Amphibians and Reptiles
- Created by: Louis James
- Created on: 08-01-13 13:31
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Biological diversity - amphibians+reptiles
- subclass Vertebrata: the tetrapods
- fossils - Devonian
- Sarcopterygiian fish. (Eusthenopteron)
- Intermediate forms - some amphibian+some fish characteristics. (Tiktaalik+Livoniana)
- Tetrapods - amphibian characteristics (Acanthostega)
- tracks found - 400 mya - indicative - tetrapod gait+limb position
- limb position not splayed - digits distinct+separate
- unlikely earliest vertebrates - very terrestrial. pelvic+pectoral girdles unable - support weight - long
- Carboniferous (300 mya) - giant amphibians = Labyrinthodonts
- like giant salamanders - limbs, pelvic+pectoral girdles strengthened - support weight
- gas exchange - lungs+skin - size attainable - O2 concentration increased - Carboniferous. modern amphibian sixe limited - atmosphere O2 availability
- subclass vertebrata: class Amphibia
- frogs+salamanders - 2 different groups 250 mya
- intermediate form = frogmander - both features
- 1st modern frog - fossil 70 mya
- 3 orders, 7000 species
- Anura (frogs+toads)+Caudata (newts+salamanders)+Gymnophiona (caecilians)
- class Amphibia: order Gymnophiona
- population - giant (1m long) caecilians - Brazil 2011
- largest lungless vertebrates. sealed nostrils
- muscles - jaw not seen - any vertebrates
- Caecilians diverged - salamander-like ancestors. early
- fossil record poor: Eocaecilia = primitive caecilian - limb - buds
- burrowing+aquatic lifestyles - limblessness (snakes = convergent evolution)
- high levels - parental care
- subclass Vertebrata: class Amphibia
- ectothermic - temperature varies - environment
- most - metamorphosis. aquatic herbivourous tadpoles - carnivorous adults
- moist permeable skin - gas exchange
- diverse reproductive strategies+life histories increased global distribution
- class Amphibia: order Caudata
- newts+salamanders
- relatively unchanged - body form - ancestral tetrapods
- many vertebra, reduced ribcages, long postanal tail
- more aquatic - adults+post metamorphic juveniles: emerge onto land - feed+hibernate
- respiratory systems = diverse
- gills = internal (amphiuma)+external (axolotl)
- lungs = newts need - surface (guff)
- both = cave olms
- neither = lungless salamanders breathe via skin
- neoteny/paedomorphy = retention - juvenile characteristics, adults - caudates = common
- lungless salamanders = tiny (skin breathing limits size) suggets evolution through neotomy
- Bolitoglossids paedomorphic features evident - feet = reduced, cartilaginous digits - suction pad
- class Amphibia: order Anura
- frogs+tails = more terrestrial - caudates
- specialised - jumping locomotion
- long, muscular hind legs, reduced ribcage, short vertebra, fused hip+tarsal bones, caudal bones - urostyle
- well developed lungs - reduce dependency - skin, gas exchange - exploit dry environments
- toads = keratinised skin cells = lower permeability
- Phyllomedusine tree frogs apply waxy lipid layer
- casque - headed frogs: ossification - skin - head
- tree frogs…
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