Chapter 05

Life Cycles, Food Chains & Habitats

Primary

Every animal grows up through its own set of stages, every meal connects to another meal in a chain, and every creature lives in a home suited exactly to its needs. This chapter connects the dots between them.

At a glance
Core ideaLife cycles, food chains and habitats weave into one web of life.
Key termFood chain — arrows show energy flowing from producer to consumer.
You can…Predict how breaking one link affects animals further along the chain.
Watch outDon't forget decomposers — they recycle every link back to the soil.
1 Theory

Life cycles

A life cycle is the series of stages a living thing passes through as it grows up. A butterfly's life cycle has four stages: egg → caterpillar (larva) → pupa (chrysalis) → adult butterfly. A frog's is similar: egg → tadpole → froglet → adult frog.

Food chains

A food chain shows "who eats whom," with arrows meaning "energy flows to":

Sun → Grass (producer) → Rabbit (eats grass) → Fox (eats rabbit)

Plants are called producers because they produce their own food. Animals are consumers because they consume (eat) other living things. When something dies, decomposers like worms, fungi and bacteria break it down and return nutrients to the soil.

Sun Grass producer Rabbit consumer Fox consumer Each arrow means "energy flows to" — decomposers recycle every link when it dies.
A simple food chain: energy passes from the Sun to grass, to the rabbit that eats it, to the fox that eats the rabbit.

Habitats

A habitat is the natural home of a plant or animal, providing exactly what it needs to survive — food, water, shelter and the right conditions. A polar bear's thick fur habitat is the icy Arctic; a camel's habitat is the hot, dry desert.

Grass producer Grasshopper Rabbit Frog Fox Hawk apex
A food web links many chains: each arrow means "energy flows to", and one animal (the hawk) can sit atop several chains at once.
2 Explanation

How it all connects: the web of life

These three ideas are not separate — they weave together. An animal's life cycle keeps its species going generation after generation. Its habitat must supply everything each life-cycle stage needs (a tadpole needs water; a froglet needs both land and water). And every creature in that habitat is a link in a food chain, connected to the plants and animals around it. If one link breaks — say, a habitat is destroyed and the grass disappears — the whole chain suffers: rabbits go hungry, and then foxes go hungry too. This is why scientists say nature is a connected web, not just separate pieces.

Key idea

Removing just one part of a food chain — even a small one, like grass or insects — can affect every animal further along the chain. Nothing in a habitat lives completely alone.

3 Practical

Activity: build your own food chain

  1. Draw four cards. Draw or write: Sun, Grass, Rabbit, Fox — one per card.
  2. Put them in order. Arrange the cards so each one is a food source for the next.
  3. Add arrows. Draw an arrow from each card to the next, and label each arrow "energy flows to."
  4. Add a decomposer. Draw a worm card with an arrow from the fox back to the worm, showing that when the fox eventually dies, decomposers recycle it.
  5. Try a new chain. Now build a second food chain for a pond habitat (try: Sun → Algae → Small fish → Heron) and explain each link out loud.
4 Q&A

Test yourself

Q1 What stage comes right after "caterpillar" in a butterfly's life cycle?

The pupa (chrysalis) stage — a resting stage in which the caterpillar's body completely transforms before it emerges as an adult butterfly.

Q2 In the food chain Sun → Grass → Rabbit → Fox, what would likely happen to the fox population if all the grass died?

The fox population would likely fall. Less grass means fewer rabbits can find food and survive, so there are fewer rabbits for foxes to eat, so foxes would struggle to find food too. A break early in the chain affects every link after it.

Q3 Name three things a fish's habitat must provide for it to survive.

Any three of: clean water to swim and breathe in (via gills), food (like smaller fish, insects or plants), shelter from predators (like rocks or plants to hide in), and the right water temperature for its body.

Q4 Why are decomposers, like earthworms, important in a habitat?

Decomposers break down dead plants and animals and return their nutrients to the soil. Without decomposers, dead material would just pile up forever, and the soil would run out of the nutrients that new plants need to grow — so decomposers keep the whole food chain supplied with a fresh start.

Concept mind map

How the ideas connect

Every key idea in this chapter, branching from the core concept — use it to see the whole picture at a glance.

egg to adultproducersconsumerspredator and preyhabitatweb of lifeLife Cycles & Food Chains
Infographic

The process, step by step

Step 1ProducerA green plant makes food using sunlight, e.g. grass.
Step 2Primary consumerA plant eater feeds on the producer, e.g. a rabbit.
Step 3Secondary consumerA meat eater eats the plant eater, e.g. a fox.
Step 4Arrow ruleEach arrow points the way energy flows, from eaten to eater.
Solved examples

Worked problems, step by step

Follow each solution line by line, then try to reproduce it on paper before moving on.

Example 1Put in order: caterpillar, egg, butterfly, chrysalis.

  1. A butterfly lays an egg
  2. It hatches to a caterpillar, then a chrysalis

Example 2In grass -> grasshopper -> frog, what eats the grasshopper?

  1. Follow the arrow after grasshopper
  2. The arrow points to frog
Practice problem set

Now you try

Work each one out first, then tap to reveal the worked answer.

1What is a habitat?
A habitat is the natural home where a plant or animal lives and finds what it needs.
2What is a producer in a food chain?
A producer is a plant that makes its own food and starts the food chain.
3Which way do food chain arrows point?
Arrows point from the food to the animal that eats it, showing energy flow.
4Give an example of a predator and its prey.
An owl is a predator and a mouse is its prey.
5Why is it called a web of life?
Many food chains link together like a web because animals eat more than one food.
6Name a stage in a frog life cycle.
A tadpole is a young stage; it hatches from an egg before becoming a frog.