4: Community and Population Ecology
Learning Outcomes
- Describe how ecologists measure population size and density
- Describe three different patterns of population distribution
- Give examples of how the carrying capacity of a habitat may change
- Explain how humans have expanded the carrying capacity of their habitat
- Discuss the long-term implications of unchecked human population growth
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- 4.1: Population Demographics and Dynamics
- Populations are dynamic entities. Their size and composition fluctuate in response to numerous factors, including seasonal and yearly changes in the environment, natural disasters such as forest fires and volcanic eruptions, and competition for resources between and within species. The study of populations is called demography.
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- 4.3: The Human Population
- Concepts of animal population dynamics can be applied to human population growth. Earth’s human population and their use of resources are growing rapidly, to the extent that some worry about the ability of Earth’s environment to sustain its human population. Long-term exponential growth carries with it the potential risks of famine, disease, and large-scale death, as well as social consequences of crowding such as increased crime.
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- 4.4: Community Ecology
- Populations typically do not live in isolation from other species. Populations that interact within a given habitat form a community. The number of species occupying the same habitat and their relative abundance is known as the diversity of the community. Areas with low species diversity, such as the glaciers of Antarctica, still contain a wide variety of living organisms, whereas the diversity of tropical rainforests is so great that it cannot be accurately assessed.
Thumbnail image - Asian carp jump out of the water in response to electrofishing. The Asian carp in the inset photograph were harvested from the Little Calumet River in Illinois in May, 2010, using rotenone, a toxin often used as an insecticide, in an effort to learn more about the population of the species. (credit main image: modification of work by USGS; credit inset: modification of work by Lt. David French, USCG)