1. Species are groups of organisms that can potentially interbreed to produce fertile offspring.

• Describe limitations of the biological species concept.

• Define species according to the biological species concept.

2. Members of a species may be reproductively isolated in separate populations.

• Define population.

• Outline how reproductive isolation can lead to speciation.

3. Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).

4. Consumers are heterotrophs that feed on living organisms by ingestion.

5. Detrivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.

6. Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.

7. A community is formed by populations of different species living together and interacting with each other.

• Define species, population and community.

• Give an example of a community of organisms.

8. A community forms an ecosystem by its interactions with the abiotic environment.

• Define abiotic and ecosystem.

9. Autotrophs obtain inorganic nutrients from the abiotic environment.

10. The supply of inorganic nutrients is maintained by nutrient recycling.

11. Ecosystems have the potential to be sustainable over long periods of time.

• Define sustainability.

• Give an example of an unsustainable practice.

• Outline three requirements of a sustainable ecosystem.

1. Classifying species as autotrophs, consumers, detrivores or saprotrophs from a knowledge of their mode of nutrition.