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Population Ecology

This comprehensive overview explores the characteristics of populations, focusing on key concepts like population density, age structure, survivorship curves, and the factors influencing population dynamics. It highlights the method of mark-recapture for estimating population size and distinguishes between density-dependent factors, which vary with population size, and density-independent factors, like weather and disasters, that affect populations uniformly. Additionally, it examines human population statistics through age pyramids, presenting insights into birth and death rates across different life stages.

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Population Ecology

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  1. Population Ecology

  2. Characteristics of Populations • Population - individuals of a single species that simultaneously occupy the same general area using the same resources that have a high likelihood of interacting with one another. • Population density - number of individuals per unit area or volume.

  3. Mark - Recapture Method • Device used to estimate population size through random field sampling of a population. • The Equation is as follows: • Number x Total catch • marked second time • N = • Number of Marked Recaptures

  4. Age Structure • Relative number of individuals of each age in a population usually represented by age pyramids (fig. 52.23). • Humans - birth rate is highest among 20-year-old women • Humans - death rate is highest in first year and in old age

  5. Age Pyramid 2000 (US)

  6. Age Pyramid 2025 (US)

  7. Age Pyramid 2050 (US)

  8. Age Structure 1955 (US)

  9. Survivorship Curves • A graphic way of representing some of the data in a life table. • Type I - low death rates during early and middle life then dropping steeply as death rates increase at older ages. (large mammals) • Type II - mortality is constant over the lifespan (hydra, annual plants, rodents…) • Type III - high death rates for young but slow for older individuals (crustaceans, insects…)

  10. Survivorship Curves (con’t)

  11. Density-Dependent Factors • Density - dependent factors intensify as populations increase by decreasing reproduction of increasing the death rate. • Establishes the carrying capacity of a population • nutrients, disease, territory, mates, water, shelter, crowding, density

  12. Density - Dependent Factors (con’t)

  13. Density-Independent Factors • Density- independent factors affect the same percentage of individuals regardless of population density. • Weather • Disasters • Climate

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