BIOL1263 Lecture 9 Amphibians and Reptiles 2024 PDF

BIOL1263 Living Organisms II 9. Conquest of the land II: Amphibians and Reptiles One group of lobe-finned fish gave rise to the tetrapods. Amphibians are limited to damp habitats by water loss from skin used in gas exchange, and aquatic larvae. Amphibians have lungs filled by buccal pumping,...

BIOL1263 Living Organisms II 9. Conquest of the land II: Amphibians and Reptiles One group of lobe-finned fish gave rise to the tetrapods. Amphibians are limited to damp habitats by water loss from skin used in gas exchange, and aquatic larvae. Amphibians have lungs filled by buccal pumping, and double circulation with a three-chambered heart. Orders Gymniophona (caecilians – blind burrowers); Urodela (salamanders – tailed); Anura (frogs – tailless). Reptiles have the amniote egg, with four extraembryonic membranes, allowing terrestrial development. Reptiles also have waterproof skin, more complex lungs, uric acid excretion, behavioural thermoregulation. Orders Testudines (turtles – shell); Squamata (lizards and snakes – scales); Crocodylia (crocodilians – parental care). 1 Origin of the Tetrapods The tetrapods evolved from a third branch of lobe-finned fish which combined muscular fins with bones, and lungs. The first amphibians appeared 370 mya. 2  Phylogeny of the Tetrapods Modern amphibians (Lissamphibians) are monophyletic, appeared about 250 mya; other amphibian taxa extinct; anamniotes. 3  Terrestrial living Some terrestrial benefits: High oxygen content in air; Varied habitats for exploitation Some terrestrial costs: Low substrate density – requires strong limbs and skeletal adaptations; Highly variable temperature – requires thermoregulatory strategies 4 Amphibians – incompletely terrestrial animals Features of non-arthropod land invertebrates: a) Internal fertilisation – Not in most amphibians b) Direct development – Not in most amphibians c) Limited to damp environments – Yes Frog eggs in water – mostly jelly 5 Amphibian simple life cycle, indirect development 6 Cutaneous respiration in amphibians Amphibian skin – epidermis thin compared to dermis, poorly keratinised outer layer 7 Respiration in amphibians Ventilation of lungs by buccal pumping https://www.youtube.co m/watch?v=Pct4xaFp4i8 8 A poll! Respiring through the skin limits amphibian diversity in some habitats due to ____ loss 9 Amphibian double circulation Fish Functional separation by Oxygenated blood Deoxygenated blood conus arteriosus. 3 chambers 10  Classification of Amphibians Class Amphibia Living species Order Anura (frogs and toads) 4000 Order Urodela (salamanders) 450 Order Gymnophiona (caecilians) 200 Caecilians – limbless, worm-like, burrowing tropical amphibians; internal fertilisation, mostly with live young, blind. 11 Order Urodela – salamanders and newts Newt egg Plethodon sp. Ambystoma sp. – Axolotl Lungless salamander, Paedomorphic adult https://www.youtube.com/watch?v=uQi- respires through skin yDXBn9c 12 Order Anura – frogs and toads Rhinella marina Xenopus sp. Cane toad – native here, African clawed frog – introduced to control cane research in molecular, cell, pests on other islands and developmental biology13  Order Anura – frogs and toads Golden tree frog Glass frog https://www.youtube.com/ https://www.youtube.com/w watch?v=cBkWhkAZ9ds Rain frog atch?v=mZ7b4spjXhw Suriname toad  The amniote egg Pore Four extraembryonic membranes: chorion (below the shell); amnion (surrounds embryo); yolk sac (stores food); allantois (stores waste). Calcified shell with pores for gas exchange. https://www.youtube.com/watch?v=Qq0kMEWzdHg 15 Nitrogenous excretion Very soluble in water Not very soluble in water – little water loss 16 Reptile skin - waterproof Squamates – Crocodiles – scales Turtles – dermal scales and osteoderms bones and scutes 17 Reptile lungs – more efficient than those of amphibians Amphibian lungs: frog Reptile lungs: A) crocodile; B,D) lizards, C) turtle. Greater surface area; Movement of rib cage 18 Reptile behavioural thermoregulation Ectotherms use external heat source; poikilotherms allow body temperature to fluctuate. 19  Endothermic Ectothermic Homeothermic Poikilothermic http://minerva.union.edu 20 Repeat Poll! What sort of taxon is “Reptiles”? 21 Classification of living reptiles – a paraphyletic taxon Class Reptilia Living species Order Testudines (turtles) 350 Order Squamata (lizards and snakes) 9,600 Order Crocodylia (crocodilians) 25 22 Order Testudines – turtle shell and nesting Scutes (left) Bones (right) Tortoise hatching from calcified egg Dermochelys coriacea Leatherback sea turtle 23 Order Testudines – turtles and tortoises Kinosternon scorpioides Chelonia mydas Scorpion mud turtle Green sea turtle Chelonoidis denticulata Apalone spinifera Yellow-footed tortoise Softshell turtle 24  Order Squamata – lizards Iguana iguana – green iguana Skink https://www.inaturalist.org/observations?pla ce_id=7375&subview=grid&taxon_id=35342 Anguis sp. – slow worm Amphisbaena alba – amphisbaenian 25  Order Rhynchocephalia -Tuatara: Not a lizard… (or a Squamate) Differs in skull and jaw structure https://www.theguar dian.com/world/202 4/sep/26/henry- new-zealand- tuatara-age-130 Henry - Reproductively active at 130 years old 26  Order Squamata – snakes Micrurus lemniscatus – large coral Chemical senses Kinetic skull Toxins: Neurotoxic; haemorrhagic Lachesis muta – bushmaster, Mapepire zanana 27  Order Squamata – snakes Leathery eggs Live birth Leptotyphlops sp. – worm snake Eunectes murinus – anaconda  Order Crocodylia – Archosaurs (with birds) Caiman crocodilus – Alligator female at nest spectacled caiman Mostly unchanged for 200m years Sex is temperature-dependent 4-chambered heart (convergent with birds and mammals) Female Nile crocodile with hatchling 29  Field guide for T&T! Ask at Zoology Museum or ttfnc.org 30