Chapter 5

Populations

5.1 How Populations Grow

3 Important Characteristics of a population: Geographic Distribution Density Growth Rate

Population Density

The number of individuals per unit area Example: Cactus in Desert vs. Other plants

Population Growth

3 factors affect population growth: Number of Births Number of Deaths Number of individuals that enter or leave a certain

area

Population Growth

Population growth can be positive or negative.

Example: Penguins

Example: Penguins

At the beginning of the year there were 1200 penguins and 1600 at the end of the year.

What was the population growth? An increase of 400 penguins.

Example: Penguins

Suppose 250 chicks died during the year. What is the population growth?

A net increase of 150 penguins

Example: Penguin

Suppose that 200 adults died during the year. What is the populations growth?

A net decrease- or negative growth- of 50 penguins.

Population Growth

Immigration: Movement into an area This can increase a populations growth

Population Growth

Emigration: Movement out of an area This can decrease the populations growth Food shortages can lead to emigration

Exponential Growth

Individuals in a population reproduce at a constant rate

At first the growth is slow, then it becomes larger and larger

Logistic Growth

Population’s growth slows or stops following a period of exponential growth

Less resources available, less growth

Logistic Growth

Follows a general S-shaped curve

Carrying Capacity: Largest number of individuals an

environment can

support

Analyzing Data Activity

Turn to page 123 Follow the directions and answer the

questions that deal with graphing for Exponential Growth and Logistic Growth

5.2 Limits to Growth

Limiting Factor: Factors that cause a population growth to

decrease. Examples:

Competition, Predation, Parasitism and disease, Drought and other climate extremes, and Human Disturbances

Density Dependent Factors

Limiting factor that depends on population size.

Includes: Competition Predation Parasitism and

Disease

Density Independent Factors

Limiting factor that does not depend on population size.

Include: Unusual Weather Natural Disasters Seasonal Cycles Certain Human Factors

5.3 Human Population Growth

Human population tends to increase with time.

Patterns of Population Growth: Demographic Transition Age Structure

Demographic Transition

Change in a population from high birth and death rates to low birth and death rates. What are some reasons why some countries have

a high growth rate and others do not? Nutrition Sanitation Medicine

Age Structure

Population growth depends on how many people make up different ages in a population.

Age Structure Diagram