4.1 & 4.2

Species, communities and ecosystems

4.1 Understandings:

Species are groups of organisms that can potentially interbreed to produce fertile offspring.
Members of a species may be reproductively isolated in separate populations.
Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
Consumers are heterotrophs that feed on living organisms by ingestion.
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
A community is formed by populations of different species living together and interacting with each other.
A community forms an ecosystem by its interactions with the abiotic environment.
Autotrophs obtain inorganic nutrients from the abiotic environment.
The supply of inorganic nutrients is maintained by nutrient cycling.
Ecosystems have the potential to be sustainable over long periods of time.

4.2 Skills:

Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.
Skill: Recognizing and interpreting statistical significance.

4.2 Understandings:

Most ecosystems rely on a supply of energy from sunlight.
Light energy is converted to chemical energy in carbon compounds by photosynthesis.
Chemical energy in carbon compounds flows through food chains by means of feeding.
Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
Living organisms cannot convert heat to other forms of energy.
Heat is lost from ecosystems.
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

4.2 Skills: