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C.2 Communities and ecosystems

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Description

Nature of science:
Use models as representations of the real world—pyramids of energy model the energy flow through ecosystems. (1.10)
Understandings:
  • Most species occupy different trophic levels in multiple food chains.
  • A food web shows all the possible food chains in a community.
  • The percentage of ingested energy converted to biomass is dependent on the respiration rate.
  • The type of stable ecosystem that will emerge in an area is predictable based on climate.
  • In closed ecosystems energy but not matter is exchanged with the surroundings.
  • Disturbance influences the structure and rate of change within ecosystems.
Applications and skills:
  • Application: Conversion ratio in sustainable food production practices.
  • Application: Consideration of one example of how humans interfere with nutrient cycling.
  • Skill: Comparison of pyramids of energy from different ecosystems.
  • Skill: Analysis of a climograph showing the relationship between temperature, rainfall and the type of ecosystem.
  • Skill: Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores and flows between taiga, desert and tropical rainforest.
  • Skill: Analysis of data showing primary succession.
  • Skill: Investigation into the effect of an environmental disturbance on an ecosystem.
Guidance:
  • Examples of aspects to investigate in the ecosystem could be species diversity, nutrient cycling, water movement, erosion, leaf area index, among others.
 Theory of knowledge:
  • Do the entities in scientists’ models, for example trophic levels or Gersmehl diagrams, actually exist, or are they primarily useful inventions for predicting and explaining the natural world?
Utilization:
  • Poikilotherms (animals that have a variable body temperature) are more effective producers of protein than homeotherms (animals that maintain a regulated body temperature) as they have a higher rate of conversion of food to biomass.
Syllabus and cross-curricular links:
Biology
Topic 4.2 Energy flow

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