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.
Three Key Features of Populations
• Population size is the number of individuals in a population.
• 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.
Modeling Population Growth
• 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
Modeling Population Growth
• 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.
• 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 –
• r (rate of growth) = birthrate – death rate
• Exponential growth rate –
• Logistic model -
Growth Patterns in Real Populations
• Density-independent factors – growth is limited by environmental conditions. (weather and climate)
• r-strategies – species found in rapidly changing environments.
• K-strategies – species that grow slowly and have small population sizes.