Questions.
- What are foraminifera; radiolaria? How do they differ from other protozoans? Of what two substances are the shells of protozoans composed?
- 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?
- 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?
- Describe the exoskeleton of a starfish. Contrast the exoskeleton of the sea urchin and the starfish. Why does a sea cucumber need no well-developed exoskeleton?
- What structure in an earthworm may be considered an exoskeleton? What other types of exoskeletons are found in segmented worms?
- 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?
- Why are mollusks so commonly called "shellfish"? What advantage in the mollusk type of skeleton? What disadvantages?
Summary.
- What type of exoskeleton is common among invertebrates?
- What are the general purposes of exoskeletons?
- What is the explanation of the various forms of exoskeletons found?
- 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.