population biology chapter 4. population dynamics population growth = increase in population size...
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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.
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