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Published byEileen Nicholson Modified over 8 years ago
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How Many Individuals Are IN a Population (Births + Immigrants) - (Deaths + Emigrants) Lead to Population GrowthLead to Population Decline
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We call these... LIMITING FACTOR = Something that keeps a population from growing infinitely LIMITING FACTORS
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There are 2 different models: 1. Exponential Growth Model 2. Logistical Growth Model
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Exponential Growth Resources are plentiful (there is a lot of food and water!) All populations grow this way until some limiting factor stops them
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Logistical Growth Model Limiting factors keep the population from growing exponentially Logistical growth = Carrying Capacity
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Carrying Capacity Carrying Capacity = highest number of organisms an area can hold - This is where the Logistical Growth Model flattens out at the top
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What determines the Carrying Capacity? LIMITING FACTORS!
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What’s the Carrying Capacity Here?... 10,000 individuals = the highest number of individuals this area can hold
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Human Population Growth Just like all other organisms, human population all grow exponentially Also, just like any ecosystem the Earth has a CARRYING CAPACITY. That is, there is a limit on the number of human beings that the Earth can support. http://www.youtube.com/watch?v=QZPk2quRmKE&f eature=related http://www.youtube.com/watch?v=QZPk2quRmKE&f eature=related
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World Carrying Capacity At some point, human population will exceed Earth’s Carrying Capacity. When this happens, human population will have to decrease (i.e. people will die) In fact, there is a lot of evidence that we are already getting very close to the Earth’s carrying capacity.
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World Carrying Capacity In developed (rich) countries, humans are exceeding the Earth’s carrying capacity by consuming too many resources. http://earthday.net/footprint/flash.html
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If Everyone Lived Like Americans If everyone lived like Americans, we would need eight Earths to provide all the food, water, and free space that we consume.
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Human Carrying Capacity In undeveloped (poor) countries, humans have exceeded their carrying capacity because there are too many people. 3.6 billion live in abject poverty (less than $2 per day) Individually consume very few resources But because there are billions of them, still exceed carrying capacity
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What Does This Mean For Us? But wait! We just learned that when a population exceeds its carrying capacity, it shrinks in size (organisms die). If we’re exceeding our carrying capacity, why aren’t people dying?
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The sad truth is, people ARE dying. Someone dies of starvation every 2.43 seconds 2,200 people will die from starvation by the end of today’s class.
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Leading cause of deaths worldwide Water pollution kills 14,000 people EVERY day
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So What Do We Do? To avoid starvation, dehydration, and war for resources, we need to reduce consumption, reduce population growth, or both. Four main strategies: Voluntarily cut consumption Find technological solutions to save resources Birth Control, education, and women's rights in the third world Planned birth policy
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So What Do We Do? We could voluntarily cut down on our consumption.
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So What Do We Do? Find technological solutions for using resources better. Norman Bourlag: The father of the Green Revolution, he is credited with saving more than 245 million lives. He invented new waves of growing crops in the developing world.
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Political Policy We could try to discourage births by providing birth control... Education......and increasing women's rights in undeveloped countries, where birth rates are highest.
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So What Do We Do? China has a planned birth policy: Since 1979, citizens have been limited to only one child per couple.
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