How Life Started on Earth?
When did life on Earth begin?
Life on a Earth began about 3500 million years ago. When Earth first formed, it was too hot for life to exist. The first living things were bacteria, which developed in deep-sea springs or muddy pools near volcanoes (right), after the Earth had cooled. The bacteria took their energy from chemicals in water, and slowly developed into more complex life forms, a process known as evolution.
How did living things develop?
Many new living things began to develop by 3000 million years ago, after some early life forms found a way of getting energy from sunlight and using it to make food. This process is called photosynthesis. During photosynthesis, living things release the gas oxygen. Many more living things then developed to breathe the new oxygen in the atmosphere.
What were the first animals like?
The first animals probably looked like a tiny tadpoles. They lived in the shallow seas that converted Earth about 1200 million years ago and thrived on the new supplies of oxygen in the atmosphere. Slowly, these tiny animals grew together in clusters and developed into the first sponges.
Where did early animals live?
Early animals, such as sponges, jellyfish and pens, all lived on the sea floor. They fed on bits of dead plants and animals in the mud or water. At this stage, there was no need for them to move because there were no predators (hunters).