EVOLUTION

1. RALLI INTERNATIONAL SCHOOL

3. INTRODUCTION
• Evolution is the change in the inherited characteristics of
biological populations over successive generations.
• Evolutionary processes give rise to diversity at every level of
biological organization, including species, individual
organisms and molecules such as DNA and proteins
ORIGIN OF LIFE
• The origin of life is considered a unique event in the
history of universe
The Universe
• Universe is about 20 billion years old
• It includes huge cluster of galaxies, which contain stars and
cloudsof gas and dust

4. THE BIG BANG
THEORY

5. 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.

6. Condition of primitive earth
• Earth was formed 4.5 billion years before
• Water vapour, methane, ammonia & carbon dioxide were
released from
• the molten mass
• The UV rays from the sun broke up water into hydrogen &
oxygen
• The lighter hydrogen gas escaped from the surface while oxygen
combined with other compounds (methane, ammonia etc.) to
form water, carbon dioxide etc.
• As the water vapour cooled, the water fell as rain & filled all
depressions
• to form oceans & other water bodies
• From the oxygen, ozone layer was also formed
• Life started appearing (origin of life) about 500 million years
after the formation of earth i.e., about four billion years ago

7. Theories of Origin of Life
• Various theories were proposed to explain the
origin of life:
1. Theory of Special Creation
2. Theory of Panspermia/ Cosmozoic theory
3. Theory of Spontaneous Generation
4. Theory of Chemical Evolution

8. iii.
1. Theory of Special Creation:
• Conventional religious literature talks about the theory of
special creation, according to which God, the supernatural
being createdthe earth, light, plants and animals
• This theory has three suggested views:
i. All living organisms (different species or types of plants &
animals) that we see today were created as such
ii. The diversity of life forms was always the same since the time
of
creation & will remain the same in future also
Earth is about 4000 years old
• All these ideas underwent drastic changes during 19th century
when Charles Darwin showed that the existing life forms
share similarities to varying degree among themselves and
also with those life forms that existed millions of life ago
• Extinctions also took place during at different phase of
geological history

9. 2. Theory of Panspermia/ Cosmozoic theory:
• Some scientist believe that life has come on earth from other
planets or outer space
• Early Greek philosophers thought units called ‘spores’ or
‘pansperms’ came on earth along with meteorites & they
mighthave evolved into present day forms

10. 3. Theory of Spontaneous Generation:
• It was also believed that living organisms (life) arose from
decaying matter like straw
• But Louis Pasteur demonstrated that life can arise only from pre-
existing life.
• He showed that no life arose from the heat- killed yeast broth that
was kept in pre- sterilized closed flask, while new organisms arose
from the heat- killed yeast that was kept in the flask left open in
the air.

11. An experiment to demonstrate Spontaneous
generation..

12. 4. Theory of Chemical Evolution:
• This theory was proposed by Oparin & Haldane
• They proposed that first life form could have come from pre-
existing non- living organic molecules (like RNA, proteins, etc.)
and that formation of life was preceded by chemical evolution, i.e.,
formation of diverse organic molecules from inorganic
constituents
• The conditions on earth that favoured chemical evolution were
very high temperature, volcanic storms & reducing atmosphere
that contained methane, ammonia, water vapour etc.

13. Experimental Proof for Chemical Evolution of Life..
• Stanley Miller & Urey created conditions similar to the
primitive
atmosphere in the laboratory using glass apparatus & tubes
• They created electric discharge using electrodes in a conical flask
containing methane, ammonia, hydrogen & water vapour at
800ºC.
• The water containing chamber was heated to provide water vapour.
• After a week, they observed the formation of amino acids.
• In similar experiments, many other scientists observed the
formation of sugar, nitrogen bases, lipids, amino acids & even
pigments
• Analysis of the meteorites also revealed the presence of similar
compounds, indicating the occurrence of similar processes
elsewhere in the space
• The chemical evolution of life was more or less accepted

15. 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 about less than 2
billion years ago.
• This is theory of abiogenesis, i.e., the first form of life arose
slowly through evolutionary forces from non- living molecules;
it is accepted by the scientists
• All life forms were in water environment only. This simple cell
evolved into complex form of present diversified life

16. • 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)

17. • 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.
12 February 1809 –
19
April 1882

18. 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.

19. 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.

20. • 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.

21. 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.

22. 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.
.

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

24. 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.
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.

25. 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 dark- winged or melanised
moths.
• Because white easily escaped from predators as it blends
with trunk colour and lichens.

26. • After industrialization 1920 there were more dark- winged
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.

27. 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.

28. • 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.

29. 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.
Theory of inheritance of acquired
character by Lamarck.
• Lamarck was aFrench
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.

30. • 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.

31. 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.

32. 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.

33. 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.

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

35. 1. Gene Migration:
• When some individuals of a population migrate to other populations,
or when certain individuals come into a population, the gene
frequencies of the given population change, i.e., some genes are lost
in the first case & added to the second.
• If this migration occurs a number of times, gene flow occurs.
2. Genetic Drift:
• Random changes in the allele frequencies of a population occurring
by chance, constitute genetic drift
• The change in allele frequency may become so drastically different
that they form new species.
• The original drifted population becomes the founder & the change in
the phenotype & genotype of the progeny, constitute the founder
effect
• This is clear with microbial experiments, where he pre- existing
advantageous mutants get selected & over a few generations
speciation occurs

36. 3. Mutations:
• Mutations are random & occurs at very slow rate.
• They create considerable genetic variation for speciation to occur.
4. Recombination:
• New combination of genes occur due to crossing over in meiosis
during gametogenesis.
5. Natural Selection:
• Natural selection is the most critical evolutionary process that leads
to changes in allele frequencies & favours or promotes adaptation
as a product of evolution.
• Coupled to increased reproductive success, natural selection
makes the population look entirely different from the original
population, i.e., speciation

37. • Natural selection process depends on the traits favoured & produce
one of the three following effects:
1. Stabilization- in which more individuals acquire mean character
value, i.e., variation is much reduced
2. Directional change, in which more individuals acquire value other
than the mean character value.
3. Disruption, in which more individuals acquire peripheral character
value at both ends of the distribution curve.

38. History of Evolution of Animals
• About 2000 million years before, the first cellular form of life appeared
on the earth.
• Slowly these single- celled organisms evolved into multicellular
organisms.
• Invertebrates were formed around 500 million years before.
• Jawless fish must have evolved around 340 million years ago.
• At around the same time, fish with stout & strong fins, that could move
on land & go back to water, must have appeared.
• The coelacanth or lobefins were the ancestors of modern day frogs &
salamanders.
• These amphibians evolved into reptiles that lay thick- shelled eggs
which do not dry up in the sun; this made the reptiles more successful
than amphibians

39. • In the next 200 million year or so, reptiles of different shapes and
sizes dominated the earth
• Some of these land reptiles moved back to water to evolve into fish
like reptiles (Ichthyosaurs) at around the same time (200 million
years ago)
• The land reptiles i.e., dinosaurs suddenly disappeared from the
earth (mass extinction) about 65 million years ago, while some small
sized reptiles continue to exist today like birds, crocodiles etc.

40. • When the reptiles disappeared,
mammals started dominating the earth
• The first mammal was like shrew
• There were mammals like horse,
hippopotamus, rabbit, bear etc., in
South America but when South
America joined North America (in the
continent drift), these animals were
over- ridden by the fauna of North
America
• Australian land mass remained
isolated & the pouched mammals
survived as there was no competition
from any other mammal

42. History of Evolution of Plants
• Some of the single celled organisms that appeared 2000 million
years ago had pigments to capture solar energy and release
oxygen, in the process of photosynthesis
• Bryophytes were the first plants to colonise lands (plants colonised
the land much before animals)
• Sea weeds & few plants existed around 320 million years ago
• About 200 million years before, giant ferns (Pteridophytes) were
present, but they all fell to form coal deposits slowly
• Herbaceous lycopods & arborescent lycopods evolved from
Zosterophyllun of palaeozoic era
• Psilophyton is the common ancestor of horsetails, ferns &
gymnosperms

43. Fossils of Lycopods & Psilophyton

45. ORIGIN AND EVOLUTION OF MAN

46. Evolution of Man
• The common ancestor of apes and man is a primate Dryopithecus,
that lived 15 million years ago
• At the same time, another genus Ramapithecus also existed
• Both Dryopithecus & Ramapithecus were hairy and walked like
gorillas & chimpanzees; Dryopithecus was more ape like, but
Ramapithecus was more man-like and is the forerunner of hominid
evolution

47. • The human evolution is as follows:
1. Australopithecines
• They probably lived 2 million years ago, in the east
Africa grass lands
• They has brain capacity of 450- 600 cc
• They hunted with stone weapons but essentially ate
fruits.
2. Homo habilis
• This is called first human like being, the hominid
• They had brain capacity of 650- 800 cc.
• They probably did not eat meat
3. Homo erectus
• Their fossils were found in java (Java man) in 1981
• They probably lived about 1.5 mya
• They had a brain capacity of about 900cc
• They probably ate meat.

48. 3. Neanderthal man (Primitive man)
• Their fossils were found in near East & CentralAsia
• He must have lived between 1,00,000- 40,000 years before
• Neanderthal man (Homo sapiens neanderthalensis) had a
brain
capacity of about 1400 cc.
• They used hides to protect the body & buried the dead
• They moved across continents & developed into distinct
races
4. Homo sapiens sapiens (Modern Man)
• Homo sapiens sapiens arose during ice age between
75000- 10000 years ago
• He spread all over the globe & learned to cultivate plants &
domesticate animals
• Pre- historic cave art developed about 18,000 years before
• Agriculture started around 10,000 years back
• Human settlements and cultivations started