Darwin’s theory of natural selection has provided us with the
explanations of the processes involved in the changes of species over
long periods of time. His theory was based on five major assumptions:
VARIATION: When Individuals within a species differ from one another
in physical characteristics and in their behaviour.
HERITABILITY: Some of the variations amongst the members of species is
inherited, meaning that the offspring tend to resemble their parents
more than the other members of the species.
COMPETITION: Members of most species produce far more offspring than
can survive. If there weren’t problems with survival Darwin figured
out that a pair of elephants could have about 19 million descendents
alive 750 years after birth! However there are those who don’t win
competitions for best food and best place to live are the ones who are
less likely to reproduce.
NATURAL SELECTION: Those who survive the competitions will then go on
to breed and these tend to have the characteristics that are better
suited to the environment than those who don’t. Thus, there is natural
selection or ‘survival of the fittest’.
ADAPTATION: Successive generations will tend to be more and more
adaptive to their environment and will have characteristics that
heighten their abilities to survive, to get food and most importantly
to reproduce and all of this is a result of the process of Natural
Selection. (Eg. If only fast moving prey survive then that species
should evolve over the generations in the direction of becoming on
average faster moving.)
Darwin believed that the increasing competition for finite resources
exerts selective pressure because those who lose, when the resources
are limited will fail to reproduce. People would believe that with the
process of natural selection and adaptation that this would make the
members of a species almost perfectly suited to their environment but
Darwin didn’t actually believe this he thought: “Natural selection
tends only to make each organic being as perfect as, or slightly more
perfect than, the other inhabitants of the same country with which it
comes into competition…natural selection will not produce absolute
Darwin presumed that evolutionary change would on the whole happen
relatively slowly over periods of hundreds or thousands of years.
However there are reasons to why some aspects of behaviour seem to
change more than others during evolution (Grier +Burke). Any...