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Population Ecology

This chapter on population ecology explores the fundamental concepts of population, including definition, size, and density. It describes exponential growth, the factors affecting population fluctuations, and the crucial idea of carrying capacity. Key influences on population dynamics include environmental resistance, which is categorized into density-independent and density-dependent factors such as food availability, predation, and disease. By understanding these concepts, we can gain insight into how populations interact within ecosystems and the balance that sustains them.

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Population Ecology

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Presentation Transcript

  1. Population Ecology Chapters 41

  2. Objectives • Define population • Define exponential growth • Understand the concept of carrying capacity • Understand what factors may cause a population to fluctuate in numbers • Understand the concept of environmental resistance

  3. What Is a Population • The term population refers to the number of organisms of the same species residing in a given area • Population size = # of individuals • Population density = # of individuals/unit of area

  4. Change in Population Size • All populations change in size over time • Birth and immigration result in an increased population size if they outnumber death and emigration • Environmental factors play a key role in the increase or decrease of a population

  5. Exponential Growth • Exponential growth results when population growth increases by a constant proportion from one generation to the next • Doubling time is used to measure the rate of population growth

  6. Carrying Capacity • No population can increase in size indefinitely • Carrying capacity is reached when population growth reaches zero • Achieved when birth and immigration equals death and emigration • Carrying capacity limits results from resource availability

  7. What Factors Influence Population Growth • Growth factors are things that cause animals to flourish. • Food, space • Reduction factors are things that cause animals to die. • Food shortages, lack of space, disease, predation, deterioration of habitat, and natural disasters • Collectively, reduction factors constitute environmental resistance.

  8. Environmental resistance can be further grouped into: Density independent factors: limit growth of organisms irrespective of number. Storms, floods, most weather phenomena Density dependant factors: limit increase or decrease of organisms depending on the density (#/area) of the organism. Competition: for food Predation: Predators shift to most populated prey Parasitism: Increase # makes transfer easier Disease: like parasites, disease spreads more readily Environmental Resistance

  9. Species Interactions • Predator – Prey relationships demonstrate one species’ ability to influence another species’ population size

  10. So, Where Are We?

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