Herpetology Exam 1 PDF

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Lecture notes from the second section of the class....

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Study Guide Exam 1: Herpetology      

Symplesiomorphy: an ancestral characteristic, all of the ancestors have had the trait Synapomorphy: a derived trait; if the trait is not shared by all of the descendants and it just “appears” it is derived Homoplasy: trait shared by species but not found in their common ancestor (arm bones in bats and birds) Homology: a trait shared by species because it came from their common ancestor Amphibians and Reptiles are NOT monophyletic (clade consisting of all of the descendants from a group) LISSAMPHIBIA(ancestor of all extant amphibians, monophyletic)/ (anapsids): - Early ancestors had scaly skin, the thin, permeable skin (H20 and gases) did not develop until the Lissamphibia branch, H20 loss and evaporation limits their activity - Most active when rate of evaporation is low, high humidity and low wind speed, found at night in moist environments - Ironically can find some in driest places (due to permeable skin it is easy to absorb more water from soil even when there is not much there) - Very complex life history: most have an aquatic larval stage and metamorphose into a terrestrial adult stage, some become completely reproductively mature while remaining a larval body form (paedomorphosis), external and internal fertilization (via spermatophores) - Vivparity: embryo develops in the oviducts and leaves the parent fully developed - direct development: skips larval form and the embryo develops directly into the adult form prior to hatching - Breeding glands: sexually dimorphic mucus glands, males develop clusters during the breeding season often on hands called nuptial pads used to grasp females during mating and some species male versus male combat - Synapomorphies: neotenic trait: (slow down of somatic traits development, type of paedomorphosis) teeth are pedicellate- crown sits on pedicel and bicuspid, two cusps on teeth; ribs are short and do not encircle body; loss several skull bones. Non-Neo traits: sound apparatus in ears has two parts 1. Stapes to receive high frequencies of airborne sound and 2. Opercular apparatus that is attached to the pectoral girdle by a muscle and receives ground vibrations and lower frequency airborne sounds; cutaneous respiration (through the skin); skin contains mucus and granular (poison) glands  CAUDATA (salamanders)

Study Guide Exam 1: Herpetology 4 libs and long tails, limbs reduced in some longer species (amphiumidae and sirenidae)  trunk segmented by coastal grooves that helps facilitate water movement over the body  external fert in 3 families: cryptobrachnids, hynobiids, and sirenidae.  Internal fert using spermatophores  Ancestral modes of reproduction: lays eggs in water, free living larvae, most metamorphose into adult  2 clades of plethodontids evolved through direct development; Viviparity in salamandra  some species exhibit facultative metamorphosis were they change depending on the environmental factors  found on every continent except Australia (most in NA and Eurasia)  ANURA (frogs)  Most numerous of amphibians  Reduced skulls, enlarged tongue attached to the front of the mouth  several adaptations for jumping, or saltation  caudal vertebrae are fused into rod (urostyle: long bone fused from sacral vertebrae) helps rigidity for transmitting force from hind limbs to the vertebral column, key to jumping; radius and ulna are fused for jumping; tibia and fibula fused; 5-9 pre-sacral vertebrae  3 classes of amplexus (mating position), inguinal around waist, Axillary behind forelimbs, cephalic clasping head of female, usually species specific  lay eggs in water, free-living larvae (tadpole: are radically different from adults in morphology and ecology); larvae lack true teeth, but have tooth-like denticles used to scrape plant matter or detritus; metamorphose into terrestrial adult, radical changes to body organization  take in water through the mouth and passes over internal gills and exits through a single spiracle, unique to frogs  direct development evolved many times; Vivparity in some species  mouth-brooding: where male picks up tadpole and keeps them there or in vocal pouch until they metamorphose (Rhinoderma)  pouch-brooding, in “marsupial” frogs (Hemiphractids), develop in pouch on back of female; in Pipa pipa, eggs become enveloped in back of females’ skin and developed and burst out of skin fully formed 

Study Guide Exam 1: Herpetology

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 diverse but mostly found in the tropics  GYMMOPHIONA (caecilians “naked snake”)  elongate and limbless, burrowing amphibians, both terrestrial and aquatic, very secretive, non-observable, not much known because of this  many features reduced because of burrowing nature; no limbs or pectoral/pelvic girdle in extant species; eyes greatly reduced and often covered by skin (even possibly bone); reduced but present dermal scales; annular grooves; tentacles on their head (specialized chemosensory organ extending out of an opening in the skull between the eye and nostril); narrow, heavily ossified skulls  internal fert, males have copulatory organ called phallodeum  mostly show oviparity, 5-1000 eggs, females remain with eggs until they hatch; lay eggs in moist environments which hatch into free living aquatic animals who have gill openings, caudal fin, and lateral line system (all of these traits are lost during metamorphosis); some oviparous species have dermophagy (larvae eat outer layer of mothers skin, she regenerates, and they eat it again, shown in no other species)  direct development evolved early on, Vivparity evolved separate in at least 3 families; young eat the lining of the oviduct  mostly pantropical, not found in Australia or on islands, patchy distributions REPTILIA(diapsids: 2 openings in the skull): - Cloaca: posterior cavity that digestive, reproductive, and urinary cavity tracts enter into (norm of the tetrapod) - Amniotes: anything but amphibians and fish (has a hard shelled egg with a yolky center covered in 4 membranes); Synapomorphies of amniotes: yolk sac filled with nutrients to support embryo, amnion (protection to embryo), chorion and allantois (primary for gas exchange and nitrogenous waste storage); in viviparous amniotes these are modified into an embryotic portion of the placenta); amniotic egg was key adaption because it broke the dependency on water for reproduction, which allowed further disposal from water sources into new terrestrial niches - Early amniotes were anapsid and then synapsid developed in mammals and extinct lineages; reptilia gave rise to openings in the skull in the temporal region

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Reptiles split into two main groups: Lepidosauria (squatmata and rhycnocephalia) and Archosauria (testudines, crocodylia, aves, dinosauria) Synapomorphies of Lepidosauria: transverse cloaca (side>side rather than anterior>posterior); ecdysis: regular shedding of epidermis; osteoderms  SQUAMATA(Lepidosauria, lizards and snakes)  cosmopolitan, except extreme arctic and antarctic  hemipenes: pair of copulatory organs (does not reside within cloaca, stored in out pocketing of hind wall of vent)  often elaborate ornamentation, that can be species specific  two patterns of tooth attachment: acrodont (tooth attached to crest of jawbone) and pleurodont (tooth attached to lingual side of jawbone)  mostly oviparous; Vivparity has evolved independently over 100x (20% are viviporous), viviparous species have rudimentary placenta that transport gas and water but several lineages have evolved an elaborate placenta that transports nutrients  parthenogenesis has evolved in many species (reproduction from an ovum without fertilization); reproduce asexually and genetically identical offspring, all female  determination of sex: temperature dependent and sex chromosomes  can “drop” tail (continues moving up to 30 min) as an escape mechanism from predators; some have intervertebral autonomy between breaking vertebrae and most have intravertebral autonomy (vertebral breaking); several caudal vertebra have fracture planes that can control when to release tail  limb reduction, evolved independently many times, completely limbless 25+ times; completely limbless: snakes, amphisbaenas, and dibamidae  venom and their delivery systems evolved many times  RHYNOCEPHALIA(Lepidosauria, tuatara, located only in New Zealand)  Sister to squatmata, highly diverse in Mesozoic but the Tuatara is the only surviving lineage, extinction coincides with the rise of the squatmata  Dig burrows (or take over burrows of sea birds), nocturnal but may bask at opening of burrow, communal nester (females migrate to communities to nest), only breed every 2-4 years and lay around 9 eggs per clutch; takes about 11-16 months to hatch,

Study Guide Exam 1: Herpetology tempterature dependent sex determination, mature in 11-13 years but take 25+ years to grow to adult size, 60 year life span.  TESTIDUNES(Archosauria, turtles, tortoises, terrapins)  Cosmopolitan including the ocean, anapsid skull (no openings, secondarily evolved), keratinous beak (lost teeth); pectoral and pelvic girdle with ribcage inset; shell in two parts plastron (ventral) and carapace (dorsal); shell develops as a fusion of vertebral column and laterally compressed ribs (everything grows together, think Charlie)  Fertilization internal via penis; courtship very elaborate, temperature dependent sex determination.  Split into two clades: o Pleurodira: fold “snake like” neck along the side of the body; 3 families of gondwanan fresh water turtles o Cryptodira: “hidden neck” turtles; can retract neck straight into its shell, freshwater, terrestrial, marine (basically everything else)  CROCODYLIA(Archosauria, crocodiles, gharials, and alligators)  Mostly pantropical, thecodont teeth (teeth set into the jawbones)  Freshwater, brackish, and marine  Most socially complex behaviors, communicate using roars, grunts, coughs, purrs, chirps.  Internal fertilization via penis, elaborate courtship, and very extensive parental care. ORIGINS OF TETRAPODS  It is unique of tetrapods to develop Vivparity multiple times  challenges of land dwelling 1. Gravity: Skeletal system for support 2. Feeding: cannot suction feed as in water 3. Desiccation: must prevent water loss 4. Breathing: gill filaments collapse to gravity  In the late Devonian (385-360 mya), several fossil fish species start to show adaptation to overcome these challenges.  Tetrapodomorpha - all taxa more closely related to extant tetrapods than to lungfish (develops into…) A) Eusthenoptera - ~1.8m, fully aquatic in shallow marine water, pectoral fin had bones that were homologous to humerus, radia, ulna. Pelvis fin has bones homologous to femur, tibia, and fibula in tetrapods B) Panderichthyes - appeared to “walk” along the bottom of shallow water habitats, dorso-ventrally flattened, lacks dorsal fin, reduced tail fin, more

Study Guide Exam 1: Herpetology robust pectoral girdle though still attached to skull, eyes located dorsally, middle ear modifications similar to tetrapods C) Tiktaalik - similar to Panderichthyes, lacks operculum which allows flexibility of the neck, pectoral and pelvic girdles more robust, appears to be able to prop itself up D) Acanthostega - even more robust p and p girdles, more distinct neck with cervic vertebra, forelimbs and hindlimb have eight boney digits homologous to phalanges, primarily aquatic not believed to walk on land, starts to resemble modern salamander E) Ichthyostega - highly-developed girdles, very distinct neck vertebra, 7 digits in hind limb, forelimb unknown, bendable elbows, vertebral column strongly reinforced by connection between vertebra, ribs expanded into distinct rib cage which implies lungs and gills, did spend time of land (lungfish) 

Batrachomorpha: everything closely related to Amphibians

and then…. Tetrapoda - most recent common ancestor of Acanthostega and extant tetrapods (mammals, reptiles, amphibians, birds) and all descendants ** All contemporaneous and extinct 385-360 mya...