10 Examples of Natural Selection
By Diana Bocco
When we think of evolution, we usually think of primates evolving into humans, and of the evolutionary changes that
were made over thousands and thousands of years. But the truth is evolution is at work all the time. Sometimes the
changes are small and appear insignificant at first glance, but they all play a part in natural selection and the
survival of the species.
Natural selection doesn't lead to the development of a new species. In most cases, it simply allows a species to
better adapt to its environment by changing the genetic make-up from one generation to the next. The process is
actually quite predictable. If a species lacks a certain trait that will allow it to survive, there are two options: Either
the species dies out or it develops the missing trait.
Read on to see 10 prime examples of this theory and how each species puts its own spin on it.
10. Peppered Moth
Many times a species is forced to make changes as a direct result of human
progress. Such is the case with the peppered moth (Biston betularia). Up until
the Industrial Revolution, these moths were typically whitish in color with black
spots, although they were found in a variety of shades. As the Industrial
Revolution reached its peak, the air in London became full of soot, and the
once-white trees and buildings that moths used for camouflage became
stained black. The birds began to eat more of the lighter-colored moths
because they were more easily spotted than the darker ones. Over the course
of a few months, dark moths started appearing in the area and lighter moths became scarce. Once the Industrial
Revolution peak passed, lighter moths made a comeback.
9. Rat Snake
All rat snakes have similar diets, are excellent climbers and kill by constriction. They
all have the same reaction when startled (they remain motionless) and will avoid
confrontation whenever possible. Some will bite if threatened, although they are non-
venomous. However, rat snakes come in a wide variety of colors, from yellow striped
to black to orange to greenish. This is because rat snakes are found all over the
Eastern and Midwestern states, and are subjected to all types of weather and
terrain. Rat snakes are common in urban areas, but they can also be found in
wooded areas, mountains or coastal regions. As a result, rat snakes have had to
adapt to their local environments in an effort to avoid detection and hunt more effectively.
8. Pesticide-resistant Insects
The more a pesticide is used, the greater the chance that the insects targeted will develop
immunity to the chemical. Pesticide resistance is not only very common, but it also usually
happens rather quickly. Sometimes all it takes is a single generation. Imagine that a group of
insects survives the pesticide and is able to reproduce. More likely than not, the offspring will
be resistant to the pesticide from birth. Those that are not immune will die, while the
strongest will survive. Since many insects reproduce quickly, several generations can be
born within months or even weeks. By the time a few generations have passed, all insects are likely to be resistant
to the pesticide.
