Food chains
What is a trophic level?
A trophic level is the position of an organism in a food chain, food web or pyramid. Producers such as plants occupy the lowest level.
Which of the following would help farmers increase the efficiency of food production?
Animals in warm conditions will lose less energy to the surroundings, increasing the efficiency of food production.
What is transferred along a food chain?
Energy and substances are both transferred from organism to organism in a food chain. Only about 10% of the energy at one trophic level is passed to the next.
Which of the following is a reason why not all the energy at one trophic level is passed to the next level?
Energy is used in life processes such as movement, reducing the amount passed to the next level. Energy is lost to surroundings as heat, and also through faeces.
About what percentage of energy is transferred from one trophic level to the next?
Only about 10% of energy is transferred from one trophic level to the next.
What resource do plants not compete for?
Plants do not compete for food because they make their own using photosynthesis. They do compete for water, space, light and minerals.
What is a primary consumer?
Primary consumers are herbivores - animals that eat plants. Cows are an example of a primary consumer because they eat plants such as grass.
Which is the producer in this food chain? grass → cow → human
The grass is the producer. It is a plant that can make its own food by photosynthesis.
Which is the tertiary consumer in this food chain? tree → caterpillar → shrew → owl
The owl is the tertiary consumer. The tree is the producer, the caterpillar is the primary consumer and the shrew is the secondary consumer.
In a certain food chain, 45 kJ of energy is passed to the secondary consumers and 305 kJ is lost by the primary consumers. What percentage is transferred to the secondary consumers?
The total energy in the primary consumers is (45 + 305) = 350 kJ. The percentage transferred is 45 / 350 × 100 = 12.9%
