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.

_Summary._

1. Name four uses of color.

2. Name four ways an animal is protected by being like its background.

3. Name one way it is protected by being unlike its background.

4. What disadvantages in this method of protection?

#C. ANIMAL a.s.sOCIATIONS#

#To show Another Method of Protection from Enemies#

_Materials._

Specimens, charts, etc., ill.u.s.trating animal a.s.sociations.

_Definitions._

_Animal communities_, a.s.sociations of many animals of the same species in communities in which there is a greater or less division of labor.

_Gregarious_, a.s.sociations where there is but little division of labor.

_Parasitism_, an a.s.sociation where one animal lives at the expense of the other. The animal on which the parasite lives is called the host.

If there are two hosts during the life cycle of the parasite, the second host is called an intermediate host.

_Symbiosis_, an a.s.sociation where two animals live together in mutually helpful relations.

_Commensalism_, an a.s.sociation where two animals live together in relations not mutually helpful but without injury to either.

_Observations and questions._

_Note._--To find answers to many of these questions it will be necessary to refer to the reference books in the laboratory.

1. Examine a specimen of Volvox. Why may this be considered a colonial protozoan and not a many-celled animal? What is gained by the colonial habit?

2. Is the colonial habit common or rare in sponges and clenterates?

What is chiefly gained?

3. Describe the community life in one of the insects in each of the following groups:--

a. ant, honeybee, termite.

b. b.u.mblebee, paper wasp, hornet.

c. mining bee.

d. carpenter bee, mud wasp, digger wasp.

4. Name the host or hosts in the following cases: trichina, liver fluke, malarial parasite, tapeworm, hook worm. Give the life history of one or more of the parasites just enumerated. What is the effect of parasitism on the structure of the parasite?

5. What is the relation between ants and plant lice? Show how this relation is mutually helpful. Mention other cases of symbiosis that you have come across.

6. With what animal are barnacles often a.s.sociated? What is the habit of the pea or oyster crab? What are "guest bees"? What structure is lacking that is found in other bees? What are often found in the cavities of sponges? Why are these a.s.sociations called commensalism rather than symbiosis?

_Summary._

1. Into what groups can animal a.s.sociations be divided based upon the number of species concerned?

2. From the standpoint of protection, is this a good or a bad method of protection?

3. What disadvantages can you see in this method of protection.

#D. PROTECTIVE HABITS AND POWERS#

_Materials._

Specimens, charts, and books, showing habits of invertebrates.

_Definitions._

_Regeneration_, the power to grow new parts of the body when parts have been lost or injured.

_Masking_, the covering of an animal by some object or organism so as to hide its ident.i.ty.

_Nocturnal habits_, the habit of hiding in the daytime and coming out at night to feed.

_Terrifying att.i.tudes_, the protective att.i.tudes a.s.sumed at times by animals in order to ward off attack.

_Observations and questions._

1. How are Sabella and Serpula protected? What advantages and disadvantages in this habit? What changes in structure are a.s.sociated with this tube-dwelling habit?