Lab 7: Phylum Mollusca

Question 1

Define rapid radiation

Answer 1

a pattern of evolution in which there are multiple divergences from a common ancestor in a relatively short period of time

Question 2

When radiation is accompanied by ecological diversification, this is called _____ _______

Answer 2

adaptive radiation

Question 3

Define adaptive radiation

Answer 3

the genetic differentiation between populations evolves in response to differences in the environments they inhabit and the resources they use

Question 4

What type of symmetry does a mollusc have?

Answer 4

Bilateral

Question 5

Is a mollusc triploblastic or diploblastic?

Answer 5

Triploblastic

Question 6

Unsegmented protostomes belong to the clade _____

Answer 6

spiralia

Question 7

Do molluscs have complete digestive systems?

Answer 7

Yes, they have a complete gut with regional specialization, kidneys (excretory organs), and a circulatory system that is of the open type in most although few have a closed.

Question 8

How do molluscs do gas exchange?

Answer 8

With gills; there are some molluscs that have a primitive lung

Question 9

The molluscan plan is referred to as having _____

Answer 9

plasticity; their body plan can be molded like plastic to fit a variety of ecological niches

Question 10

What is a modular body plan?

Answer 10

parts of the body can be removed, and different ones put in their place

Question 11

What are the basic parts of a mollusc?

Answer 11

Ventral foot, dorsal visceral mass, mantle, and shell

Question 12

Homocoel

Answer 12

a series of interconnected spaces between tissues and organs. Blood leaves vessels and flows through these spaces outside of vessels

Question 13

What is a Gastropoda?

Answer 13

Most possess coiled shell; well-defined head, foot for crawling. Largest class of molluscs.

Question 14

What is a Bivalia?

Answer 14

Two shells dorsally hinged; suspension feeder

Question 15

What is a Polyplacaphora?

Answer 15

Broad flat foot and shell divided into 8 plates

Question 16

What is a Cephalopoda?

Answer 16

Free swimming, highly developed nervous system, predator, foot modified into tentacles, shell absent in most.

Question 17

In molluscs, the coelm is much _____. It only exists as a fluid-filled space surrounding the ____.

Answer 17

Reduced; heart

Question 18

What is the principal body cavity in a mollusc?

Answer 18

Hemocoel; functions as hydrostatic skeleton in molluscs.

Question 19

Production of what in molluscs aids in locomotion?

Answer 19

mucus

Question 20

Ventral foot is involved in ____

Answer 20

locomotion

Question 21

What is a radula?

Answer 21

Feeding structure located in the mouth of the cavity D; ribbon of teeth composed of chitlin

Question 22

What is located in the dorsal visceral mass

Answer 22

circulatory system, the reproductive system, the excretory system, and the digestive system

Question 23

What is the mantle?

Answer 23

a sheet of skin located between the visceral mass and the shell; the mantle secretes the shell

Question 24

What is the mantle cavity?

Answer 24

the space between the outside wall of the visceral mass and the mantle is called the mantle cavity; is open to the environment. (At the posterior of the generalized mollusc)

Question 25

Where are gills located?

Answer 25

Mantle cavity

Question 26

The gills are covered with _____

Answer 26

cilia

Question 27

What does the cilia do?

Answer 27

creates a current that draws water into the mantle cavity and over the gills

Question 28

How is oxygen diffused?

Answer 28

from the water into the blood in the gills; hemocyanin binds the oxygen. When blood reaches cells of the body it releases the oxygen to the cells

Question 29

What is the shell composed of and and secreted by?

Answer 29

Calcium carbonate; secreted by the mantle

Question 30

Describe a molluscs nervous sytem

Answer 30

consisting of a ganglion encircling the esophagus and nerve cords extending to the organs and foot

Question 31

Molluscs have what kind of circulatory system?

Answer 31

Open

Question 32

Why is blood flow slow in an open circulatory system?

Answer 32

it empties into a large space and the pressure cannot be maintained

Question 33

What is a molluscs digestive tract composed of?

Answer 33

Mouth, esophagus, stomach, intestine, and anus. Mouth is in the radula

Question 34

What is step one of a gas exchange in a generalized mollusc?

Answer 34

Exchange with environment and blood

Question 35

What is the second step of gas exchange in a mollusc?

Answer 35

exchange with the blood and individual cells