Biology, Seventh Edition Solomon • Berg • Martin Chapter 52 Community Ecology Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Ecological niche • Distinctive lifestyle and role of an organism in a community • Takes into account all abiotic and biotic aspects • For example, an organism’s habitat is one parameter used to describe the niche Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Connections to the size of the acorn crop Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Fundamental niche • Potential ecological niche for an organism • Realized niche • Niche an organism actually occupies • Limiting resources • Environmental factors that restrict a realized niche Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Effect of competition on an organism’s realized niche Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Competition • Two or more individuals attempting to use the same resource • Intraspecific competition –Among individuals within a population • Interspecific competition –Between different species Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Interspecific competition Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Competitive exclusion principle • Two species cannot occupy the same niche in the same community for an indefinite period • One species is excluded by another as a result of competition Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Some species reduce competition by resource partitioning • Competition among species is reduced by character displacement • Structural ecological and behavioral characteristics diverge where ranges overlap Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Resource partitioning Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Predation • Consumption of one species (the prey) by another (the predator) • Coevolution • Predator and prey both evolve more efficient ways to interact Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Ecological interactions among species Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Defenses • Mechanical defenses • Associating in groups • Cryptic coloration • Warning coloration • Müllerian mimicry Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Cryptic coloration Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Symbiosis • Mutualism –Both partners benefit • Commensalism –One partner benefits and the other is unaffected • Parasitism –One partner benefits while the other is harmed Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Mutualism Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Commensalism Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Parasitism Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Keynote species • Present in small numbers but are crucial in determining the species composition and ecosystem functioning • Dominant species • Affect the community because they are so common Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Species richness • Number of species within a community • Species diversity • Relative importance of each species within a community Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Effect of community complexity on species richness Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Ecological succession • Primary succession –Occurs in an area not previously inhabited • Secondary succession –Occurs where there is a pre-existing community and well-formed soil Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • Intermediate disturbance hypothesis • Disturbance affects succession and species richness • Species richness is greatest at moderate levels of disturbance Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology Intermediate disturbance hypothesis Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition CHAPTER 52 Community Ecology • The nature of communities • Organismic model –Views a community as a superorganism that goes through stages of development (succession) • Individualistic model –Abiotic environmental factors are primary determinants of species composition –Organisms are independent Copyright © 2005 Brooks/Cole — Thomson Learning