Charles Darwin developed the theory of evolution by natural selection based on observations he made during a 5-year voyage on the HMS Beagle. His theory proposed that all species share a common ancestor and evolve over time through gradual processes of variation, competition for limited resources, and natural selection of beneficial traits. Key evidence came from studies of finches and tortoises on the Galapagos Islands which had adapted in different ways on different islands. Darwin's theory revolutionized scientific understanding of the diversity and relatedness of life on Earth.
1. Darwin’s theory of Evolution
Evolution is the change that takes place over a period of time.
2. About Charles Darwin
Full name : Charles Robert Darwin
Birth place: England
Birth date: 12th February, 1809
He was the great English naturalist.
His work mainly focused in understanding the life on the Earth.
3. Darwin’s work
He wrote 20 books of different volumes on nature including
Origin of species, Voyage of Beagle.
Thousands of letters.
More than 200 articles.
Manuscripts.
4. Trip to HMS Beagle
Turning point in Darwin’s life.
Trip started on 27th December, 1831 and lasted for five years.
Trip conducted under the supervision of captain FitzROy.
Lots of observation made by Darwin during the trip.
Collected several evidences to support the observations.
5. Darwin’s observations during the trip
Adaptation of plants in the natural
environment.
Birth and survival of different species.
Fossils of different species that got extinct.
Fossils of species that have similarity to the
existing species.
6. The Galapagos islands
Landed on Galapagos island on 15th September , 1835.
Important fauna for Darwin’s study: iguanas, giant tortoise
and finches.
Different islands of Galapagos with tortoise variable in
looks and weight.
Iguanas on different island had variable appearance.
The beak of finches and their feeding habit differ in islands
of Galapagos.
8. Darwin’s study
After he returned from trip, he closely studied all the
specimens and evidences that he collected from
different island. His study included deep research and
findings on each species.
He was highly motivated by Hutton and Lyell theory on
earth in geology.
Hence, he linked all his findings with past theories given by
many other biologist and naturalist.
He got a letter from Alfred Russel Wallace on his findings.
9. Darwin’s result
Finally after lots of research and
findings, Darwin came to the
conclusion on origin and evolution of
species.
11. Common descent
All the organism have one common ancestor in the past
and with the change in climate and habitat, they
descended from that unknown ancestor.
Over a period of time, the changes within them got
collected resulting in their survival for the changing
environment also termed as adaptation.
12. Gradualism
Origin and evolution of new species
depends on the accumulation of
changes. After a period of time when
different changes get piled up resulting
in adaptation, then the species is said to
evolve. Hence, evolution is a slow and
gradual process.
13. Multiplication
Over a time period, changes takes place. These
changes can result in the species with similar in
appearance or completely different in
appearance and behavior. Hence, species
multiply either having similar characteristics to their
ancestor or different characteristics than that of
them.
14. Natural selection
Darwin termed natural selection as the major mechanism in origin and
evolution of species.
Overproduction
Competition Variation Adaptation
Natural
selection
15. Overproduction
Every species in this planet have potential to give
birth to young ones and increase in its number. This
is known as overproduction where there is no limit
set for any species to give birth a particular
number of offspring's.
16. Competition
More the number of species , higher will be the
competition for their survival. It is because, our
environment have finite resources that supports the
survival of only some species. Hence, those offspring who
meets the environmental criteria can survive. Thus even
after overproduction the population of species generally
remain constant with slight variation in the overall data.
17. Variation
Variation is the key ingredient for survival of the
species. Those species who have suitable variation
that benefits them have higher chances of survival
than those species who have no variation or who
lack beneficial variation. Hence, as a result of
variation species possess morphological and
character differences.
18. Survival of the fittest
Species that have variation and can tackle the
environmental condition are fit for reproduction and
survival. Hence, fitness depends upon the adaptation of
species to the particular environment. Therefore, any
species with low fitness die and that with higher fitness
can survive.
19. Natural selection
After a particular time period, the changes or variation
acquired by the species results in natural selection. This
means that nature selects the beneficial variation and
increase the survival rate of offspring having those
characters.
20. Example of natural selection
Drug resistance in
bacteria.
Shape of beak in
finches.
The peppered moth
Differential color in
beetles
21. Natural selection and artificial selection
Natural selection
It operates in the natural method.
It is a slow process and takes time.
It does not require human
interference.
Moth color, beak shape of finches.
Artificial selection
It operates in the artificial or man
made method.
It is fast process.
It requires human ideas and effort.
Breeding, artificial insemination.
23. Convergent evolution
Convergent means to converge at a point. Hence, species that
have no common origin but looks or behaves in similar way due to
adaptation to same environmental condition comes under this
group.
The best example for this is humming bird and sunbirds. Both these
birds are from different family but their feeding habit is same. Other
examples include silk spider and silk moth, bat and birds etc.
24. Divergent evolution
Divergent means landing at different points.
Hence, species that have common origin but
have difference in morphology or show difference
in their behavior comes under this group. Example
include limbs with five digit of bat and whale; that
evolved from common ancestor but their use and
function are different.
25. Co-evolution
Co-evolution refers to effect of two species
on each other’s evolution. This can be seen
in insects and plants where one act as
predator and other as prey thus affecting
the morphology of each other.
26. Learn more on Darwinism
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