Life Process

Living things need food to stay alive. They take in oxygen when they breathe. With the help of oxygen, their bodies break down food to get energy.

The body also makes waste, things it doesn’t need. Living things throw these out.

• Animals, including humans, get rid of carbon dioxide, sweat, urine and feces.
• Plants give out carbon dioxide and water vapor as gases. Some also ooze resin or latex from their bark, stems and leaves.

Living things also make young ones like themselves. This is reproduction.

All these jobs, done again and again all through life, are the life processes. In Grade 5 you will study five of them:

1. Nutrition: getting food.
2. Respiration: getting energy from food, with oxygen.
3. Transportation: carrying things around inside the body.
4. Excretion: getting rid of waste.
5. Reproduction: making young ones.

Here is what they found out.

Green plants make their own food. They use water, carbon dioxide and sunlight, with the help of their green chlorophyll.

• The roots take in water from the soil. The stem carries it up to the leaves.
• Carbon dioxide from the air enters the leaves through tiny holes called stomata.
• Chlorophyll catches the sunlight. The leaf uses the light’s energy to make food.

This way of making food is called photosynthesis. Living things that make their own food are autotrophs. Green plants are autotrophs.

Animals, mushrooms and plants without chlorophyll can’t make their own food. They take food from others. They are heterotrophs.

• A mushroom gets its food from rotting things.
• Herbivores (goats, rabbits, deer) eat plants.
• Carnivores (leopards, tigers, lions, jackals) eat other animals.
• Omnivores (people, crows, bears) eat both plants and animals.

Living things get energy from food. With that energy, the body carries out all its life processes. Without them, there is no life.

• Herbivores get energy by eating green plants.
• Carnivores get it by eating herbivores.

So every animal depends on green plants for its food, directly or through other animals.

All living things need oxygen. Plants and animals on land take oxygen from the air. Fish and water plants use the oxygen dissolved in water.

Breathing takes oxygen into the body. The oxygen reaches every part of it. There, oxygen breaks down food. This gives energy, and makes carbon dioxide and water.

That energy keeps all the life processes going, every moment: nutrition, transportation, excretion, breathing and reproduction.

Breathing organs of animals

Different animals breathe with different body parts.

• Fish and tadpoles breathe with gills.
• Humans and most land animals (mammals, birds and reptiles) breathe with lungs.
• Insects breathe through tiny holes along their sides, called spiracles.
• Frogs breathe through their skin when they are in water. On land, they use their lungs as well.

Two words sound alike, but they mean different things.

• Breathing is taking in oxygen and giving out carbon dioxide. It happens in the breathing organs, such as the lungs.
• Respiration is breaking down food inside the body, to get energy. It makes carbon dioxide and water. It happens in every part of the body.

Animals don’t need carbon dioxide. But green plants do: they use it for photosynthesis. So the carbon dioxide that living things give out is used again by green plants. And plants give oxygen back to the air.

In this way, the oxygen and carbon dioxide in the air stay balanced. Plants and animals can go on living.

To stay alive, a living thing must move things around inside its body.

• Food, water, oxygen and other useful things must reach every part of the body.
• Wastes made in different parts must be taken to the organs that throw them out.

In plants

• The roots take in water and minerals from the soil. They go up through the stem to the leaves.
• The food made in the green leaves goes through fine tubes in the stem to every part of the plant: the branches, the leaves, the flowers, the fruits and the roots.

In animals

• In most animals, blood does this job. The heart pumps the blood all round the body.

Carrying food, water, oxygen, minerals and wastes around inside the body is called internal transport (or internal transportation).

When a living thing carries out its life processes, its body also makes unwanted, harmful things. Getting rid of these wastes is called excretion.

Animals get rid of:

• feces (dung or stool);
• urine;
• sweat;
• carbon dioxide, when they breathe out.

Plants get rid of:

• carbon dioxide, given out in respiration;
• oxygen, given out while making food;
• extra water, given off from the leaves as water vapor;
• resin and latex, which ooze from the stem.

Plants take in water through their roots. It flows up the stem to the leaves. The extra water leaves the plant as water vapor, through tiny holes in the leaves called stomata. Giving off extra water as vapor through the stomata is called transpiration.

A mustard plant makes mustard seeds. A new mustard plant grows from each seed. An orange tree grows oranges, with seeds that can grow into new orange trees.

• Birds, crocodiles, snakes, frogs, fish and insects lay eggs. The young ones hatch out of them.
• Humans, dogs, cats, rats and most other mammals give birth to young ones like themselves.

Making young ones like themselves, so that their kind goes on, is called reproduction.

1. True or false?

2. Fill in the blanks

blood, carbon dioxide, transpiration, oxygen, eggs

3. Choose the correct answer

4. Answer these questions