Journey Of Charles Darwin | Theory Of Natural selection | Class 12 Biology
About This Video ........................
In This Video Lecture You Will Learn Basic Concept Of Journey Of Charles Darwin
Charles Darwin was born in Shrewsbury, in Western England, in 1809. He joined ’ the
ancestral form by the gradual accumulation of adaptations to different environments,
A particularly puzzling case of geographical distribution was the fauna of the Galapagos
American mainland and then diversified on the different 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 different 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 different 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 different regions of the continent had a definite South American stamp,
islands. Most of the animal species on the Galapagos live nowhere else in the world,
species were distributed on two or more islands that were close together.
This is apparently what happened to the Galapagos finches.
By the early 1840s, Darwin had worked out the major features of his theory of natural
But before it could be published Alfred Wallace, a young naturalist working in the East
selection as the mechanism of evolution. In 1844, Darwin wrote a long essay on the
the Linnaean Society of London on July 1, 1858. Darwin quickly finished The Origin of
origin of species and natural selection.
Indies developed a theory of natural selection essentially identical to Darwin’s. Wallace’s
paper, along with extracts from Darwin’s unpublished 1844 essay, were presented to
Species and published it the next year. In this book Darwin developed two main points:
2. Natural Selection and Adaptation :
their local environments through natural selection. Darwin’s theory of natural selection
hereditary constitution of the surviving individuals. Those individuals whose inherited
Darwin suggested that populations of individual species become better adapted to
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
1. Production of more individuals than the environment can support, leads to a struggle
characteristics it them best to their environment are likely to leave more offspring
for existence among individuals of a population, with only a fraction of offspring
2. Survival in the struggle for existence is not random,, but depends in part on the
was based on the following observations.
than the less it individuals.
surviving each generation.
generations thus leading to the evolution of a new species.
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