What this chapter is about
This chapter helps you understand what makes something alive. You see many things around you — a cat, a stone, a plant, a bicycle, water. Some of these are living and some are non-living. But how do you tell the difference?
You will learn the special characteristics that all living things share. These are features like breathing, growing, moving, needing food, and responding to changes around them. A plant and a dog seem very different, but both share these basic life processes.
After studying this chapter, you should be able to look at any object and explain whether it is living or non-living. You will also understand why things like a car (which moves) or fire (which needs air) are still not alive.
Key ideas
- Living things are organisms that show all the characteristics of life, such as breathing, growing, and reproducing.
- Non-living things do not show these life processes. A rock does not breathe, grow on its own, or produce baby rocks.
- All living things need food to get energy. Plants make their own food using sunlight, while animals eat plants or other animals.
- Living things breathe or respire. They take in air (or gases from water, like fish do) to release energy from food.
- Living things grow. A puppy grows into a dog. A seed grows into a tall tree. Non-living things do not grow on their own.
- Living things respond to stimuli. A stimulus is any change in the surroundings. If you touch a mimosa plant (called touch-me-not), its leaves fold. If you clap loudly, a bird flies away.
- Living things reproduce, which means they produce young ones or offspring of their own kind. A hen lays eggs that hatch into chicks.
- Living things excrete, which means they remove waste from their bodies. You sweat and urinate to get rid of waste.
- Living things have a lifespan. They are born, they live for some time, and eventually they die.
Formulas and facts to remember
1. Characteristics of living things: Need food, breathe, grow, respond to stimuli, reproduce, excrete, move, and have a definite lifespan.
2. Stimulus: Anything in the environment that causes a living thing to react. Example: light, sound, touch, heat.
3. Response: The reaction of a living thing to a stimulus. Example: pulling your hand away from a hot cup.
4. Respiration: The process by which living things use air (oxygen) to release energy from food.
5. Excretion: The removal of waste materials produced inside the body.
6. Reproduction: The process by which living things produce new individuals of their own kind.
7. Movement in plants: Plants cannot walk, but they show movement. A sunflower turns towards the sun. Roots grow downward.
8. All living things are made of tiny units called cells, which are too small to see without a microscope.
Worked examples
Example 1: Is a cloud living or non-living?
Let us check the characteristics:
- Does a cloud need food? No.
- Does a cloud breathe? No.
- Does a cloud grow? It may get bigger, but only because more water vapour joins it — not because it is alive.
- Does a cloud reproduce? No, it does not make baby clouds.
Since a cloud does not show the characteristics of life, it is non-living.
Example 2: Why is a car not alive even though it moves?
A car moves, but it needs a driver to start it. It does not move on its own to find food. A car does not breathe, grow, or reproduce. It does not respond to stimuli by itself — the driver does that. So, a car is non-living.
Example 3: How does a cactus show characteristics of life?
- Food: A cactus makes its own food using sunlight (like all green plants).
- Breathing: It takes in gases through tiny pores.
- Growth: A small cactus grows bigger over the years.
- Response: If there is no water, its roots grow deeper to find moisture.
- Reproduction: It produces seeds or small baby plants.
A cactus shows all life characteristics, so it is a living thing.
Common mistakes
Thinking that anything which moves is alive → Movement alone is not enough; wind moves but is not alive. Living things show all characteristics together.
Believing plants are not alive because they do not walk → Plants are alive; they grow, breathe, make food, and respond to light and water.
Confusing growth with just getting bigger → A balloon getting bigger when you blow air is not growth. True growth happens from inside, using food.
Thinking fire is alive because it needs air and spreads → Fire does not eat food, does not have cells, and does not reproduce. It is a chemical reaction, not a living thing.
Forgetting that living things also die → Every living thing has a lifespan. This is one important characteristic.
Quick revision
- Living things need food, breathe, grow, respond, reproduce, excrete, and eventually die.
- A stimulus is a change around you; a response is how you react to it.
- Plants are living things — they just cannot move from place to place.
- Non-living things may show one or two features (like movement) but not all life characteristics.
- All living things are made of cells.
- If something does not show all the characteristics of life, it is non-living.