How Populations Grow Learning Objectives List the characteristics

How Populations Grow

Learning Objectives § § List the characteristics used to describe a population. Identify factors that affect population growth. Describe exponential growth. Describe logistic growth.

Describing Populations • Geographic range • Density and distribution • Growth rate • Age structure

Geographic Range • The area inhabited by a population is called its geographic range.

Density and Distribution

Growth Rate Growth rate = 1 Population size is unchanged. Growth rate > 0 Population size is growing. Growth rate < 0 Population size is decreasing. Bacterial population

Population Growth Births Deaths Immigration Emigration

Exponential Growth Under ideal conditions with unlimited resources, a population will grow exponentially. Population is rapidly increasing.

Logistic Growth When a population’s growth slows and then stops, following a period of exponential growth Phase III

Carrying Capacity The maximum number of individuals of a particular species that a particular environment can support Population stabilizes at carrying capacity.

Overview: How Populations Grow 1. “Ten individual per square hectare” is a description of population. density 2, When resources are limited, a population will grow logistically. 3. When growth rate is greater than zero , the population is growing.

Historical Population Growth The size of the global human population is still increasing, but the rate of global population growth is decreasing.