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Unit 2: Communities & Populations
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Change in the community…
Part of ecology is studying the constant cycles of change that occur within an ecosystem Factors affecting change Loss of Habitat Shortage of Resources Population Growth Disease
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Changes in the community…
Succession: a series of predictable changes that occur in a community over time -can be a drastic change or just a change of seasons.
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Succession (cont.) Primary succession: form of succession where growth begins in an area that had no living organisms Example: Growth beginning on new land formed by cooling lava. Pioneer species: 1st species to populate the area in primary succession
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Succession (cont.) Secondary succession: when a disturbance changes a community and the community must grow back again Ex: when land is cleared for farming and then trees are allowed to grow back
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Primary Succession Secondary Succession
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Population Dynamics Characteristics of Populations
Geographic Distribution (where people live) Density Growth rate
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Population Dynamics Factors that affect population growth:
Number of births Number of deaths Number of organisms entering or leaving the ecosystem
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Population Growth Exponential Growth
Reproduction occurs at a constant rate Growth is unlimited Forms a J-shaped curve
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Population Growth Logistic Growth
Growth slows as less resources become available Carrying capacity: maximum number of organisms the ecosystem can hold Forms a S-shaped curve Number of Yeast Cells Time (hours) Carrying capacity
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Population Growth Limiting Factors: factors that cause population growth to decrease Limiting Growth Factors Amount of nutrients (food, water, etc.) Competition Predation Disease (Parasitism)
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Population Growth Density Dependent Factors: factors that depend on the number of organisms in a population Examples: competition, predation, parasitism, resource availability
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Population Growth Density Independent Factors: factors that affect a population in the same way no matter what size the population is Examples: Weather, Natural disasters, Human activities
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Human Population Growth
The human population remained relatively stable until approximately 500 years ago Advances in medicine, agriculture and technology have increased humans rate of survival Today the human population is above 6 billion and still growing
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Human Population Growth
Industrial Revolution begins Agriculture begins Bubonic plague Plowing and irrigation
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Human Population Growth
Distribution of population by age for industrialized and developing countries U.S. Population Rwandan Population Males Females
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Math Connections The human population increases on average 1.4% every year. If the population is 6 billion now what would the population be next year? 6,000,000,000 x = 84,000,000 people Next years’ population would be 6,084,000,000 If the human population continues this growth the size would double in the next 50 years!
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Reflection What affect might the increase in human population have on the environment and other people? What will happen when humans reach their carrying capacity? What do you think is the human carrying capacity on Earth?
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