end show slide 1 of 22 copyright pearson prentice hall how populations grow
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How Populations Grow
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Characteristics of Populations
Characteristics of Populations
Three important characteristics of a population are its:
• geographic distribution
• density
• growth rate
# / unit area# / unit area
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Population Growth
Population Growth
Four factors can affect population size & thus growth rates:
• Natality (the number of births)
• Mortality (the number of deaths)
• Immigration (the number of individuals that enter the population)
• Emigration (number of individuals that leave the population)
When can a population grow then?
When will a population decrease in size?
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Exponential Growth
Exponential Growth
Under ideal conditions with unlimited resources, a population will grow exponentially.
J-Shaped curve
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Logistic Growth
Logistic growth is characterized by an S-shaped curve. What causes this type of growth?
What?What?
Why?Why?
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Warmup review
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Limits to growth
Density Dependent Factors:differ with the biome/environmentAmount foodDiseaseCompetitionParasites
Versus Density-Independent:Abiotic factorsHabitat disruption
Which type of populations more prone to density-dependent factors? Density –independent?
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Predatory Prey cycles
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Many of our animal populations are in danger
Current Situation
What are some things we are trying to do to ensure survival of many of our species?