chapter 40 section 1

Question 1

ossicle

Answer 1

a calcium carbonate plate that makes

up the endoskeleton of an echinoderm;

Question 2

test

Answer 2

a test is
the compact, rigid endoskeleton of a sea urchin or
sand dollar.

Question 3

tube foot

Answer 3

A tube foot is a small, movable extension of an
echinoderm’s water-vascular system that aids in
movement;

Question 4

ampulla

Answer 4

; an ampulla is a bulblike sac at the

upper end of each tube foot

Question 5

both echinoderms and chordates

Answer 5

are deuterostomes

Question 6

One characteristic that is found only in echinoderms is

Answer 6

water vascular system

Question 7

The surface that is opposite the mouth in a sea star is called the

Answer 7

aboral surface

Question 8

Sexual reproduction among sea stars usually involves

Answer 8

separate sexes and external fertilization.

Question 9

What do the larvae of echinoderms indicate about the evolution of echinoderms?

Answer 9

Echinoderm larvae are bilaterally symmetrical,
which indicates that echinoderms probably
evolved from bilaterally symmetrical ancestors

Question 10

Describe the organization of a sea star’s nervous system

Answer 10

A nerve ring circles the mouth, a radial nerve runs
from the nerve ring along the length of each arm,
and a nerve net extends near the body surface. The
sea star also has an eyespot near the end of each
arm and several tentacles that respond to touch.

Question 11

Why is the lack of cephalization not a disadvantage for a sea star?

Answer 11

Since sea stars are radially symmetrical, no particular
part of a sea star always leads when the animal
moves through its environment. Therefore,
there is no advantage to having sensory structures
and a neural center concentrated at one end.