Amniotes & Reptiles TEST 3

Anapsids, synapsids, & diapsids

-3 groups distinguished from each other by the number of openings in the temporal region of the skull -Anapsids= solid skull with NO OPENINGS -Synapsids- have ONE PAIR OF OPENINGS in the skull associated with the attachment of jaw musckes -Diapsids- have TWO PAIRS OF OPENINGS in the skull roof

Modern Reptiles: SC-diapsids O-Squamata

-95% of all living reptiles including these 3 suborders 1. sauria- lizards 2. serpents- snakes 3. amphisbaenia- worm lizards -diapsid skull of squamates has been modified from the ancestral condition by the loss of bone behind & below the temporal opening -most have kinetic skull, which has moveable joints that allow the snout & upper jaw to be moved against the skull & raised

Dinosaurs

-Saurishica & Ornithischia are two order, with division based on shape of pelvic bone -Saurischian pubis juts forward, & its ischium points backwards -the Ornithischan pubis & ischium both point backward -order Ornithischians- all herbivorous & include 3 suborders- Ornithopoda, Marginocephalia, & Thyreophora -Saurischian- largest herbivorous & carnivorous dinosaurs & includes suborders- Theropoda (bird-like) & sauropodomorpha

Vision

-accommodation is the process of focusing light on the retina & this can occur in several ways -snakes- increased pressure in the vitreous humor generated by muscles near the iris pushes the lens forward -most reptiles, birds, & mammals- curvature of lens is altered by ciliary (annular) muscles

Monitor lizards

-active predators that feed on wide variety of prey -positive pressure gular pump to assist the axial muscles in lung ventilation. this enhanced respiration; enable them to sustain high activity levels -komodo dragons; mouth contains diverse stew of bacteria & bites inevitably become infected

Respiration

-air comes into the organism via the mouth & trachea into the brochus and then into each lung & then into the chambers of the lungs -rely on suction pumps to ventilate the lung -ventilatory cycle is triphasic- divided into 3 phases 1. inspiration (suction pump) 2. breath-hold 3. expiration (passive) -most reptiles (not turtles) breathe by expanding & compressing the pleurpoperitoneal cavity by movements of the ribs produced by contacting the intercostal muscles -turtles cannot move their ribs & instead use specialized sheets of muscle to expand & contract the lungs

Turtle reproduction

-all are oviparous & eggs are laid in a nest in sand or soul that the female excavates using her rear limbs -incubation temp. plays a major role in sex determination (temperature dependent sex determination) -higher incubation temperatures produce the larger sex, which in turtles=females -adults provide no parental care

Crocodiles

-all have their teeth set in sockets; a trait found only in mammals -complete palate which enables them to breathe even if the mouth is filled with water or food (like mammals) -the palate has a special path from the nostril to the glottis that bypasses the mouth. the nostrils are closed during submergence -posses a 4 chambered heard -crocodile has cerebral cortex (no other reptile) -have a functional equivalent diaphragm, by incorporating muscles used for aquatic locomotion in to respiration -air in crocodile lungs makes a circuit, moving in only 1 direction through the parabronchi. the air first enters the outer branch, moves through the parabronchi, & exits the lung through the inner branch -extensive vasculature around the parabronchi are where oxygen exchange takes place -the muscles used to open a crocodiles mouth are quite weak, but those used to close the jaws are massive and powerful -snout contains large # of pressure & touch receptors; these enable the animal to lunge at a prey animal in darkness or immediately snap the jaws closed on a fish or other animal that brushes against the animals open mouth -salt glands are present in the tongues of crocodiles & they have a pore-opening on the surface of their tongue -do not have sweat glands & release heat through their mouths. often sleep with their mouths open & may pant like a dog -narrower & longer heads with a more V-shaped than a U-shaped snout in compared to alligators -upper and lower jaw are same width & teeth in the lower jaw fall along the edge or outside of the upper jaw when the mouth is closed; therefore all teeth are viable unlike an alligator, which possesses small depressions in the upper jaw where the lower teeth fit into -have more webbing on toes of the hind feet than alligators -can tolerate saltwater due to specialized salt glands for filtering out salt; alligators can not tolerate salt water BC their salt glands are present but not functional- they are restricted to only freshwater

Difference b/w reptiles & amphibians: respiration

-although reptilian respiration primarily depends on lungs, some gas exchanges takes place across the skin, inside of mouth and in the cloaca particularly in turtles

Kidneys

-amniote embryos- mesonephros function for a short period of time after hatching or birth -mesonephros formd by corpuscles & tubules that develop caudal to pronephric region; form connections with existing mesonephric duct -after birth a metanephros kidney is formed; drained by a duct called metanephic duct or ureter

Geckos

-among the smallest lizards; occur on every continent but Antarctica -modified scaled of their feet (setae) that allow them to cling to vertical surfaces

VNO

-amphibians- VNO recessed area off the main nasal cavity. -reptiles- VNO separate pit to which tongue & oral membranes deliver chemicals -mammals; isolated area of olfactory within nasal cavity that is connected to mouth via a nasopalatine duct. -function of vomeronasal organs= detecting conspecific odors, but useful in prey detection -VNO= jacobsons organ

Gonads

-arise as paired ridges just medial to mesonephroi -due to fusion or failure of 1 ridge to differentiate, some vertebrates (agnathans, some female lizards & crocodilians, & most female birds) have a single testis or ovary -hormones cause differentiation of early gonads into either testes or ovaries

Anapsids

-characterized by having no temporal openings behind the eye sockets -represented today by turtles

Faveolar lung

-contain millions of tiny passages known as para-bronchi, connected at both ends by the dorsobranchi. the airflow through the lung always travels in the same direction- posterior to anterior (in birds) -this is in contrast to the mammalian system, in which the direction of airflow in the lung is tidal, reversing b/w inhalation & exhalation

Diapsids

-derived from the stem amniotes -split into 2 major lineages- the Lepidosauria (snakes & lizards) & the Archosauria (extinct dinosaurs, birds)

Amniote classification

-disagreement b/w cladistics & traditional classification of the amniotes -traditional classification recognizes 3 classes: 1. Reptilia: reptiles 2. Aves- birds 3. Mammalia- mammals -b/c the class reptilian does not include all the descendants of their most common ancestors (birds), the reptiles are a paraphyletic group -birds & crocodilians share a most common ancestor & thus form a monophyletic group (archosauria), which include the extinct dinosaurs -birds & crocodilians are more closely related to one another then to other reptiles

Synapsids

-diverged from the Sauropsida(anapsids & diapsids) & radiated into group "pelycosaurs" (lizard-like)- large sail on back which played role in thermoregulation -therapsids diverged from the pelycosaurs=lineage gave rise to mammals

Order Squamara: SUBORDER- Sauria-the lizards

-diverse group includes terrestrial, burrowing, aquatic, arboreal & even gliding members -hottest areas by evolving a suite of adaptations that make survival in deserts possible; these include: thick skin that contains lipids which reduce water loss, & the excretion of uric acid which minimizes water loss -reptiles are ectothermic and adjust their body temperature by moving from one microclimate to another -found in tropics, deserts, grasslands, forests, & alpine regions -have good vision & an external ear & have eyelids -most have 4 limbs -well known species include: geckos, iguanas, chameleons

Pterosaurs

-flying reptiles -the 1st vertebrates to evolve true flight -derived from bipedal, cursorial(running) archosaur -wing supported by an elongated 4th digit -keeled sternum for attachment of flight muscles -a short and stout humerus (the first arm bone) & hollow but strong limb bones and skull bones -modified scaled that were wing-supporting fibers & possibly formed hairlike structures to provide insulation- bird feathers are analogous to the wing fibers of pterosaurs -scales thought to have evolved for purpose of thermoregulation, suggesting that both pterosaurs & earliest birds were endothermic -early pterosaurs had long tails that assisted balance, later pterosaurs had no tails & may have been more adept flyers

Urinary bladder

-found in all vertebrates except agnathans, snakes, crocodilians, some lizards, & birds (except ostriches) -void urine when desired rather than continuously as it is formed

Turtles

-have a shell that consists of dorsal carapace & ventral plastron( both made of dermal bones overlain by horny scutes) -ribs & vertebrae are fused to the shell & the limbs can be withdrawn into it -flexible areas called hinges are found in shells of many tutrtles -no teeth; keratinized beak -large body sizes; thermal stability- larger animals heat & cool more slowly then smaller ones & large size may make temp. regulation difficult in habitats where shade is scarce

Alligatoridae

-includes alligators & caimans; found in freshwater & have broader snouts the crocodiles -exhibit unidirectional movement of air through the lungs (like birds- falveolar lungs) -air in alligator (like crocs) lungs makes a circuit, moving in only one direction through the parabronchi. the air first enters the outer branch, moves through the parabronchi, & exits the lung through the inner branch -extensive vasculature around the parabronchi are where oxygen exchange takes place

Pit receptors of reptiles

-infrared receptors; 2 types 1. labial pits- found in pythons; nerve endings lie at bottom of several recessed labial pits 2. loreal pits also called facial pits- present in snakes

The amniotic egg

-is hard shelled & is called the amniotic egg b/c the embryo develops within a sac called the amnion -the embryo feeds on yolk from a yolk sac & deposits its waste into another sac called the allantois -the allantois & another membrane, the chorion, together lie against the shell, & being richly supplied with blood vessels, exchange gases with the outside through the pores in the shell -unlike amphibians, amniotes lack a larval stage & after hatching develop directly into the adult form -evolutionary origins of amniotic egg= unclear b/c fossils are scarce -the earliest amniotes were probably amphibious. they probably inhabited humid habitats and eggs may have been laid out of water initially perhaps to reduce their risk of predation. gradually eggs may evolved to become less vulnerable to dessication

Amphisbaenians

-legless -burrow by ramming their heads against the soul & pushing dislodged material to the sides -head is heavily keratinized & there is variation in head shape that relates to the particular mode of tunneling used -for example, those with shovel-shaped snouts ram their heads into the end of the tunnel and then compress the material into the roof -skin is distinctive & rings called annuli encircle the body -integument has only a few connections to the body so that the trunk is free to move within a tube of skin -to move, the anima contracts integumentary muscles b/w selected annuli. this bunches the skin so it presses against the tunnel & the trunk then slides forward within the tube of skin

Order Squamata: SUBORDER serpentes: the snakes

-limbless & usually lack both the pelvic & pectoral girdle -numerous vertebrae, which are shorter & wider than those in other vertebrates and allow them to make undulatory movements -many species have skulls with many more joints than lizard ancestors, enabling them to swallow prey much longer than their heads with their highly mobile jaws -to accommodate their narrow bodies, snakes paired organs (such a kidneys) appear one in front of the other instead of side by side, & most have only one functional lung (left lung if present is vestigial) -3 lineages of snakes= Scoleophidia, Alethinophidia, & Colubroidea -the large constrictors primarily use rectilinear motion to move -alternate section of ventral integument are raised off the ground and pulled forward by muscles that connect the ribs and ventral scales -waves of muscle contraction travel down the snake which moves in a straight line -most have poor vision and limited hearing ability; they use sense organs to track prey -have pit-like Jacobsons organ in the roof of the mouth, which are olfactory organs. their forked tongue when extended samples the air and pick up molecules that are delievered into the Jacobsons organ when the tongue is withdrawn -crotaline vipers (pit vipers such as rattlesnakes) have heat-sensitive pit organs on their heads b/w the nostrils & eyes

Kinetic Skull

-mobility of the skull allows squamates to seize & manipulate prey and also increases the force of the bite

Crocodies & alligators- Order crocodilia

-modern crocodiles & birds are only survivors of the archosaurian lineage that included dinosaurs -crocodilians are diapsid

Chameleons

-most arboreal lizards -zygodactylous feet (the toes are fused together) allow them to grip branches firmly & they have a prehensile tail -eyes are raised on small cones that can rotate independently. this arrangement allows chameleons to gauge distance accurately, which is very important for prey capture; capture by projecting their long tongue

Circulation

-most reptiles have 3-chambered heart consisting of two atria & one partitioned ventricle & two aortas that lead to the systemic circulation -in contrast to the situation in amphibians, the ventricle in reptiles has developed a septum that partially divided the ventricle into separate right and left chambers. In crocodialians (and birds) the separation of the ventricle in complete. This greatly reduces the mixing of deoxy and oxy blood -all of crocodilians have 4-chambered heart; allows to have reduced mixing of deoxy and oxy blood

Gharial

-narrow snout & is a specialist fish predator -only extant crocodilian with visible sexual dimorphism -males have a boss; the "boss" is used to modify & amplify "hisses" snorted through the underlying nostrils. the boss is a hollow bulbous nasal protuberance developed at sexual maturity -function of nasal boss- used as a visual sex indicator

Skull of amniotes

-one of the major characteristics used to classify amniotes= structure of the skull -the stem group (coylosaurs) of amniotes diverged into 3 lineages= synapsids, anapsids, & the diapsids -temporal fenestration used to classify amniotes- taxa such as anapsida, diapsida, euryapsida, & synapsida -temporal fenestra are large holes in side of skull -function of holes- debated but many believe that they allow muscles to expand and lengthen -the resulting greater bulk of muscles result in a stronger jaw musculature & the longer muscle allows an increase in gape

Modern reptiles

-paraphyletic group including anapsids & diapsids -turtles= anapdis ORDER TESTUDINES

T. rex senses

-rapid & coordinated eye & head movements -enhanced ability to sense low frequency sounds that would allow to track prey movements from long distances -enhanced ability to smell- very large olfactory bulbs & olfactory nerves relative to brain size -very long cochlea of ear- hearing acuity

Respiration

-reptiles depend on lungs to oxygenate their blood & reptilian lungs are more developed then amphibians -in amphibians, lungs are simple sacs, but in reptiles they have divided chambers & subchambers (faveoli) which increase the SA for gas exchange -faveolar lung= small chambers that open from a common space

Difference b/w reptiles and amphibians

-reptilian skin= dry & scaly which limits water loss -the reptiles amniotic egg frees reptiles from the need to lay eggs in water & thus can occupy drier habitats -reptilian jaws are more powerful and can apply a crushing grip -the openings in the skull provide additional surface area for muscle attachment allowing greater pressure to be exerted . in snakes, skull & jaw flexibility allows very large prey to be swallowed -with the exception of turtles, which have a horny beak (sometimes serrated), all reptiles possess teeth & many have them on both the palate & jaw -most reptiles have homodont dentition, but partial heterodonty occur in snakes & lizards -monitor lizards have incisors, canine-like teeth & molars -in amphibians, such as salamanders, the orientation of the limbs is outward from the main axis of the body, in most reptiles, the appendages are rotated towards the body & the long axis of the limbs lies more parallel to the body's main axis -the angle b/w the upper & lower limbs is reduced so the limbs are overall straighter. in the forelimb, the elbow is oriented towards the tail -these modifications provide better support for the weight of the body & raise it higher off the ground. Together these changes make greater agility & speed possible -reptiles= internal fertilization & males have copulatory organ, either penis or hemipenes -reptiles have more efficient nervous system & circulatory system -reptiles are the first truly terrestrial vertebrates & the cardiovascular system reflects the loss of gills & the need for efficient pulmonary circulation to bring blood to and from the lungs

Tuataras: order sphenodonta

-retain many features of ancestor diapsid skull & associated complete arches & a well-developed parietal "3rd eye" on top of its skull -parietal eye has a lens, cornea, & retina but has degenerated nervous connection to the brain. NOT used for vision but may help regulate day-night cycles & absorb UV rays to manufacture vitamin D -adult=nocturnal and live in seabird burrows -two rows of teeth; on upper jaw- one on maxilla and other on palatine bones -when they bite, the single row of teeth on the lower jaw fits b/w those on the upper jaw -eat shorebirds

Therapsid to mammal transition

-series of evolutionary changes occurred in the therapsids that were passed on to their surviving descendants- the mammals. These include: *an efficient upright stance with the limbs positioned under the body rather then sprawled to the side *homeothermy- cross sections of bones show Haversian canals- are characteristic of fast-growing, warm blooded animals *diaphragm *heterodont teeth- differentiation of teeth into multiple specialized types *secondary bone palate- separating nasal from oral cavities *turbinate bones in nasal cavity- increase retention of body heat *3 inner ear bones & single jaw bone

Venomous snakes

-snake venoms are highly modified salivas & complex in constitution including a variety of proteins & enzymes -elapid venom is neurotoxic & works by shutting down the respiratory system whereas viper venom is more painful and attacks the vascular system bringing about coagulation of blood & clotting of arteries as well as often severe tissue damage

Predation

-snakes use one of three methods to catch prey & kill prey: grab & swallow, venom, constriction -most catch by grabbing it and swallowing it alive

Visceral Receptors

-special visceral receptors- olfactory (smell) & gustatory (taste): -olfacation- involves receptors located in nasal passages; olfactory epithelium contains basal cells (replacement cells), supporting cells (secrete mucus), & olfactory receptor cells -vomeronasal organs- only in tetrapods but absent in most turtles, crocodiles, birds, some bats, primates, & aquatic mammals. amphibians- VNO recessed area off the main nasal cavity. reptiles- VNO separate pit to which tongue & oral membranes deliver chemicals

Amniote origins & classification

-the possession of shelled egg unites the mammals, birds, & reptiles into a monophyletic group- the amniotes -the shelled egg freed the amniotes from the need to reproduce in water, allowing them to spread into varying habitats

Intromittent organs-single penis

-turtles, crocodilians, a few birds, & mammals- exhibit an unpaired erectile penis -penis- usually a thickening of floor of cloaca consisting of spongy erectile tissue (corpus spongiosum) which grooves to direct sperm & ending in a glans penis -sensory endings on glans penis when stimulated cause ejaculation

Urine in amniotes

-used of urine: *reproduction (providing males with information concerning the reproductive status of female) *odor communication- scent marking *moisten soil( some freshwater turtles use urine to soften the ground and make it easier to dig holes for egg-laying)

Intromittent Organs

-useful when fertilization is internal -introduce sperm into female reproductive tract -snakes & lizards- have pair hemipenes (pocketlike diverticula of wall of cloaca)

Reptile subclasses (5)

1. SC- Anapsida O. Cotylosauria- stem reptiles O. Chelonia- turtles & tortoises - identified by bony dermal plates to which ribs & trunk vertebrae are fused 2. SC- Lepidosauria O. Rhynchocephalia O. Squamata- lizards, geckos & snakes 3. Archosauria O. Thecodonita- stem archosaurs O. Pterosauria O. Saurischia- 2 major groips= sauropods & theropods O. Crocodilia 4. SC- Euryapsida- marine reptiles 5. SC- Synapsida O. Pelycosauria- first stage in evolution of mammals O. Therapsida

Reptilia characteristics

1. dry skin that is keratinized to protect against desiccation 2. internal fertilization usually involving an intromittent or copulatory organ to maximize transfer & survival of gametes 3. development of shelled amniotic egg in which the embryo forms in a protective fluid environment 4. no larval stage of development 5. except for snakes & some lizards, the body is supported by girdles & appendages that permit effective terrestrial locomotion. 6. enlarged sensory portion of the brain & 12 pairs of cranial nerves 7. single occipital condyle- the articulation b/w skull and the atlas vertebrae of the vertebral column is through a single bony protuberance. Reptiles & birds have this arrangement in contract amphibians & mammals have double occipital condyles 8.ectothermy- of the extant vertebrates only the birds & mammals are homeothermic (metabolically generating a consistent body temperature) or endothermic. All other vertebrates are ectothermic and are dependent on environmental factors to ensure a functional body temperature. Some reptiles are able to maintain consistent body temperature through behavioral adaptations (sunbathing)

Class Reptilia- the first amniotes

1. scaly 2. clawed 3. large, yolk-laden, shell-covered eggs laid on land

Reptile Subclasses- classified according to presence or absence e of temporal openings

1. synapsid type- mammal-like reptiles 2. anapsid type- stem reptiles & turtles 3. diapsid type- rhynchocephalians, lizards & snakes 4. euryapsid type= extinct plesiosaurs