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
• 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.
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
• 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.
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
• 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.
• Oparin – Haldane theory of Biochemical origin of
• 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.
• 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
• He created electric discharge in a
closed flask to raise temperature
upto 800oC . It was in primitive
• He Used CH4 H2, NH3 and water
vapor inside the flask.
• He observed the formation of
amino acids in condensed liquid
• 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
• 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
• Charles Darwin made a sea voyage in HMS
• First voyage (1826–1830)
• Second voyage (1831–1836)
• Third voyage (1837–1843)
12 February 1809 – 19
• Darwin on his observation and
collection during voyage
proposed theory of Natural
• 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.
EVIDENCES FOR EVOLUTION
Fossils are hard parts of life found in rocks.
Different-aged rock sediments contain fossils of
• A study of fossils in different sedimentary layers
indicates the geological period in which they
• The study showed life forms are restricted to certain
• Hence new lives have arisen at different times in
the history of earth.
• Comparative anatomy and morphological evidence:
• It is the Comparison of body structures among different
• It shows similarities and differences among organisms
of today and those that existed years ago.
• Certain anatomical similarities among species are the
• 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.
• 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.
• 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.
• Ex 3. Flippers of Penguins and Dolphins.
• Ex 4. Sweet potato (root modification) and potato
• Divergent evolution:
• It is the origin of new species from common
• Homologous organs supports common ancestor.
• Convergent evolution:
• It is the independent development of species
having similarities to adopt similar environment.
• Analogous organs supports it.
• 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.
• Evolution by natural selection:
• observation of moth population in England 1850
• 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.
• 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
• 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
• 14 different species
of finches are
• They have same
body plan and short
tail. But differes in
beak shape and size
which is adopted to
different food habit.
• Theories of evolution:
• Three major theories explains the mechanism of
• 1. Theory of inheritance of acquired character by
• 2. Theory of natural selection by Darwin.
• 3. Mutation theory by Hugo De Vries.
Theory of inheritance of
acquired character by Lamarck.
• Lamarck was a French
• He said that evolution of life
had occurred by use and
disuse of organs and
inheritance of acquired
• He gave the example of
Giraffes .the ancistor giraffe
are small donkey like animals.
• In first attempt to get
leaves on tall trees had
to adapt by elongation of
• This character has
acquired and elongated
neck inherited to
• Giraffes, slowly over the
years, came to acquire
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.
5. Survival of fittest.
6. Natural selection.
• But Darwin did not explained the mechanism of
variation and inheritance of characters.
. Mutation theory by Hugo De Vries.
• According to De Vries, mutaions are
the main cause of evolution and
• The sudden change in gene that
results in variation in phenotype is
• According to him speciation occurs in
a sudden change in a single step.
• Mutations are random and
• The main objections of this theory
• Mutations are negative and
• Rate of mutation is slow compare to
• 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
• (p + q)2 = p2 + 2pq + q2 = 1.
• Five factors are known to affect Hardy-Weinberg
• Gene migration or gene flow.
• Genetic drift.
• Genetic recombination.
• Natural selection.
• 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
• 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
• 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.
• 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
• 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.
• 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.
• 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.
• 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
• By the time of 500 million years ago invertebrates
were formed and active.
• Jawless fish probably evolved around 350 million
• Sea weeds and few plants existed probably around
320 million years ago.
• in 1938 Coelacanth a lobe finned fish discovered in
South Africa. It evolved into first amphibians.. These
were ancestors of modern day frogs and
• 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.
• The biggest dinosaurs are Tyrannosaurus was about
20 feet in height and had huge fearsome dagger like
• 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.
• ORIGIN AND EVOLUTION OF MAN.
• Human are belongs to the order primates of class
• Primates also includes
monkeys, gibbons, gorilla, chimpanzee, loris etc.
• 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.
• 2 mya Australopithecines is found in East African
• They hunted with stone weapons.
• Essentially ate fruit.
• The first human-like
being the hominid was
• Brain capacity was
between 650 – 800 cc.
• They did not eat meat.
• 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
• Probably ate meat.
• 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.
• Homo sapiens:
• Evolved in Africa. As they
moved across continents
and developed distinct
• Pre historic cave art
developed about 18,000
years ago are found.
• Agriculture and human
settlement came around
10,000 years back.