Communities and ecosystems

Nature of science:

Use models as representations of the real world—pyramids of energy model the energy flow through ecosystems. (1.10)

• 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.

• 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

• Examples of aspects to investigate in the ecosystem could be species diversity, nutrient cycling, water movement, erosion, leaf area index, among others.