Amphibians Flashcards
Origins of the tetrapods:
- devonian origins
- lobe-finned fish as ancestors
- aquatic origins of legs
- possible advantages in colonisation of land
Modern class of amphibia and its three orders…
- Apoda
- Urodela
- Anura
Transitional group>?
- first vertebrate to live on land, but early amphibians retained fish-like features
- from amphibians, the amniotes evolved, radiating into reptiles, birds & mammals
Opposed view of modern amphibians
-they are animals which have failed to make full transition from water to land
or
-they exploit a common habitat (margins of freshwater & terrestrial environments)
origins of tetrapod
- when animals first evolved with 4 legs (tetrapods) in the mid -to late Devonian
- 391-385mys
Order Gymnophiona - the caecilians (APODANS)
- the leg-less amphibians
- burrowing, worm-shaped tropical animals
Order Caudata - newts and salamanders (URODELES)
- the tailed amphibians
- primarily north temperate
- most are interphase (aquatic & terrestrial)
- plethodontids -terrestrial and lungless
Order Anura - the frogs and toads
- the tail-less amphibians
- worldwide distribution
- hindlimbs powerful for jumping
- some aquatic, some terrestrial, some interphase
- most abundant group of amphibians
- 1/3 species endangered
toad vs frog
frogs-moist skins, poweful hindlimbs for jumping, wetter habitats
toads - drier skins, slimmer hindlimbs for running
success and characteristics
- ectotherms
- aquatic eggs and larvae
- skin restricts colonisation of some terrestrial habitats(moist)
poikilothermic
body temp closely tracks environmental temperature
bimodal respiration
-both lungs and skin used as respiratory exchange surfaces
adaptions to adapt to terrestrial environments
- waxy skin secretions to minimise water loss
- bladder = water reservoir
- water absorption through skin in absence of free water
caecilians
frogs
salamanders
