Chapter 32 Review

Question 1

cleavage

Answer 1

succession of rapid cell divisions without significant growth during early embryonic development; converts zygote to a ball of cells

Question 2

blastula

Answer 2

a hollow ball of cells that marks the end of cleavage stage during early embryonic development in animals

Question 3

gastrula

Answer 3

stage that encompasses the formation of three germ layers

Question 4

larva

Answer 4

free-living, sexually immature form that may differ from the adult animal in morphology, habitat, and nutrition

Question 5

metamorphosis

Answer 5

a developmental transformation that turns an animal larva into either an adult-like stage that is not yet sexually mature

Question 6

Common ancestor of living animals

Answer 6

may have been a suspension feeder similar to present-day choanoflagellates

Question 7

2 hypotheses for the Cambrian Explosion

Answer 7

1. Predators acquired new adaptations to help them catch prey, while prey acquired new defenses. Natural selection could have also led to the decline and rise of species.
2. There could have been an increase in atmospheric oxygen.

Question 8

grade

Answer 8

a group of organisms that share the same level of organizational complexity or key adaptation

Question 9

body plan

Answer 9

a set of morphological and development traits that are integrated into a functional whole

Question 10

radial symmetry

Answer 10

symmetry in which the body is shaped like a pie or barrel and can be divided into mirror-imaged halves by any plane through its central axis

Question 11

bilateral symmetry

Answer 11

body symmetry in which a central longitudinal plane divides the body into two equal but opposite sides

Question 12

dorsal

Answer 12

pertaining to the top of an animal with radial/bilateral symmetry

Question 13

ventral

Answer 13

pertaining to the bottom of an animal with radial/bilateral symmetry

Question 14

anterior

Answer 14

pertaining to the front of a bilaterally symmetrical animal

Question 15

posterior

Answer 15

pertaining to the rear of a bilaterally symmetrical animal

Question 16

cephalization

Answer 16

an evolutionary trend toward the concentration of sensory equipment at the anterior end

Question 17

germ layers

Answer 17

one of the three main layers in a gastrula

Question 18

endoderm

Answer 18

innermost layer; gives rise to liver, pancreas, lungs; lines archenteron, digestive tract

Question 19

ectoderm

Answer 19

outermost layer; gives rise to outercovering and sometimes nervous system, inner ear, and lens of the eye

Question 20

archenteron

Answer 20

endoderm-lined cavity that develops into digestive tract