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Essay
On Darwin's Theory of Evolution by Natural Selection
Darwin's Theory of Natural Selection says that nature selects
organisms with the best features for survival, while getting rid of
inferior species. Natural selection is how we get new species from
existing ones. Components of this theory include over reproduction,
variation, competition, survival of the fittest, inheritance and
adaptation.
Many species have more offspring every year than the
environment they live in can support. This is called over
reproduction. The high rate of growth results in a struggle for the
resources they need to survive and a higher mortality rate within this
species.
In every species there is variation. Even brothers will vary in
color, height, and weight. There are other variations such as the
number of limbs or the number of eyes that do not vary as often. Some
populations show more variation than others. A good example is the
Galapagos Islands that are geographically isolated and show more
variation and species evolve very distinct characteristics.
Most organisms have variations, some do not affect survival
like eye color in humans, but some improve the chances of survival. A
rabbit that runs faster than all the other rabbits is more likely to
escape predators. Algae that are more efficient at getting energy from
the sun will grow faster. Over time a fast rabbit will breed with
other fast rabbits and their children will be even faster. This is an
example of survival of the fittest.
Traits that give individuals a reproductive advantage can be
passed from parent to child. Even if the reproductive advantage is
very small over time and many generations the advantage will become
stronger and stronger. Some species have traits that are strongly
influenced by inheritance.
Beneficial mutations and adaptations remain in organisms
because they aid in their survival. Beneficial mutations are passed on
from generation to generation and overtime the result is an entirely
different organisms. One example of adaptation is the turtle
population who ate food that was loaded the ground and had short legs
and straight shells. When the turtles moved to another island and the
food source was much higher up only the turtles with longer legs
survived. Over many years their necks and legs grew and their shells
became rounded to reach the food. This is adaptation is natural
selection.
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