co46 - CHAPTER 46 ECOLOGY OF POPULATIONS Chapter Outline...

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CHAPTER 46 E COLOGY OF P OPULATIONS Chapter Outline 46.1 Scope of Ecology A. Ecology 1. Ecology is the study of interactions of organisms with their environment. 2. Concept of ecology was first voiced by German zoologist Ernst Haeckel. 3. Ecology studies how environmental factors determine the distribution and abundance of populations. 4. Ecology and evolution are related because ecological interactions are natural selection pressures that have long-term effects. 5. A habitat is the place where an organism exists. 6. A population is a group of the same species occupying a certain area. 7. A community consists of all populations at one locale (e.g., a coral reef population). 8. An ecosystem contains the community organisms and abiotic factors (e.g., energy flow, chemical cycling). 9. The biosphere is the layer on the earth where living organisms can live. 10. Modern ecology is both descriptive and predictive, with applications to wildlife management, agriculture, and many other problems. B. Density and Distribution of Populations 1. The population density of organisms refers to how many live per unit of area or volume. 2. The population distribution is the pattern of dispersal; it varies from uniform to random to clumped. 3. Ecologists study the causes for any “patchiness” of organisms across space and through time. 4. Distribution can be due to both biotic (living) and abiotic (physical) factors. 5. The physical (abiotic) factors include types of precipitation and amounts, averages, and daily and seasonal variations in temperature, type of soil or nutrients; moisture or temperature may serve as limiting factors . 6. Biotic factors can be illustrated by red kangaroos that are limited to inland Australia by the grasses that grow there. 46.2 Characteristics of Populations A. Population Size 1. The population size is the number of individuals contributing to the gene pool of the population. 2. At any one point in time, a population has a certain size. 3. Future population size depends on natality and mortality (births and deaths), and immigration and emigration (although immigration and emigration are often presumed equal). 4. Birthrate and death rate are used to calculate the intrinsic rate of natural increase. 5. The intrinsic rate of natural increase is used to calculate the growth of a population per unit time. B. Population Growth Models 1. There are two patterns of population growth. a. In discrete breeding, organisms reproduce once and cease to grow as adults; they expend energy in reproduction and die. b. In continuous breeding, organisms reproduce throughout their lifetime, which invests energy in their future survival. 2. Most organisms do not exactly fit these two patterns. a.
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This note was uploaded on 10/24/2009 for the course BIO 172 taught by Professor Clark during the Fall '08 term at University of Michigan.

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co46 - CHAPTER 46 ECOLOGY OF POPULATIONS Chapter Outline...

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