Grade 4 Science & Technology Study Notes

Welcome to Strand 1 — Living Things and Their Environment

This strand is about living things and where they live. It has three topics:

• Sub-strand 1.1 — Plants: What makes plants living things, how their parts work, and how to care for them.
• Sub-strand 1.2 — Animals: What makes animals living things and how we group them.
• Sub-strand 1.3 — The Human Digestive System: What happens to food inside your body.

What you will study in Sub-strand 1.1

1. Characteristics of plants as living things
2. Functions of external parts of a plant
3. The need to care for plants

Characteristics of plants as living things

A characteristic is a feature that shows something is alive. Plants are living things. A stone, a chair, or a glass of water is a non-living thing — it is not alive.

Plants show seven characteristics of living things:

1. Feeding
2. Growth
3. Movement
4. Reproduction
5. Removal of waste
6. Response to changes in the environment
7. Death

Each characteristic is explained in the blocks that follow.

Living things compared to non-living things

A plant shows all seven characteristics. A stone shows none. That is why plants are grouped as living things and stones are not.

In your notebook, copy Table 1.1(a) from the book and complete it by ticking Yes or No for each characteristic.

Feeding

Feeding means taking in or making food to get energy and to grow. All living things feed.

Plants make their own food. They make it in their leaves using sunlight. Animals cannot do this — they must find and eat food from outside their bodies.

Growth

Growth means getting bigger over time — increasing in height, length and width. All living things grow.

A seedling is a young plant. It grows into a tall, fully grown plant over time.

Movement

Movement is a characteristic of living things. Plants do not walk, fly or hop. But they do move in other ways:

• Some plants turn their leaves and stem toward sunlight.
• Roots grow downward toward water in the soil.

These movements are slow. You may not notice them straight away, but they are real — and they show the plant is alive.

Reproduction

Reproduction means giving rise to a young one of the same kind.

Plants reproduce by producing seeds. A seed falls into the soil. With water and sunlight, it grows into a new seedling of the same kind as the parent plant.

Removal of waste

All living things produce waste and must remove it. Plants remove excess water through tiny holes in their leaves called stomata. One hole is called a stoma. Stomata are found mostly on the underside of leaves.

Water leaves through the stomata as water vapour. The process of removing excess water through the stomata is called transpiration.

Response to changes in the environment

Living things respond — they react when something around them changes.

Plants respond too. When there is very little water, some plants wilt — their leaves droop and their stem bends over. Wilting is the plant's response to a drop in water supply.

Death

All living things eventually die. When a plant dries up and stops living, we say it has died. A dead plant no longer feeds, grows, moves or reproduces — all its processes stop.

Plants may die from: lack of water, lack of sunlight, disease, or being uprooted.

The fact that plants die proves they are living things — only living things can die.

Leaves: food storage

A third function of some leaves is food storage. Some plants store food in their leaves. These leaves are edible — they can be eaten.

Four examples from the book:

• Cabbage — a large round head of tightly overlapping leaves, pale to mid-green.
• Spinach — soft, dark green, oval leaves on individual stalks, slightly wrinkled.
• Kale (sukuma wiki) — large, broad, dark green leaves with a thick central rib and slightly wavy edges.
• Lettuce — large, soft, loosely packed leaves, pale green.

When you eat any of these vegetables, you are eating the food the plant stored in its leaves.

Leaves: removal of excess water (transpiration)

A second function of leaves is the removal of excess water. After using what it needs, the plant removes extra water through stomata in the leaves as water vapour. This process is called transpiration.

The experiment that proves it (Figure 1.1(m))

Setup: Two plants are covered with separate glass jars. Plant A has all its leaves. Plant B has had all leaves removed — only a bare stem remains.

What you observe after 2–3 hours:

• Jar over Plant A (with leaves): water droplets and water vapour appear on the inside walls of the jar.
• Jar over Plant B (no leaves): the inside walls are dry — no droplets.

What it proves: It is the leaves that release the water through their stomata. No leaves means no transpiration.

Leaves: food making (photosynthesis)

Leaves are the flattened parts of a plant attached to the stem or branches. Most leaves are green.

Why are leaves green?

Leaves contain a green colouring matter called chlorophyll. Chlorophyll makes most leaves green and is needed for food-making.

How plants make food

Green plants make food in their leaves. This process is called photosynthesis. The leaf uses sunlight, chlorophyll, water (from the roots, through the stem) and air to make food for the whole plant.

Leaves are also the breathing parts of a plant — air enters and exits through the stomata.

Stem: support

A third function of the stem is support. The stem holds up the branches, flowers and fruits above the ground. This keeps them where they can receive sunlight and be reached by insects.

Stem: passage of water and mineral salts

The part of the plant above the roots is called the stem. Its first function is to allow the passage of water and mineral salts upward from the roots to the leaves.

Inside the stem are very narrow tubes running from bottom to top. Water and mineral salts absorbed by the roots travel upward through these tubes to reach the leaves.

This was shown in the book's experiment: the colour in the coloured water appeared in both the cut stem and a cut leaf — proving water was carried all the way up.

Roots: support

A second function of roots is support. Roots hold the plant firmly in the ground. They spread out and grip the soil so the plant does not fall over — even in strong wind.

Roots also protect soil from erosion. They hold soil particles together so rain cannot wash them away and wind cannot blow them away. This is why farmers plant cover crops such as grass on bare soil.

Roots: absorption of water and mineral salts

The roots of most plants grow underground. Their first function is absorption.

Absorption is the process by which roots take up water and mineral salts from the soil. Mineral salts are dissolved in the soil water. The roots take them both up together.

The absorption experiment

A young plant is placed in a container of coloured water. After about two hours, the stem is cut across. The colour of the water appears inside the cut stem. This proves the roots absorbed the coloured water and it moved up through the stem.

Plain water is not used because it is invisible — the colour makes the movement easy to see.

Functions of external parts of a plant

The word external means on the outside. The three main external parts of a plant are:

• Roots
• Stem
• Leaves

Each part has a function — the job it does for the plant. All parts work together. Without any one part, the plant cannot grow well.

In your notebook, draw the plant in the diagram below. Label the three parts: roots, stem and leaves. Compare your drawing with Figure 1.1(c) in the book.

Stem: passage of food

A second function of the stem is to allow the passage of food.

Food is made in the leaves. But every part of the plant also needs food — the roots, the flowers, the fruits, the branches. The stem has tubes through which food is transported to all parts of the plant.

The stem carries two things in two separate sets of tubes: water upward, and food from the leaves to all other parts.

Roots: food storage

A third function of some roots is food storage. Some plants store food in their roots. These roots become thick and swollen. They are edible — they can be eaten.

Three examples:

• Cassava — several thick, elongated roots with rough brown outer skin and white inside.
• Carrot — a single long, smooth, orange root, wider at the top and tapering to a point.
• Beetroot — a round, dark red-purple root with a thin tail at the bottom and leafy tops.

Stem: food and water storage

A fourth function of some stems is food and water storage. Some plants store food and water in their stems. These stems become thick. They are edible.

Example: Sugarcane. The stem is tall, thick and jointed — it has horizontal bands at regular intervals. Inside, it is packed with moist, sweet juice. The sweetness is stored food (sugar). When you chew sugarcane, you are eating the food stored in the stem.

Stem: protection

A fifth function of some stems is protection. Stems protect plants in three ways:

• Height: Tall stems hold leaves and flowers high above the ground, out of reach of grazing animals such as goats.
• Thick bark: Some stems have a thick outer covering called bark that protects the soft inner parts of the stem.
• Thorns: Some stems have sharp pointed spikes called thorns that keep animals away.

Safety: some stems produce poisonous substances. Always handle plants with care.

The need to care for plants

Plants need care to grow well. Here are five ways to care for plants:

• Watering: Water plants regularly, especially during the dry season.
• Mulching: Mulch is dry grass or weeds placed around the base of a plant. It reduces water loss from the soil by evaporation, keeping the soil moist longer.
• Adding manure: Manure gives the soil nutrients that plants need for healthy growth.
• Avoiding damage: Do not break branches, pick flowers needlessly or uproot food crops. Use uprooted weeds as mulch or animal feed.
• Planting cover crops: Planting grass on bare soil protects it from erosion — the roots hold the soil in place.

Why we should care for plants

We get food from plants. We eat their different parts:

• Roots: cassava, carrots, beetroots
• Stems: sugarcane
• Leaves: kale, spinach, cabbage, lettuce

Plants are also important to other living things in the environment.

Caring in different settings

• At school: Water plants in the school garden; do not uproot or break plants in the compound.
• At home: Water food crops; apply mulch; add manure.
• In the community: Do not cut down trees unnecessarily; plant cover crops on bare ground.

Making a plan to protect plants

The book asks you to identify a problem affecting plants in your area — for example, trees being cut for firewood. Then write a short plan like this:

• Problem: Trees near our school are being cut down for firewood.
• What I will do: Tell my teacher and parents. Suggest planting fast-growing trees to replace those cut.
• Who I will tell: My teacher, parents and community members.

Write your own plan in your notebook and share it with your teacher or parents.

Key Points — Sub-strand 1.1: Plants

Characteristics of plants as living things

• A characteristic is a feature that shows something is alive.
• Plants show seven characteristics: feeding, growth, movement, reproduction, removal of waste, response to changes, and death.
• Plants make food in their leaves using sunlight.
• Plants move — for example, by turning toward light.
• Plants reproduce by producing seeds.
• Plants remove excess water through stomata in their leaves — this is called transpiration.

Functions of external parts of a plant

The need to care for plants

• Watering — regularly, especially in the dry season.
• Mulching — dry grass at the base; reduces water evaporation.
• Adding manure — nutrients for healthy growth.
• Avoiding damage — do not break or uproot unnecessarily.
• Planting cover crops — roots hold soil and prevent erosion.

Key vocabulary

Characteristics of animals as living things

Animals are living things. Like plants, they share the characteristics of living things. But animals show eight characteristics — one more than plants. The extra characteristic is breathing.

The eight characteristics of animals as living things are:

1. Feeding
2. Growth
3. Breathing
4. Reproduction
5. Removal of waste
6. Movement
7. Response to changes in the environment
8. Death

In your notebook, copy Table 1.2(a) from the book and complete it by ticking Yes or No for each characteristic.

Animals compared to non-living things

A cow shows all eight characteristics. A rock shows none. That is why animals are grouped as living things.

Growth

Growth is a characteristic of animals. Young animals grow to become mature (fully grown) animals. As they grow, they get bigger and heavier.

Examples:

• A calf grows into a cow.
• A chick grows into a chicken.
• A kitten grows into a cat.
• A puppy grows into a dog.

Breathing

Breathing is one of the characteristics of animals. All animals breathe in air.

Different animals breathe in different ways:

• Land animals such as cows, dogs, goats and birds breathe through lungs.
• Fish live in water and breathe through gills. The gills take in air dissolved in water.
• Insects breathe through tiny holes called spiracles on the sides of their bodies.

Although animals breathe in different ways, all of them take in air. This is why breathing is listed as a characteristic of animals.

Reproduction

Reproduction means giving rise to young ones of the same kind. It is a characteristic of all animals.

Animals reproduce in two main ways:

• Some animals give birth to live young ones. Examples: cows, dogs, cats, goats, human beings.
• Some animals lay eggs that hatch into young ones. Examples: hens, fish, frogs, snakes, crocodiles.

In both cases, the young one is the same kind as the parent.

Removal of waste

All animals produce waste inside their bodies and must remove it. This is the characteristic of removal of waste.

Examples of waste removed by animals include:

• Faeces (solid waste) — removed through the anus.
• Urine (liquid waste) — removed through the body.
• Sweat — removed through the skin.

Waste from some animals is useful. Farmers collect dung (animal faeces) and use it as manure to improve the soil for crops.

Movement

Movement is a characteristic of animals. Unlike plants, animals are able to move from one place to another. They move to search for food and to run away from danger.

Animals move in many different ways. Here are some:

• Walking and running — cows, dogs, horses.
• Flying — birds, bats, butterflies.
• Swimming — fish, frogs, ducks.
• Slithering — snakes.
• Crawling — caterpillars, tortoises.
• Hopping and leaping — frogs, rabbits.
• Waddling — ducks.

In your notebook, copy Table 1.2(b) from the book and write examples of animals under each type of movement.

Response to changes in the environment

Animals respond to changes around them — they react when something in their environment changes. This is a characteristic of all living things.

Examples of how animals respond to changes:

• Hot weather: lizards bask in the sun to warm up; animals look for shade to cool down.
• Cold weather: people wear warm clothes; some animals grow thicker fur.
• Danger: a rat runs away when it sees a cat; a millipede recoils (curls up) when touched.
• Camouflage: a chameleon changes colour to match its surroundings.

In your notebook, copy Table 1.2(c) and complete it with examples of how animals respond to changes.

Death

All animals eventually die. Death is a characteristic of living things. Animals die because of:

• Disease
• Old age
• Being killed by other animals for food
• Drought — lack of food or water during the dry season

The fact that animals die proves they are living things — only living things can die. A stone cannot die because it was never alive.

Feeding

Feeding is the first characteristic. All animals feed — they take in food to get energy and to grow.

Animals cannot make their own food like plants do. They must find and eat food from outside their bodies. Different animals eat different things:

• Some animals eat plants — e.g. cows eat grass, goats eat leaves.
• Some animals eat other animals — e.g. lions eat zebras, cats eat mice.
• Some animals eat both plants and animals — e.g. human beings, chickens.

Vertebrates and invertebrates

Animals can be grouped into two main types based on whether they have a backbone or not.

A backbone is the row of bones running down the back of an animal's body. It is also called the spine.

• Animals with a backbone are called vertebrates.
• Animals without a backbone are called invertebrates.

In your notebook, copy Table 1.2(d) from the book and give examples of animals with and without a backbone.

Invertebrates

Invertebrates are animals that do not have a backbone. The book gives these examples of invertebrates:

• Worms
• Insects (e.g. ants, grasshoppers, butterflies)
• Snails

Invertebrates are the largest group of animals on Earth. Most animals you see around you — ants, flies, butterflies, grasshoppers, snails, worms — are invertebrates.

Making a portfolio

The book asks you to cut out pictures of animals from old magazines and newspapers, sort them into vertebrates and invertebrates, and stick them into a scrapbook. This is called a portfolio. Display your portfolio during a class presentation.

Vertebrates

Vertebrates are animals that have a backbone. The book gives these examples of vertebrates:

• Fish
• Frogs
• Snakes
• Tortoises
• Cows
• Chickens
• Dogs
• Goats

These animals look very different from each other, but they all have a backbone inside their bodies.