1. Charles Darwin established the theory of evolution by natural selection, proposing that all species descended over time from common ancestors and that evolutionary branching resulted from natural selection of heritable traits that increased fitness. 2. Darwin's theory explained that only the fittest individuals survive and pass their traits to offspring, with environmental factors selecting for variants that increase survival. 3. Evidence for evolution includes analogous and homologous structures across species, vestigial organs, fossil records showing progression of life forms, and "connecting links" with traits of ancestral groups.

1. 1
Origin of Life
and
Evolution
Gurudatta K Wagh
Charles Robert Darwin FRS
12 February 1809 - 19 April 1882

2. 2
Darwin
- Established that all species of life
have descended over a time from
common ancestors
- Proposed the scientific theory that this
branching pattern of evolution resulted
from a process that he called natural
selection
- 'On the Origin of Species' (1859)

3. 3
Darwin's theory of natural selection
Only the fittest survive. Plants and
animals which are not fit die. Fit
species reproduce and pass on the
relevant characteristics to the
following generation which in turn
would make them fit for survival.
Natural selection - The process of
selection of characteristics that
contributes to the fitness for survival.

4. Rule of the nature - Organisms which
cannot adjust to their surrounding
have no right to survive
Selection of variants by
environmental factors forms the
basis for evolutionary processes
The "Evolution of Life" (organic
evolution) is the most widely
accepted theory
4

5. 5
Life on earth
A life-substance appeared on the
earth in sea water. It developed into
a unicellular form of life. Gradual
and orderly changes took place in
this unicellular form and it
developed into multicellular forms of
greater and greater complexity over
a prolonged period of nearly 300
crore years.

6. Evidence for organic evolution
Processes like growth, reproduction and
metabolism are essentially the same in all
organisms.
Analogous: Organs that are
fundamentally unlike except in function
a) Tail fin of lobster and flukes of whale
b) Wings of fly and wings of a bird
c) Eyes of arthropods and vertebrates
6

7. 7
Homologous: Organs which are
fundamentally the same in structure,
but perhaps modified for widely
different functions
a) The forelimbs of man (adapted for
handling), bat and bird (adapted for
flying), Whale and seal (adapted for
swimming) have the same principal
skeletal composition

8. 8
b) The scales of an ovulate pine cone
correspond with the carpels of a
flower and the scales of the staminate
cone correspond with the stamens of
a flower
Similarities observed between the
homologous organs are due to the
fact that evolution leads to modify the
existing structures for new modified
functions creating a new structure

9. 9
Vestigial organs (functionless in the
course of evolution)
The same organ may be functional in
one organism but vestigial in another.

10. 10
Vermiform appendix of man: Human
ancestors ate uncooked food with
considerable cellulose content in
them. The normal function of caecum
and appendix in mammals is the
digestion of cellulose.
Other examples are ear muscles,
wisdom teeth, plica semilunaris
(representing nictitating membrane of
the eye), coccyx (reduced tail) etc.

11. Monotropa uniflora. Indian pipe plant
is parasitic. Leaves are scale-like,
without chlorophyll.
11

12. 12
Palaeontological evidence
The process of fossilization takes a
very long period of time.
In order to study the fossil, the land is
excavated. The deepest layers have
fossils of invertebrates. In layers above
them are found prehistoric fish-like
animals, amphibians, reptiles, birds
and mammals respectively in that
order.

13. 13

14. Connecting Links
Organisms referred to as 'connecting
links' are those which are structurally
intermediate between two different
groups. Connecting links can be found
among organisms that are still living.
14

15. 15
Duck-billed platypus
Lays eggs like reptiles
Has hair and mammary
glands like mammals.
'Peripatus' has
segmental nephridia,
thin cuticle and
parapodia - like
appendages as in
Annelida. At the same
time it has trachea and
open circulation as in
Arthropoda.

16. Lung fish though
a fish breathes air
through its lungs.
These organisms point strongly to the
fact that Mammals have evolved from
Reptiles and Amphibia from fishes.
16

17. 17
Embryological evidence
Embryology - study of development of an
organism from an embryo.
Comparative study of embryos of
different generation of vertebrates
exhibits that the embryos in their early
stages of development show a great deal
of similarities, but differ in the later stages
of development - suggesting common
ancestry for these animals.

18. 18

19. Natural selection
After several generations the adapted
individuals may also be very different
from the original species.
Criterion for the natural selection
Successful adaptation for growth and
reproduction in the given environment.
19

20. 20
Industrial revolution
and the
Birmingham moths

21. Typica and carbonaria morphs on the
same tree. The light-coloured
typica (below the bark's scar) is nearly
invisible on this pollution-free
tree, camouflaging it from predators.
Biston betularia f. typica, the
white-bodied peppered moth
Biston betularia f. carbonaria,
the black-bodied peppered
moth
21

22. As a result of industrial revolution,
there was an increase in the level
of pollution. Owing to this, there
was hardly any growth of algae or
fungi on the tree trunks.
22
Instead, the tree trunks got covered by soot which gave
them a black colour. Now, it were the black moths that
began to get protection and the grey ones were easily
detected by their predators and consumed by them.
Nowadays in the surroundings of Birmingham black
moths are found in large numbers.

23. 23
How an individual plant or animal
acquired factors that made it better
adapted to its surroundings?
This was answered by the discovery of
the laws governing heredity and
mutation and thus Darwin's theory
came to be universally accepted.

24. 24
Please click the link in the next slide
Theory of Evolution
https://www.youtube.com/watch?v=p
Qp2lFcDEbw

25. 25
Thank you
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