20.1–20.6: Animal body structures reflect their functions.

At all levels of animal organization, from molecules to whole organisms, the physical features of a structure are closely related to its function.

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Question 20.20

Which of the following is not one of the major categories of vertebrate muscle cells?

  • a) smooth muscle
  • b) cardiac muscle
  • c) respiratory muscle
  • d) skeletal muscle
  • e) All of the above are major categories of vertebrate muscle cells.

Question 20.21

Neurons generally have all of the following components except:

  • a) dendrites.
  • b) a cell body.
  • c) an axon.
  • d) glial processes.
  • e) a nucleus.

Question 20.22

With the exception of _______, all animals have some tissues organized into organs.

  • a) sponges and some cnidarians
  • b) insects
  • c) roundworms and flatworms
  • d) sponges and insects
  • e) amphibians

Question 20.23

Which of the following explains why complex multicellular organisms face a major challenge in maintaining homeostasis?

  • a) Most of the body cells are not in direct contact with the external environment.
  • b) Most of the body cells are protected from harsh or changing environmental conditions.
  • c) There is less extracellular fluid from which to gather nutrients.
  • d) There are more chemical reactions per cell that require energy and nutrients.
  • e) Nutrients and waste materials enter or leave the cells too quickly.

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