Evolution is a very complex, irreversible and extremely slow process. the events related to theories of evolution and evidences of evolution are discussed. Theories of origin of life are as follows. 1)Theory of Special creation or devine origin 2) The theory of spontaneous generation/ Abiogenesis 3)Spallanzani experiment 4) Redi Experiment (1680) 5) Pasteurs Experiment (1864) 6) Panspermia 7) Theory of Catastrophism ( G,Cuvier) 8) Naturalistic theory ( Oparin & Haldane, 1920)

1. EVOLUTION

3. USE AND DISUSE THEORY : INTERNAL URGE , DEVELOPMENT OF NEW ORGANS
INHERITANCE OF ACQUIRED CHARACTERS
OBJECTIONS:
1.AUGUST WEISMANN EXPERIMENT WITH RATS
2.ABSENCE OF MUSCLES IN SPORT PERSON CHILDREN
3. MAKING PERFORATION IN EAR PINNA
NEO LAMARCKISM : COPE, OSBORN, PACKARD, SPENCER – SCIENTIFIC APPROACH
1. ADAPTATIONS ARE UNIVERSAL
PAUL KAMMARER OBSERVED DEVELOPMENT OF NORMAL EYES AND SKIN COLOUR IN
PROTEUS ANGUINUS.
LAMARKISM

6. • Darwin observed the Galapagos finches while
traveling on the H.M.S Beagle.

7. Evolution
• The change in a POPULATION’S genetic makeup (gene pool)
over time (successive generations)
– Those with the best phenotype and genotype survive to reproduce
and pass on traits
– All species descended from earlier ancestor species
• Microevolution
– Small genetic changes in a population such as the spread
of a mutation or the change in the frequency of a single
allele due to selection (changes to gene pool)
– Not possible without genetic variability in a pop…
• Macroevolution
– Long term large scale evolutionary changes through which
new species are formed and others are lost through
extinction

8. Microevolution
• Changes in a population’s gene pool over time.
– Genetic variability within a population is the catalyst
• Four Processes cause Microevolution
– Mutation (random changes in DNA—ultimate source of
new alleles) [stop little]
• Exposure to mutagens or random mistakes in copying
• Random/unpredictable relatively rare
– Natural Selection (best produce most offspring)
– Gene flow (movement of genes between pop’s)
– Genetic drift (change in gene pool due to random/chance
events)
• Peppered moth of England; El Nino Galapagos

9. Darwinian Natural Selection
• Three conditions necessary for evolution by natural
selection to occur:
– Natural variability for a trait in a population
– Trait must be heritable (has a genetic basis so that it can be
passed onto offspring)
– Trait must lead to differential reproduction
– Must allow some members of the population to leave
more offspring than other members of the population w/o
trait)
• A heritable trait that enables organisms to survive is
called an adaptation (Lamark is wrong…)

10. DARWINISM
1. PRODIGALITY OF PRODUCTION OR OVER PRODUCTION
2. CONSTANT IN POPULATION
3. STRUGGLE FOR EXISTENCE - INTRASPECIFIC, INTER SPECIFIC, STRUGGLE WITH
ENVIRONMENT
4. VATIATIONS
5. NATURAL SELECTION OR SURVIVAL OF THE FITTEST
6. ORIGIN OF SPECIES
CRITICISM & OBJECTIONS TO DARWINISM
NEODARWINISM

12. Darwinian Natural Selection
n Three conditions necessary for evolution by
natural selection to occur:
– Natural variability for a trait in a population
– Trait must be heritable (has a genetic basis so that it can
be passed onto offspring)
– Trait must lead to differential reproduction
– Must allow some members of the population to leave
more offspring than other members of the population
w/o trait)
n A heritable trait that enables organisms to survive
is called an adaptation.

13. The Case of the
Peppered Moths
n Industrial revolution
– Pollution darkened tree trunks
n Camouflage of moths increases survival from
predators
n Directional selection caused a shift away from
light-gray towards dark-gray moths

17. EVIDENCES FROM PALAEONTOLOGY
Study of prehistoric life through fossils
moulds, casts, petrifactions, coprolites.
Geologists arranged fossils in a chronological sequence
or the history of evolution in the form of geological time
scale.
Eras Periods Epoch
Archaeozoic – Ancient primitive life
Proterozoic – Era of former life
Palaeozoic – Era of Ancient life
Mesozoic – Age of reptiles
coenozoic – Age of mammals

21. EVIDENCES FROM COMPARATIVE
ANATOMY
• HOMOLOOUS ORGANS – ADAPTIVE
RADIATION OR DIVERGENT EVOLUTION
• ANALOGOUS ORGANS – CONVERGENT
EVOLUTION
• VESTIGIAL ORGANS
• ATAVISTIC ORGANS
• CONNECTING LINKS

26. • Convergent Evolution: Similar evolved
structures in unrelated animals.
Copyright © 2010 Ryan P. Murphy

29. EVIDENCES FROM CELL AND
MOLECULAR BIOLOGY
• SEROLOGICAL TESTS – H.F. NUTTEL
• BIOCHEMICAL RECCAPITULATIONS - EXCRETA

37. FORCES OF EVOLUTION
MUTATIONS - ULTIMATE SOURCE OF MUTATION,
SPONTANEOUS, SOMATIC, GERM LINE
GENE FLOW – EXCHANGE OF GENESBETWEEN
POPULATIONS
GENETIC DRIFT – SUDDEN CHANGES IN
FREQUENCIES, SMALL POPULATIONS
SELCTION – FORMS ADAPTIVE EVOLUTIONARY
CHANGES

38. Gene Flow and Genetic Drift
• Gene Flow
– Flow of alleles
• Emigration and immigration of individuals
• Genetic Drift
– Random change in allele frequencies over generations
brought about by chance
– In the absence of other forces, drift leads to loss of
genetic diversity

44. NATURAL SELECTION
1. DIRECTIONAL SELECTION – ex: INDUSTRIAL
MELANISM, RESISTANCE TO DDT
2. STABILIZING SELECTION - ex: HUMAN BIRTH
WEIGHT MORTALITY RATE
3. DISRUPTIVE SELECTION - ex: BLACK AND WHITE
COAT RABBITS

45. Directional Selection
Natural
selection
New average Previous
average
Numberofindividuals
Coloration of snails
Individuals from one side of distribution reproduce
Population Looks Different Over Time—Mean changes
(e.g., peppered moths)
Numberofindividuals
Snail coloration
best adapted
to conditions
Average
Coloration of snails
Average shifts

46. Stabilizing Selection
Coloration of snails
Light snails
eliminated
Dark snails
eliminated
Numberofindividuals
Coloration of snails
Snails with
extreme
coloration are
eliminated
Numberofindividuals
Average remains the same
Number of individuals with
intermediate coloration increases
Eliminates Fringe Individuals
Natural
selection

47. Diversifying Selection
Environment favors extreme uncommon
Individuals
Greatly reduces those with average traits
Coloration of snails
Numberofindividuals
Snails with light and dark
colors dominate
Coloration of snails
Numberofindividuals
Light
coloration
is favored
Dark
coloration
is favored
Intermediate-colored snails
are selected against
Natural
selection

48. ISOLATION
Reproductive isolation is the Segregation or
separation of population by certain barriers is
called as isolation.

49. Reproductive Isolating Mechanisms
• Any heritable feature of body, form, functioning or
behavior that prevents breeding between one or
more genetically divergent populations
• Pre zygotic Isolation
• Post zygotic Isolation

50. Pre mating/Pre-Zygotic Isolating mechanisms
Mating or zygote formation is blocked – stops interbreeding
among the population.
• Temporal Isolation – different species do not mate. Ex – different frog
species in same pond
• Behavioral Isolation – potential mates meet – selection of mate Ex – some
crickets are morphologically same but respond to species specific mating
song.
• Mechanical Isolation – copulation is attempted but transfer of sperm does
not takes place
• Ecological Isolation – bush insects have distinctly shaped genitalia that will
only other members of the same species
• habitat isolation – Ex: Tiger and Lion don’t mate but in capture can do
successfully forms Tiglon.
• Geographical or spatial isolation – Allopatric species (separate species)

51. Post Mating /Post Zygotic Isolating
Mechanisms
Gametic incompatibility, hybrid inviability or
sterility.
• Gametic incompatibility – sperm transfer takes
place but zygote is not formed. Ex. Sea urchins
• Zygotic mortality- egg is fertilized, but zygote does
not develop. Ex: plants
• Hybrid inviability – hybrid embryo develops but
reduced variability Ex- Goat and Sheep
• Hybrid sterility- hybrid is viable but adult is sterile.
Ex: horse and Donkey results in Mule
• Hybrid breakdown- first generation are viable but
F2 are inviable or sterile. Ex: in plants

52. Temporal Isolation in Apple Maggots

54. Post-Zygotic Isolation
• Hybrids don’t work
– Zygotic mortality - Egg is fertilized but zygote or
embryo dies
– Hybrid inviability - First generation hybrid forms but
shows low fitness
– Hybrid infertility - Hybrid is fully or partially sterile

55. Speciation
• Two species arise from one
– Requires Reproductive isolation
• Geographic: Physically separated
• Temporal: Mate at different times
• Behavioral: Bird calls / mating rituals
• Anatomical: Picture a mouse and an elephant hooking up
• Genetic Inviability: Mules
• Allopatric
– Speciation that occurs when 2 or more populations of a species are
geographically isolated from one another
– The allele frequencies in these populations change
– Members become so different that that can no longer interbreed
• Sympatric
– Populations evolve with overlapping ranges
– Behavioral barrier or hybridization or polyploidy

56. Speciation
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Gray Fox
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Spreads
northward
and
southward
and
separates
Southern
population
Northern
population
Early fox
population

57. Copyright © 2010 Ryan P. Murphy

60. Allopatric Speciation
• Physical barrier
prevents gene flow
between populations
of a species
– Archipelago hotbed of
speciation

61. Allopatric Speciation
• New arrival in species
– Poor habitats on an
isolated archipelago
– Start of allopatric
speciation
Hawaiian Honeycreepers

62. Sympatric Speciation
• New species forms within home range
– Polyploidy leads to speciation in plants
– Self-fertilization and asexual reproduction

63. Extinction
• The ultimate fate of all species just as death is for all
individual organisms
• 99.9% of all the species that have ever existed are now
extinct
– To a very close approximation, all species are extinct
• Background vs. Mass Extinction
– Low rate vs. 25-90% of total
– Five great mass extinctions in which numerous new species
(including mammals) evolved to fill new or vacated niches in
changed environments
– 10 million years or more for adaptive radiations to rebuild
biological diversity following a mass extinction

64. Extinction in the context of Evolution
• If the environment changes rapidly,
• The species living in these environments do
not possess genes which enable survival in the
face of such change &
• Random mutations do not accumulate quickly
• All members of the unlucky species may die.

65. Ordovician: 50%
of animal families,
Devonian: 30% of animal families,
Permian: 90% of animal families, including
over 95% of marine species; many trees,
amphibians, most bryozoans and
brachiopods, all trilobites.
Triassic: 35% of animal families, including
many reptiles and marine mollusks.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Current extinction crisis caused
by human activities.
Species and families experiencing
mass extinction
Bar width represents relative
number of living species
Extinction
Millions of
years ago
PeriodEra
PaleozoicMesozoicCenozoic Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Today
65
180
250
345
500
Extinction
Extinction
Extinction
Extinction
Extinction

66. Biodiversity
• Speciation – Extinction=Biodiversity
• Humans major force in the premature extinction of species.
Extinction rate increased by 100-1000 times the natural
background rate.
• As we grow in population over next 50 years, we are expected
to take over more of the earth’s surface and productivity. This
may cause the premature extinction of up to a QUARTER of
the earth’s current species and constitute a SIXTH mass
extinction
– Genetic engineering won’t solve this problem
– Only takes existing genes and moves them around
• Know why this is so important and what we are
losing as it disappears….

67. THANK YOU