🌱 How Plants Change in Autumn

Look at the photograph at the start of the unit. It shows trees in Srinagar, Kashmir, during autumn. In many parts of the world, autumn is the season when leaves change from green to yellow and red.

🌿 Why Leaves Are Green

Plant leaves are green because they contain a green substance called chlorophyll. The chlorophyll in the leaves helps to produce food for the tree. During autumn, days become shorter and there is less sunlight. The leaves are no longer able to produce food for the tree.

🍁 What Happens to Leaves in Winter

The chlorophyll begins to break down, leaving the leaves yellow and red and then brown. After a few weeks the leaves fall off the tree.

🌳 How Trees Survive the Cold

During the cold winter months the tree has no leaves at all. It is dormant or sleeping. In spring, when the days begin to warm up, we see new leaf buds on the branches. By summer the trees are covered in green leaves again.

🐾 How Animals Adapt to Winter

S ome animals cannot find food to eat during the winter. These animals have two choices to stay alive: stay where they are and hibernate or migrate to a warmer region.

😴 What Is Hibernation?

H ibernation describes how the animal’s body goes into a deep sleep for a long period of time. When an animal hibernates, its heart rate and breathing slow down, and its temperature goes down.

🐻 Preparing for Hibernation

A t the end of autumn the days are getting shorter and colder. Animals like bears eat a lot of food to give them an extra layer of fat to help them survive the long, cold winter.

🐿️ How Other Animals Prepare

O ther animals, like mice, collect a pile of nuts and seeds to last them through the winter. They find an underground home for the winter and go to sleep.

🌼 Waking Up in Spring

W hen spring arrives the animal wakes up.

🦓 Why Animals Migrate

W hen seasons change and there is no longer enough food to eat, some animals migrate to warmer regions where food is available.

🦓 Migration of Grazing Animals

A nimals that eat grass need grass throughout the year. But in many places grass dries up during the hot, dry summer. The animals must travel long distances to find regions where new grass is growing. This movement is called migration.

It shows wildebeest (also called gnu) in central Africa. Two million wildebeest migrate 3000 km every year to find food. Their migration depends on the seasons and where the rains are. They know the rains will bring new grass.

🦓 Bird Migration Patterns

M any types of birds migrate. As late summer arrives and the days get shorter, birds begin their migration. They eat more food so they have the strength to survive the long journey. Huge groups of birds fly long distances to places where food is available.

🦓 Example: Siberian Crane Migration

F or example, Siberian cranes migrate from Russia and northern Europe to India. They leave at the end of summer and fly south to India where it is warm and they can find food.