Darwin was
born in 1809 in The Mount, Shrewsbury, Shropsphire, England. He studied
medicine but hated. He loved the nature and become a naturalist. He went on
HMS-Beagle from 1831 to 1836. He observed geology, fossils and made biological
observations. He published his book “On the Origin of Species by Means of Natural Selection” on 22nd November 1859.

                       He visited Galapagos
Island. This island was named after the large tortoises which were its
inhabitant. Those tortoises had weight up to 250kg. The diameter of their
shells was 1.8m. Their life span was probably 200-250 years. He also noticed
that the shape, size and physical appearance of those tortoises was somehow
different from the tortoises of other islands. He observed that the tortoise
with shorter neck were favored in moist regions while the tortoise have long
necks favored in dryer regions.

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                        On the other hand, he
noticed the finches of Galapagos Island. He observed that all the finches were
originated by a single common ancestor finch. Their ancestor was probably
inhabitant of South America. He said that 14 new species arose from ancestral
group on the basis of dietary adaptation which reflected in size of their bill.

                       Main points on which his book was
based were:

·      
Over production

·      
Variation

·      
Struggle for existence

·      
Survival of the fittest

·      
Natural selection

 Over Production:

                     When specie is in stress,
it will lead to overproduction to ensure survival of their successive
generations.

 

Variation:

                    Individual vary from one
another. Some variations are advantageous and some are disadvantageous to the
species.

Struggle for
Existence:

                
Over production or
increased population create fewer resources and thus caused struggle among
species for existence.

Survival of The Fittest:

                     Females of many species lay millions of eggs but only those eggs are
hatched or become adult which are fittest of the fittest and can survive in
extreme conditions.

Natural Selection:

                     Females of many species
lay millions of eggs but only those eggs are hatched or become adult which are
fittest of the fittest and can survive in extreme conditions.