Dr.Nirav Soni

1. EVOLUTI0N
Dr.Nirav Soni

3. Evolution
 Evolutionary Biology is the study of history of life
forms on earth
 Flora :- Plant group and fauna :- Animal Group
 The Origin of life is considered unique event in
the history of universe
 The universe is vast

4.  The word evolution means to unfold or unroll or to
reveal hidden potentialities. Evolution simply
means an orderly change from one condition to
another.
 It can be best explained by Darwin’s concept of
‘Descent with modification’.
 This is the story of origin of life and evolution of life
forms or biodiversity on Planet earth in the context to
evolution of earth and against the background of
evolution of universe itself.
What is Evolution?
Evolution term was introduced by Herbert Spencer.

5. THEORIES FOR ORIGIN OF LIFE:
1. Theory of special creation:
2. Cosmic panspermia theory:
3. Theory of spontaneous generation
(Abiogenesis/Autogenesis)
4. Others like
 Biogenesis (F. Reddy),Harvey and
Huxley
 Meteority Theory :- (Other planet,
(Suddenly Evolution from cosmozoa),
 Theory of catatrophs:- (Qvier
Propoesed, Sudden revoultion at
different intervals time)

6. 1. Theory of special creation:
The greatest supporter of this theory was Father
Suarez.
This is mythology based theory.
All elements were created within Six days
This theory has three connotations –
(a) All living organisms that we seen today were
created as such.
(b) The diversity was always the same since
creation and will be the same in future.
(c) The earth is about 4000 years old.
From fossils records and their dating, we can
conclude that earth is very old, not thousands of
years as was through earlier but billions of years
old

7.  2. Cosmic panspermia theory:
Some scientists believe that life
came from outer space.
Early Greek thinkers thought units
of life called spores were
transferred to different planets
including earth.
‘Panspermia’ it still a favorite idea
for some astronomer.

8.  3. Theory of spontaneous generation
(Abiogenesis /Autogenesis)
 This hypothesis was supported by ancient
Greek philosophers.
 According to this theory life came out of
decaying and rotting matter like straw,
mud, etc spontaneously.
 They believed that the mud of Nile river
could give rise to fishes, frogs, crocodiles
etc when warmed by light rays.

9. BIG BANG THEORY
Proposed by Abbe Lemaitre.
 According to it, the universe originated about 20
billion years ago due to a thermonuclear
explosion of a dense entity.
 This single huge explosion which is
unimaginable in physical terms, is called as big
bang.
 It attempts to explain to us “ Origin of
Universe”
 Universe Explosion and Expanded, temp. came
down.
 Hydrogen and helium sometime formed later.

10.  Gases condensed under gravitation and formed
disc like structure is called nebula (made up of
small particles and atoms ) e.g Solar nebula
formed solar system) and formed Milky way.
 The very hot central part of solar nebula
became still hotter and converted into the sun.
This is called Nebular Hypothesis
 Later on, due to condensation of atoms and dust
particles moving around the sun other planets
were formed. In the solar system of the Milky Way
galaxy, earth was supposed to have been formed
about 4.5 billion years back
 There were no atmosphere on early earth.

15. THEORIES OF ORGANIC EVOLUTION
Historically there are 3
Theory
1. Lamarck
2. Darwin
3. De vries Mutation

16. EVIDENCED FOR EVOLUTION
 MORPHOLOGY
 EMBRYOLOGY
 PHYSIOLOGY
 PALAENTOLOGY- Study of fossils is called
palaeontology. E.G. Print fossils: Fossilized
impressions of foot, wings, leaves, stem
etc…………..