How Populations Grow

Populations and Species : 

Populations and Species How Populations Grow

Objectives : 

Objectives Distinguish among the three patterns of dispersion in a population. Contrast exponential growth and logistic growth. Differentiate r-strategists from k-strategists.

Populations : 

Populations Population: A group that consists of all the individuals of a species that live together in one place at one time. They are not reproductively isolated. Population Size: The number of individuals in a population. The size of a population is limited by the availability of resources in the population’s range.

Population Features : 

Population Features Population Density: The number of individuals that live in a given area. If the members are widely spaced then they rarely encounter each other making mating more difficult. Dispersion: The way that the members of a population are scattered or arranged throughout their habitat. There are three patterns of dispersion.

Dispersion Patterns : 

Dispersion Patterns Random Distribution: Individuals are scattered randomly throughout the space. The location of each individual is determined by personal preference or by chance. Even Distribution: Individuals are scattered evenly throughout the space. They are located at regular intervals with the maximum amount of space between each individual. This is common when predator ranges overlap. It allows for limited contact between individuals and makes the most of available resources.

Distribution Patterns : 

Distribution Patterns Clumped Distribution: Individuals are spread over the range in groups or herds. This is the common pattern for herd animals as it affords them the protection of numbers and limits the odds of a predator taking any one individual. Population Model: A hypothetical population model that attempts to display the key characteristics of the real population

Modeling Populations : 

Modeling Populations Population Growth Rate: The difference between the birth rate in a given population and its death rate. Exponential Growth Rate: A curved graph that shows the rate of population growth changing throughout the course of the mapped period. Linear Growth Rate: A straight line population growth chart that shows population growth at a constant rate. This is not a very realistic graph.

Resources and Population Size : 

Resources and Population Size As a population invades an area, the growth rate follows a predictable pattern. The initial growth is slow as few individuals are present. Then there comes a time of fast population growth as breeding becomes rapid in the presence of abundant resources. Finally, as resources are consumed and become scarce, population slows and then flattens out. Carrying Capacity: The population that an environment will sustain. Density-Dependent Factor: Food, water, shelter, and other factors on which populations depend.

Logistic Model : 

Logistic Model Logistic Model: A population model in which exponential growth is limited by density-dependent factors.