5.3 populations

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5.3 populations

  1. 1. 5.3 Populations Topic 5 – Ecology & Evolution
  2. 2. 5.3 Populations 5.3.1 Outline how population size is affected by natality, immigration, mortality and emigration.
  3. 3. 5.3 Populations • Natality – offspring are produced and added to the population • Mortality – individuals die and are lost from the population • Immigration – individuals move into the area from somewhere else and add to the population • Emigration – individuals move out of the area and are lost from the population
  4. 4. 5.3 Populations 5.3.2 Draw a graph showing the sigmoid (Sshaped) population growth curve.
  5. 5. 5.3 Populations 5.3.3 Explain reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases.
  6. 6. 5.3 Populations Exponential Phase Population increases exponentially because the natality rate is higher than the mortality rate. This is because there is an abundance of food, and disease and predators are rare.
  7. 7. 5.3 Populations Transitional Phase Difference between natality and mortality rates are not as great, but natality is still higher so population continues to grow, but at a slower rate. Food is no longer as abundant due to the increase in the population size. May also be increase predation and disease.
  8. 8. 5.3 Populations Plateau Phase Natality and mortality are equal so the population size stays constant. Limiting Factors: • shortage of food or other resources • increase in predators • more diseases or parasites If a population is limited, then it has reached its carrying capacity
  9. 9. 5.3 Populations Carrying capacity The maximum population size that can be supported by the environment
  10. 10. 5.3 Populations 5.3.4 List three factors which set limits to population increase. Limiting Factors: 1. shortage of food or other resources 2. Increase in predators 3. More diseases or parasites
  11. 11. 5.3 Populations The IBO assessment statements:
  12. 12. 5.3 Populations 5.3.1 Outline how population size is affected by natality, immigration, mortality and emigration. •Aim 7: Simulation exercises can be performed. 5.3.2 Draw and label a graph showing a sigmoid (Sshaped) population growth curve. 5.3.3 Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases. 5.3.4 List three factors that set limits to population increase.

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