C.2 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)

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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