Flowers, fruits and seeds
We all notice when a plant bursts into flower - bright colours appear among its leaves. The colours are produced by the petals. We may also notice that the flowers smell. There are hairs on the petals, which produce a scent. The colour and the scent are not for us, although they give us pleasure. They are for insects. The petals are like an advertisement. They tell the insect that food is available. The food is nectar. It is a sugary solution and contains a great deal of energy. This is just what flying insects need to keep them in the air. As the insects descend on a flower for a drink, the flower prepares to make use of the insect. Just inside the bowl made by the petals is a ring of whiskers called stamens. At the tip of each whisker is a swelling. Inside this swelling the plant makes pollen grains. When the pollen grains are ready an unusual thing happens. The swelling turns itself inside out. This exposes the pollen grains to the air and any passing insects.

When most insects land on a flower they behave as if they do not have pollen grains on their mind. They dive into the centre of the flower to find the nectaries ? the place where nectar is made. As the insect passes the stamens, pollen is brushed onto its body. The pollen has a spiky coat. The spikes hold onto hairs on the insect's body. When the insect has finished drinking the pollen, it flies away taking the pollen with it.

Later, the insect may land on another flower. Its stamens may be withered but at the centre is a sticky pad held up in the air on a stalk. The insect pays no attention to this and dives down for another drink. This sticky pad is called the stigma and the stalk below it is called the style. As the insect brushes against the stigma, the pollen loses its grip of the hairs. It is pulled onto the stigma and the insect flies away probably unaware that it has helped the plant reproduce.

The pollen grain is not solid. It is a case which contains a substance that the plant needs to make seeds. In a short time a tube grows out of every pollen grain on the stigma. It grows down through the stigma and the style to the ovary. This may be shaped like a small bottle. Inside it are egg-shaped lumps called ovules. When the pollen tubes reach inside the ovary, each one seeks out an ovule and plugs into it. The substance in the pollen grain travels down the tube and into the ovule where it meets a second substance. When the two substances meet, fertilisation is said to have taken place. After fertilisation, the ovules turn into seeds and the ovary turns into a fruit. The petals dry up and fall away, as there is no longer any need to attract bees and butterflies. If the plant uses animals to spread its seeds and fruits, they will need to be much bigger than insects.

Do all plants use insects to carry their pollen?
No. Many plants use the wind. These plants do not produce flowers with bright colours and scents because they do not need to. The flowers then are often small and green. When the flower is ready to release its pollen, it may hang its stamens outside the flower. The wind blows on the long stalk of the stamen and this rocks the tip and shakes the pollen lose.

Is the pollen carried by insects like that carried by the wind?
No. Pollen carried by the wind is smaller and lighter in weight than pollen carried by insects. The pollen of the pine even has a pair of tiny hollows, like balloons, attached to it to help it float in the air. Pollen carried by the wind is also smooth. It has no need for spikes.

Do any other animals carry pollen?
Yes. In tropical countries birds such as the humming bird may pick up pollen on its head as it drinks nectar with its long beak. The Bird of Paradise flower has long, tough horizontal stamens. They are so strong that birds can perch on them. When they do, the birds pick up pollen on their feet. The century plant produces a large amount of nectar to that it can give bats a drink. When the bat visits the flower it picks up pollen on its head.

What is the substance that a pollen grain carries?
If you have read about What is a life cycle? you will know that living things are made from cells. There are many types of cell and each type does a particular task in the life of a living thing. In the pollen is a male reproductive cell. This travels down the pollen tube into the ovule.

What is the substance in the ovule that takes part in fertilisation?
This is another cell. It is the female reproductive cell. When fertilisation takes place the male and female reproductive cells fuse together. They make a cell, which can then grow into a plant.

Why can't a male or female reproductive cell grow into a plant on its own?
Each cell has only half the instructions for making a plant. It needs to join with the other so a complete set of instructions is made.

Why do the plants go to all the bother of making reproductive cells and transferring them?
When a plant makes a reproductive cell, it rearranges the instructions a little. When the new cell is made from the two reproductive cells, it contains slightly different instructions from either of its parents. These new instructions may improve the plant's chances of survival. This is why both plants and animals produce male and female cells.

Can the pollen from one flower pollinate any other flower?
No. The pollen from one kind of plant can only pollinate the flowers of another plant of the same kind. If pollen from the wrong kind of flower lands on a stigma it simply does not produce a pollen tube.

Can a flower pollinate itself?
Some plants produce self-pollinating flowers. The stamens and stigma develop at the same time so the pollen can transfer. Many plants have their stamens producing pollen before their stigma is ready for it. This means that all the flower's pollen has left by the time the stigma grows. The stigma then collects pollen from other flowers of the same kind, which are still producing pollen. The transfer of pollen from one plant to another is called cross-pollination.

Do all plants have flowers with both male and female parts?
No. Some plants just have flowers that produce stamens. These are male plants. There are also plants which just produce an ovary, style and stigma. These are female plants. The holly has male and female trees. This is why you may see berries on some trees (the female trees) and not on others (the male trees).

Food from around the world
The first people lived in Africa. In time they spread out to most places in the world. Wherever they went they ate the plants and animals they found around them. What would it have been like to have lived in those times? Imagine you were one of those people and it was about time to get up in the morning.

You wake up on a bed of leaves. Over your head are some branches and leaves which you have joined together to make a shelter. You climb out of bed and run down a grassy bank to a river to wash and drink. On your way back you may grub about in the soil, find a juice root and chew it.

By now other people in your group are awake. They bathe and drink too and look for food. Someone finds a bone with pieces of meat stuck to it. They pull off the raw meat and spend some time chewing hard before swallowing it. The group divides into two to look for food. The men and older boys go hunting. The women, girls and children look for food among the plants.

You are told to join the second group and begin to join in searching for berries, seeds and roots. Some of the older women know what to find while others try all kinds of leaves and berries. Some they find have a bitter taste and they spit them out. As you search for food you come upon a bees' nest. A woman got a long branch and broke into the nest. The bees fly around but she manages to pull out some honeycomb rich in honey and everyone has a sweet-tasting picnic.

Eventually you see the men in the distance. They are calling to each other and running. A herd of deer breaks out through the bushes near you and runs away. The men appear and chase after them. Some of the men carry sticks and others carry stones. You try and follow but the deer and men are soon gone. You keep walking along following the path of broken plants that the deer and men have left behind. In a while you see the men in the distance. They have stopped running and are gathered in one place. As you approach you can see a body of a deer on the ground. Some of the men are busy cutting away the fur with sharp stones and pulling out strips of meat. They give the meat to the others, who eat it greedily. When you reach their side they give you some of the raw meat too.

When everyone has had their fill of the raw meat the rest of the deer is cut up and its meaty joints are carried back to the camp for the rest of the group. On the way back you see some fruit high above your head and climb up the tree to reach it. When you get to the fruits you pull them off their stalks and drop them to a friend. Together, you carry the fruit back to the camp. On the way your friend eats a fruit and finds some caterpillars on it. He eats them too.

Back at the camp everyone is tucking into the raw meat. The people have seen fires started by lightning but have not discovered how to make it for themselves. When they do, they will find that the meat is easier to chew and digest after roasting in the flames and it will taste better too.

As it grows dark you may go down to the river for one last drink then walk up to your shelter. You are very tired after spending all day searching for food. As you drift off to sleep on your mat of leaves, your body rests and prepares itself for another day of hard physical work.

In time, the people in Africa spread out through the rest of the world. Most of them stopped hunting animals and gathering food from plants. They began farming. They made meals from the plants and animals they reared. Some meals became favourites and are still eaten today. We call them traditional meals. They may be made with rice, maize, potatoes and bananas. Perhaps you will enjoy one tonight from the local take-away. It will be much tastier and warmer than the meals the first people ate.

Can all plants be eaten?
No. Many are poisonous. The first people found out what was safe to eat by trial and error. This means that they ate the food and, if they were not ill, they ate some more of it. This was a very dangerous way to find out about food but they had no choice. However, they soon came to know which foods were safe to eat and people shared what they knew. This meant that if a person picked up a poisonous plant they were warned by the others not to eat it.

If a fruit or a root can be eaten can the whole plant be eaten?
You can eat some plants such as celery or bean sprouts but many plants have only one part that can be eaten. The tomato is the only part of the tomato plant that is not poisonous. Sometimes a part which is edible may become inedible. For example, if potatoes were allowed to turn green, they would make you ill if you ate them.

How did people learn to make fire?
They learnt by rubbing two sticks together and placed some very dry fibres close by. The heat of friction warmed up the fibres so much that they caught fire. A second way, used later, was to strike a piece of metal on a rock called flint to make a spark. If dry fibres were close by the sparks set them alight and fire could be started.

Did early people eat anything else besides meat and plants?
Yes. They ate fish and shellfish such as shrimps, cockles and mussels.

When people settled in different places could they grow the same crops?
No. The reason for this is because the different places had different kinds of weather. For example sweet potatoes grow in warm wet weather that is found in some tropical regions while cereals such as oats and rye grow in cool damp climates that are found in Northern Europe.

Do people farm different animals in different parts of the world?
While people may grow different crops in different parts of the world they farm the same kinds of animals. These animals are cattle, sheep, pigs, chickens and duck. In some parts of the world where the grazing land is poor the people farm goats and camels and in Africa they farm the African buffalo.