40-minute lesson
Primary 2 Science: Growing and changing
Lesson objective
- Describe a life cycle as the stages a living thing goes through as it grows.
- Put the stages of a frog's life cycle in order and describe how a marsupial joey grows in a pouch.
- Compare young animals with their parents.
Success criteria:
- I can explain what a life cycle is.
- I can order egg, tadpole, froglet and adult frog.
- I can say how a young animal is the same as and different from its parent.
Materials
- Pictures (drawn or printed) of the four stages of a frog's life cycle
- Paper plate and a pencil to draw a life-cycle circle
- Photos of family members as babies and as adults (optional)
- Picture books about animals and their young
Introduction
4 minIntroduce today's words:
- life cycle: The stages a living thing goes through as it is born or hatches, grows, becomes an adult and has young of its own.
- young: The babies of an animal. Also called offspring.
- tadpole: A young frog that lives in water, has a tail and breathes with gills.
- froglet: A young frog that has legs but still has a short tail.
- marsupial: A mammal whose tiny babies grow in a pouch on their mother's body.
- joey: The baby of a marsupial, such as an opossum or a wallaby.
Ask your child what they already know about growing and changing.
Explanation
8 minAll living things grow and change. The stages a living thing goes through, from the start of its life to being an adult that has young of its own, are called its life cycle. Then the cycle starts again.
A frog's life cycle has big changes:
- Egg: a frog lays lots of soft, jelly-covered eggs in water.
- Tadpole: a tadpole hatches. It has a tail, lives in water and breathes with gills.
- Froglet: back legs grow first, then front legs. The tail gets shorter and the froglet starts to breathe air.
- Adult frog: the tail is gone. The frog can live on land and in water and can lay eggs of its own.
A marsupial is a mammal that carries its baby in a pouch. A marsupial baby, called a joey, is born tiny, pink and without fur. A newborn opossum is about as small as a bee. The joey crawls into its mother's pouch, drinks her milk and grows fur. When it is big enough, it leaves the pouch, but it stays close to its mother for a while.
Some young animals look a lot like their parents, only smaller, such as kittens, puppies, lambs and chicks. Others look very different, such as tadpoles and caterpillars, and change shape as they grow.
People have a life cycle too: baby, child, teenager, adult.
Worked examples
6 minOrder the frog life cycle
Put these in order: adult frog, tadpole, egg, froglet.
Step 1: What comes first? The egg.
Step 2: What hatches from the egg? A tadpole.
Step 3: The tadpole grows legs and becomes a froglet.
Step 4: The froglet loses its tail and becomes an adult frog, which lays eggs again.
Answer: Egg, tadpole, froglet, adult frog (and back to egg).
A joey in the pouch
How does a marsupial joey grow?
Step 1: It is born very tiny, without fur, and cannot see.
Step 2: It crawls into its mother's pouch.
Step 3: It drinks milk in the pouch and grows bigger and furrier.
Step 4: When it is big enough it comes out of the pouch, then later lives on its own.
Answer: It grows inside its mother's pouch, drinking milk, until it is big enough to come out.
Kitten and cat
How is a kitten like its mother, and how is it different?
Step 1: Same: fur, whiskers, four legs, a tail, the same body shape.
Step 2: Different: smaller, a newborn kitten's eyes are closed, it drinks milk, and it cannot hunt yet.
Answer: A kitten looks like a small cat but is smaller and cannot do everything an adult can.
Guided practice (do together)
8 min1. What hatches from a frog's egg?
(a) A froglet (b) A tadpole (c) An adult frog (d) A fish
2. Which legs does a tadpole grow first?
(a) Front legs (b) No legs ever (c) Back legs (d) Six legs
3. Where does a marsupial joey grow after it is born?
(a) In a nest (b) In an egg (c) In the water (d) In its mother's pouch
4. Which young animal looks most like its parent?
(a) A kitten (b) A tadpole (c) A caterpillar (d) A frog egg
Independent practice
10 min5. What is a life cycle?
(a) A bike with three wheels (b) The stages a living thing goes through as it grows and has young (c) How far an animal can run (d) The food an animal eats
6. Egg, tadpole, froglet, adult frog. Which stage comes first?
7. What is the baby of a marsupial called?
8. A caterpillar makes a chrysalis and changes into what insect?
Questions to check understanding
- Can you explain what a life cycle is?
- Can you order egg, tadpole, froglet and adult frog?
- Can you say how a young animal is the same as and different from its parent?
- What was the trickiest part today?
Answer guide
1. A tadpole — A tadpole hatches from a frog's egg.
2. Back legs — Tadpoles grow their back legs first, then their front legs.
3. In its mother's pouch — Marsupial joeys grow in their mother's pouch.
4. A kitten — A kitten looks like a small cat. Tadpoles and caterpillars change shape a lot.
5. The stages a living thing goes through as it grows and has young — A life cycle is the set of stages from young to adult and back again.
6. egg — A frog's life starts as an egg.
7. joey — Marsupial babies are called joeys.
8. butterfly — A caterpillar forms a chrysalis and changes into a butterfly.
Review
4 minRecap the success criteria together. Watch for these common misconceptions:
- Children often think a tadpole is a fish or a different animal. It is a young frog at an early stage of its life cycle.
- Some children think all babies look like their parents. Frogs and butterflies change shape completely as they grow.
- Children may think a joey is born big or hatches from an egg in the pouch. Marsupial babies are born live and very tiny, then grow in the pouch.
Extension activities
- Make a paper-plate life-cycle wheel for a frog or a butterfly.
- Visit a pond and look for frogspawn or tadpoles without disturbing them.
- Read about another marsupial and draw its joey in the pouch.
Suggested follow-up
- Revisit growing and changing tomorrow with two or three quick questions from memory.
- Try the online practice check for this topic and look at any questions that need another go.
Tips for parents
- Compare baby photos of your child with photos now and talk about what has changed.
- Draw life cycles as a circle with arrows to show that the cycle starts again.
- Safety: if you watch frogs or tadpoles, check local rules before collecting any; it is often best to observe them in a pond. Wash hands after touching pond water or animals.