Natural selection
In nature all organisms compete with each
other to survive.
This applies to organisms of the same species
as well as organisms from different species.
The concept of survival of the fittest derived
from Darwin's work On The Origin Of Species.
In simple terms, there are slight variations
in each organism and in any given environment,
some of these variants perform better.
A modern example of this is bacterial resistance
to antibiotics.
This is Tim, he has a stomach ache caused
by a bacterial infection
This bacteria cell is one of many causing
Tim's infection
This particular cell divides a number of times
It has a number of copies that have different
mutations to their cell walls.
These copies start having their dividing as
well, carrying their particular mutation
Suddenly Tim takes some anti-biotics which
begin to attack the cells.
As you can see, the black bacteria cells have
been wiped out.
The blue and green cells are almost wiped
but not completely.
The pink and the red cells took a hit but
most managed to survive.
Over a period of time, the characteristics
that allowed these cells to survive become
more dominant within the species.
Coupled with the cell wall mutation these
cells carry, more chances of mutations are
possible increasing the variation of the bacteria
