotic tetrapods girdle, scales, amniotic egg -opishocoelus -procoelus Amniotes – evolved in response to terrestrial -amphicoelus arthropods / becline in non-amniotes -Evolved probably from a reptilomorpha – 340 -stronger centra + processes (that interlocked mya (carboniferous Permian early) adjacent vertebrae) flexibility and prevent -4 changes in the evolution of amniotes twisting of the vertebrae column 1. Evolution of stronger more efficient jaw muscles -adaptation of the girdle and vertebral column, 2. Evolution of more effective locomotion on amphibians were able to lift their bodies and land use their limbs to move about 3. Development of amniotic egg 4. Development of scales (reptile and birds) 3. Desiccation -moisture lost from lungs and skin Classification of amniotic -adaptation -Traditionally based upon the features of the 1. Can tolerate high conc. of salt tissue in tissue skull –temporal fenestration x3 body -Anapsid – without opening 2. Behavioral adaptations -Synapsid – with one opening 3. Permeable skin – reabsorb water from -Diapsid – with 2 openings bladder 5 subclasses were used in this system -restrictions to reproduce -anapsid, synapsid, arcinosauria (class), Water needed to reproduce lepidosauria (lizard, snake)  Lay eggs in moist environment Split between synapsida and anapsida, diapsid Tetrapods and their adaptations overview much later on, more heavily modified 1. Terresterial streamline not as important as in fish Amniotes 2. neck advantageous – improve feeding an division without reducing streamlining Cotylosauria = Amniota + Diadectomorphs 3. Loss of median fins; paired fins limbs 4. Stronger limbs, firmer attachment to girdle Synapsida sauropsida increase strength to vertebral column Mammal’s mammal-like reptiles/birds 5. gills  lungs and pulmonary circulation Sauropsida divides Separated from edge of shield by subteryporal Parareptiles – contains many lineages that are fossa not related to modern amniotes except for turtles 3. Dermal skull roof or dermatocranium Shield of membrane or dermal bone Eureptiles splits -covers top and sides of the head  Lepidosauromorpha –lizards and snakes shed -extends down to jaw rims in one big place Archosauromorpha – dino, bird, gizzard -in non-amniotes and stem reptile the dermal upright stance skull is unbroken -temporal muscles are inside the solid dermal Adaptation of amniotes roof of the cheek or temporal region 1. modified skull, cranial vertebrate joints, limbs, girdle, scales, and egg -When jaw close – muscles shorten and expand in breadth We have glandular skin and can’t excrete uric -little room for expansion under shield acid Early tetrapods 1. mod/evolution of skull Amniotes – changes in jaw muscle attachment -skeletal structure found in head region to the skull -Chondrichthyes – chrondocranium and upper  Stronger and more efficient jaw Several lineages developed openings in the -osteichthyes  mammals dermal skull roof -skull a fused units – braincase is added to and Muscle exits skull and attaches to outer welded together by a series of dermal bones surface of cranium Evolved independently several times -skull of early tetrapods -labrinthodont Cranial Vertebral Joing -3 major units. Neurocranium, splandocranium, Fish – amphicoelus dermal elements Amphibians – occipital condyle, ball socket joint between skull and first vertebrae only move 1) Chrondocranium –braincase, head up and down splandocranium, dermal elements Amniotes – atlas, axis joints allow a lot of 1. Chrondocranium – braincase, formed flexibility. Side to side and up and down originally as cartilage, if ossified – movements Neurocranium Cranial vertebrae joint 2. Palatal complex –ossification of -joint between vertebrae palatoquadrate cartilage (upper jaw) and some -some vertebral elements get incorp to the back dermally, derived membrane bone – forming of the skull the roof of the mouth -pro atlas very small on tip of atlas Atlas (1 vertebrae) Anura (frogs/toads) – 6 bones -neural arch of vertebrae 1 = atlas Labryinodonts (early non-amn tetrap) – 6 bones -intercentrum of vertebrae 1  only found in Stem reptiles – 5 bones atlas Synapsida – 5 bones Monotremes – 5 bones Axis – composite bone Birds – 3 bones -neural arch of vertebrae 2 = axis Mammals -2 bones (scapula and clavical) -pleurocentrum of vertebrae 2 strength, fewer bones, fewer suture lines -pleurocentrum of vertebrae 1 Obontoid process Pelvic girdle Fish – pelvic girdle doesn’t attach to vertebral column (no bone-bone contact between girdle/spine) Vertebrae 3,4,5 Labryinodonts – pelvic girdle articulates 1 -pleurocentrum, neural arch vertebrae strength to C.V joint Pubis/ilium/ischeum all verts with bones have 3 flexibility bones in pelvic girdle rotation in neck area -elongation of bone to increase SA for muscle Advantages attachment 1. increase feeding opportunity 2. reposition head which improves the sense organs and locomotion Birds pelvic girdle fuse to many vertebrae + bones in lower back (synsacrum) Girdles and limbs -stem reptiles Reptiles – 2 vertebrae attatched to girdle Structure of girdles and limbs very similar to Mammals –sacrum (4-5 vertebrae) non-amniotic tetrapaods Pelvic girdle attached to 4-5 girdle -short legs -legs came out at right angles to body more vertebrae attatched  stronger -move legs in horizontal planes -thrust of limbs and body undulation Girdles and limbs -limbs move directly beneath the body -amniotes giirdles/limbs more effective support and locomotion Appendicular skeleton more suitable for -therapsid (ancestors to mammals) terrestrial environment -archosaurs (dinosaurs, ancestors to birds) 1. reduction in the number of bones in the -in advanced amniotes the elbows rotate pectoral girdle backwards, knees forward feet now point forward faster, more efficient locomotion increase length of stride, facilitates fast running -in modern reptiles (snakes excluded) 2)outer epidermal layer seperates at the locomotion very similar to early amniotic separation zone tetrapods 3)outer skin is shed 4)upper-cell die, dry out and form new scales 4) scales Cornified scales increase amniotic tetrapods Formation of scales ability to live in terrestrial environment -scales form by folus in the integument -each bump consists of epidermis and Generalized skin of vertebrates underlying dermis papilis Has 2 principle layers 1)epidermis –superficial stratified into several Papilli have different growth (cells on anterior layers: derived from ectoderm outer surface grows faster than cells on 2)dermis – deeper derived posterior inner surface) Epidermis Strantum conerum becomes thicker, one scale -strantum germinatium – living inner layer overlaps the next -stranum cornium – dead outer layer of cells filled with a protein called keratin Function of scales 1) thick layers of keratin reduces water loss Fish skin  less dependent on moisture in environment Epidermis 2 protection from abrasion Thickness varies , dermis, a cellular “bony scales” embedded in this layer Amniotic egg -derived from bony plates of ostracoderms Cotylosaruia  amniotia + Diadectomorphs several special extra –embryonic membranes Amphibian skin -allow development independent of H20 -lack bony plates AS SIGNIFICANT AS JAWS TO THE EVOLUTION -epidermis is very thin OF VERTEBRATES -strantum cornium is very thin, with little keratin Strucutre of an egg -large mucus glands – retain moisture Reptiles have a telolecithal egg large amount of yolk, unevenly distributed Reptile skin small amount of protoplasm in germinal disk -epidermis forms a complete body covering of Cleavage only occurs in germinal disc keratilized scales (meroblastic cleave) -epidermis consists of strantum germination and outer straum cocneum (VERY THICK) Development of the egg -Molting Periphery of disc spreads out over yolk -several times per year the epidermis is Eventually covers entire yolk replaced by molting YOLK SAC 1)strantum germinaum proliferates to form a Yolk sac is infiltrated by blood vessels new set of inner epidermal layer NutRIENT FROM YOLK TO EMBRYO Other extra-embryonic membranes expand up Success over the embryos to form coelom between the 1. amniotic eggs ended the dependence on h20 two layers for reproduction 2. keratinized epidermis Extra – embryonic membranes 3. better jaw operation 4 membranes 4. better modes of locomotion 1) yolk sac 5. changes to head articulation 2) amnion – envelops the embryo 3) chorion –outer membrane Dominant vertebrate life on land during the 4) allantois – Mesozoic era! We get amniotic cavity – umbilical cord Paleozoic 375 mya Advantages of the layers -mesozoic lasted 180 million years Provides the embryos with a fluid medium for -end of Mesozoic – massive extinction of development reptiles -embryo floats -cenozoic era covers the last 65 million years no compression from gravity -age of mammals -protects the embryo from dessication first originated in Triassic -fluid acts as a shock absorber  birds originated in Jurassic even pressure on all sides of the embryo Pangea started to break up during early Jurassic Disadvantages laurasia and Gondwanaland -isolate the embryo from environment creates epicontinental seas and oceans chorion and amnion prevent embryo from being near surface – little access to O2 -late Jurassic, Gondwanaland breaks up to form  problem with gas exchange asia, Africa, Australia, antartica and S.A) -no means of disposing of nitrogenous waste -mesozoic –diversification of vertebrates Allantois Triassic –dinosaurs and first mammals, -storage of waste sphenodontids, turtles, crocodiles, ancestor of -develops from hind gut of embryo frog -from the allantois sac -expands very rapidly to fuse with chorion Jurassic – birds (archaeopteryx) -develops blood vessels on the surface which are connected to umbilical cord Cretaceous -also the respiratory organ for the embryo S.A seperates from Africa, antartica and Australia evolution of snakes, modern types of croc, monotremes, marsupials, placental mammals -land connections between N.A and sibera -Traditional systematic (early Eocene another with Greenland) -class aves and class reptilian -loss of land bridge results in isolation of populations and prevent gene flow -Sauriscian dinosaurs -massive rearrangement of land masses 1.sauropodomorpha -modified water bodies 2. theropsida -changes in climate –cooling trend -period of glaciations -birds + all saurischian dinosaurs which more closely resemble birds than to the -Archosauria gave rise to birds sauropodomorph dinosaurs -two independent radiation of flying vertebrates Theropsida 1.pterasauria -these general types of animals 2.dinosauria 1. large predators –jaws used as weapons -certosaurs, allosaurs, tyrannosaurs -diapsids 2. fast moving predators –forelimbs to capture -legs were held close to body prey –ornithomids -many were bipedal 3. fast moving predators – huge claw on hind saurschia foot used to attach pray -theropoda –carniverous, bipedal -dromeasaurs -sauropodomorpha + quadraped/herbivores Birds evolved form small mini raptorian Pterasaurs coelusaurian dinosaurs -late Triassic to cretaceous -great range in size -sinosauropteryx –fringe of hair like or down – -some sparrow sized like structure along neck, backbone and flanks -some larger had wing spands of 13 meters -closely related to basal coelusaurs -membrane forms the surface of the wing -not precursors to birds -caudipteryx and protoarcaeopteryx -different in the structure of the wing -long feathers with central rachis (shaft) -4 digit is elongated –supported membrane, -possibly interlocking –barbs skin of wing -digits 1,2,3 present as claws Birds now viewed as the most derived form of -birds – remaining digits are fused together therapod dinosaurs -tip of wing supported 3 digit -similarities of birds and therapods -2 and 4 digit were reduced 1. elongate, mobile S-shaped necks -covered in feathers 2. tridactly fod with a digigrade posture 3. intertarsal ankle joint -Thomas Huxley 4. hollow, pneumatic bones -birds are nothing but glorified reptiles -class sauropsida -differences 1. features associated with flight and -running, flapping to capture prey endothermy -short flights to escape predators Characteristics of basal coelusaurs and birds -class AVES -feathers 1. subclass archeorniths –all extinct by end of -furcula Jurassic -enlarged sternum -archaeopteryx -long arm and hands 2.subclass neorinthes -sideways flexing wrist -28 extant orders -nesting behavior -157 families, 8700 species -rapid growth rates -two major radiations 1. Eocene (mainly water fowl and non-pusserine Archaeopteryx forest dwelling birds) -oldest known birds are form the late Jurassic 2. Miocene (passerine birds)(perching birds) -more dinosaur-like than living birds -only one fossilized impression of a feather 1.modified diapsids -seven fossilized skeleton, some with very 2. single occipital condyle –mammals have 2 distinct impressions of feathers 3. lower jaw composed of several elements – -crow size quadrate and articular 4. single ear ossicle (middle ear) –columella Characteristics of archaeopteryx 5. unicate process 1. feathers, in places where modern birds have 6. ankle joint is between two rows of tarsal feathers bones 2. vertebrate possibly amphicoelus 7. pubis extends backwards 3. forelimbs wing-like, but ended with 3 clawed 8.epidermal scales on legs and feet digit 9. few glands in skin 4. 5 trunk vertebrae fused to form synsacrum 10.respiratory air sacs associated with lungs , air 5. long tail sacs increase volume of air in body X9 vertebrae form central axis of tail 11. amniotic egg with shell extant birds- feathers attached to pygostyle 6.forelimbs relatively short and rounded Nonreptilian characteristics -capable of short flights 1. high metabolic ratel high body +temp – endothermi
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