EVOLUTION TINA CHOPRA M.Sc - PowerPoint Presentation

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EVOLUTION

TINA CHOPRA

M.Sc

(Hons), Zoology

Panjab University, Chandigarh

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ORIGIN OF UNIVERSE

BIG BANG THEORY

Thermonuclear explosion

Origin of universe occurred 20 bya.

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ORIGIN OF EARTH

NEBULAR HYPOTHESIS

Condensation of gases under Gravitational force

Origin of Solar system occurred 4.5 bya.

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ORIGIN OF LIFE

THEORIES ON ORIGIN OF LIFE

Theory of special creation

Theory of catastrophismCosmozoic TheoryTheory of Spontaneous Creation/ AbiogenesisTheory of Biogenesis

Theory of Chemical Evolution

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Theory of Chemical Evolution of Life

Given by Oparin and Haldane

Oparin’s book- Origin of Life

“Abiogenesis first and Biogenesis ever since”

3 phases of chemical evolution

Chemogeny

Biogeny

Cognogeny

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SEQUENCE

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EXPERIMENTAL EVIDENCE OF CHEMICAL EVOLUTION

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CHANGES AFTER OXYGEN EVOLUTION

Oxidising

EnvironmentOzone formationOrigin of Aerobic forms of life

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EVIDENCES OF EVOLUTION

Morphological and Anatomical evidences

Biogeographical Evidences

Paleontological EvidencesEmbryological EvidencesBiochemical Evidences

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MORPHOLOGICAL & ANATOMICAL EVIDENCES

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HOMOLOGOUS ORGANS

 Arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale 

2.  Forelimbs of a frog, a bird, a rabbit and a lizard 

 3. Pelvis of a dog, of a cat and of a human and of a snake4. Tailbone of a human being and the tail of a monkey 

5.  leaves of a pitcher plant, a Venus fly trap, a cactus 

6. mouthparts and the antennae of different insects 

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ANALOGOUS ORGANS

1. Potato is a stem while sweet potato is a root

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ADAPTIVE RADIATION IN MARSUPIALS

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Adaptive convergence in placental mammals and Australian marsupials

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VESTIGIAL ORGANS

Vermiform appendix.

Hind limbs is a

vestigeal

organ of python.

Muscles of ear pinna

Wisdom teeth

Caecum

Body hair

Mammary glands in males

Nictitating membrane

Coccyx

Splint bones in horse

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ATAVISM

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CONNECTING LINKS

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EMBRYOLOGICAL EVIDENCES

The development from zygote to adult shows many similarities in various organisms

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PALEONTOLOGICAL EVIDENCES

FOSSILS

Father of

PaleontologyFather of modern PaleontologyFather of Indian Paleontology

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Fossil Dating methods

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BIOCHEMICAL EVIDENCES

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BIOGEOGRAPHICAL EVIDENCES

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GEOLOGICAL TIME SCALE

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THEORIES OF EVOLUTION

LAMARCKISM

DARWINISM

MUTATION THEORYMODERN THEORY

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LAMARCKISM

Theory of Inheritance of Acquired characters

Book “

Philosphic Zoologique”1. New needs:So according to Lamarck, an existing individual is the sum total of the characters acquired by a number of previous generations and the speciation is a gradual process.

2. Living organisms or their component parts tend to increase in size.

3. Production of new organ is resulted from a new need.

4. Continued use of an organ makes it more developed, while disuse of an organ results in degeneration.

5. Acquired characters (or modifications) developed by individuals during their own lifetime are inheritable and accumulate over a period of time resulting a new species.

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Evidences in

favour

of Lamarckism

Increase in their evolution from simple to complex forms.2. Development of present day long-necked and long fore-necked giraffe from deer-like ancestor3. limbless snakes with long slender body from the limbed ancestors due to continued disuse of limbs 

4. Development of webs between their toes for wading purposes in aquatic insects.

5. Development of flightless birds like ostrich from flying ancestors due to continued disuse of wings

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Evidences against Lamarckism

August Weismann who proposed the “Theory of continuity of germplasm”

Boring of pinna of external ear and nose in Indian women;

Tight waist, of European ladies small sized feet of Chinese women etc are not transmitted from one generation to another generator.Eyes which are being used continuously and constantly develop defects instead of being improved. Similarly, heart size does not increase generation after generation though it is used continuously.Presence of weak muscles in the son of a wrestler Reduction in the size of organs e.g. among Angiosperms, shrubs and herbs have evolved from the trees.So, Lamarckism was rejected.

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DARWINISM

Theory of Natural Selection

Main postulates of Darwinism are:

1. Geometric increase.

2. Limited food and space.

3. Struggle for existence.

4. Variations.

5. Natural selection or Survival of the fittest.

6. Inheritance of useful variations.

7. Speciation.

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EXAMPLES OF DARWINISM

Evidences in

favour

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Darwinism is not able to explain:

The inheritance of small variations in those organs which can be of use only when fully formed e.g. wing of a bird. Such organs will be of no use in incipient or underdeveloped stage.

2. Inheritance of vestigial organs.

3. Inheritance of over-specialised organs e.g. antlers in deer and tusks in elephants.4. Presence of neuter flowers and sterility of hybrids.5. Did not differentiate between somatic and germinal variations.6. He did not explain the causes of the variations and the mode of transmission of variations.7. It was also refuted by Mendel’s laws of inheritance which state that inheritance is particulate.

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MUTATION THEORY

1. The evolution is a discontinuous process and occurs by mutations.

2. Elementary species are produced in large number to increase chances of selection by nature.

3. Mutations are recurring so that the same mutants appear again and again. This increases the chances of their selection by nature.

4. Mutations occur in all directions so may cause gain or loss of any character.

5. Mutability is fundamentally different from fluctuations (small and directional changes).

He worked on evening primrose

(

Oenothera

lamarckiana

).

Evolution is a discontinuous and jerky process ,so that new species arises from pre-existing species in a single generation (

macrogenesis

or saltation) and not a gradual process as proposed by Lamarck and Darwin.

“Mutations are the fountain head

of evolution.”

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Evidences in

favour

of Mutation theory

1. Appearance of a short-legged sheep variety, Ancon sheep from long-legged parents in a single generation2. It can explain the inheritance of vestigial and over-specialized organs.3. It can explain progressive as well as retrogressive evolution.

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Evidences against Mutation theory:

It is not able to explain the phenomena of mimicry and protective

colouration

.2. Rate of mutation is very low, i.e. one per million or one per several million genes.3. Oenothera lamarckiana is a hybrid plant and contains anamolous type of chromosome behaviour.

4. Chromosomal numerical changes as reported by de Vries are unstable.

5. Mutations are incapable of introducing new genes and alleles into a gene pool.

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THE MODERN SYNTHETIC THEORY

FACTORS RESPONSIBLE FOR EVOLUTION ARE :

NATURAL SELECTION

MUTATION

HYBRIDISATION

ARTIFICIAL SELECTION

CROSSING OVER

GENETIC DRIFT

MIGRATION

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HARDY WEINBERG PRINCIPLE

allele

 and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

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FACTORS WHICH DISTURB HWE

NATURAL SELECTION

CROSSING OVER

MIGRATION

GENETIC DRIFT

RECOMBINATION

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FOUNDER’S EFFECT

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BOTTLE NECK EFFECT

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TYPES OF NATURAL SELECTION

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HORSE EVOLUTION

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HUMAN EVOLUTION

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PREVIOUS YEAR QUESTIONS

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