Question

which of these are correct characteristics of all extant vertebrates?

a. triplobastic

b. The opening formed first during gastrulation becomes the mouth

c.cranium d. internal fertilization

e.amniotic egg

f. close circulatory system

4. The presence of a swim bladder allows the typical ray-finned fish to:

a. store food

b.use its lateral line system

c.breath air underwater

d. amplify the sound of predators nearby

e. Reduce the energy required for swimming

Answer 1

The answer should be Cranium.

There are many triploblastic animals (even non-chordates). Vertebrates are deuterostomes (first opening become anus, not mouth which is the case in protostomes). Internal fertilization is not the case in all vertebrates (like fishes or amphibians). Same as amniotic egg (only in birds and mammals). Only vertebrates have a cranium and all the extant vertebrates have a cranium.

4. Reduces the energy required for swimming.

The swim bladder is an organ filled with gas inside the body of bony fishes and helps to control their buoyancy. It has a flexible wall which can contract or expand depending on their surrounding pressure. It helps the fish to maintain their depth without spending any energy.