Ecdysozoans

Question 1

is a firm, nonliving covering that is difficult to penetrate and
provides an animal with both protection and support.

Answer 1

exoskeleton

Question 2

pose a huge problem: They cannot grow as the animal body inside
them grows.

Answer 2

Exoskeletons

Question 3

They shed, or molt, the
outgrown exoskeleton and expand and harden a new, larger one.

Answer 3

ecdysozoans

Question 4

The presence of the exoskeleton required the evolution of new forms of

Answer 4

movement and respiration.

Question 5

Some ecdysozoans have wormlike bodies covered by thick and flexible
exoskeletons called

Answer 5

cuticles.

Question 6

three phyla with thin cuticles include the

Answer 6

Priapulida, Kinorhyncha, and
Chaetognatha.

Question 7

allows the exchange of gases, minerals, and water across the body
surface, but restricts the animal to moist habitats.

Answer 7

thin cuticle

Question 8

Their bodies are supported primarily by hydrostatic skeletons, not by their thin
cuticles.

Answer 8

Priapulida, Kinorhyncha, and
Chaetognatha.

Question 9

some wormlike ecdysozoans developed a layer of
protective material called

Answer 9

chitin

Question 10

a strong, flexible, waterproof polysaccharide

Answer 10

chitin

Question 11

does not allow wormlike movement; such animals require
appendages that can be manipulated by muscles.

Answer 11

rigid body

Question 12

evolved several times late in the Precambrian era, leading to the
phyla collectively called the arthropods.

Answer 12

Appendages

Question 13

Appendages evolved several times late in the Precambrian era, leading to the
phyla collectively called the

Answer 13

arthropods