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POPULATIONS

POPULATIONS. Honors Biology. REVIEW . What is ecology? What do the following terms mean: Organism Population Community Ecosystem Biosphere What is the difference between abiotic and biotic factors? Name examples. OBJECTIVES.

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POPULATIONS

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  1. POPULATIONS Honors Biology

  2. REVIEW • What is ecology? • What do the following terms mean: • Organism • Population • Community • Ecosystem • Biosphere • What is the difference between abiotic and biotic factors? Name examples.

  3. OBJECTIVES • Explain difference between population size, density and distribution • What are the three main patterns of population dispersion? • What are the three types of survivorship curves? • Explain difference between exponential and logistic models of population growth. • What is the difference between density dependent and density independent factors?

  4. WHAT IS A POPULATION • A group of organisms that belong to the same species and live in a particular place at the same time.

  5. PROPERTIES OF POPULATIONS • Population Size: • Number of individuals it contains • May be hard to measure (too many, too mobile) • May need to sample • Population Density: • How crowded a population is • Density of country vs. city

  6. PROPERTIES OF POPULATIONS • Dispersion • Spatial distribution of individuals in the population • Three Types • Clumped: resources are clumped; social behavior (herds and flocks) • Even: social interactions; birds flying • Random: seed dispersal

  7. POPULATION DYNAMICS • All populations are dynamic (change in size and composition over time) • Birth Rate: number of births in a period of time • Death Rate: number of deaths in a period of time • Life Expectancy: how long individual is expected to live

  8. POPULATION DYNAMICS • Age Structure: Population Pyramids • Survivorship curves: likelihood to survive at different ages • Type 1: Humans and elephant likely to live long; mortality increases with advanced age • Type 2: Same chance of dying throughout life • Type 3: High chance of dying young but if survive  live a long time; insects and salmon

  9. MEASURING POPULATIONS • Measuring Growth Rate: how a population’s size changes over time • Increases: birth and immigration • Decreases: death and emigration • Growth = birth rate – death rate

  10. EXPONENTIAL MODEL • Population that increases rapidly • J shaped curve • Only for period of time • Limiting factors

  11. LOGISTIC MODEL • Exponential with limiting factors • Birth rates decline and death rates rise as population grows • K = carrying capacity • S curve

  12. POPULATION FLUCTUATIONS • Density Independent Factors: • Effect populations • Size of population doesn’t matter • Ex. Weather, floods and fires • Density Dependent Factors: • Depend on size of population • Resource limitations • Food shortages and nesting sites • Population Fluctuations: lynx and hare

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