Essential idea: Changes in community structure affect and are affected by organisms.
Between the two coral heads is a crown of thorns sea star. These predators graze the corals. If too successful they will change the community structure of the reef so that it becomes dominated by algae rather than coral. This in turn forces the sea star to migrate to other reefs where coral dominates the community structure.
Understandings, Applications and Skills
| C.2.U1 | Most species occupy different trophic levels in multiple food chains. |
| C.2.U2 | A food web shows all the possible food chains in a community. |
| C.2.U3 | The percentage of ingested energy converted to biomass is dependent on the respiration rate. |
| C.2.U4 | The type of stable ecosystem that will emerge in an area is predictable based on climate. |
| C.2.U5 | In closed ecosystems energy but not matter is exchanged with the surroundings. |
| C.2.U6 | Disturbance influences the structure and rate of change within ecosystems. |
| C.2.A1 | Conversion ratio in sustainable food production practices. |
| C.2.A2 | Consideration of one example of how humans interfere with nutrient cycling. |
| C.2.S1 | Comparison of pyramids of energy from different ecosystems. |
| C.2.S2 | Analysis of a climograph showing the relationship between temperature, rainfall and the type of ecosystem. |
| C.2.S3 | Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores and flows between taiga, desert and tropical rainforest. |
| C.2.S4 | Analysis of data showing primary succession. |
| C.2.S5 | Investigation into the effect of an environmental disturbance on an ecosystem. [Examples of aspects to investigate in the ecosystem could be species diversity, nutrient cycling, water movement, erosion, leaf area index, among others.] |
[Text in square brackets indicates guidance notes]
Presentation and NotesThe presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.
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Use the Cornell style template to collate your own notes for Topic C.2 Communities and ecosystems.
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Nature of Science
Use models as representations of the real world—pyramids of energy model the energy flow through ecosystems. (1.10)
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?
