K327 / K328 / 2027

Organisms and their environment

Try it without your notes

Choose an answer or explain your thinking. Then check what you understand.

Quick checks

0 answered / 0 correct. Your first try counts; you can try again any time.

Check your understanding

A caterpillar eats a leaf, and a bird eats the caterpillar. Which statement is correct?

  1. The caterpillar is a primary consumer and the bird is a secondary consumer in this chain.
  2. The arrow runs from the bird to the caterpillar, because the bird is the one that hunts and eats it.
  3. The leaf is a decomposer because it eventually dies.
Show the answer

The caterpillar is a primary consumer and the bird is a secondary consumer in this chain.

The caterpillar feeds on the producer and the bird feeds on that primary consumer.

Check your understanding

A lower level contains 8,000 kJ and the next level contains 600 kJ of new biomass energy over the same period. What is the transfer efficiency?

  1. 1,333%, because 8,000 should be divided by 600.
  2. 7.5%
  3. 10%, because all chains have the same efficiency.
Show the answer

7.5%

Correct: 600 / 8,000 x 100 = 7.5%. Use the given values rather than assuming every transfer is 10%.

Check your understanding

Producers in a food chain capture 20 000 kJ. About 10% is passed on at each step. How much energy reaches the secondary consumers?

  1. 2 000 kJ
  2. 20 kJ
  3. 200 kJ
  4. 18 000 kJ
Show the answer

200 kJ

20 000 x 0.1 = 2 000 kJ for primary consumers, and 2 000 x 0.1 = 200 kJ for secondary consumers.

Check your understanding

Why can a single tree have a narrow bar in a numbers pyramid but a broad bar in a biomass pyramid?

  1. The tree makes more energy than it receives, so its biomass bar must be wider.
  2. The numbers diagram is always incorrect.
  3. It is one organism but has a large mass compared with individual insects.
Show the answer

It is one organism but has a large mass compared with individual insects.

Counting individuals and measuring their biomass answer different questions.

Check your understanding

One oak tree supports 5 000 caterpillars, which feed 20 birds. Which describes the pyramid of numbers?

  1. Three bars of about the same width, one per level
  2. A narrow base, a wide middle and a narrow top
  3. A narrow base that widens steadily towards the top
  4. A wide base that narrows steadily towards the top
Show the answer

A narrow base, a wide middle and a narrow top

One tree is a small number, the caterpillars are many and the birds are few.

Check your understanding

Which process transfers carbon from atmospheric carbon dioxide into a plant's organic molecules?

  1. Combustion.
  2. Respiration in the leaf cells.
  3. Photosynthesis.
Show the answer

Photosynthesis.

The carbon in carbon dioxide becomes part of organic molecules formed by the plant.

Check your understanding

Which explanation of deforestation and warming is most complete?

  1. Clearing only affects oxygen and cannot affect carbon dioxide.
  2. Every replacement seedling immediately stores as much carbon as a mature forest.
  3. Clearing can release stored carbon and reduce future photosynthetic uptake.
Show the answer

Clearing can release stored carbon and reduce future photosynthetic uptake.

Both the release of stored carbon and the loss of uptake can increase atmospheric carbon dioxide.

Explain your thinking

Write a short answer, then compare it with a sample and check for missing ideas.

Question 1 of 8

Explain a feeding and energy pathway

5 marks

In an original chain, grass feeds grasshoppers, which feed frogs. New biomass energy over the same area and year is 15,000 kJ in grass and 1,800 kJ in grasshoppers. Identify feeding roles, calculate the transfer efficiency and explain why energy does not cycle back through decomposers. [5]

Connect arrows, trophic roles, calculation and the eventual fate of energy.

Loading saved work...

0 / 6000
Ctrl / Cmd + Enter

Use the checklist to compare your answer. This is a self-check, not an exam mark.

Keep one idea for tomorrow

Try a question again without looking at the answer. If you get stuck, revisit its lesson.

Open the chapter summary