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Ecology CH 5 Section 3 Populations Population Introduction Ecosystems evolve Species evolve to fit a niche As species evolve populations change Population Growth 1798 Thomas Malthus Economist Stated the human population can outgrow the environment’s ability to support it Leads to famine and disease More offspring are born than can survive Frogs and other massive egg laying species Sheep twins Caught the eye of Charles Darwin Yes that Charles Darwin! Population Growth Charles Darwin “There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair” Theorized that on pair of elephants could produce 19,000,000 in 750 years with unlimited resources Exponential Growth •Only possible for a short time in real life •Resources are always limited Carrying Capacity As populations grow resources become more limited Decrease in resources leads to competition Those who lose die and the death rate of the population goes up At the same time the birth rate goes down When these two are equal the population levels off S-shaped curve parabola Carrying Capacity- The number of individuals that can be supported by an ecosystem Limiting Factors Forces that slow the growth of a population Density-dependent limiting factors 1. • • • Depend on the population size Food, water, space, disease, predation S-shaped curve Density-independent limiting factors 2. • • • Not linked to population size Natural disaster, climate, human impact Boom and bust curve Boom and Bust Curve Thrips S-Shaped Curve Rabbits Human Population Still exponential Can’t continue forever Technology, agriculture, and medicine Resources will become limited Population will level off Showing signs of strain Activity 5.2 Procedure steps 1&2 Analysis and Conclusion Questions Homework MC 1-10 WC 1-5 CR 3-5 TC 1-4 GA 1-4 http://quickfacts.census.gov