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How does energy from the Sun pass through living things in a food chain?

Describe food chains and food webs, and explain how energy flows from the Sun through producers and consumers

A scaffolded answer to the N(A)-Level Biology outcome on food chains. Producers and consumers, how food chains link into food webs, and why energy is lost at each step so chains are short.

Generated by Claude Opus 4.87 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this dot point is asking

This outcome wants you to describe food chains and food webs, name producers and the different consumers, and explain how energy flows from the Sun through living things. You should be able to explain why energy is lost at each step and why food chains are therefore short. The marks reward correct use of the words producer and consumer, putting the chain in the right order, and a clear account of energy loss.

The answer

Producers and consumers

A food chain shows what eats what, and how energy passes from one living thing to the next. The members are grouped by how they get their food:

  • A producer makes its own food by photosynthesis. Producers are green plants (and some other organisms). They are always at the start of a food chain.
  • A consumer gets its food by eating other living things. A herbivore eats plants (a primary consumer); a carnivore eats animals. Consumers can be secondary, tertiary, and so on, as you move along the chain.

For example: grass (producer) to grasshopper (primary consumer) to frog (secondary consumer) to snake (tertiary consumer). The arrows point in the direction the energy flows.

Where the energy comes from

The energy in every food chain originally comes from the Sun. The producer captures light energy by photosynthesis and stores it as food. When the producer is eaten, that energy passes to the consumer, and so on along the chain.

Food webs

In real life, most animals eat more than one kind of food, and most foods are eaten by more than one animal. So many food chains link together into a food web, which shows all the feeding relationships in a place. A food web gives a fuller picture than a single chain.

Energy loss along the chain

At each step, only some of the energy is passed on. A lot is lost:

  • used up in respiration for movement and keeping warm, then lost as heat;
  • lost in waste (droppings) and in parts that are not eaten.

Because so much energy is lost at every step, there is less and less available further along, which is why food chains rarely have more than four or five links.

Examples in context

Example 1. Why there are many more plants than top predators. Because energy is lost at each step, there is far more energy at the producer level than near the top of a food chain. This is why an area can support huge numbers of grass plants but only a few large predators such as eagles. It shows energy loss shaping the whole community.

Example 2. Why removing one species affects many others. In a food web, species are linked, so removing one, such as a key prey animal, affects everything that eats it and everything it ate. This is why protecting one species often protects many. It shows why a web, not just a single chain, describes nature better.

Try this

Q1. State what a producer is. [1 mark]

  • Cue. A green plant (or similar organism) that makes its own food by photosynthesis.

Q2. State where the energy in a food chain originally comes from. [1 mark]

  • Cue. The Sun.

Q3. Explain why energy is lost at each step of a food chain. [2 marks]

  • Cue. Much of the energy is used in respiration for movement and warmth and lost as heat, and some is lost in waste, so less passes to the next level.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original4 marksIn the food chain grass to grasshopper to frog to snake, name the producer and the consumers, and state where the energy in the chain originally comes from.
Show worked answer →

The producer is the grass, because it makes its own food by photosynthesis. The consumers are the grasshopper (a herbivore, the primary consumer), the frog (which eats the grasshopper, a secondary consumer) and the snake (which eats the frog, a tertiary consumer).

The energy in the chain originally comes from the Sun. The grass captures light energy by photosynthesis and stores it as food, and this energy then passes along the chain when each animal is eaten.

What markers reward: grass as the producer (photosynthesis), the animals as consumers (with the herbivore first), and the Sun as the original source of energy. Calling an animal a producer is a common error; only plants make their own food.

Original4 marksExplain why a food chain rarely has more than four or five links.
Show worked answer →

At each step in a food chain, only some of the energy is passed on to the next organism. A lot of the energy is lost, mainly used up in respiration (for movement and keeping warm) and lost as heat, and some leaves in waste and uneaten parts.

Because so much energy is lost at every step, there is less and less energy available further along the chain. After four or five links, there is not enough energy left to support another level of consumer, so the chain ends.

What markers reward: energy lost at each step (especially through respiration and heat), so less energy is available higher up, meaning there is not enough to support many links. Saying the animals run out of food without mentioning energy loss scores only partly.

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