11.1.9 11.4–11.12: Invertebrates—animals without a backbone—are the most diverse group of animals.

Invertebrates, defined as animals without a backbone, are the largest and most diverse group of animals comprising 96% of all living animal species. The invertebrates are not a monophyletic group, however, and include protostomes and some (but not all) of the deuterostomes.

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Question 11.17

Sponges are sessile, meaning that they:

  • a) reproduce asexually.
  • b) are parasitic and depend on their host for a constant supply of nutrients.
  • c) have exoskeletons that they must shed as they grow.
  • d) live within shells they find on the ocean floor.
  • e) live attached to a solid structure and do not move around.

Question 11.18

In cnidarians, cnidocytes are primarily used for:

  • a) creation of water flow across the body wall.
  • b) formation of free-living medusas.
  • c) secretion of digestive enzymes.
  • d) prey capture and defense.
  • e) muscular contraction during movement.

Question 11.19

The mollusk’s mantle is used primarily for:

  • a) feeding.
  • b) gas exchange.
  • c) producing the shell.
  • d) excretion.
  • e) reproduction.

Question 11.20

The phylum Arthropoda includes all of the following kinds of animals except:

  • a) snails.
  • b) crabs.
  • c) crayfish.
  • d) butterflies.
  • e) scorpions.

Question 11.21

For which of the following groups of organisms is it most difficult to estimate species numbers?

  • a) bees, wasps, and ants
  • b) bacteria
  • c) tropical trees
  • d) beetles
  • e) mammals

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Question 11.22

Which of the following echinoderms has radial symmetry during its larval stage?

  • a) sea star
  • b) brittle star
  • c) sea urchin
  • d) sand dollar
  • e) None of the above have radial symmetry during the larval stage.

Question 11.23

Which one of the following characteristics distinguishes all chordates from all other animals?

  • a) a vertebral column
  • b) a dorsal hollow nerve cord
  • c) collar cells
  • d) bilateral symmetry during embryonic or larval development
  • e) an amniotic egg

Question 11.24

Which of the following are chordates?

  • a) fishes
  • b) humans
  • c) frogs
  • d) All of the above are chordates.
  • e) Only a) and c) are chordates.

Question 11.25

Which of these animals is a tetrapod that does not produce amniotic eggs?

  • a) salamander
  • b) human
  • c) monkey
  • d) elephant
  • e) python

Question 11.26

Why is the amniotic egg considered a key evolutionary innovation?

  • a) It prohibits external fertilization thereby facilitating the evolutionary innovation of internal fertilization.
  • b) It has an unbreakable shell.
  • c) It greatly increases the likelihood of survival of the eggs in a terrestrial environment.
  • d) It enables eggs to float in an aquatic medium.
  • e) It extends the time of embryonic development.