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Populations in Ecology

Lesson # 27. Populations in Ecology. ECOLOGY. It is the study of the interaction that living things have with each other and with their environment. Importance of Ecology. It provides the information base that society can use to make decisions about the environment . E C O L O G Y .

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Populations in Ecology

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  1. Lesson # 27 Populations in Ecology

  2. ECOLOGY It is the study of the interaction that living things have with each other and with their environment Importance of Ecology It provides the information base that society can use to make decisions about the environment

  3. E C O L O G Y

  4. For Ecology, life is organized into: 1- Population All the members of a single species that live together in a specific geographic region. 2- Community The population of all species living in a single region. 3- Ecosystem It is the community plus all the non-living elements that interact with it (rainfall, chemicals nutrients, soil). 4- The Biosphere It is the interactive collections of all the Earth’s ecosystems.

  5. 25,000 22,000 19,000 16,000 13,000 10,000 7,000 4,000 1,000 1 4 7 10 13 16 19 22 25 Populations: Size and Dynamics Arithmetic growth

  6. 256,000 128,000 Water flea Daphnia 64,000 32,000 16,000 8,000 1 4 7 10 13 16 19 22 25 Exponential growth

  7. Populations growth exponentially because each living thing is capable of playing part in giving rise to more units.

  8. Environmental Resistance CharlesDarwin: “There is not exception to the rule that every organic being naturally increase at so high a rate, that, if not destroyed, the Earth would soon be covered by the progeny of a single pair”. Logistic growth: Population starts growing exponentially, but eventually the rate of growth slows and finally ceases altogether, stabilizing at a certain level (K).

  9. Factors that limit population growth Environmental Resistance 1- Water supply 2- Food supply All the forces of the environment that act to limit population growth. 3- Living space 4- Diseases 5- Predators 6- Wastes produced by the organisms

  10. Environmental Resistance Carrying capacity (K) It is the maximum population density of a given species that a defined geographical area can sustain over time.

  11. When species stabilize their rate of growth to a certain level they are known as “equilibrium species” The growth of the population of equilibrium species is limited by carrying capacity (K)

  12. Favorable weather Fly population increases enormously Abundant food supply Change in temperature Fly population decreases enormously Food is gone In contrast to equilibrium species, other species like houseflies tends to fluctuate greatly in reactions to variations in its environment When population size tends to fluctuate greatly in reactions to variations in its environment they are known as “opportunistic species”

  13. The population sizes of these species tend to be only limited by their reproductive rate ( r ). r-selected species: Species whose population sizes tend to be limited by reproductive rate.

  14. POPULATION SIZE Limited by carrying capacity (K) Limited by reproductive rate ( r ) Density dependent Density independent Relatively stable Relatively unstable ORGANISMS Larger, long-lived Smaller, short-lived Produce fewer offspring Produce many offspring Provide greater care for offspring Provide no care for offspring

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