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.