How Populations Grow

What is a Population? A population consists of all individuals of a species that live together in one place at one time. A population consists of all individuals of a species that live together in one place at one time.

Three Key Features of Populations Population size is the number of individuals in a population. Population size is the number of individuals in a population. Population density is the number of individuals that live in a given area. Population density is the number of individuals that live in a given area. Dispersion is the way the individuals of a species are arranged in space. Dispersion is the way the individuals of a species are arranged in space.

Modeling Population Growth A population model is a hypothetical population that attempts to exhibit the key characteristics of a real population. A population model is a hypothetical population that attempts to exhibit the key characteristics of a real population. Exponential growth curve is a curve in which the rate of population stays the same as a result the population growth stays the same, as a result the population size increases steadily. Exponential growth curve is a curve in which the rate of population stays the same as a result the population growth stays the same, as a result the population size increases steadily.

Exponential Growth Curve

Modeling Population Growth Carrying capacity is the population size that an environment can sustain. Carrying capacity is the population size that an environment can sustain. Density-dependent factors is when limited resources are affected by the density of the population that uses them. Density-dependent factors is when limited resources are affected by the density of the population that uses them. Logistic model is a population in which the exponential growth is limited by a density-dependent factor. Logistic model is a population in which the exponential growth is limited by a density-dependent factor.

Logistic Growth Curve

Population Growth Models Calculating the population growth rate – Calculating the population growth rate – r (rate of growth) = birthrate – death rate r (rate of growth) = birthrate – death rate Exponential growth rate – Exponential growth rate – Logistic model - Logistic model -

Growth Patterns in Real Populations Density-independent factors – growth is limited by environmental conditions. (weather and climate) Density-independent factors – growth is limited by environmental conditions. (weather and climate) r-strategies – species found in rapidly changing environments. r-strategies – species found in rapidly changing environments. K-strategies – species that grow slowly and have small population sizes. K-strategies – species that grow slowly and have small population sizes.