Food Chains Questions & MCQ — Practice with Answers

What is a food chain?

A food chain shows how energy flows from one living thing to another through food. Every food chain begins with energy from the Sun, which green plants use to make their own food through photosynthesis. The energy then passes along the chain as one organism is eaten by the next.

A simple food chain looks like this: Sun → grass → grasshopper → frog → snake → eagle. The arrows show the direction that energy flows — from the organism being eaten to the organism doing the eating.

Producers

Producers are organisms that can make their own food. Green plants are producers because they use sunlight, water, and carbon dioxide to make food through photosynthesis. They are always the first living thing in a food chain because they convert the Sun's energy into food energy that other organisms can use.

Without producers, no other organisms in the food chain would have food. They form the foundation of every food chain.

Consumers

Consumers are organisms that cannot make their own food and must eat other organisms to get energy. There are different levels of consumers:

• Primary consumers eat producers (plants). They are also called herbivores. Examples: grasshoppers, caterpillars, rabbits.
• Secondary consumers eat primary consumers. They are carnivores or omnivores. Examples: frogs, small birds.
• Tertiary consumers eat secondary consumers. They are usually top predators. Examples: eagles, snakes.

Predators and prey

A predator is an organism that hunts and eats other animals. A prey is an organism that is hunted and eaten by a predator. The same organism can be both a predator and a prey — for example, a frog is a predator of insects but is also prey for snakes.

In a food chain, the predator-prey relationship shows how energy transfers from one animal to another. The population of predators and prey are closely linked: if the prey population decreases, the predator population will also decrease because there is less food available.

What happens when a population changes

If one organism in a food chain is removed or its population changes, it affects the other organisms in the chain. For example, in the food chain grass → rabbit → fox:

• If the rabbit population decreases, the grass population would increase (less grass is eaten) and the fox population would decrease (less food is available for foxes).
• If the rabbit population increases, the grass population would decrease (more grass is eaten) and the fox population would increase (more food is available for foxes).

These changes ripple through the food chain in both directions. This is why every organism in a food chain plays an important role in keeping the ecosystem balanced.

“The Sun is a producer in the food chain.” The Sun is not a producer. The Sun is a source of energy, but it is not a living thing and does not produce food. Producers are green plants that use the Sun's energy to make their own food through photosynthesis. A food chain starts with the Sun as the energy source, but the first organism in the chain is always a producer (a green plant).

“Arrows in a food chain show what eats what.” This is one of the most common mistakes in PSLE Science. The arrows in a food chain show the direction of energy flow, not “what eats what”. The arrow points from the organism being eaten to the organism doing the eating. For example, grass → rabbit means energy flows from the grass to the rabbit (the rabbit eats the grass). If you read the arrow as “what eats what”, you would get it backwards.

“Removing one organism only affects the next organism in the chain.” When one organism is removed from a food chain, it creates a ripple effect that affects organisms in both directions. If rabbits are removed from the chain grass → rabbit → fox, the grass population would increase (nothing eating it) and the fox population would decrease (no food). The effects do not stop at just one link — they travel along the entire chain.

“All animals are consumers and all plants are producers.” While all green plants are producers, not all plants carry out photosynthesis equally (some parasitic plants do not). More importantly, students sometimes forget that decomposers (bacteria and fungi) are neither producers nor typical consumers. Decomposers break down dead matter and return nutrients to the soil, playing a different but essential role in the food chain.