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Ch. 5 Populations

Ch. 5 Populations. Characteristics of Populations. **3 important characteristics of a population are Population Density. Population Growth. ** 3 factors can affect pop size: Birth rate Death rate Individuals entering and leaving the pop. * birth rate > death rate =

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Ch. 5 Populations

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  1. Ch. 5 Populations

  2. Characteristics of Populations • **3 important characteristics of a population are • Population Density

  3. Population Growth • ** 3 factors can affect pop size: • Birth rate • Death rate • Individuals entering and leaving the pop. • * birth rate > death rate = • * death rate > birth rate = • * birth rate = death rate –

  4. Immigration / Emigration • Immigration • Add or subtract? • Emigration • Add or subtract?

  5. Population Growth • Put 4 bacteria cells in a culture of infinite food / unlimited about of bacteria can grow. • After 5 mins.  the bacteria reproduce to make 2x the original # of bacteria

  6. Exponential Growth GEN TIME # BACT

  7. Exponential growth • Happens only at near perfect conditions • Does not happen in nature. Why? • In natural populations, 100 % of new offspring do not survive to reproduce • What adds and subtracts members from a population?

  8. Growth Rate • All these factors; birth, death, immigration, and emigration determine growth rate.

  9. Carrying Capacity • Carrying Capacity • * When death rate = birth rate* at capacity. • What factors determine carrying capacity?

  10. 2 factors that limit population growth • Density – dependent limiting factors

  11. Competition • Competition • The struggle for use of the same resources that are limited. • Animals  • Plants  • Competition is most fierce between the same species. Why?

  12. Predation • All consumers are predators • The organism eaten by the consumer • Prey • Changes in the size of a predator – prey population often occur in cycles. • Ex lynx and hare populations

  13. The S – Shaped Curve • Population begins to grow – little competition • Grows until

  14. Logistic Growth • Growth that has a carrying capacity

  15. Density – Independent limiting factors • Winters, droughts, seasons • Specific organisms – insects and grasses • DILF  exponential growth followed by a sudden collapse of the population

  16. Human Population • How do factors such as improved medical care and increased availability of food impact the birth rates of humans? • Scientist believe the earth’s total carrying capacity for humans is 15 to 20 billion people. What changes in lifestyle would be required in order to accommodate 15 to 20 billion people?

  17. Exponential growth of humans • Currently, the human population is growing at an exponential rate. 7 billion now.

  18. Projected Population Growth

  19. Patterns of Population Growth • Demography • Demographic transition • A dramatic change in birth rates and death rates • Age – Structure Diagrams

  20. Figure 5-13 Age Distribution Section 5-3 U.S. Population Rwandan Population Males Females Males Females

  21. There must be a carrying capacity. • What happens when a population starts to reach it’s carrying capacity? • What type of graph represents this? • Can you predict what will happen if the population does not level off?

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