Population Biology

Chapter 4

Population Dynamics

• Population growth = increase in population size over time.

• Linear vs. exponential growth

Limits to growth

• Space

• Food

• water

Rapid life history patterns

• Unpredictable and Changing Environments

• Small body size

• Mature rapidly

• Reproduce early

• Short life span

• Population fluctuates

Slow life history Patterns

• Predictable and Unchanging Environments

• Large body size• Reproduces and matures

slowly• Long life span• Maintain population size

Limiting Factors- Density Dependent

• Density dependent factors are influenced by the total population size.

• Food

• Disease

• Competition

• Parasites

Limiting Factors-Density Independent

• Temperature

• Storms

• Floods

• Droughts

Population Changes

Effects of predation on a population:

• Eliminates young• Eliminates old• Eliminates sick or weak• Leaves more resources for the

strong and those able most likely to reproduce.

Effects of overcrowding on a population:

• Causes organisms to exhibit differing signs of stress– Aggression

– Lack of parental care

– Decreased fertility rate

– Decreased resistance to disease

Human Population Growth

• Demography- study of population growth, distribution, age structure, etc.

• Growth rate = Birth rate – Death rate

• Birth rate = # of births

• Death Rate = 3 of deaths

• Fertility Rate = average # of offspring a female will have in a society.

• Doubling Time = Time needed for populations to double

• Doubling Time = 70 .annual percent growth

• Age structure- Age of a population (has great affect on population growth)

Population mobility

• Migration- Move from one population or region to another–Has no effect on world

population

–Has effect on local populations

• Immigration- People move into a population.– Puts stress on a local population

• Increase need for fire, police, schools, roads, infrastructure.

– Increases $$ in U.S.

• Emigration- People moving out of an area (exit)– Puts stress on local economy from loss of $$,

job, etc.