They are the result of the changes in the molecular
structure of the DNA, at a certain speed of mutation, the mutagenics
can influence in the greater or smaller speed.
In great populations the chance can give like result
some variation of the frequencies of the genes which can be predicted
by means of the law of the balance of Hardy Weimberg, these variations
normally are so small that they can be as insignificant.
Most of the populations they are not very great
because if we considered the number of individuals that can generate
we see that it is a very small number. It can happen that a certain
one I stupefy once appears single (recesivo) and the chance produces
that it disappears vice versa in the following generation or, to
this is known him as it derives genic.
Stebbens indicates that any species that we consider
tends to maintain a number of individuals determined, but between
alive beings of life cuts the populations fluctuan of year in year.
LEVELS OF EVOLUTIONARY CHANGE
There are two basic models for the evolution, the
evolution that follows a sequence regular, is of one or alleles
in a population divergent evolution and the modification generation
in generation when from a single ancestral population are two lines
of divergent population.
Savage proposed a classification of the levels
of evolutionary change:
||All the processes better give alive
beings provided to live in the environment in which they are
Process by means of as new species from a given
population are developed. According to the isolation mechanism
we spoke of:
Allopatric , when the segments of a population are
aislan geograficamente. The two isolated portions can accumulate
enough genetic differences throughout the time (microevolution),
arrives a little while in which auqnue is joined cannot be crossed
between if, many espcies can have appeared by this cause,
Sympatric, in a population of a species a single
mutation in a part of the population gives rise to that this part
is isolated of the other and each one evolves.
It is the evolution of groups over the species level.
It such uses mechanisms that the microevolution, but the speed
and amount are greater, occupied habitats empty. The marine vegetables
can undergo processes of Species and microevolution, but also
of macroevolution when occupying semiacuaticas or terrestrial
When a population changes of an adaptive zone to
another one successfully. All the groups of a population do not
contain the adapted genes so that these changes take place, most
on attempts are not successful.
GENERAL RULES OF THE EVOLUTION
When a group begins in an adaptive sense becomes
the inverse sense impossible.
Law of Dolo, the evolution is an irreversible process
Law of Cope, the tendency to the increase of size
is common in the beings better adapted
Law of Gause, two espcies with identicos ecological
requirements cannot occupy the same ecological niche indefinitely.