Population Ecology

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.

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

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

Age Pyramid 2000 (US)

Age Pyramid 2025 (US)

Age Pyramid 2050 (US)

Age Structure 1955 (US)

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…)

Survivorship Curves (con’t)

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

Density - Dependent Factors (con’t)

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