amphibians, reptiles, birds Flashcards
(19 cards)
What is a tetrapod?
A vertebrate that has limbs and is capable of moving on land.
When did the first tetrapods appear?
~365 mya (late Devonian period).
What are the three major lineages of living tetrapods?
- Amphibians
- Mammals
- Reptiles
What is the limbs-from-fins hypothesis?
The hypothesis that limbs evolved from the fins of lobe-finned fishes.
What is the significance of lungfishes in the study of tetrapod evolution?
Most living species inhabit shallow, oxygen-poor water and breathe with lungs.
Which ancient fish is known for its lobe-like fin?
Eusthenopteron (~385 mya).
What is a key feature of the limb structure in tetrapods?
Each fin or limb has a single bony element closest to the body, articulating with two bones next to a series of elements farthest from the body.
What are the primary characteristics of amphibians?
- First tetrapods to live on land
- Lay eggs in water
- Undergo metamorphosis
- Gas exchange occurs across skin
What does ‘autotomy’ refer to?
Self-severing or self-amputation.
What is an amniote?
A lineage that includes all tetrapods other than amphibians.
What is the purpose of the amniotic egg?
Protective covering that reduces the rate of drying.
What are the four inner membranes of the amniotic egg?
- Amnion
- Yolk sac
- Allantois
- Chorion
What adaptations do reptiles have for life on land?
- Watertight skin composed of keratin
- Well-developed lungs
- Shelled, amniotic eggs
What are the four major lineages of reptiles?
- Lizards and snakes
- Turtles
- Crocodilians
- Birds
What are feathers primarily composed of?
Keratin.
How did flight evolve in birds?
Feathers evolved in steps, with adaptations making powered, flapping flight more efficient.
What are some hypotheses regarding the origin of flight in birds?
- Flight evolved from running species that jumped and glided
- Flight evolved from tree-dwelling species that glided
What adaptations were necessary for flight in birds?
- Reduced size compared to ancestors
- Development of hollow bones
- Retention of juvenile proportions in heads
