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Primary Science · Year 5Chapter 2 · Life cycles of animals
Year 5 Science · Life cycles of animals · Lesson 2.1

Year 5 Science: What is a life cycle?

Part of the Year 5 Science life cycles of animals chapter. Chapter overview · whole chapter on one page

2.1

What is a life cycle?

Year 5
LH1: describe the differences in the life cycles of a mammal, an amphibian, an insect and a bird
Story. Class 5 looks at pictures of four animals: a cat, a frog, a butterfly and a blackbird. “Each one starts as something small, and then grows,” says Mr Patel. “Let’s find out how they are different.”

A life cycle is the series of stages that a living thing goes through. It starts as a young animal, grows into an adult, and can have young of its own. The cycle then goes round again.

The four groups in this chapter start life in different ways. A mammal is usually born alive and fed on milk. An amphibian usually starts as an egg in water. An insect starts as an egg and changes its shape. A bird starts as an egg with a hard shell.

GroupExampleHow the young startWhere the young developWhat the young need first
Mammalcatborn alive (most mammals)inside the mother, then fed on milkmilk from the mother
Amphibianfrogeggs laid in water, as spawnin water, as tadpoleswater to breathe through gills
Insectbutterflyeggs laid on a leafas a caterpillar, which eats leavesleaves to eat
Birdblackbirdeggs with hard shells, in a nestin the egg, then fed by its parentswarmth and food from its parents
Number of stages shown for each life cycle3Mammal4Amphibian4Insect4Bird
Bar chart: the number of stages shown for each life cycle. Mammal 3, amphibian 4, insect 4, bird 4.

Key ideas

  • A life cycle is the series of stages a living thing goes through, from young to adult, and round again.
  • Mammals are usually born alive, and fed on milk.
  • Amphibians, insects and birds usually start life as eggs, but in different ways.
  • Most mammals give birth to live young. Not every animal lays eggs.
Worked example 2.1.1
Look at the table in section 2.1. Which group lays its eggs in water, as spawn? Write the word.

Method. Read the column about how the young start.

  1. Find the column. The column How the young start tells us how each group begins life.
    How the young start
  2. Find the row with spawn. The amphibian row says eggs laid in water, as spawn.
    in water, as spawn
  3. Write the answer.
    amphibian

Check. A frog is an amphibian, and its spawn is laid in water. ✓

Worked example 2.1.2
Look at the table in section 2.1. Which group starts life as an egg laid on a leaf? Write the word.

Method. Read the row for each group.

  1. Compare the rows. The row for the insect says eggs laid on a leaf.
    eggs laid on a leaf
  2. Name the group. The insect is the group that starts life as an egg laid on a leaf.
    insect
  3. Write the answer.
    insect

Check. A butterfly lays its eggs on a leaf. ✓

Worked example 2.1.3
Which group of animals is usually born alive, and fed on milk from its mother? Write the word.

Method. Think about how mammals begin life.

  1. Think about the young. Most mammals give birth to live young, and feed them on milk.
    born alive, fed on milk
  2. Name the group. The group that does this is the mammal group.
    mammal
  3. Write the answer.
    mammal

Check. A cat feeds its kittens on milk. ✓

Watch out

Watch out: not every animal hatches from an egg. Most mammals give birth to live young. Do not say that all animals lay eggs.

Try it (with your teacher or a grown-up). Look at pictures of four animals in a library book, or on a poster, with your teacher. Write each animal’s name in a table. Then write what its young look like when they are born or hatched. Which animals start life as eggs?

Exam tip

Grown-up tip. Ask: “How does this animal start its life? What does it need when it is young?” Let your child use the words life cycle and stage.

Exercise 2A  What is a life cycle?

1
FWhat is the name for the series of stages an animal goes through, from young to adult and back to young again? Write the words.
2
FWhich group of animals is usually born alive, rather than hatching from an egg? Write the word: mammal, amphibian, insect or bird.
3
FWhich group lays its eggs in water, as spawn? Write the word: mammal, amphibian, insect or bird.
4
FWhich group has eggs with hard shells, laid in a nest? Write the word: mammal, amphibian, insect or bird.
5
FWhich group has six legs? Write the word: mammal, amphibian, insect or bird.
6
FHow many stages does the bird life cycle in section 2.5 show? Write the number.
7
FLook at the bar chart in section 2.1. How many stages does the mammal life cycle show? Write the number.
8
PSLook at the bar chart in section 2.1. How many of the four groups show 4 stages? Write the number.
9
PSPriya says every animal lays eggs. Is she right? Write yes or no.
10
PSWrite the word for the young stage of an insect that eats leaves and looks different from the adult.
11
PSWorking scientifically. Compare two groups. Which group has young that start as eggs with hard shells, laid in a nest, and fed by their parents? Write the word.
12
RExplain why a life cycle is called a cycle. Write one sentence.

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