2. Evolutionary biology
Evolutionary biology is the subfield of biology that studies the evolutionary
processes (natural selection, common descent, speciation) that produced
the diversity of life on Earth.
3. EVOLUTION
The process by which different
kinds of living organism are
believed to have developed
from earlier forms during the
history of the earth.
.
4. ORIGIN OF LIFE
Life is inherent capacity that an organism posses to maintain and reproduce itself. The origin or
beginning of life is a unique event in history of universe. Let us first aquaint ourselves with origin of
universe.
The Big Bang model, states that the universe began as an incredibly hot,
dense point roughly 13.7 billion years ago.
the universe gradually cooled and continued to expand.
Dark matter gradually gathered, forming a foam-like structure
of filaments and voids under the influence of gravity.
Giant clouds of hydrogen and helium were gradually drawn to the places
where dark matter was most dense, forming the first galaxies, stars, and
everything else seen today.
1) Big Bang theory
5. Theories on origin of life
Theory of special creation
Theory of Abiogenesis / spontaneous generation
Theory of Biogenesis
Theory of Catastropism
Theory of Panspermia
Cosmozoic Theory
Theory of chemical evolution / Oparin – Haldane Hypothesis
6. Theory of special creation
The theory of Special Creation was purely a
religious concept, acceptable only on the
basis of faith. It has no scientific basis.
The book of Genesis is the basis of this
religion and in it, it states that the Earth was
a void of darkness and that God over a
period of 6 days created night and day,
water and land, vegetation, the sun and
moon and evidently living creatures.
7. Theory of Abiogenesis
or
Theory of spontaneous
generation
The hypothetical process by which living organisms
develop from nonliving matter.
According to that theory, pieces
of cheese and bread wrapped in rags and left in a
dark corner,
Ffor example, were thus thought to produce mice,
because after several weeks there were mice in the
rags.
Many believed in spontaneous generation
because it explained such occurrences as the
appearance of maggots on decaying meat.
8. Theory of Biogenesis
Given by
Experiment performed by Pasteur in 1859
Lazzaro Spallanzani in 1768
Francesco Redi 1668
9. Pasteur's Experiment
He boiled a meat broth in a flask that had
a long neck that curved downward, then
upward, like a goose neck.
The bend in the neck prevented
contaminating particles from reaching the
broth, while still allowing the free diffusion
of air.
He remove that long neck of flask the
broth would then quickly become clouded
with bacterial growth.
10. Lazzaro Spallanzani
In1745, John Needham ,wanted to test and see if
microorganisms would still appear after boiling a liquid. He boiled
chicken broth, put it into a flask, sealed it, and waited. Soon
enough, microorganisms grew.
when Spallanzani heard of this experiment, he did not believe it.
Spallanzani proposed that the microorganisms could have entered
the flask after it was boiled, and before it was sealed.
Spallanzani put broth in a flask, sealed the flask so that way no air
could get in, and boiled it. No organisms grew in that flask. Many
people said that all that Spallanzani did was prove that
Spontaneous Generation did not occur when there was no air.
11. Francesco Redi
Francesco Redi placed fresh meat in open containers .
the rotting meat attracted flies, and the meat was soon
swarming with maggots, which hatched into flies.
When the jars were covered so that flies could not get in
[middle], no maggots were produced.
To answer the objection that the cover cut off fresh
air necessary for spontaneous generation,
Redi covered the jars with porous gauze [right] instead
of an air-tight cover.
Flies were attracted to the smell of the rotting meat,
clustered on the gauze, which was soon swarming
with maggots, but the meat itself remained free of
maggots.
12. Theory of Catastropism
Proposed by Baron Georges Cuvier (1769–
1832).
According to him , world undergoes a
catastrophe which kill all living organisms,
then god create new life from inorganic
matter.
13. Theory of Panspermia
Proposed by Arrhenius (1908)
The panspermia hypothesis states that the
"seeds" of life exist all over the Universe and
can be propagated through space from one
location to another. Some believe that life
on Earth may have originated through
these "seeds".
15. Theory of chemical
evolution/Oparin-Haldane
hypothesis
The Oparin-Haldane hypothesis suggests that
life arose gradually from inorganic molecules, with
“building blocks” like amino acids forming first
and then combining to make complex polymers.
16. FREE ATOMS SIMPLE ORGANIC
MOLECULES AND
COMPOUNDS
FIRST ORGANIC
COMPOUNDS
SIMPLE ORGANIC
COMPOUNDS
COMPLEX ORGANIC
COMPOUNDSFIRST LIFE FORM
PROCESS OF CHEMICAL ORIGIN
17. Source of energy in primitive atmosphere
High temperature
Cosmic radiation from outer space due to lack
of ozone layer
High voltage electric current from lightening
Reducing atmosphere (ammonia, methane
etc.)
