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Science B1b Evolution
The Theory of evolution
The idea behind "the theory of evolution" is that all species have from simple life forms.
Life began on earth 3 billion years ago.
Natural selection
according to the theory of evolution species evolve by natural selection
Individuals in the species show a wide range of variation. This variation is because of
difference in genes
Individuals are most likely to survive to produce are those well suited to their environment.
Individuals who are poorly suited to their environment may not survive to reproduce.
genetic variation is inherited
One major source of evidence is the record of fossil remains.
The meaning of fossil is pieces of rock and minerals which have replaced the remains of
organisms, or preserved their external form.
These fossils within the layers of rock in the ground are referred to as the fossil record, but
But not all organisms fossilise well, some are destroyed by the earth's movement, and may
have not yet been found, so there are no gaps in the record.
One animal we can track through the record for millions of years is the horse.
Being over 60 million years ago as a dogsized creature.
During the evolutionary process the foot has changed from a multitoed one adapted to
walking across the forest floor, to the hove of the modern horse that are suited to running over
open country.
If an individual is poorly adapted to its environment then it can die before it has a chance
to reproduce.
For large numbers of individuals from a species, then over time the number of individuals
of that species that remain gets smaller and smaller, until finally gone.
When this happens the species is said to have become extinct.
The reasons to this are:

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Science B1b Evolution
o Climate change
o new diseases
o new predators
o new competitors.
Fossil record shows many species have become extinct since life began on our planet,
and this process is still happening.
Individuals compete for space, food and water.…read more


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