Evidence for early forms of life comes from fossils.
Fossils are the ‘remains’ of organisms from many years ago, and are found in rocks. Fossils may be formed in various ways:
- from the hard parts of animals that do not decay easily
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- when parts of the organism are replaced by other materials as they decay
- as preserved traces of organisms, eg footprints, burrows and rootlet traces.
Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.
We can learn from fossils how much or how little organisms have changed as life developed on Earth.
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