Eating, growing, moving and changing
A puppy is probably one of the liveliest of living things. It runs around and chases its tail, gasps for breath when it is tired, cocks its ears when it hears another dog bark, feeds clumsily, wets the carpet and grows quickly. When it is fully-grown it may have puppies of its own. The puppy shows the seven features, or characteristics, of life very well. Some living things do not show these features so well and you have to watch them a long time to decide that they are really living.

The features of life are all linked to each other. All living things need energy. Without it they simply die. Food provides energy for living things. Some living things, the plants, make their own food. They get the energy from the sunlight that shines on their leaves. Inside the leaves some of this light energy is trapped and stored in the food. The plant gets the materials it needs to make food from air, water and minerals in the soil. Animals cannot trap energy in sunlight like plants. They must get their energy by eating food. Some animals, like the rabbit, eat plants. They use some of the energy in their food to live but they also store some energy in their bodies. This means that they can form the food of other animals. For example, the rabbit is eaten by foxes.

The energy in food has to be released before it can be used. Most living things need oxygen to release the energy in their food. We call the taking in of oxygen, breathing. Animals have special organs in their bodies where oxygen is taken in. For example, we have lungs and fish have gills. Plants also use oxygen and take it in through holes in their leaves and stems when they need it. When we need extra energy after running around we gasp for breath just like a puppy. The process of releasing energy from food in plants and animals is called respiration.

Once the energy has been released from food the body can use it in many ways. Animals can use it to make their muscles move. Plants do not have muscles so cannot use it in this way. All living things use some of the energy to grow. When plants grow they also move parts of their bodies.

Living things need to be aware of their surroundings. Changes are always taking place. Some of the changes help the living thing survive and some can be harmful. For example, a rabbit may detect that a nourishing plant is growing not far from its burrow and will hop across the field to reach it. As it reaches the plant a fox comes trotting into view so the rabbit dashes back to its burrow. Animals have sense organs such as eyes and ears to help them detect changes. They can act quickly too, because they have nerves in their body which send rapid messages from the sense organs to the brain and muscles, so the animal can decide what to do. Plants are sensitive to some things in their surroundings but they do not have nerves and muscles so they can only act slowly by growing.

You can also think of the body of a living thing as a chemistry set. It takes in chemicals from the food and the air and uses them to make useful materials. In these processes some chemicals are made that are not needed. They are called wastes. The body gets rid of these chemicals by a process called excretion. This is why the puppy wets the carpet and people must get rid of liquid wastes at a toilet. Even trees excrete but they do not produce water. They put their waste chemicals in their leaves and drop them to the ground in the autumn.

All these six features of life allow the seventh one to take place. This is breeding. Living things need to breed in order to keep their kind, or species surviving. If a species of living thing does not breed it will die out or become extinct.

Next time you see a puppy playing or tree shedding its leaves think of the features of life that are going on inside their bodies.

Mushrooms can grow in the dark. Where do they get their energy from?
Mushrooms are not plants. They belong to a separate kingdom called the Fungi. A fungus cannot trap sunlight shining on it so it cannot make food. It acquires its food by feeding on the dead bodies of other living things or on their wastes. For example, you can grow mushroom on a mixture of manure and straw. The mushroom grows threads, which move from the manure and feed on it. The mushroom gets its energy from the manure. Other fungi, such as moulds, get their energy by feeding on damp bread.

Mosses and ferns grow in shady places. Do they use sunlight to make food?
Yes, they do. They have become adapted to the low level of light in places like woods. It is important to remember that all green plants make food using sunlight. It does not matter whether they have flowers, cones or reproduce by making spores, like mosses and ferns. If they have green leaves they can make their own food.

Why do some plants feed on insects?
These plants grow in habitats where the soil does not supply enough minerals for proper growth and development. The insectivorous plant has a way of trapping insects and feeding on their bodies. They get the extra minerals they need from the insects' bodies. Some insectivorous plants, such as the sundew, have sticky drops on their leaves to catch insects. The Venus flytrap snaps part of its leaves shut to catch its prey. The pitcher plant makes the ends of its leaves into a bottle with a slippery neck. When an insect lands on the neck, it loses its grip and falls inside. There is a watery mixture in the pitcher, which drowns and digests the insects. The pitcher plant can kill and digest larger animals such as mice and lizards.

How can the Venus flytrap work when the plant has not got any muscles?
The rapid movement is due to a rapid movement of water inside the leaf. You may have put a large seed like a broad bean in water and seen it swell up slowly over a day. A similar but much faster movement of water can take place inside the leaf of the Venus flytrap. It allows the leaves to snap shut in three hundredths of a second. This is too fast for the fly to make its escape. It takes about a day for the plant to digest a fly. Slower movements of water open the leaf again ready for the next meal. A leaf is worn out after it has digested four insects and the plant replaces it with a new one.

Is manure produced by excretion?
No. Manure from animals and solid wastes from humans are produced from undigested food. This is why manure can be spread on the ground as it contains minerals and energy. Fungi, like the mushroom, can feed on manure. Excretion is the removal of waste chemicals that the body has made. It is released into the urine. In fact one of the waste chemicals is called urea and the word 'urine' has been made from the word 'urea'. Carbon dioxide is a chemical that all living things produce as a waste. It is made in the process called respiration. We excrete carbon dioxide in our breath.