How Populations Grow

1
How Populations Grow
2
Learning Objectives

• Describe how ecologists study populations.
• Identify factors that affect population growth.
• Describe exponential growth.
• Describe logistic growth.

3
Describing Populations

• Growth rate
• Age structure

• Geographic range
• Density and distribution

4
Geographic Range
5
Density and Distribution
6
Growth Rate

• Growth rate 1
• Population size is unchanged.
• Growth rate gt 0
• Population size is growing.
• Growth rate lt 0
• Population size is decreasing.

Bacterial population
7
Age Structure

• Only certain age groups can reproduce.
• Only females produce offspring.

8
Population Growth
Immigration
Births
Emigration
Deaths
9
Exponential Growth

• Under ideal conditions with unlimited resources,
  a population will grow exponentially.

Population is rapidly increasing.
10
Logistic Growth

• When a populations growth slows and then stops,
  following a period of exponential growth

Phase II
Phase III
Phase I
11
Carrying Capacity

• The maximum number of individuals of a particular
  species that a particular environment can support

Population stabilizes at carrying capacity.
12
Overview How Populations Grow

• 1. Ten individual per square hectare is a
  description
• of population .
• 2, When resources are limited, a population will
  grow
• .
• 3. When growth rate is
  , the population is growing.

density
logistically
greater than zero
13
Student Worksheet Answers