Ecological Level of Organization

Populations What is a population? population – consists of all the individuals of a species that live together in one place at one time demography – the statistical study of all populations; demographers study the composition of a population and try to predict how the size of the population will change

Three Key Features of Populations: (Factors that determine the population’s future.) population size – the number of individuals in a population population density – the number of individuals that live in a given area dispersion – the way the individuals of the population are arranged in space

Patterns of Dispersion: Random Even Clumped

How Populations Grow: A population’s future survival is determined by its size, density, and dispersion. For example; (1) Studies have shown that very small populations are among those most likely to become extinct. (2) Small populations tend to experience more inbreeding (breeding within relatives) which leads to a more genetically uniform population and an increase in homozygous recessive traits.

(3) If the individuals of a population are few and are spread widely apart, they may seldom encounter one another making reproduction rare. (4) Dispersion patterns affect how populations grow as well. If individuals are randomly spaced, the location of each individual is determined by chance.

Carrying Capacities Organisms within a population are limited by resources such as space, food, shelter, and disease. The carrying capacity is the number of individuals that a stable environment can support. As the population approaches its limit, starvation will increase. What is the carrying capacity of the population above (about how many organisms of this species can be supported in this ecosystem)?

Population Growth Curve Carrying Capacity