Why do leaves change colour in autumn?
The answer is they don't change colour. The colour green starts to disappear and the yellow, ambers, reds and browns are already present except now we can see them because the green colour is no longer there.
Why are there leaves on a tree?
The main job of a leaf is to provide nutrients to a tree. Leaves use energy from the sun to create nutrients for the tree by combining c02 from the atmosphere and water from the ground. This combinations makes sugars. This whole process is known as photosynthesis.
Why are leaves green during the summer?
Chlorophyll is a green pigment. It is a very important pigment that is responsible for absorbing the sunlight to provide enough energy for the leaf to make nutrients.
When the days become shorter, there is less sunlight available and therefore less energy available to create food. The leaf eventually no longer makes food and the green colour chlorophyll disappear.
What other colours are present in a leaf?
Caroteneoid is also a pigment. Carotenoid is the yellow, orange and brown colour in the leaf and this is what is left over when the chlorophyll disapears.
Anthocyanin is another pigment that is present. This is the red colours that we see. This has a special purpose which allows the tree to recover any left over nutrients from the leaves.
All the nutrients are stored up for the winter until the days become longer again and the whole process starts over again.