Fossil Evidence Background Information
Objective
The student knows that the Earth’s surface is constantly changing and consists of useful
resources. The student is expected to identify fossils as evidence of past living organisms and the
nature of the environments at the time using models.
Foundation
The remains or traces of animals and plants which lived thousands or even millions of years ago
are called fossils. By the time we find a fossil, it is in the form of stone, since the natural flesh
decayed long ago. Fossils have been located in various places for hundreds of years, but it has
only been in the last century or so that we have been able to discover and understand what they
are…evidence of organisms which lived in the distant past and which may not even exist today.
For an organism to become a fossil, the conditions have to be just right, since when most animals
or plants die, they simply decay or are eaten by another animal. But sometimes an organism will
die and will be quickly covered by sediment, either on land or at the bottom of a body of water.
In time, as layer upon layer of sediment packs on top of the organism, the sediment turns to stone
and the encased organism decays, but in doing so, it leaves a mould of its shape in the stone. In
time, water brings minerals into the mould, and the minerals form a stone cast of the organism.
Eventually the fossil is exposed to the Earth’s surface through weathering and is discovered.
Sometimes a fossil is found that simply shows where an animal or plant has been. Footprints and
imprints of animals and plants can be covered with sediment and preserved for millions of years
until the fossil is exposed to the Earth’s surface again through weathering.
By studying fossils and the remains of animals and plants, scientists can determine the ages of
organisms and how long life has existed on Earth. Scientists can determine how and where they
lived, what they ate, and reach conclusions about what the Earth’s environment was like millions
of years ago. Comparing this information of the past to the present, we can make predictions of
how the Earth may appear in the future.