2. The Big Bang theory

3. The Big Bang theory:
• The Big Bang is a singular huge explosion which is
unimaginable in physical term.
• The universe expanded and hence the temperature
came down.
• Hydrogen and Helium formed sometime later.
• The gases condensed under gravitation. They
formed the galaxies of the present day universe.
• In the solar system, earth was formed about 4.5
billion years back.

5. Condition of primitive earth:
• Earth formed about 4.5 billion years ago.
• There was no atmosphere on early earth.
• Water vapor, methane, carbon dioxide and
ammonia released from molten mass covered the
surface.
• The UV rays from the sun broke up water into
Hydrogen and oxygen. The lighter H2 escaped.
• The ozone layer was formed by O3.
• As earth cooled, the water vapor fell as rain. It fill all
the depressions and form oceans.

7. Origin of life:
• Special creation theory: According to this theory
God created earth and living organism. But it does
not had any scientific prof.
• Theory of spontaneous generation: According to
this theory living organism are originated from
decaying and rotting matter like straw, mud etc.
• Theory of biogenisis: Louis Pasteur experimentation
demonstrated that life comes only from pre-existing
life.
• He showed that, in pre-sterilized flasks life did not
come from killed yeast. The new living
microorganism arose from ‘killed yeast when flask
open in to air.

9. • Oparin – Haldane theory of Biochemical origin of
life:
• A.I. Oparin and Haldane proposed that life could
have come from pre- existing non-living organic
molecule (e.g. RNA, protein etc.).
• According to them life originated from non-living
matter by a gradual process of physicochemical
reaction on primordial earth.
• The conditions on primitive earth were –
1. High temperature.
2. Volcanic storms.
3. Absence of oxygen.
4. Reducing atmosphere containing CH4, NH3 etc.

10. • Urey and Miller experiment:
• Stanley Miller conducted an
experiment in self-designed spark
discharging apparatus. In 1953 he
conducted physicochemical test
for origin of life.
• Miller created similar conditions
of primordial earth in a
laboratory scale.
• He created electric discharge in a
closed flask to raise temperature
upto 800oC . It was in primitive
earth.
• He Used CH4 H2, NH3 and water
vapor inside the flask.
• He observed the formation of
amino acids in condensed liquid
water.

11. • Origin of first cell:
• The first non-cellular forms of life may originated 3
billion years back.
• They have been giant molecules like
RNA, proteins, Polysaccharides etc.
• These giant molecules are called capsules. They
reproduced their molecules to form coaservates.
• The first cellular life formed are unicellular.
• All life forms were in water environment only. This
simple cell evolved into complex form of present
diversified life

12. • Evolution of life: Theories.
• Evolution is the process that results in heritable
changes in a population. It spread over many
generations leading to diversity of organisms
on earth.
• Charles Darwin made a sea voyage in HMS
Begale ship.
• First voyage (1826–1830)
• Second voyage (1831–1836)
• Third voyage (1837–1843)

13. 12 February 1809 – 19
April 1882
• Darwin on his observation and
collection during voyage
proposed theory of Natural
selection.
• He observed that various form
of life exist on earth share
some similarities. There had
bean extinction of old one and
evolution of new one.
• The struggle for existence and
survival fittest leads to
reproductive fitness. Over a
period of time it leads to
formation of new species.

14. •
•
•
•
EVIDENCES FOR EVOLUTION
Paleontological evidence:
Fossils are hard parts of life found in rocks.
Different-aged rock sediments contain fossils of
different life-forms.
• A study of fossils in different sedimentary layers
indicates the geological period in which they
existed.
• The study showed life forms are restricted to certain
geological time-span.
• Hence new lives have arisen at different times in
the history of earth.

15. • Comparative anatomy and morphological evidence:
• It is the Comparison of body structures among different
species
• It shows similarities and differences among organisms
of today and those that existed years ago.

16. • Certain anatomical similarities among species are the
same.
• Ex skeletal elements make up the forelimbs of
man, horse, whale and bat are same. But each of them
performing different function.
• All of them have
humerus, radius, ulna, carpals, metacarpals and
phalanges in their forelimbs.

17. • Homologous organ: These are the organs having
same basic structure but different function.
• Ex 1. fore limb of human, cheetah, whales and bat.
• Ex 2. Thorn of Bougainvillea and tendrils of
Cucurbita represent homology.

18. • Analogous organ: These are the organs having
different anatomical structure but same function.
• Ex 1: wings of butterfly, bird and bat.
• Ex 2. Eye of octopus and eye of mammals.
.

19. • Ex 3. Flippers of Penguins and Dolphins.
• Ex 4. Sweet potato (root modification) and potato
(stem modification)

20. • Divergent evolution:
• It is the origin of new species from common
ancestors.
• Homologous organs supports common ancestor.
• Convergent evolution:
• It is the independent development of species
having similarities to adopt similar environment.
• Analogous organs supports it.

21. • Biochemical evidences:
• Similarities in proteins and genes performing a
same function among different organisms.
• Embryological support for evolution:
• Certain features during embryonic stage common to
all vertebrates that are absent in adult.
• Ex gill slits of vertebrates found in embryo.

22. • Evolution by natural selection:
• observation of moth population in England 1850
supports it.
• Before industrialization, it was observed that there
were more white-winged moths on trees than darkwinged or melanised moths.
• Because white easily escaped from predators as it
blends with trunk colour and lichens.

23. • After industrialization 1920 there were more darkwinged moths in the same area.
• Because of smoke, tree trunk become dark after
industrial revolution. The white months are easily
noticed and captured by predators. The dark winged
were escaped.

24. • Adaptive radiation:
• It is the process of evolution of different species in a
given geographical area radiating to other areas.
• Ex :Darwin's finches in the Galapagos Island.
Finches are sparrow like small birds found in
Galapagos island.

25. • 14 different species
of finches are
observed by
Darwin.
• They have same
body plan and short
tail. But differes in
beak shape and size
which is adopted to
different food habit.

26. • Theories of evolution:
• Three major theories explains the mechanism of
evolution.
• 1. Theory of inheritance of acquired character by
Lamarck.
• 2. Theory of natural selection by Darwin.
• 3. Mutation theory by Hugo De Vries.

27. Theory of inheritance of
acquired character by Lamarck.
• Lamarck was a French
Naturalist.
• He said that evolution of life
had occurred by use and
disuse of organs and
inheritance of acquired
character
• He gave the example of
Giraffes .the ancistor giraffe
are small donkey like animals.

28. • In first attempt to get
leaves on tall trees had
to adapt by elongation of
their necks.
• This character has
acquired and elongated
neck inherited to
succeeding generations.
• Giraffes, slowly over the
years, came to acquire
long necks.

29. Theory of natural selection by Darwin.
• The main concept of Darwin's theory are,
1. Over production.
2. Limitation of food and space.
3. Struggle for existence.
4. Variations.
5. Survival of fittest.
6. Natural selection.
7. Speciation.
• But Darwin did not explained the mechanism of
variation and inheritance of characters.

30. . Mutation theory by Hugo De Vries.
• According to De Vries, mutaions are
the main cause of evolution and
speciation.
• The sudden change in gene that
results in variation in phenotype is
called mutation.
• According to him speciation occurs in
a sudden change in a single step.
• Mutations are random and
directionless
• The main objections of this theory
are
• Mutations are negative and
retrogressive.
• Rate of mutation is slow compare to
evolution.

31. Hardy-Weinberg
principle:
• It states that allele frequencies in a population are
stable and constant from generation to
generation, if a population has no selection, no
mutation, no migration, no genetic drift, and are
random mating.
• (p + q)2 = p2 + 2pq + q2 = 1.

32. • Five factors are known to affect Hardy-Weinberg
equilibrium:
• Gene migration or gene flow.
• Genetic drift.
• Mutation.
• Genetic recombination.
• Natural selection.

33. • Gene flow: movement of genes into or through a
population by interbreeding or by migration.
• Genetic drift: Changes in the frequencies of alleles
in a population that occur by chance, rather than
because of natural selection.
• Gene pool: All the genes in a population at a
particular time.

35. • The geologic time scale (GTS):
• It is a system of chronological measurement of
Earth's history and evolition of life.
• It is constructed by geological and paleontological
studies.
• Geologic time scale has 6 divisions or era.
• Eras are subdivided into periods.
• periods are subdivided into epochs.
• The 6 ears are:
• 1. Azoic era: 4600 to 4200 mya. no life
• 2. Archaeozoic era: 4200 to 3800 mya.- origin of
life. Evolution of prokaryotes.

36. • 3. Proterozoic era: 1600 to 600 mya –origin of first
animal, evolution of algae and insect.
• 4. Paleozoic era: 600 to 280 mya.
• In this Cambrian period all invertebrates and marine
algae evolved.
• In Devonian period 400 to 345 mya fishes evolved. It is
the golden age of fishes.
• In carboniferous period 345 to 280 mya amphibians
and retails evolved.

37. • 5. Mesozoic era: 280 to 65 mya origin of
mammals, ferns, gymnosperms and birds occurred.
• In this, Jurassic period is the golden age of reptiles
and dinosaurs are dominant.
• In cretaceous period birds are evolved.

38. • 6. Coenozoic era: 65 to 2 mya origin of placental
mammals and angiosperms seen.
• Origin of man occurs in 2 mya.
• The modern man evolved 1 mya. The culture and
agricultural practices started in 10,000 years ago.

39. • A BRIEF ACCOUNT OF EVOLUTION:
• About 2000 million years ago the first cellular forms
of life appeared on earth.
• Some cellular form had the ability to release O2.
• Slowly single cell organisms became multi-cellular
life forms.
• By the time of 500 million years ago invertebrates
were formed and active.
• Jawless fish probably evolved around 350 million
years ago.
• Sea weeds and few plants existed probably around
320 million years ago.

40. • in 1938 Coelacanth a lobe finned fish discovered in
South Africa. It evolved into first amphibians.. These
were ancestors of modern day frogs and
salamanders.
• The amphibian evolved into reptiles.
• Reptiles’ lays eggs which don not dry up in sun
unlike those of amphibians.
• Giant ferns (pteridophytes) were present but they
fell to form coal deposits slowly..
• The land reptiles were the dinosaurs.

41. • The biggest dinosaurs are Tyrannosaurus was about
20 feet in height and had huge fearsome dagger like
teeth.
• About 65 million years ago the dinosaurs suddenly
disappeared from the earth.
• Some of them evolved into birds.
• The first mammals were like shrews. Their fossils
were small sized.
• Mammals were viviparous and protected their
unborn young ones inside the mother’s body.
• Due to continental drift, pouched mammals of
Australia survived. Because of lack of competition
from any other mammals.

42. ORIGIN AND EVOLUTION OF MAN:

43. • ORIGIN AND EVOLUTION OF MAN.
• Human are belongs to the order primates of class
mammals.
• Primates also includes
monkeys, gibbons, gorilla, chimpanzee, loris etc.

44. • About 15 mya primates Dryopithecus
and Ramapithecus were existing.
• They were hairy and walked like
gorillas and chimpanzees.
• Ramapithecus was more man like
while Dryopithecus was more apelike.

45. • 2 mya Australopithecines is found in East African
grasslands.
• They hunted with stone weapons.
• Essentially ate fruit.

46. • The first human-like
being the hominid was
Homo habilis.
• Brain capacity was
between 650 – 800 cc.
• They did not eat meat.

47. • in 1891 Fossils
discovered in Java focus
on the next stage i.e.
Homo erectus. It lived
about 1.5 mya.
• Had large brain around
900 cc.
• Probably ate meat.

48. • Neanderthal man:
• Lived in east and central
Asia between 1, 00,00040,000 years back.
• Brain size 1400 cc
• They used hides to
protect their body.
• Buried their dead.

49. • Homo sapiens:
• Evolved in Africa. As they
moved across continents
and developed distinct
races.
• Pre historic cave art
developed about 18,000
years ago are found.
• Agriculture and human
settlement came around
10,000 years back.