Evolution of Life
DNA is capable of encoding an enormous amount of information and this can be passed to offspring genetically.
However, if organisms are to survive and to reproduce they must be capable of responding to changes in the
environment. Evolution is a process whereby the data encoded in the DNA can change in successive
generations of a species.
Natural Selection
When species reproduce, the information encoded in the DNA of the parents is transmitted to the offspring,
but because of genetic mutation, limited variation is possible. Most mutations
either have little effect
or cause the offspring to die before reproducing. However, occasionally a mutation will convey a survival
advantage on the mutant because of changing environment. This process is called natural selection,
and is the engine driving evolution.
A Simple Example
For example, suppose in a time of decreasing
temperatures (for example, an ice age) a mammal is born with a mutation that causes thicker hair growth than usual.
Under normal conditions, this mutation would probably have little effect, but in this case it might convey a
distinct survival advantage. The mutant is thus more likely to survive to reproduction age, and if it reproduces
it can pass on this trait to its offspring, some of which will also have more hair than normal. They too
will have a survival advantage and over many generations this new trait (thicker hair) may
become more common in the species as it is "selected" by the environmental pressure of colder temperatures.