Which of the following statements about skeletons is true?
a. Chi...

Question

Which of the following statements about skeletons is true?
a. Chitin is a major component of vertebrate skeletons.
b. Loss of forelimbs in snakes involved little change in the axial skeleton.
c. Most cnidarians must shed their skeleton periodically to grow.
d. Vertebrate bones contain living cells.

Accepted Answer

Hi everyone. Welcome back. Here's our next question. How do mollusks adjust their exoskeletons while they grow? Well let's look through our answer choices here. We've got choice A. They shed their exoskeletons and replace them with larger ones. Well this is not correct. That's arthropods that do this along with some other animals. But arthropods have an exoskeleton made of chitin and once it hardens it can't expand. So as they grow they need to shed the whole thing and grow a new one. But mollusks have shells made of calcium carbonate, not kitten, so they have a different strategy and that's in choice B. Here they enlarge the diameter of their shell by adding to their outer edge. And mollusks have this mantle which is an extension of their bodily tissue and it secretes calcium carbonate. So as they grow and spread they just secrete another layer gets added to the outer edge. Makes their exoskeleton their shell larger. So that's pretty straightforward there. Um Well just to be thorough look at the other answer choices. I see they look for bigger empty shells and use them. Um That would be like hermit crabs. Not what models do they keep the same shell. Just keep on secrete calcium carbonate to make it larger and choice d they adjust their muscles so they will still fit in their shells. That's not correct. They're growing getting bigger and just expand the diameter of their shells. So again how do malice congest their exoskeletons while they grow? Choice B. They enlarge the diameter of their shell by adding to the outer edge. See you in the next video.

Which of the following statements about skeletons is true? a. Chitin is a major component of vertebrate skeletons. b. Loss of forelimbs in snakes involved little change in the axial skeleton. c. Most cnidarians must shed their skeleton periodically to grow. d. Vertebrate bones contain living cells.

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