How To Study Living Animals


6. A COMPARATIVE STUDY OF EXOSKELETONS
Materials.

Charts, specimens, etc. Since this is partly a review exercise, your notes and drawings of invertebrates should be at hand.

Definitions.

Exoskeleton,

a protective covering developed on the outside of an animal herunterladen.

Questions.

1. What are foraminifera; radiolaria? How do they differ from other protozoans? Of what two substances are the shells of protozoans composed?

2. How are the spicules formed in a simple sponge? What are glass sponges? Give reasons why the skeletons of sponges may or may not be considered exoskeletons herunterladen?

3. What are stone corals? What is the relation of the coral polyp to the skeleton? What is the appearance of the coral when expanded as compared with its appearance when contracted? Of what substance is the coral composed?

4. Describe the exoskeleton of a starfish. Contrast the exoskeleton of the sea urchin and the starfish microsoft office kostenlos downloaden vollversion deutsch chip. Why does a sea cucumber need no well-developed exoskeleton?

5. What structure in an earthworm may be considered an exoskeleton? What other types of exoskeletons are found in segmented worms?

6. Of what substance is the exoskeleton of arthropods composed? What additional substance is found deposited in the shell in the case of crustaceans? What advantage in the arthropod type of exoskeleton?

7. Why are mollusks so commonly called “shellfish”? What advantage in the mollusk type of skeleton? What disadvantages?

Summary.

1. What type of exoskeleton is common among invertebrates?

2. What are the general purposes of exoskeletons?

3. What is the explanation of the various forms of exoskeletons found?

4. Of what substances are exoskeletons composed?

B. Protective Coloration

To show how Color may be Protective

Materials.

Specimens such as the Kny-Scheerer mimicry collections, diagrams, etc.

Definitions.

General protective resemblance,

the general resemblance between the color of an animal and its surroundings.

Variable protective resemblance,

the changing of the color of an animal to correspond to the change in its background.

Special protective resemblance,

the resemblance of an animal to some object found in its background in color and form.

Mimicry,

the resemblance of an unprotected animal to a well-protected one.

Warning colors,

bright colors which protect animals by causing other animals to avoid it.

Questions.

1. Show how the transparent color of a paramecium, the green color of a cabbage worm, or the green color of a certain species of hydra may result in protecting an animal from its enemies. Mention as many other examples as you can.

2. What is gained by the ability of a squid to change its color? How is this change brought about?

3. Explain the protective coloration of the following: Dead-leaf butterfly, walking stick, geometrid larva. Hunt up other examples.

4. Explain the protective coloration in the following: Hover flies, clear-winged moths, viceroy butterflies.

5. Make a list of several invertebrates that are protected by their bright color. Explain the reason for the bright color.

6. How may the difference between the color of the upper and lower surfaces of animals be explained on the basis of use to the animal?

7. (Optional) Find out some other uses of color to an animal aside from protection.