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Biology, 6/e
Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University

Community Ecology

Answers to Review Questions

Chapter 25 (p. 532)

1. Interspecific competition is competition among different species. Intraspecific competition is competition among individuals of a single species. Gause's principle essentially states that no two species can occupy the same niche.

2. The terms niche and habitat are not synonymous. The habitat is part of the niche, but only the physical part; an organism's niche additionally included behavior, seasonal factors, and daily patterns. The theoretical niche is the potential niche if there were no competitors present, and the actual niche is what the organism occupies under natural circumstances.

3. Defense structures include thorns, spines, prickles, sticky plant hairs, and high levels of silica.

4. The adult viceroy butterfly exhibits Batesian mimicry; the larval monarch butterfly exhibits aposematic coloration; and the larval viceroy butterfly exhibits cryptic coloration.

5. Predation reduces competition in the community. The reduced competition allows greater species diversity.

6. Larger populations compete more intensely for limited resources, resulting in greater survival by the best competitor. Predation reduces population size and, with it, competition.

7. Three factors have produced this altered concept: (1) climate is continually changing; (2) succession is a slow process; and (3) the nature of a region’s vegetation is greatly affected by human activities. The organisms often associated with early stages of succession are those that exhibit symbiotic relationships: lichens = algae + fungi; legumes = plant + bacteria; and mycorrhizae = plant + fungi. Disturbance will cause succession in the disturbed area to revert to an earlier stage. Patchy disturbances may result in increased richness of species diversity.