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# Populations

## on Sep 27, 2010

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## PopulationsPresentation Transcript

• Population Dynamics How populations change in any given area
• How Populations Grow Geographic distribution – the area in which a population lives (its range)
• Population Density : the number of individuals in an area
• Population Growth
• Measures how populations grow over time
• Affected by 4 factors:
• Number of births for a species
• Number of deaths for a species
• Emigration (out) # of individuals who leave an area
• Immigration (in) # of individuals who come into an area
• In the city of East Bumble, if 45 babies are born in the year 2008 and 15 people died that same year, what was the growth rate for the city? Give answer in units of: _____ babies per year. Positive Growth rate = population increase Negative Growth rate = decrease Is the growth positive or negative?
• Exponential Growth : organisms reproduce at a constant rate.
• Occurs under ideal conditions (no limits)
• J-shaped curve
• This shows that as time goes on, the population just continues to get larger
• This RARELY happens because of competition for resources like food.
Types of growth
• Types of growth
• Logistic growth: as resources become less available, growth slows or stops.
• S-shaped curve
• Carrying capacity: The number of organisms an environment can support.
• no growth occurs beyond this because of limited resources in the habitat.
• Where population growth equals zero.
• Types of growth
• Limiting factor: any factor in an organism’s environment that causes population growth to decrease
• The following factors are dependent on current population density:
• amount of food
• amount of water
• amount of space (for living/home building)
• predators
• disease
• competition
• Some limiting factors are not dependent on population density: (density-independent factors) - Unusual weather - Natural disasters - Some human activities Types of growth