Learning focus
Use precise biological vocabulary, interpret diagrams and data, explain mechanisms as linked sequences, and evaluate biological applications and environmental decisions.
Producer and consumer
A producer makes organic nutrients, usually by photosynthesis. A consumer obtains organic nutrients by feeding. Herbivores feed on plants, carnivores feed on animals, and omnivores feed at more than one type of level.
Trophic levels
Each feeding position is a trophic level. Producers form the first trophic level, primary consumers the second, and secondary consumers the third. One species may occupy different levels if its diet changes.
Arrows
An arrow points from the food organism to the feeding organism because it shows the direction of energy transfer. It does not point towards what is eaten. Correct arrow direction is essential when constructing chains.
Decomposers
Decomposers, mainly fungi and bacteria, obtain nutrients from dead material and waste. They act on material from every trophic level and recycle mineral nutrients, so they are not simply placed at the end of one straight chain.
Practical or data skill
Construct several chains from organism lists and label producer, herbivore, carnivore and trophic level.
Examination tip
Food-chain arrows point from food to feeder.
Review questions and suggested answers
Question 1
What is a producer?
Suggested answer
An organism that makes organic nutrients, usually by photosynthesis.
Question 2
What does an arrow represent?
Suggested answer
Direction of energy transfer.
Question 3
What is a primary consumer?
Suggested answer
An organism feeding on a producer.
