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The evolution of the species is the phenomenon of change,
not necessarily in the best way, of the phenotype , visible
and direct expression of individual species of the
genotype.
J.B. Lamark was one of the first scientists
proposing an evolution theory. His theory was
based on some principles:
There is a spontaneous attitude of living
beings to become more complex;
The principle of use and non-use;
The inheritance principle of the acquired
characters.
In each environment the individuals of each
population are in competition among them to reach
natural resources. In this surviving fight, the
environment operates a selection called natural
selection.
The evolution theory of Darwin is based on
five important observations:
 The species are equipped of a large fertility
and products. Some descendants can
reach the adult stage;
 Populations of each species include about
the same number of individuals;
 Food resources are limitated, but
relatively constant during the time;
 Identical individuals are not produced by
sexual reproduction. There are plenty of
changes;
 A lot of these changes are due to the
inheritance principle.
This is why Darwin, in his book “The origin of species”, says
that:
In a world which has stable populations, where each individual
has to fight for surviving, the living beings (gifted with the best
characteristics) will have more possibilities to survive and so to
transmit their descendants the favorable characteristics. From
generation to generation the advantageous characteristcs will
become dominant among populations. This is the natural
selection that can produce some changes in a population,
leading to the formation of new species (speciation) .
He said also that fossil documentation can be an important
support to his observations, being itself a demonstration of the
process. Finally, he theorized that every living species was a
descendant from an old common ancestor. The modern test of
DNA supports and attests this idea.
This work has been produced by:
Nicola Berloco
Francesco Careccia
Annalisa Poggiani
Valeria Reale