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Chapter 21.2 Studying Populations

Chapter 21.2 Studying Populations. Determining Population Size. Direct Observation count all the members Indirect Observation observe signs (nests) Sampling measure a small area and then multiply to find the number in a larger area Mark and Recapture. Changes in Population Size.

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Chapter 21.2 Studying Populations

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  1. Chapter 21.2 Studying Populations

  2. Determining Population Size • Direct Observation • count all the members • Indirect Observation • observe signs (nests) • Sampling • measure a small area and then multiply to find the number in a larger area • Mark and Recapture

  3. Changes in Population Size • Births and Deaths • If the birth rate is higher than the death rate than the population size will increase • If the death rate is higher than the birth rate the population size will decrease • Immigration (moving into an area) • Emigration (moving out of an area)

  4. Population Density • Definition – the number of individuals in an area of specific size • Formula – Number of individuals / unit area Ex: 20 butterflies / 10 m2 = 2 butterflies/m2

  5. Limiting Factors • Definition: An environmental Factor that causes a population to decrease • Food and Water • Space • Weather • Carrying capacity – the largest population size an area can hold

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