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Unformatted text preview: 1 Chapter 54 Community Ecology learning objectives and study guide Exp lain the relationship between sp ecies richness and relative abundan ce and exp lain how both contribute to sp ecies d iversity . Bio geo grap hy of distribution of speices. Distinguish b etween a food ch ain and a food web . Describe two ways to simplify food webs. Sum marize two hyp otheses that exp lain why food chains are relativ ely short. Exp lain the exp erim ental evid ence that supp orts the energetic hy p othesis. Exp lain how do min ant and k ey stone sp ecies exert strong control on comm unity structure. Describe an examp le of each. Exp lain how a found ation sp ecies m ay facilitate the survival and reproduction of other species. Species diversity Species Diversity of a community is the variety of organisms that make up the community It has two components: is the is the Why is species diversity important ? Plant biodiversity Food 30,000 or more plant species have edible parts; 7,000 species are grown and used as food by humans; 20 species feed the majority (90%) of the world's population; . Genetic resources Fuel, construction, paper production n n n n n n n n n n n n n n n n n n Community S tructure Species diversity Species richness Relative abundance jus t 3 s pecies are the major world-wide s taples (rice , whe at, and corn) total number of different species in the community proportion each species represents of the total individuals in the community 2 Pharmaceuticals 80% of the people in less- developed countries rely heavily or entirely on drugs derived from natural sources (More than 20,000 species have been used for medicinal purposes. Of the drugs used in the U.S., 25% are derived from plants, 13% from m icroorganism s (including m any antibiotics), 3% from anim als. Overall, But this biodiversity is currently threatened. Habitat loss Habitat change Competition from exotic species Predation by exotic species O ver harvesting Poisoning Future: climate change (spets will be at most risk). # of species # of species Fig. 54-9 Ecologists calculate indexes of diversity Shannon diversity ( ): = –? ln = 1 where is species richness and is the proportion of each species in the community. Do you see these differences in Species diversity In a global scale? Concept 54.4: Biogeographic factors affect community biodiversity Latitude and area are two ke y factors that affect a community’s species diversity Num ber of species tends to increase in tropics and decrease at high latitudes Is diversity always desirable? 41% of our prescription drugs have their active ingredients derived from living organisms. Species Diversity of Communities n n n n n n n n n n n n n n n n n So what is diversity ?...
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- Spring '09