general and in particular
For a more comperehensive treatment, look here.
argument behind evolution is actually quite simple, though the details of
course are often extremely complicated, and often unknown.
argument goes like this:
population all individuals are genetically different.
These genetic differences courses some individuals to be better suited to
survive and reproduce in the given environment.
individuals will on average leave more offspring to the next generation than
the average of the total population.
characteristics of these individuals will spread in the population.
This process is what is called 'Natural Selection'.
to actually work, there has to be a steady supply of new genetic variation.
Otherwise the population will soon run out of variation, and all individuals will
be identical. The supply of genetic variation comes in the form of mutations,
of which there are several forms.
For several reasons the vast majority of mutations are neutral or nearly
neutral, when it come to survival and reproduction.
Some of the
mutations have to be beneficial to the carrier.
Some of the mutations must result in new genetic information, eventually
leading to novelty in anatomy, physiology or biochemistry. Look here for details.
story: The evolution of bees and flowers.
The bee and
the flower seem to defy the process just described. Isn’t there a kind of
chicken-and-egg problem here? If bees came first, how did they survive before
the first flowers came about? If flowers came first, how did flowering plants
reproduce before the bees (or other pollinating insects) came around? How could
such a system possible evolve, when both are dependent on the other?
think about it the solution is not that hard.
Think of a wind pollinated plant, which is used as source of food by a
pollen-eating insect. Each time an insect visits a plant, some of the pollen
stick to the insect and is carried along to the next plant helping the
pollination. Those plants that are better at attracting the insects will have a
more efficient pollination. Those insects that are better at finding the pollen,
will get more food. The plant will benefit from any genetic change in the plant
that makes it easier for the insects to find the pollen. The insect will
benefit from any genetic change in the insect that makes it easier for the
insect to find the pollen. The plant will benefit from any color or smell that
happens to attract the insects. The insect will benefit from any ability to
recognize the site of pollen. If the plant produces an additional food-source,
such as nectar, it will be even more efficient in attracting insects, and
thereby the plant will get a more efficient pollination. In the course of time the pollen eating insect could gradually change its diet towards the nectar, eventually becomming dependent on nectar. In the course of time, the plant could stop releasing its pollen into the wind, and become dependent on pollination by insects.
of this process is flowers with colors, smell and nectar, and insects with high
affinity to such flowers.
Of course there are lots of genetic details in such an evolution. But the chicken-and-egg problem is gone.
A comment to history
The term 'Survival of the Fittest' is not, as you might think, invented by Charles Darwin, but by a man called Herbert Spencer. Darwin didn't use it in the first four editions of 'The Origin of Species'. This shows that the term is not a necessary part of the argument.
It is actually not very accurate either. For at least two reasons.
First: It has been critizised for being a tautology (a statement which is correct by definition). What is the definition of fitness if not survival?
Second: The important ability is reproduction more than survival.