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This article explores the three important characteristics of a population, including geographic distribution, population density, and growth rate. It also discusses the different types of population growth patterns and factors that limit population growth. Additionally, it examines the study of human population growth, demographic transition, and age structure diagrams, and suggests possible solutions to slow down population growth.
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Three important characteristics of a population • Geographic distribution • Where and how much space a population has • Population density • Number of individuals per unit area • Growth rate • How quickly a population is increasing
Increases Births Immigration New individuals enter into a population Decreases Deaths Emigration Individuals leave a population Changes to population density
Exponential growth • Population size doubles • 248163264128… • With unlimited resources, no predation or disease – a population will grow exponentially
Logistic Growth • As resources become scarce population growth slows or stops • K=carrying capacity • The number of individuals of one population that an environment can support
Review of graphs: • What type of growth pattern does the fruit fly population exhibit? • What type of growth pattern does the rabbit population exhibit? • Does either graph indicate that the population has reached its carrying capacity? Explain. • What might happen to the rabbit population if foxes came into the environment?
Limits to growth • Limiting factor: a factor that causes a population’s growth to slow or decrease
Density-dependent: Factors that only become limiting when the population density is high Example: Competition Predation Parasitism Density-independent: Factors that affect all populations in similar ways Examples: Weather Natural disasters Some human activity Damming rivers Clear cutting forests Types or limiting factors
Predator Prey Relationships:Answer the Questions in your notes • How do the peaks in the snowshoe hare population compare to the peaks in the lynx? • If the lynx died out in a particular region, what would happen to the hare population?
Studying the Human population • Demography • The study of human populations • Predicting growth rates of populations • Birth rate • Death rate • Age structure
Demographic Transition • A dramatic change in birth and death rates indicate the country is entering a new demographic stage
Age structure diagrams • Show population of a country broken down by gender and age • Show distinct patterns when compares by growth rate
Future of the human population • In what areas of the world will the human population grow the most? • What can we do to slow this down?