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About This Video ........................
In This Video Lecture You Will Learn Basic Concept Of Charles Darwin Theory Of Evolution
ancestral form by the gradual accumulation of adaptations to diferent environments,
A particularly puzzling case of geographical distribution was the fauna of the Galapagos
American mainland and then diversiied on the diferent islands. Among the birds
of specimens of diverse fauna and lora of South America. He noticed that the fauna
although they resemble species living on the South American mainland. It was as
American in their resemblance to the living plants and animals of that continent.
expedition on Beagle to South American coastline. He observed and collected thousands
Darwin collected on the Galapagos were 13 types of inches that, although quite similar,
After returning to Great Britain in 1836, Darwin perceived the origin of new species
seemed to be diferent species. Some were unique to individual islands, while other
two populations could become dissimilar enough to be designated as separate species.
that Darwin found, though clearly diferent from modem species, were distinctly South
though the islands were colonized by plants and animals that strayed from the South
separated from original habitat by geographical barriers. Over many generations, the
very distinct from the life forms of Europe. Furthermore, the South American fossils
and adaptations as closely related processes. A new species would arise from an
and lora of the diferent regions of the continent had a deinite South American stamp,
islands.
By the early 1840s, Darwin had worked out the major features of his theory of natural
organisms. At each fork of the evolutionary tree is an ancestor common to all lines of
the Linnaean Society of London on July 1, 1858. Darwin quickly inished The Origin of
Darwin suggested that populations of individual species become better adapted to
paper, along with extracts from Darwin’s unpublished 1844 essay, were presented to
But before it could be published Alfred Wallace, a young naturalist working in the East
from some common ancestor that lived in the remote past. In the Darwinian view, the
selection as the mechanism of evolution. In 1844, Darwin wrote a long essay on the
1. Production of more individuals than the environment can support, leads to a struggle
history of life is like a tree, with multiple branching and rebranching from a common
2. Survival in the struggle for existence is not random,, but depends in part on the
Species and published it the next year. In this book Darwin developed two main points:
was based on the following observations.
Indies developed a theory of natural selection essentially identical to Darwin’s. Wallace’s
their local environments through natural selection. Darwin’s theory of natural selection
hereditary constitution of the surviving individuals. Those individuals whose inherited
evolution branching from that fork.
1. Descent with Modiication :
2. Natural Selection and Adaptation :
Darwin believed in perceived unity in life, with all organisms related through descent
3. This unequal ability of individuals to survive and reproduce will lead to a gradual
change in a population, with favourable characteristics accumulating over the
characteristics it them best to their environment are likely to leave more ofspring
for existence among individuals of a population, with only a fraction of ofspring
trunk all the way to the tips of the living twigs, symbolic of the current diversity of
than the less it individuals.
origin of species and natural selection.
surviving each generation.
generations thus leading to the evolution of a new species.
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