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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.