Population Dynamics

Characteristics of a population

• Geographical distribution – Describes area inhabited by population

• Density – The # of individuals / area

• Growth Rate – The change in # within a population due to births, deaths, immigration, & emigration

• Age Structure

Exponential Growth

• Occurs when individuals in a population reproduce at a constant rate

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

Logistic Growth

Occurs when resources become less available (Slows population growth rate)

Slow population growth rate due to 1. Decrease in birthrate2. Increase in deathrate3. Immigration decreases4. Emigration increases

Carrying Capacity

The largest # of individuals an environment can support

Limits to population growth

Limiting Factor – causes population growth to decrease Density Dependent Limiting Factors Factors which work best with a large dense population• Interspecific competition• Intraspecific competition• Predation• Disease• Parasitism Density Independent Limiting Factors• Tornado, hurricane, drought, temperature• Human disturbance (Clear-cutting forests or damming

rivers)

Competition

Competitive exclusion principle• No two species can occupy the same

niche in the same habitat at the same time

• Interspecific competition occurs between two species for similar resources

• Intraspecific competition occurs within a species for similar resources

Why Competition?

Limited resources• Food• Water• Space• Shelter• Mates• Sunlight

Predation

Prey have evolved defense mechanisms to prevent predation

• Poison (Monarch butterflies & Dart frogs)• Mimicry• Camouflage• Shells• Slime

Poison

•

Batesian mimicry

• Monarch butterfly or viceroy butterfly?

Mertensian mimicry (Warning coloration)

• Coral snake or King snake?

Camouflage in nature

Industrial melanism of the peppered moth

Shells as Defense

Slime as Defense

Human Population Growth

Exponential growth due to:

• Agriculture

• Industry

• Better healthcare / medicine

• Reduced death rate

• High birth rate

Demography

The scientific study of human populations

• Birthrates• Deathrates• Age structure

U.S. Age Distribution

South Africa Age Distribution

South Africa and U.S.