The document discusses the origin and evolution of life, covering theories such as chemical evolution, Lamarckism, and Darwinism, alongside evidence supporting organic evolution from various scientific fields. It details the timeline of life from Earth's formation 4.6 billion years ago to the emergence of unicellular and multicellular organisms, as well as the significance of transitional fossils and biogeography. The document also explores concepts like natural selection, the role of genetic material, and the biochemical similarities across species that indicate common ancestry.

1. SEMESTER IV
USZO401 COURSE-8
Unit 1 : Origin and evolution of Life
By: Veena D

2. 1.1 Introduction
Origin of universe
Chemical evolution - Miller-Urey experiment, Haldane and Oparin theory
Origin of life
Origin of eukaryotic cell
1.2 Evidences in favour of organic evolution
Evidences from:
Geographical distribution
Paleontology
Anatomy
Embryology
Physiology and Genetics
1.3 Theories of organic evolution
Theory of Lamarck
Theory of Darwin and Neo Darwinism
Mutation Theory
Modern Synthetic theory
Weismans germplasm theory
Neutral theory of molecular evolution
Unit 1 : Origin and evolution of Life

3. 1.1 Introduction
Origin of Universe
Chemical evolution
Miller-Urey experiment
Haldane and Oparin theory
Origin of life
Origin of eukaryotic cell

5. • Universe formed 13 billion years ago (Big Bang)
Galaxies formed from mass of matter, stars,
dust and gas– required tremendous energy
• Earth formed 4.6 billion years ago
Life - ~ 3.5 b.y.a.
Origin of Universe

6. Origin of Universe
Expansion of universe due to collection of
matter into clouds-condensation and rotation
Formation of galaxies
Galaxy-Milky way
Solar system-Solar nebula
Formation of celestial bodies –later formed sun
and planets -

7. Earth: The Planet
• Temperature
– Distance from Sun
– Geothermal energy from core
– Temperature fluctuated only 10-20o
C over 3.7
billion years despite 30-40% increase in solar
output
• Water exists in 3 phases
• Right size (=gravitational mass to keep atmosphere)
• Resilient and adaptive
• Each species here today represents a long chain of
evolution and each plays a role in its respective
ecosystem

8. Origin of Life on Earth
4.7-4.8 Billion Year History
• Evidence from chemical analysis and measurements
of radioactive elements in primitive rocks and fossils.
• Life developed over two main phases:
Chemical evolution (took about 1 billion years)
• Organic molecules, proteins, polymers, and
chemical reactions to form first “protocells”
Biological evolution (3.7 billion years)
• From single celled prokaryotic bacteria to
eukaryotic creatures to eukaryotic multicellular
organisms (diversification of species)

9. Summary of Evolution of Life
Formation
of the
earth’s
early
crust and
atmosphere
Small
organic
molecules
form in
the seas
Large
organic
molecules
(biopolymers)
form in
the seas
First
protocells
form in
the seas
Single-cell
prokaryotes
form in
the seas
Single-cell
eukaryotes
form in
the seas
Variety of
multicellular
organisms
form, first
in the seas
and later
on land
Chemical Evolution
(1 billion years)
Biological Evolution
(3.7 billion years)

10. Origin of Life on Earth
• Age of Planet Earth - 4.6 billion years
• Oldest fossils - 3.5 billion years
• Possible Formation of the First Cells
– Inorganic molecules reacted to form organic molecules
– Organic molecules polymerized to become
macromolecules
– Plasma membrane formed
– Protocells formed

11. Earth’s atmosphere was ‘reducing’ in the early days. It did not
contain oxygen gas until after plants started photosynthesising
The atmosphere contained:
Hydrogen
Nitrogen
Water vapour
Methane
Ammonia
Hydrogen sulfide
All molecules public domain from Wikimedia Commons, Background image http://www.flickr.com/photos/lrargerich/4587244190/
The gases came from
abundant volcanic activity

12. Chemical (Evolution) Beginnings

13. Stage 1: Abiotic synthesis of organic
molecules such as proteins, amino
acids and nucleotides
Hydrocarbons, water and ammonia are
the raw materials for amino acids.
Stage 2: Joining of small molecules
(monomers) into large molecules
Stage 3: Origin of self-replicating
molecules that eventually made
inheritance possible
Stage 4: Packaging these molecules
into pre-cells, droplets of molecules
with membranes that maintained
an internal chemistry
Origin of Life

14. The atmosphere of the primitive earth was rich in hydrogen,
both in the elemental state and united with carbon in methane,
with nitrogen to form ammonia, and with oxygen as water
vapor.

15. The view that life emerged through
a long process of chemical
evolution was set forth by the
Russian biochemist Alexander
Oparin in 1924 .
Transformation of lifeless chemicals
into living matter extended over a
period of almost a billion years.
Such a transformation would not be
possible today, since any particle
approaching the form of life would
be decomposed by the oxygen of
the air or destroyed by
microorganisms.
Chemical evolution - Haldane and Oparin theory

16. Chemical evolution - Miller-Urey experiment

17. Origin of Life
• Evolution of Small
Organic Molecules
– Early life may have
arose near the surface
of the ocean
– Miller and Urey
Experiment (1953)
• Formation of small
organic molecules

18. However, synthesis of amino acids is
just a first step. In 1964, Sidney Fox
heated a mixture of 18 amino acids to
temperatures of 160-200ºC. for
varying periods of time. He obtained
stable, proteinlike macromolecules
which he termed proteinoids.

19. When the proteinoid
material was cooled and
examined under a
microscope, Fox
observed small,
spherical units that had
arisen from proteinoid
aggregations. These
microspheres showed a
general resemblance to
simple bacteria.

20. Origin of Life
• Evolution of Small
Organic Molecules
– Some scientists
hypothesize life began
in hydrothermal vents
deep in the ocean

21. Four Steps of Abiogenesis
• Step 1: Synthesis of organic monomers from inorganic
molecules
•Step 2: Organic Monomers  Organic Polymers
Catalysts?
•Step 3: Protobionts form
Protobiont = Organic molecules surrounded by
membrane- like structure
Life-like properties:
─ Reproduce
─ Simple Metabolism
─ Membrane potentials
Proteinoids + H2O  microspheres
Liposomes + H2O  lipid membranes
•Step 4: Heredity
Pass instructions to offspring
Controls protein synthesis
1st
genetic material: RNA?

22. Possible Sequence of Protocells
membrane-bound proto-cells
living
cells
self-replicating system enclosed in a
selectively permeable, protective lipid sphere
DNA RNA
enzymes and
other proteins
formation of
protein-RNA systems,
evolution of DNA
formation of
lipid spheres
spontaneous formation of lipids,
carbohydrates, amino acids, proteins,
nucleotides under abiotic conditions
PROTOCELLS
(Origin of the Plasma Membrane)
• Self-replicating molecules and products of
early synthetic reactions would have
floated away from one another unless
something enclosed them. In modern
cells, a plasma membrane serves this
function.
• Overtime, lipids produced by reactions
inside a chamber could have accumulated
and lined the chamber wall forming a
protocell.
• All living cells carry out metabolic
reactions, are enclosed within a plasma
membrane, and can replicate themselves.
• A protocell is a membrane-enclosed
collection of interacting molecules that
can take up material and replicate.
• Protocells are hypothesized to be the
ancestors of cellular life or believed to be
intermediate stage between chemical
evolution and biological forms.

23. PROTOCELLS
• The Protocell
– Aleksandr Oparin’s experiments
• Under specific conditions of pH, ionic composition, and temperature
concentrated mixtures of macromolecules form coacervates
– Lipid and protein membranes
– Coacervate droplets absorb and incorporate many substances
– May form a semi permeable boundary around droplet
– Chemical reactions may take place inside
– ‘reproduce’ by splitting when they get large
– The cell is very structured and has a great interdependence between its various parts.
– The information on how read the DNA, replicate it and apply the results of the replication is
all contained in the DNA.
– In lipid environment, phospholipids are known to automatically form liposomes-
may be the way plasma membranes first formed
• The Heterotroph Hypothesis
– Nutrition was plentiful in the ocean
– Protocells were most likely heterotrophs
• Implies that heterotrophs preceded autotrophs
– Protocells probably used preformed ATP at first
• Natural selection favored those that could extract ATP from carbohydrates
• Fermentative process because oxygen was not available

24. MODEL PROTOCELLS
When proteins or other polymers are introduced into water under controlled ionic
and pH conditions, they tend to cluster together into distinct droplets called
coacervates (colloidal droplets of proteins, nucleic acids and sugars surround by a
water shell formed spontaneously from abiotically produced organic compounds).
The coacervate surround itself with a boundary layer that is selective in admitting
kinds of molecules, thus increasing in size. On reaching critical size and mass, they
divide spontaneously (shears in two), a process characteristic of cells.
This is not true reproduction as the coacervates are not
Living entities.
Then its growth resumes, only to divide again. The droplets
become more selective through the formation of a more
complex membrane beneath the watery shell.
Thus coacervates have some of the properties of life – selective intake of materials,
growth, division and increased numbers.
Oparin experimented using selected substances and enzymes under controlled
medium to induce metabolic activity in produced coacervates. Under contrived
conditions some of their behaviour simulated life.

25. Origin of the First Cell(s)

26. Origin of Life
• Macromolecules
– RNA-first Hypothesis
• In some instances RNA can function as both a substrate and an
enzyme
• If RNA evolved first it could function as both genes and enzymes
– Protein-first Hypothesis
• Amino acids can form polypeptides when exposed to dry heat
• Form microspheres when introduced back into water

27. Origin of Life
• Macromolecules
– Cairnes-Smith hypothesis
• Clay attracts small organic molecules and also contains iron and
zinc
• Iron and zinc may have served as inorganic catalysts for
polypeptide formation
• Clay also collects energy from radioactive decay and releases it
under specific environmental conditions
– Could have served as energy source for polymerization

28. Origin of Life
• The Protocell
– Aleksander Oparin’s experiments
• Under specific conditions of pH, ionic composition, and temperature
concentrated mixtures of macromolecules form coacervates
– Coacervate droplets absorb and incorporate many substances
– May form a semi permeable boundary around droplet
– In lipid environment, phospholipids are known to automatically form
liposomes-may be the way plasma membranes first formed

29. 27.1 Origin of Life
• The Heterotroph Hypothesis
– Nutrition was plentiful in the ocean
– Protocells were most likely heterotrophs
• Implies that heterotrophs preceded autotrophs
– Protocells probably used preformed ATP at first
• Natural selection favored those that could extract ATP from
carbohydrates
• Fermentative process because oxygen was not available

30. 27.1 Origin of Life
• The True Cell
– Membrane-bounded structure that can produce proteins (enzymes)
that allow DNA replication
• DNA RNA Protein
– RNA-first hypothesis suggests that RNA developed before DNA, so
first true cell would have had RNA genes
• Some viruses have RNA genes
• Reverse transcriptase produces DNA from RNA
• Suggests a mechanism as to how cells evolved to have DNA genes

31. 27.1 Origin of Life
• The True Cell
– Protein-first hypothesis suggest proteins evolved first
• Complex enzymatic processes may have been necessary for formation of
DNA and RNA
• Enzymes may have been needed to produce nucleotides and nucleic acids
– The Cairnes-Smith hypothesis suggests RNA and protein evolved at
the same time
• RNA genes could replicate because proteins were already present to
catalyze the reactions
• But this supposes that two unlikely spontaneous processes would occur
at once- formation of RNA and formation of protein

32. 27.1 Origin of Life
• The True Cell
– Once protocells had genes that could replicate,
they became cells capable of reproducing, and
biological evolution began.

33. “The RNA World” Hypothesis
The egg and chicken paradox: Which
came first, DNA or protein?
Some researchers believe that the
predecessor of the current DNA-
RNA-protein world was an RNA
world, in which RNA encoded both
information, like DNA does (genetic
information storage), and function,
as protein does (catalysis).
Q: Why DNA and proteins were
eventually chosen?

34. What is Evolution?
• Evolution is the changes that have occurred in living
organisms since the beginning of life.
• Very simply Evolution is “DESCENT WITH MODIFICATION”
• Direction of change is from simple to complex
• Change in genetic makeup of a population over time
• Time …in terms of “MILLIONS OF YEARS”
• Evolution is defined as “common descent”
– Descent with modification

35. 1.2 Evidences in favour of
organic evolution
Evidences from:
Geographical distribution
Paleontology
Anatomy
Embryology
Physiology and
Genetics

38. Evidences of Evolution
• Fossil Evidencess
–Hard body parts are preserved in most
cases
–Often embedded in sedimentary rocks
–Deposited in layers called strata
• Each stratum is older than the one
above and younger than the one below
–Transitional fossils
• Especially significant
• Represent evolutionary links

39. Transitional Fossils

40. 27.2 Evidences of Evolution
• Geological Timescale
– History of Earth is divided into eras, then periods, and
then epochs
– Based on dating of fossil evidence
• Relative Dating Method
– Determines the relative order of fossils and strata but not
the actual date
• Absolute Method-
– Radioactive dating techniques are used to assign an actual
date to a fossil
– Technique is based on the half-life of radioactive isotopes

43. Summary
• Earth forms 4.6 billion years ago
• Solid surface forms 4 billion years ago
• Life starts (?) 3.8 billion years ago
• Age of Bacteria: Archaean era
• Oxygen atmosphere develops 2 billion years ago
• Eukaryotes develop. Proterozoic era
• Edicarian life: 650 million years ago. First multicellular life, forms
unknown today
• Cambrian explosion: most current life forms appear 550 million years ago
• Paleozoic era: 550 – 250 million years ago. Marine invertebrates, fishes,
amphibians, invasion of the land. Coal formation
• Permian mass extinction: 250 million years ago. 95% of all life dies; end of
Paleozoic
• Mesozoic: 250-65 million years ago. Age of the dinosaurs (reptiles).
Mammals, birds, and flowering plants appear
• Cretaceous mass extinction: asteroid hits the Earth, killing much of life,
including the dinosaurs
• Cenozoic era: 65 million years ago till present. Mammals dominant

44. 27.2 Evidence of Evolution
• Mass Extinctions
– Large numbers of species become extinct in a short
period of time
• Remaining species may spread out and fill habitats left
vacant
– Five Major Extinctions have occurred
• Earth may currently be experiencing a sixth mass extinction due
to human activities

45. 27.2 Evidence of Evolution
• Biogeographical Evidence
– Biogeography is the study of the distribution of species
throughout the world
– The Earth has six biogeographical regions
• Each has its own distinctive mix of species
– Barriers prevented evolving species from migrating to other regions
– Continental Drift
• The positions of continents and oceans has shifted through time
• The distribution of fossils and existing species allows us to
determine approximate timeline

47. CONVERGENT EVOLUTION

49. Continental Drift

50. Evidences of Evolution
• Anatomical Evidences
– Common descent offers explanation for anatomical
similarities
• Homologous Structures
– Same function and same basic structure, indicating a common
ancestor
– Ex: human arm and whale forelimb
• Analogous Structures
– Same basic function but different origins
– Ex: wing of bird and wing of an insect
• Vestigial Structures
– Anatomical structures fully functional in one group and reduced,
nonfunctional in another
– Ex: Modern whales have a pelvic girdle and hind leg bones

51. Homologous Structures

54. Homology Extends to Embryological Development

58. Evidences of Evolution
• Biochemical Evidences
All organisms use same basic biochemical molecules
DNA
ATP
Identical or nearly identical enzymes
Many developmental genes are shared
Degree of similarity between DNA base sequences and
amino acid sequences indicates the degree of relatedness

59. Significance of Biochemical Differences

65. The “endosymbiont hypothesis” suggests that
organelles like mitochondria originated as
endosymbiotic bacteria living within the cell
membranes of other organisms.

78. Evolution is the gradual change occurring in living
organisms over a period of time.
Formation of new species due to changes in specific
characters over several generations as response to
natural selection, is called evolution.
The natural changes occuring is explained through
the theories of evolution as proposed by Lamarck
and Darwin.

79. 1.3 Theories of organic evolution
Theory of Lamarck
Theory of Darwin and Neo Darwinism
Mutation Theory
Modern Synthetic theory
Weisman’s germ plasm theory
Neutral theory of molecular evolution

82. Jean Baptiste Lamarck (1744 -1829) was a French naturalist, well
known for his theory of evolution.
Lamarck’s theory of evolution was published in ‘Philosophic
Zoologique’ in the year 1809.
It is popularly known as ‘Theory of inheritance of Acquired
Characters” or “Use and Disuse theory” or Lamarckism.
Principles of Lamarckism
i. Internal vital force
Living organisms or their component parts tend to increase in size
continuously. This increase in size is due to the inherent ability of
the organisms.
ii. Environment and new needs
A change in the environment brings about changes in the need of
the organisms. In response to the changing environment, the
organisms develop certain adaptive characters. The adaptations of
the organisms may be in the form of development of new parts of
the body.

83. iii. Use and disuse theory
Lamarck’s use and disuse theory states that if an organ is used
constantly, the organ develops well and gets strengthened. When
an organ is not used for a long time, it gradually degenerates.
The ancestors of giraffe were provided with short neck and short
forelimbs. Due to shortage of grass, they were forced to feed on
leaves from trees. The continuous stretching of their neck and
forelimbs resulted in the development of long neck and long
forelimbs which is an example for constant use of an organ. The
degenerated wing of Kiwi is an example for organ of disuse.
iv. Theory of Inheritance of acquired characters
When there is a change in the environment, the animals respond to
that change.
They develop adaptive structures. T e characters developed by the
animals during their life time, in response to the environmental
changes are called acquired characters. According to Lamarck, the
acquired characters are transmitted to the offspring by the process
of inheritance.

86. Theory of Lamarck

89. Theory of Darwin and Neo Darwinism

91. Mutation Theory

92. Modern Synthetic theory of Evolution
Is a combination of Darwin’s theory of evolution by natural selection
with modern genetics
Explains why individuals in a population vary?
How species adapt to their environment?

94. The Modern Synthetic Theory of Evolution describes the evolution of life in terms of
genetic changes occurring in the population that leads to the formation of new species.
It also describes the genetic population or Mendelian population, gene pool and the
gene frequency.
The concepts coming under this synthetic theory of evolution include the genetic
variations, reproductive and geographical isolation and the natural selection.
The Modern Synthetic populations of Evolution describes the merging of the Darwinian
evolution with the Mendelian genetics, resulting in a unified theory of the evolution.
This theory is also referred to as the Neo-Darwinian theory.
Synthetic theory of Evolution was introduced to us by few legendary evolutionary
biologists naming T. Dobzhansky, J.B.S. Haldane, R.A. Fisher, Sewall Wright, G.L.
Stebbins, Ernst Mayr in the years 1930 and 1940.

95. Evolution is “the changes occurring in the allele frequencies within the populations, ”
which emphasizes on the genetics of evolution.
The modern synthetic theory includes scientific evidence from genetics.
What happens when the allele frequency of the population changes.
when the changes are great enough, there is a formation of new species.
A species is a group of individuals who are capable of interbreeding and producing a
fertile offspring.
Factors of Modern Synthetic Theory of Evolution
Migration of the individuals from one form of the population to other, hybridization
between the races of species increases the genetic variability of the population.
Recombination or Variation
Recombination of the new genotypes from the existing genes.
The gene combinations having same indi­
viduals with two kinds of alleles, mixing of the
chromosomes during sexual reproduc­
tion of two parents produce new individuals, an
exchange of the chromosomal pairs of alleles during the meiosis which is called
crossing overproduce the new form of gene combinations. Chromosomal mutations
like deletion, inversion, duplication, translocation, polyploidy result in the
recombination.
Mutation

96. The changes that occur in the gene due to phenotypic effect differential as
the mutation. This produces a variety of changes that may be harmful. Many
of the mutant forms of genes are recessive to the normal genes in a
homozygous condition. These mutations cause variations in offsprings.
Heredity
The transmission occurring in the variations from the parents to their
offsprings is a primary mechanism in the evolution. The organisms which
possess hereditary properties are favoured in the struggle for the existence.
By this, the offsprings benefit from the characteristics of parents.
Natural selection
Natural selection produces a change in the frequency of the genes from one
generation to the other favouring the differential form of the reproduction.
The natural selection process creates an adaptive relation between the
environment and the population through various combinations of genes.
Isolation
It is one of the significant factors responsible for the synthetic theory of
evolution. The isolation helps in preventing the interbreeding of related
organisms which is a reproductive form of isolation.

97. Neutral theory of molecular evolution

99. Darwinism or Theory of Natural Selection
Charles Darwin (1809-1882) was one of the great naturalist and philosopher of
18th century. He was born in England in 1809. While studying in college through his
friendship with Professor J.S.Henslow he was fascinated towards nature. At that
time the British Admiralty planned a voyage of exploration for 5 years on a ship
named H.M.S. Beagle around South America. Dr Henslow was asked to nominate a
young naturalist for the voyage. Darwin was given the opportunity. During his five
years (1831–1835) voyage he visited many parts of the world, a number of islands
including the Galapagos island and Pacific island.
Darwin made elaborate observations on nature of the land, plants and animals of
the regions he visited. He further worked for a period of 20 years to develop the
theory of natural selection.

100. Principles of Darwinism
i. Overproduction
Living beings have the ability to reproduce more individuals and form their
own progeny. They have the capacity to multiply in a geometrical manner. This
will increase reproductive potential leading to overproduction.
ii. Struggle for existence
Due to over production, a geometric ratio of increase in population occurs. The
space to live and food available for the organisms remain the same. This creates
an intense competition among the organisms for food and space leading to
struggle. The struggle for existence are of three types:
a. Intraspecific struggle: Competition among the individuals of same species.
b. Interspecific struggle: Competition between the organisms of different
species living together.
c. Environmental struggle: Natural conditions like extreme heat or cold,
drought and floods can affect the existence of organisms
iii. Variations
The occurrence of variation is a characteristic feature of all plants and
animals. Small variations are important for evolution. According to
Darwin favourable variations are useful to the organism and unfavourable
variations are harmful or useless to the organism.
iv. Survival of the fittest or Natural selection During the struggle for
existence, the organisms which can overcome the challenging

107. Weisman’s germ plasm theory