OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What happens to leaves on trees in autumn?

1. They grow larger to absorb more sunlight

2. They change color and remain on the tree

3. They fall off to prepare the tree for winter

4. They become thicker to trap moisture

The correct answer is: They fall off to prepare the tree for winter

In autumn, leaves on trees undergo a process called senescence, during which they change color and eventually fall off the tree. This shedding is a survival strategy that helps the tree conserve water and energy during the colder winter months when resources are scarcer. By losing their leaves, trees minimize water loss through transpiration and reduce the risk of damage from heavy snow or ice accumulation on their branches. This process is also critical for preparing the tree for winter dormancy. Without leaves, the tree enters a state of rest that helps it survive the extreme conditions of winter. The loss of leaves allows the tree to drop its energy expenditure, as maintaining foliage would require significant resources. Although some trees do change color in autumn, leaving the leaves on the tree is not an adaptive feature of the season. Growing larger leaves or becoming thicker are not relevant adaptations for autumn since the focus is on conserving resources and preparing for the upcoming winter.