5.1 Communities and Ecosystems5.1.4: Describe what is meant by a food chain giving three examples, each with at least three linkages (four organisms).• A food chain is a sequence of relationships between trophic levels where each member feeds on the previous one.
5.1 Communities and Ecosystems5.1.5: Describe what is meant by a food web.• A food web is a a diagram that shows the feeding relationships in a community. The arrows indicate the direction of energy flow.
5.1 Communities and Ecosystems5.1.6: Define trophic level.• A trophic level is where an organism is positioned on a food web. – Producer – Primary consumer – Secondary consumer – Tertiary consumer
5.1 Communities and Ecosystems5.1.9: State that light is the initial energy source for almost all communities.• Reference to communities that start with chemical energy is not required. Such as deep sea ocean vents.
5.1 Communities and Ecosystems5.1.10: Explain the energy flow in a food chain.• Energy losses between trophic levels include material not consumed or material not assimilated, and heat loss through cell respiration.
5.1 Communities and Ecosystems5.1.11: State that when energy transformations take place, including those in living organisms, the process is never 100% efficient, commonly being 10–20%.
5.1 Communities and Ecosystems5.1.12: Explain what is meant by a pyramid of energy and the reasons for its shape.• A pyramid of energy shows the flow of energy from one trophic level to the next in a community. The units of pyramids of energy are therefore energy per unit area per unit time, e.g. J/m2/yr.
5.1 Communities and Ecosystems5.1.13: Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled.• Energy enters as light and usually leaves as heat.• Nutrients do not usually enter an ecosystem and must be used again and again. Nutrients such as Carbon dioxide, Nitrogen, and Phosphorus
5.1 Communities and Ecosystems5.1.14: Explain the role of saprotrophic bacteria and fungi (decomposers) in recycling nutrients.• The digestive enzymes secreted by saprophytes breaks down the organic molecules in dead material releasing the nutrients that were ‘locked up’