Science Curriculum Preview Committee Clarification of Learning Results

Revised 04/08/04

9-12

B3: Analyze the factors that affect population size (e.g., reproductive and survival rates).

Curriculum Organizing Questions

  • What are some of the environmental factors that affect this population of organisms' growth?
  • What other organisms are linked to the natural swings in population for this organism?
  • How has this population changed over time?
  • What are the birth rates, mortality rates, emigration rates, and immigration rates for this population?
  • Does this population show signs of linear or exponential growth?
  • What factors influence human populations?
  • What are some strategies for reducing the human population growth?
  • What is the carrying capacity of this ecosystem for this organism?
Elaboration

This learning result covers the basic ideas of population growth in general, as well as, some of the specifics of human population growth

Specific Ideas
  • As any population of organisms grows, it is held in check by one or more environmental factors: depletion of food or nesting sites, increased loss to increased number of predators, or parasites.Benchmarks 5D1
  • Like many complex systems, ecosystems tend to show cyclic fluctuations around a state of approximate equilibrium.Benchmarks 5D2
  • In the long run ecosystems always change when climate changes or when one or more new species appear as a result of migration or local evolution. Benchmarks 5D2
  • The amount of life any environment can support is limited by the available energy, water, oxygen, and minerals, and by the ability of ecosystems to recycle the residue of dead organic materials.Benchmarks 5E2
  • Living organisms have the capacity to produce populations of infinite size, but environments and resources are finite.NSES C4d
  • Populations grow or decline through the combined effects of births or deaths, and through emigration and immigration.NSES F2a
  • Populations can increase through linear or exponential growth, with effects on resource use and environmental pollution.NSES F2a
  • For human populations various factors influence birth rates and fertility rates, such as average levels of affluence and education, importance of children in the labor force, education and employment of women, infant mortality rates, costs of raising children, availability and reliability of birth control methods, and religious beliefs and cultural norms that influence personal decisions about family size. NSES F2b
  • Populations can reach limits to growth. Carrying capacity is the maximum number of individuals that can be supported in a given environment.overs the basic ideas of population growth in general, as well as, some of the specifics of human population growth. NSES F2c
Developmental & Instructional Implications

Students of all ages think that some populations of organisms are numerous in order to fulfill a demand for food by another population. Research shows that students have a poorly developed understanding of the relationships among populations within a community and connections between populations and other ideas such as competition for resources. If, for example, students are asked about the size of populations and why some populations would be larger, they often simply describe rather than reason about interdependence or energy flow. Benchmarks p.342

Examples

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