Amphibians Flashcards
What were the reasons for fish to move onto land?
Cyclic weather and drying so less habitat for fish
Abundant prey on shore
Escape from marine predators
How do we track the evolution onto land?
The evolution of limbs
What happened during the evolution of limbs as fish came onto land?
Decreased number of fingers - evolved the pentadactyl limb
Got thicker and shorter
Acanthostega - had 8 fingers
Ichthyostega - had 6 1/2 fingers
Eryops - had 5 fingers
What is proposed to be the closest ancestor to the tetrapods?
An ancestor of the lungfish
Had lungs and nostrils
Had eggs and larval stages - like modern day amphibians
Mitochondrial DNA of lungfish is the closest match to modern day amphibians
What period did the amphibians dominate?
The carboniferous
Are amphibians monophyletic?
Yes
What were the challenges to moving onto land?
UV light
Physical support
Sensory modification
Variable temperatures
Water loss through breathing air
Water loss through skin and excretion
Desiccation of sperm and eggs
What are the main features of amphibians?
Lungs
Epidermis
Chromatophores which absorb UV
Some keratin to reduce water loss
Mucous to protect the skin and help reduce water loss
Blood capillaries in skin to allow gas exchange
Has skeleton and paired appendages
Pentadactyle hind limb
How are amphibians adapted as they mature into an adult?
Lateral line system lost
Change in eye shape and form tear ducts
Evolution of an ear
Divided intestine (large and small)
Gills in larvae and lungs in adults
Ectothermic
3 chambered heart
What was the ancient amphibian?
Labyrinthodonts
Also gave rise to the reptiles
What are the three types of modern amphibians?
Newts and salamanders
Frogs and toads
Caecilians
What is neoteny?
Sexual maturity is reached in larval stage
What are the main features of caecilians?
Subterranean and tropical
Most are blind but can distinguish light/dark
Tentacles are probably olfactory (along with nose)
Worm like due to convergent evolution
