Lecture 16 – Chordates and the emergence of Vertebrates
Know 4 characteristics shared by all Chordates
Understand that chordate features are only seen in larval Urochordates (ascidians).
Could the ancestor of all vertebrates have been an early-maturing ascidian larva? Why or why not? Compare this idea to the hypothesis that the first Bilaterian may have been a larva of a primitive Cnidarian.
Know the distinctive characteristics of the vertebrates (subphylum Vertebrata ) .
Referring to the phylogenetic tree of vertebrates, know when major features appeared that contributed to the success of different groups.
What primitive features do hagfish and lampreys possess?
What characteristics made the fish belonging to groups Chondrichthyes + Osteicthyes so successful? Why are bony fish much more speciose than sharks + rays?
Understand that the ancestor of modern bony fish had a lung . Why was this an important preadaptation to life on land for some descendents of this ancient fish? What did the ancestral lung evolve into in modern ray-finned fishes?
Why are most commercial fisheries at the point of collapse?
Understand how, through natural selection, vertebrates became adapted to survive in terrestrial environments (meaning on dry land). As you move from fish to reptiles to birds + mammals, know how these features changed:
- fish scales
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tough scales covering reptiles
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feathers and hair
- fins
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limbs (tetrapods)
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wings (birds, bats)
- external fertilization
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internal fertilization
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amniotic egg
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placental mammals
- ectothermy
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endothermy (what 2 groups are endothermic?)
Compare amphibians and bryophytes; why are both groups still tied to water?
What feature is made of keratin in reptiles? birds? mammals? What function does each feature serve?
What specific effect may global warming have on reptile populations? Why? How might this affect their chances for survival in the next century?
Discuss some of the adaptations that make snakes effective predators.
How long ago did chimpanzees and humans share a common ancestor?