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 birthrate 2.Increase in deathrate 3.Immigration decreases 4.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.