Plants make food from sunlight, water and carbon dioxide and minerals. They use this food for growth and for making flowers, seeds and fruits in the reproduction process. If they made just enough food for their needs they would not survive, because a wide range of animals attack them for their food.

The main food producing part of a plant is the leaf. This is the part that many herbivores attack. Caterpillars cling to the edge of a leaf and munch away easily with their strong jaws. Some small insects even burrow into a leaf to get at the food. You can see the path of their tunnels as white lines on the leaf surface. Larger animals simply bite off the leaves.

A common plant defence against herbivores is to produce more leaves to replace the ones they have lost. This works well until the plant is attacked too frequently or is visited by a large number of herbivores such as a swarm of locusts. When this happens all the leaves are lost and the plant may die.

Some plants such as the holly have spikes on the edges of their leaves. Some spikes turn upwards and some turn downwards to protect the leaf from different directions of attack. The holly defends itself from browsing animals like deer in this way.

On the African plains there are a wide range of herbivores. They can attack a tree at different heights. There is no part of the tree that escapes. Even the tops are attacked by giraffes. Some plants such as the acacia defends itself by producing sharp spines on its twigs and branches. When an large herbivore tries to eat the leaves the spines stick in its mouth and make it back away. This method is not completely successful as giraffes have a very long tongue and can use it to pull off some of the leaves without touching the spines.

Plants are not only in danger from animals they are also in danger from the weather. When the weather conditions become harsh plants cannot move away and shelter. They have to survive where they grow. Woody plants have a thick layer of bark to protect their stems. The bark can protect the inside of the stem from the cold of a winter snow storm or from the heat of a fire started by lightning. Many plants without woody stems can still survive in harsh conditions. They lose their shoots but have underground stems packed with food to keep them alive. When more favourable conditions return and the plants grow new shoots again.