rav65819_ch55_1145-1166

rav65819_ch55_1145-1166 - ;;;;;;;;;;; 55 chapter Population...

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Unformatted text preview: ;;;;;;;;;;; 55 chapter Population Ecology introduction ECOLOGY, THE STUDY OF HOW organisms relate to one another and to their environments, is a complex and fascinating area of biology that has important implications for each of us. In our exploration of ecological principles, we first consider how organisms respond to the abiotic environment in which they occur and how these responses affect the properties of populations, emphasizing population dynamics. In chapter 56, we discuss communities of coexisting species and the interactions that occur among them. In subsequent chapters, we discuss the functioning of entire ecosystems and of the biosphere, concluding with a consideration of the problems facing our planet and our fellow species. concept outline 55.1 The Environmental Challenge ■ Organisms are capable of responding to environmental changes that occur during their lifetime ■ Natural selection leads to evolutionary adaptation to environmental conditions 55.2 Populations: Groups of a Single Species in One Place ■ A population’s geographic distribution is termed its range ■ Ranges undergo expansion and contraction ■ Individuals in populations exhibit different spacing patterns ■ A metapopulation comprises distinct populations that may exchange members 55.3 Population Demography and Dynamics ■ Sex ratio and generation time affect population growth rates ■ Age structure is determined by the numbers of individuals in different age groups ■ Life tables show probability of survival and reproduction through a cohort’s life span ■ Survivorship curves demonstrate survival probability changes with age 55.4 Life History and the Cost of Reproduction ■ Investment per offspring is geared to maximize Ftness ■ Reproductive events per lifetime represent an additional trade-off ■ Age at Frst reproduction correlates with life span 55.5 Population Growth and Environmental Limits ■ The exponential growth model applies to populations with no growth limits ■ The logistic growth model applies to populations that approach their carrying capacity 55.6 Factors that Regulate Populations ■ Density-dependent effects occur when reproduction and survival are affected by population size ■ Density-independent effects include environmental disruptions and catastrophes ■ Population cycles may reflect complex interactions ■ Resource availability affects life history adaptations 55.7 Human Population Growth ■ Human populations have grown exponentially ■ Population pyramids show birth and death trends ■ Humanity’s future growth is uncertain ■ The population growth rate has declined ■ Consumption in the developed world further depletes resources 1145 rav65819_ch55_1145-1166.indd 1145 rav65819_ch55_1145-1166.indd 1145 12/7/06 6:40:38 PM 12/7/06 6:40:38 PM 55.1 The Environmental Challenge The nature of the physical environment in large measure determines which organisms live in a particular climate or region. Key elements of the environment include:climate or region....
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch55_1145-1166 - ;;;;;;;;;;; 55 chapter Population...

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