What are living things?
Millions of years ago a piece of molten rock was moving below the surface of the ground. It was under a volcano and the volcano was erupting. The rock flowed quickly upwards, moving faster and faster until it burst out into the air with ash, gas and smoke. As a cloud of steam billowed in the air above the volcano the molten rock hurried away down its sides. Eventually it cooled down and became a solid black rock called basalt.

A short time ago the rock was broken up into small pieces, called chippings, and brought on a lorry to a road, which was having its surface remade. Hot tar had been sprayed on the road and the chippings were spread on top of it. The purpose of the chippings was to make the surface firm for cars and lorries to travel on. When the first car went by its tyres threw up a cloud of chippings and they fell like raindrops on the roadside.

One of the chippings fell between two rock-like objects. To its left was a small object with a wrinkled surface. On the right was an object with a spiral cut into its surface. By the end of the day a shower of rain fell. It moistened the surface of the chipping and made it shine. But the water made the objects by its side change in other ways. The object on its left gradually began to lose its wrinkles and increase in size. The spiral-shaped object began to rock.

The cause of the rocking movement was a slimy body, which seemed actually to be coming out of the object. In a few moments the body had tipped over the spiral shell a little and had put out two tentacles each with an eye on the end. A pair of smaller tentacles were put out beneath them and touched the ground as if they were tasting it. When the tentacles had checked that the surroundings were safe the animal, a snail, moved off into the grass.

The following morning the other object by the chipping had a smooth surface and had increased in size. In a few days its surface cracked open and a structure a little like the snail's tentacle poked out. It moved much more slowly than the snail's tentacle and took two days to grow a centimetre. As it grew it turned towards the ground and eventually pushed its way into the soil. The object was a seed and it had germinated. Seeds do not produce tentacles when they germinate. They produce a root. It grows down into the ground to collect water and hold the plant in place. This seed was lucky. Its root had found enough water in the soil to keep the plant growing. In a few days, a stem with leaves pushed its way out of the seed as the plant established itself in its habitat.

In the months ahead the plant grew to its full size, made seeds and released them. At the end of the year the plant died. During the same time the snail laid eggs which hatched into baby snails. Later, the old snail died but its offspring lived on. Only the chipping remained the same.

How can you tell a living thing from a non-living thing?
A living thing has a number of features. It needs food, it grows, it moves, it breeds and is affected by changes around it. A non-living thing has none of these features.

You find bones in the ground. Are they non-living?
They are now but they were part of a living thing once. Some people like to divide up non-living things into those that were once alive and those that have never lived. If you group things in this way then you think about objects that were once parts of living things, such as the bones from a body or wood from a tree and put them in the 'once alive' group. You would put rock like basalt in the 'never lived' group.

What about limestone? Isn't that made from living things?
Yes, it is. Limestone is made from the shells of sea creatures which lived millions of years ago. Although you could say that the shells belong to the 'once alive' group the rock they made has never been alive and belongs to the 'never lived' group. You can see that using the 'once alive' and 'never lived' groups can be confusing. You may have found similar confusions when you have made groups in the past. It is probably best to divide things into living and non-living groups but remember that some member of the group may have been formed from living things in the past.

Can living things be put into groups?
Yes, they can. This is much easier to do than trying to put non-living things into groups. When scientists began dividing living things into groups they made two large groups called kingdoms. These groups are the plant kingdom and the animal kingdom.

How can you tell a plant from an animal?
A plant makes its own food from air, water, sunlight and minerals in the soil. An animal cannot make its own food. Animals survive by eating plants or other animals. The body of a plant is made from a substance that is not found in animals. This substance is called cellulose. It gives strength to the plant's body. The cellulose is often arranged in strands in stems. When you eat celery you can see and feel the cellulose. It makes the celery crunchy and forms the fibres, which can become stuck between your teeth.

Can the plant and animal kingdoms be divided into smaller groups?
Yes, they can. The main groups of plants are the mosses, the ferns, the conifers and the flowering plants. The animal kingdom is divided into two very large groups called the vertebrates and the invertebrates. Vertebrates have an inside skeleton made of bone and gristle. Invertebrates do not have bones to support them. They have shells on the outside of the body, like a lobster, or water inside them to hold them up, like a slug or an earthworm.

Are trees found in the plant kingdom?
Yes, they are. In the conifer group are trees such as the Norway spruce, which produce cones. You will have seen many without knowing their name. It is the Christmas tree. Another conifer is the pine. You may have a collection of pinecones or some furniture made from pinewood. All the other trees, such as oak, ash and sycamore, which do not make cones, are in the flowering plant group. These trees are really large flowering plants with woody stems.

Which group of living things do we belong to?
We are in the vertebrate group. This group is divided into five smaller groups. They are the fish, amphibians, reptiles, birds and mammals. Fish have fins and a body covered in scales. Amphibians have a skin without scales and have a young stage called a tadpole. Reptiles have a skin covered in scales and lay eggs with a leathery shell. Birds have wings, feathers and lay hard-shelled eggs. Mammals have a skin covered in hair and the females feed their young on milk. We belong to the mammal group.