3.2M Classification of Living Things

Chapter 2: Classification of Living Things | P3 Science
Chapter 2 · Primary 3 Science
Classification of
Living Things
📚 Section A — Revision Notes

🎯 What I Will Learn

  • What are some groups of living things?
  • What are the characteristics of plants?
  • How are plants classified?
  • How are animals classified?
  • How are plants different from animals?
  • What are fungi?
  • What are bacteria?
1
What Are Some Groups of Living Things?
  • Living things are similar to one another in some ways and different in other ways.
  • We can classify living things based on their similarities or differences.
  • Living things can be classified into different groups. Some groups are plants, animals, fungi and bacteria.
Living things grouped into plants, animals, fungi and bacteria Living things Plants Animals Fungi Bacteria
💡 Memory Trick — Mnemonic
Peel A Fresh Banana!
P
Plants
A
Animals
F
Fungi
B
Bacteria
🎯
Get It Right!
✗ Wrong There are only four groups of living things — plants, animals, fungi and bacteria.
✓ Correct There are many ways to classify living things into groups. Plants, animals, fungi and bacteria are some of the groups. There are others, such as protists (which include algae). Seaweed looks like a plant but is not — it is an algae.
2
What Are the Characteristics of Plants?
  • Plants are living things.
  • Plants need air, water and food to survive. They can grow, reproduce and respond to changes.
  • Plants have parts such as leaves, a stem and roots. Some plants may also have flowers and fruits.
  • The parts may look different in different plants (e.g. leaves can be larger or smaller).
  • Plants make their own food in the presence of light.
  • Plants do not move from place to place. They can only move their parts (e.g. bending towards sunlight).
Parts of a plant — leaf, stem, roots, flower, fruit Parts of a plant roots stem leaf flower fruit
3
How Are Plants Classified?
By where they grow
  • Some plants grow on land — in soil, on buildings, or even on other plants.
  • Some plants grow in water — in ponds, lakes or rivers.
Flowering vs Non-flowering Plants
  • Plants can also be classified into flowering plants and non-flowering plants.
🌸 Flowering Plants 🌿 Non-flowering Plants
Bear flowers Do not bear flowers
Flowers develop into fruits with seeds inside Reproduce from structures called spores
Seeds grow into new plants Spores found in spore bags on the underside of leaves
Examples: orchid, mango, chilli Examples: ferns, mosses
Flowering vs non-flowering plants Left: orchid (flowering plant) with flowers and fruits. Right: fern (non-flowering) with spore bags on leaf underside. 🌸 Flowering Plant — Orchid 🌿 Non-flowering Plant — Fern flowers → fruits → seeds Spore bags (underside of leaf) 🟤 spore bags reproduces by spores (no flowers)
4
How Are Animals Classified?
  • Animals are living things. They have a head and a body, and may also have legs and a tail.
  • Scientists have classified animals into six groups based on their similarities and differences.
💡 Memory Trick — Mnemonic
My Father Is A Big Rockstar!
M
Mammals
F
Fish
I
Insects
A
Amphibians
B
Birds
R
Reptiles
🐸
Amphibians
  • Can live both on land and in water
  • Have strong legs and webbed feet to swim
  • Breathe through skin (in water) and lungs (on land)
  • Most have moist skin — prevents drying out on land
  • Most reproduce by laying eggs in water
  • Young live in water; adults can live on land and in water
Examples: frogs, toads, newts, salamanders
🐦
Birds
  • Outer covering of feathers
  • Have a pair of wings, a pair of legs and a beak
  • Wings and feathers help them fly
  • All birds reproduce by laying eggs
  • Most birds can fly — some cannot (ostriches, emus, penguins, kiwis)
Examples: crows, eagles, penguins
Parts of a bird Bird diagram showing beak, feathers, wings and legs with labels. Parts of a bird beak wing feathers leg (×2)
🐟
Fish
  • Usually live only in water
  • Outer covering of scales
  • Have fins and a tail to swim
  • Have gills to breathe in water (protected by a gill cover)
  • Most reproduce by laying eggs; some give birth (guppies, mollies, some sharks)
  • Some fish (e.g. mudskippers) can live on land briefly — breathe through skin
Examples: goldfish, sharks, tilapia, koi
Parts of a fish Fish diagram showing fin, tail, scales, gill cover with labels. Parts of a fish fin tail scales gill cover (gills underneath)
🐛
Insects
  • Have a hard, shell-like outer covering
  • Have six legs and a pair of feelers
  • Body divided into three parts: head, thorax and abdomen
  • Some have no wings (ants), one pair (mosquitoes), or two pairs (butterflies)
  • Most reproduce by laying eggs
Examples: cockroaches, grasshoppers, houseflies, honeybees
Parts of an insect Bee diagram showing head, thorax, abdomen, six legs, two feelers and wings with labels. Parts of an insect (bee) abdomen thorax head feelers (×2) wings legs (×6) 3 body sections head · thorax · abdomen 6 legs · 2 feelers
🦎
Reptiles
  • Have dry and scaly skin
  • Breathe through their lungs
  • Most reproduce by laying eggs
  • Cold-blooded — body temperature changes with their environment
  • Most have four legs; some (snakes) have none
  • Some (tortoises) have a shell to protect their body
Examples: crocodiles, snakes, tortoises
🐘
Mammals
  • Have hair or fur as their outer covering
  • Most reproduce by giving birth to their young
  • Females have mammary glands — feed young with milk
  • Warm-blooded — maintain a constant body temperature
  • Skin has structures that produce sweat — helps cool down when hot
Examples: humans, cats, dolphins, bats
🎯
Get It Right!
✗ Wrong All birds can fly. / Birds that cannot fly do not have wings.
✓ Correct All birds have wings. However, not all birds can fly (e.g. ostriches, emus, penguins, kiwis).
🎯
Get It Right!
✗ Wrong Bats are birds. / Whales and dolphins are fish.
✓ Correct Bats are mammals — they have hair and feed young with milk. Whales and dolphins are also mammals — they have hair on some parts of their body, give birth and feed young with milk. They are not fish even though they live in water.
💡
Exam Tip — Insects phrasing
These two sentences have different meanings — choose carefully:

1. “The body of an insect is divided into three parts.” — refers to 3 sections (head, thorax, abdomen) ✓
2. “An insect has three body parts.” — incorrectly implies only 3 parts total ✗

An insect has more than 3 body parts (head, 6 legs, 2 feelers, wings, etc.). Always use sentence 1.
👍
Good to Know
  • Jellyfish, silverfish, starfish, cuttlefish and crayfish have “fish” in their names but are not fish. They belong to different animal groups.
  • Frogs have moist skin; toads have thick, dry and bumpy skin — toads spend more time on land so their skin doesn’t need to stay moist.
  • An ostrich cannot fly but can run at 70 km per hour — it is the fastest running bird. Ostrich eggs are the largest of all eggs.
Unique Characteristics Summary
Animal Group Unique Characteristic(s)
🐸 Amphibians Can live both on land and in water
🐦 Birds Have feathers · Have a beak
🐟 Fish Live only in water · Have gills · Have fins
🐛 Insects Have six legs · Body divided into three parts
🦎 Reptiles Have dry and scaly skin
🐘 Mammals Have fur or hair · Give birth · Feed young with mother’s milk
📋 Checkpoint 2.1
1. Name the six animal groups.
Amphibians, Birds, Fish, Insects, Reptiles, Mammals.
(Mnemonic: My Father Is A Big Rockstar!)
5
How Are Plants Different from Animals?
  • Similarity: Both plants and animals are living things.
  • Differences: Plants and animals are different in some ways.
🌿 Plants 🐘 Animals
✔Have leaves, a stem and roots ✗Do not have leaves, a stem and roots
✔Make their own food (in presence of light) ✗Cannot make their own food
✗Do not move from place to place ✔Can move from place to place
⚙️ Worked Example 2.1 — Flow Chart (D, E, F)
Flow chart: Animals → Does it live in water?
  • No → D
  • Yes → Does it have gills?
    • No → E
    • Yes → F

Which best represents D, E and F from: Giraffe, Whale, Catfish?
How to solve:
D does not live in water → Giraffe (lives on land).
E lives in water but has no gills → Whale (mammal, breathes through lungs).
F lives in water and has gills → Catfish (fish).

Answer: D = Giraffe, E = Whale, F = Catfish → Option (4)
6
What Are Fungi?
  • Fungi (singular: fungus) are a group of living things that do not make their own food.
  • Fungi grow on other things, which may be living or dead.
  • They produce a substance to break down the thing they grow on into simpler substances, then absorb the simpler substances as food.
  • Fungi reproduce through structures called spores. Spores are small and light — easily carried by wind. When they land on a suitable place, they grow into new fungi.
  • Spores of mushrooms are found in the gills under the cap.
  • Fungi grow and reproduce quickly in warm and moist places.
Parts of a mushroom — cap, gills and stalk Parts of a mushroom cap gills (spores found here) stalk
Fungi can be useful or harmful
✔ Useful Fungi ✗ Harmful Fungi
Some mushrooms can be eaten Some mushrooms are poisonous
Yeasts help bread dough rise Bread mould can make us sick
Used to make cheese and tempeh Athlete’s foot is a disease caused by harmful fungi
Penicillium mould makes the medicine penicillin Can grow on and spoil food and leather goods
🎯
Get It Right!
✗ Wrong Mushrooms are plants. / All fungi can be eaten.
✓ Correct Mushrooms cannot make their own food like plants do — they are fungi. Not all fungi can be eaten — some are poisonous. Bread mould is harmful and should not be eaten.
👍
Good to Know
Fungi grow quickly in warm and moist places. A pack of bread left on the kitchen counter will grow bread mould more quickly than one kept in the refrigerator.
📋 Checkpoint 2.2
1. State one difference between a plant and a fungus.
Plants can make their own food in the presence of light. Fungi cannot make their own food — they break down the thing they grow on and absorb it as food.
7
What Are Bacteria?
  • Bacteria (singular: bacterium) are a group of microorganisms — they can only be seen under a microscope.
  • Bacteria are found in different sizes and shapes.
  • Like fungi, bacteria also grow on other things, which may be living or dead.
Microorganisms — living things that can only be seen clearly under a microscope. A microscope is an instrument that allows us to see very small things clearly.
🎯
Get It Right!
✗ Wrong Bacteria are not living things.
✓ Correct Bacteria are living things. Like all living things, they need air, water and food. They can grow, respond to changes and reproduce.
Bacteria of different shapes and sizes as seen under a microscope Four types of bacteria shapes: rod-shaped, spherical clusters, spiral, and irregular branching forms. Bacteria shapes (as seen under a microscope) rod-shaped spherical spiral branching Bacteria can only be seen under a microscope (microorganisms)
Bacteria of different shapes and sizes as seen under a microscope Four types of bacteria shapes: rod-shaped, spherical clusters, spiral, and irregular branching forms. Bacteria shapes (as seen under a microscope) rod-shaped spherical spiral branching Bacteria can only be seen under a microscope (microorganisms)
Bacteria can be useful or harmful
✔ Useful Bacteria ✗ Harmful Bacteria
Help us break down food in our body Can enter our body and make us sick
Used to make yoghurt, cheese and pickles Found all around us — important to wash hands before eating
📋 Checkpoint 2.3
1. How does washing our hands before eating protect our body from harmful bacteria?
Bacteria are found all around us, including on our hands. When we wash our hands before eating, we remove the harmful bacteria from our hands. This way, harmful bacteria cannot enter our bodies through the food we eat.

⚡ Chapter Summary

  • Living things can be classified into plants, animals, fungi and bacteria (mnemonic: Peel A Fresh Banana!).
  • Plants have leaves, stem, roots; make their own food; do not move from place to place.
  • Plants are classified as flowering (seeds) or non-flowering (spores).
  • The 6 animal groups are Mammals, Fish, Insects, Amphibians, Birds, Reptiles (My Father Is A Big Rockstar!).
  • Plants make their own food; animals cannot — this is a key difference.
  • Fungi do not make food — they break down other things and absorb food. Reproduce by spores.
  • Bacteria are microorganisms — only visible under a microscope. Can be useful or harmful.
  • Wash hands before eating to stop harmful bacteria entering our body.

✏️ Test Yourself

1. A crocodile (Animal X) and a fish (Animal Y) are shown. What characteristic do both animals have in common?
  • 1Both breathe through gills.
  • 2Both give birth to their young.
  • 3Both have fins to move in water.
  • 4Both have scales as an outer covering.
2. Look at the mushroom shown.

(a) Which group of living things does it belong to?
Fungi
(b) State one way in which a mushroom is different from a plant.
Accept any one of the following:
• Plants can make their own food in the presence of light. Mushrooms (fungi) cannot make their own food.
• Plants have leaves, a stem and roots. Mushrooms do not have leaves, a stem and roots.
• Plants reproduce through seeds or spores from spore bags on their leaves. Mushrooms reproduce through spores found in the gills under the cap.
✏️ Test Yourself — Take the Chapter 2 Quiz →

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P3 Science Chapter 2 — psle.edu.sg

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