Lecture 31 Amphibians Flashcards
what are derived characters of tetrapods?
- have some specific adaptations
- four limbs, feet with digits
- a neck, which allows separate movement of the head
- fusion of the pelvic girdle to backbone
- absence of gills (except some aquatic species)
- ears for defecting airborne sounds
what are two groups of the extant tetrapods?
- amphibia
- amniota
what was an early amphibian?
ichthyostega: ancient semi-terrestrial tetrapod which was an amphibian in build and habitat
- primitive fish-like traits: tail with fin rays, gills, more than five digits (terrestrial vertebrates were until recently thought to be descended from ancestors with 5 digits per limb)
what are derived traits of early amphibians?
- amphibian skull structure
- limbs attached to vertebrae (3 part pelvis)
- weight bearing joints (wrists, elbows, knee, ankle)
- lungs as a primary breathing apparatus
- forelimbs for locomotion and tail for balance
what are characteristics of amphibians?
- ectothermic
- buccal pump to inflate lungs
what makes a species ectothermic?
- cold blooded
- dont maintain their body temp through internal physiological processes – rely on environmental factors
- low metabolic rate (low food and energy requirements)
- require constant temperature environment or behavioural thermoregulation
what is the buccal pump?
- air drawn into the oral/throat cavity through nostrils or mout
- mouth and nostrils are sealed and cavity is contracted to force lungs into the mouth
what are characteristics of amphibians?
- ectothermic
- buccal pump to inflate lungs
- three chambered heart (2 atria, 1 ventricle)
- gills (in larvae, retained into adulthood by some salamanders)
- life cycle tied to water
what is the buccal pump?
- air drawn into the oral/throat cavity through nostrils or mout
- mouth and nostrils are sealed and cavity is contracted to force lungs into the mouth
- in amphibians this is the sole mean of inflating the lungs
what kind of fertilization do amphibians exhibit?
external, almost all are in water
what is the amphibian life cycle?
“amphibian” – both ways of life
- refers to the metamorphosis of aquatic larva into terrestrial larvae
- remains very fishlike, not fully adapted to land
- most lay eggs in water
what are the three extant orders of amphibians
- urodela: salamanders which have tails
- anura: frogs and toads which lack tails in adult stages
- apoda: includes caecilians which are legless and resemble worms
what is order anura?
- lose tails in adult stage
- long hind legs are modified for jumping but lack legs in early larval stage
- vocal cords well developed
- ear modified for reception of airborne sound waves
- some spp exhibit parental care
- toads differ from frogs in having poison glands behind eyes
- most feed on algae as larvae and invertebrates, sometimes vertebrates in adults
- frog tongue - attached in front of the mouth, hydraulic pressure
what is order Urodela?
- salamanders and newts
- superficially lizard like appearance
- have tails as larvae and adults
- larvae have external gills, some remain aquatic, some become terrestrial
- typically lay eggs in water and have aquatic larvae but also great variation in lifecycles
- walk rather than jump
- legs set laterally, long backbone
- move slowly on land with lateral movements – less energetically efficient
- predators of invertebrates as larvae and adults
- members of one genus can flick their tongues like frogs
what is order apoda?
- caecilians
- legless amphibians, superficially resemble worms or snakes
- legless
- tiny eyes, no hearing, thick skull, tiny sharp teeth
- burrowers
- all caecilians use internal fertilization
- most are viviparous, some with maternal care