Answer:
1. The plants released oxygen in the Earth's atmosphere. This reduced the harshness of sunlight and made Earth ideal for life.
2. The plants use sunlight and carbon dioxide for the process called photosynthesis. Photosynthesis produced oxygen which was released in the air by the plants.
3. The sunlight made the Earth very hot. This newly formed oxygen helped in shielding the Earth from the sunlight.
4. This helped in cooling the Earth and produced an environment which made it possible for other life forms to develop.