Section 30.1 (Exam 2)

Question 1

What are some characteristics of protostomes?

Answer 1

Triploblastic

Bilateral symmetry

Embryonic blastopore becomes the mouth

Spiral cleavage

Ventral nerve cord

Anterior brain that surrounds entrance to digestive track

Question 2

What are two major derived traits of protostomes?

Answer 2

Anterior brain that surrounds the entrance to the digestive tract

Ventral nervous system with paired or fused longitudinal nerve cords

Question 3

Based on DNA sequencing, what are the two major clades protostomes have been divided into?

Answer 3

Lophotrochozoans and Ecdysozoans

Question 4

Where do lophotrochozoans derive their name from?

Answer 4

Having a trochophore larva and a lophophore.

Question 5

Name the 4 groups that have a lophophore.

Answer 5

Bryozoans, entoprocts, brachiopods, and phoronids.

Question 6

What is a lophophore?

Answer 6

Circular or U-shaped ring of hollow, ciliated tentacles around mouth; functions in food collection

Question 7

Nearly all animals with a lophophore are ________ as adults.

Answer 7

sessile

Question 8

What cleavage do some lophotrochozoans have?

Answer 8

spiral

Question 9

What are some examples of lophotrochozoans with spiral cleavage?

Answer 9

flatworms, ribbon worms, annelids, mollusks

Question 10

What are ecdysozoans?

Answer 10

They have an external cuticle secreted by the epidermis. This cuticle restricts growth.

Question 11

If external cuticles restrict growth, then how do ecdyzoans increase in size?

Answer 11

To grow, the cuticle must be shed, or molted, and replaced with a larger one (ecdysis)

Question 12

What is the process of shedding an ecdysozoans external cuticle called?

Answer 12

ecdysis

Question 13

What is the purpose of the ecdysozoan cuticle?

Answer 13

Protection and support

Question 14

What is the cuticle in arthropods?

Answer 14

An exoskeleton thickened by proteins and chitins

Question 15

What is chitin?

Answer 15

a waterproof polysaccharide

Question 16

What does the exoskeleton do in arthropods?

Answer 16

restrict movements and gas exchange

Question 17

Because the arthropod exoskeletons restrict movement and gas exchange, new mechanisms needed to evolve to complete these functions. What are these mechanisms?

Answer 17

Arthropods have appendages manipulated by muscles for locomotion. Their appendages are also used for gas exchange.

Question 18

What are the uses of arthropod appendages?

Answer 18

Gas exchange, copulation, and sensory perception

Question 19

What were some benefits of the hard exoskeleton of arthropods?

Answer 19

It prevented drying up, which allowed arthropods to walk on dry land.

Question 20

How many species of arrow worms are there?

Answer 20

180 species

Question 21

Why were the evolutionary relationships of arrow worms debated?

Answer 21

The blastopore gave rise to the anal opening, which is a characteristic of deuterostomes, but they also have a ventral nerve cord and spiral cleavage, which is a characteristic of protostomes.

Question 22

Were arrow worms ultimately decided to be protostomes or deuterostomes, and what was it based on?

Answer 22

Gene sequencing identified arrow worms as protostomes.

Question 23

Arrow worms are transparent. What are the 3 main parts of an arrow worm’s body?

Answer 23

Head, trunk, and tail

Question 24

What are some characteristics of arrow worms?

Answer 24

3-part body, marine, coelomates

Small and hermaphroditic

No circulatory system or larval stage

Major predators of planktonic organisms

Question 25

Where do arrow worms live?

Answer 25

They are marine, some swim in the open sea and others live on the sea floor

Question 26

Since arrow worms are so small and don’t have room for many organ systems, how do they exchange gases and excrete waste?

Answer 26

Diffusion through the body wall

Question 27

Since arrow worms have no circulatory system, how do they move waste and nutrients in their body?

Answer 27

By using cilia that line their coelom.

Question 28

What does it mean to be hermaphroditic?

Answer 28

Each individual produces both male and female gametes