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Section 5-1 Characteristics of Populations

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1 Section 5-1 Characteristics of Populations

2 3 important Characteristics of Populations
Geographic distribution – describes area inhabited by a population Density # of organisms per unit of area # often varies from population to population Growth rate Age structure(will be discussed later)

3 Population Growth 3 factors that affect population size # of births
# of deaths # of individuals that enter or leave a population * Populations grow when birth rates exceed death rates

4 Population Growth Cont.
Immigration – movement of individuals into an area Emigration – movement of individuals out of an area

5 Exponential Growth Usually depends on having abundant space and food; lacking disease and predators Exponential growth – occurs when the individuals in a population produce at a constant rate Exponential growth does not continue in natural populations for an extended period of time Represented by “J” shaped curve See figure 5-3; page 121

6 Logistic Growth As resources become less available, the growth of a population slows or stops Logistic growth – occurs when a population’s growth slows or stops following exponential growth Represented by “S-shaped” curve Figure 5-4; page 122

7 Carrying Capacity Carrying Capacity – the largest # of individuals that an environment can support Populations reach carrying capacity when resources become less available See figure 5-4; page 122

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