Fossils

Inheritance, variation and evolution · The development of understanding of genetics and evolution · note 2 of 4

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FossilsSpec 4.6.3.5

Fossils are the 'remains' of organisms from millions of years ago, which are found in rocks.

How fossils may form

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 minerals as they decay.
As preserved traces of organisms, such as footprints, burrows and rootlet traces.

We can learn from fossils how much or how little different organisms have changed as life developed on Earth.

Why the fossil record is incomplete

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. This is why scientists cannot be certain about how life began on Earth.

Evolutionary trees

You may need to extract and interpret information from charts, graphs and tables, such as evolutionary trees. Evolutionary trees use fossil data for extinct organisms and current classification data for living organisms.

Evolutionary tree with time running upwards from a common ancestor at the bottom to four living species A to D at the present day, with two extinct branches ending in a cross. — Branches ending in a cross are extinct species, known only from fossils.