Biodiversity 6: Amphibians Flashcards
Give 3 reason why life may have evolved to land?
- Cyclic weather and drying conditions predominantly the late Devonian so less habitat for fish
- Abundant prey on shore (arthropods, abundant on land due to little predators)
- Escape from fearsome marine predators
Describe the adaptations the first tetrapods had to life in shallow swamps
Heavy skeletal struc of fins
Lungs and internal nostrils
Describe the Tiktaalik
Transition form between fish (gills and scales) and amphibians (sturdy fins)
Beginnings of a mobile neck → useful for eating prey (insects) and looking for predators
What is the closest ancestor of the tetrapods?
Lungfish
Lungs
Nostrils
Egg and larval stages like modern amphibians
Mitochondrial DNA shows it is the closest ancestor of the tetrapods
Which class dominated during the carboniferous?
Amphibians
Give some examples of amphibians
Salamanders, frogs, caecilians
What are some changes presented by life on land?
UV light (can burn thin skin)
Physical support → need bones, muscles
Sensory modification
Variable temperature → ocean temp more stable
Water loss through breathing air
Water loss through skin and excretion
Desiccation of sperm and eggs
Describe how an amphibians epidermis is adapted to life on land?
Chromatophores absorb UV (allow animal to warm itself)
Some keratin, reduced water loss
Mucous protects skin and helps reduce water loss
Blood capillaries in skin allow direct gas exchange
Describe how amphibians skeletons and appendages are adapted for life on land?
Strong vertebrae
Pentadactyl hindlimb
Flexible
= distinctive gait
Describe how an amphibians sensory organs are adapted to life on land
Lateral line system
Change in eye shape, lids and tear ducts in adult stage
Evolution of an ear: simple, 1 ossicle
Describe an amphibians metabolic adaptations to life on land
Intestine divided into small/large → efficient for food absorption
Gills in larvae and lungs in adults
Buckle breathing
Ectothermic → hibernate in winter
3 chambered heart
Other than the lungs, where does amphibians blood receive O2?
the skin (second ‘boost’ of O2
Describe why amphibians range from water is limited
Dehydrate quickly though skin and waste excretion
Require water for reproduction, eggs laid in jelly masses are subject to desiccation
Eggs develop into tadpoles (aquatic larvae with tails and gills) that need water
Give an example of an ancient amphibians
Labyrinthodonts
Describe the labryinthodonts
Ancient amphibian
Named for tooth shape
Dominated Carboniferous and Permian
Semi aquatic, up t 1m long
Also gave rise to reptiles
What organisms belong to the order Urodela?
Newts and salamanders
Describe the Urodela
‘tailed ones’
Newts & salamanders
Aquatic or terrestrial
Particularly abundant in North America
Long trunk, tail, most have well developed limbs
Most closely resemble the ancestral amphibians
Some salamanders are pedomorphic
What does pedomorphic mean? Give an example
→ sexual maturity is reached in the larval stage = neoteny
E.g Axolotl are the reproductive form of the tiger salamander (retain gills and aquatic lifestyle)
What organisms belong to the order Anura?
Frogs and toads
Describe the Anura
‘tail-less ones’
Frogs and toads
Highly diverse in tropics (warm and damp)
Better adapted to terrestrial life than salamanders
Short trunk, no tail
Ribs fused to vertebrae = solid body case that protects internal organs
Powerful hind legs for jumping
Describe the reproductive adaptations displayed by the Anura (+ examples)
Many reproduce in water, but others have evolved to life on land
Example: South African grey tree frogs lay a foam nest above ponds
Example: Male poison dart frog carry larvae on back
Example: Surinam toad’s larvae hatch out of cells on back
What organisms belong to the order Apoda?
Caecilians
Describe the Apoda
‘legless ones’
Subterranean, tropical
Most are blind but some can distinguish light/dark
Tentacles probably olfactory (along with nose)
Worm-like through convergent evolution
What are some potential causes for the major decline in amphibian diversity?
Habitat loss & fragmentation
Introduced predators
Toxic contaminants
Diseases e.g Chytrid fungus
UV radiation
Climate change
