Population Ecology

1. Population Ecology

2. Populations • A population is a group of individuals of a single species living in the same general area. They are influenced by similar environmental factors, and use the same resources. Populations evolve through natural selection.

3. Every population has specific boundaries and a specific size. • The number of individuals per unit area is called density. The pattern of spacing of within the said population is known as dispersion. • birth, immigration, death, and emigration.

4. Population DensityWolves People

5. Patterns of Dispersion • Biotic and Abiotic factors contribute to variations in population density and dispersion rates. • clumped dispersion. This is when individuals are aggregated,into patches. Often due to nutrient availability, familial living (i.e. in packs), and mating behavior. Most common • uniform dispersion. individuals are evenly spaced. Seen with territoriality. • Randomdispersion occurs in the absence of strong attractors or repulsers, or when nutrient distribution is homogenous across the observed ecosystem.

6. Demography • Demography is the study of populations and how they change over time.Ways to measure demography include • life tables, survivorship curves, and reproductive tables.

7. Carrying Capacity • Carrying capacity (symbolized as K) is the maximum population size that a particular environment can support. • Carrying capacity is not fixed, but varies over time and throughout ecosystems with the abundance of energy, shelter, nutrients, etc. • Crowding and resource limitation has an extreme effect on both carrying capacity and birth rate in populations.

8. For wolves in Wisconsin

9. Population Change and Density • A birth/death rate that does not change with population density is said to be density independent. • A death or birth rate that changes as population density changes is said to be density dependent. • Birth and death rates are examples of negative feedback. • If not, populations would increase exponentially. following are examples of factors that create this negative feedback loop.

10. Factors Influencing Negative Feedback • Competition for resources intensifies intra- and interspecific competition for declining nutrients and other resources, resulting in a low birth rate. • Territoriality also may limit density. Animals such as cheetahs use chemical communications to warn other organism of their territorial boundaries • Health can also affect density. Pathogens are more easily spread in high-density areas. • Predation reduces the concentration of species in a specific area, generally back to the ecosystem’s carrying capacity. • Toxic waste can limit reproduction and population size, poisoning organisms within an ecosystem.

11. Human Population Growth • In recent centuries, human population growth has been limited by mostly disease-based factors. In certain countries, human population growth has been reduced to almost 0 percent because of a high mortality rate, or conversely, a low birth rate. • Exponential v. Logistic growth • K v. R strategies