Presented By -Upasana Kumari(Enrollment no : CUB1403122024) M.Sc. Bioinformatics

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CENTER FOR BIOLOGICAL SCIENCES(BIOINFORMATICS)

CENTRAL UNIVERSITY OF SOUTH BIHAR, PATNA

EVOLUTION

CONTENTS

1.DEFINITION

2.EVOLUTION BY NATURAL SELECTION

3.PREVALENT IDEAS AT DARWIN’S TIME

4.DARWIN’S IDEA OF EVOLUTION

5.CHANGE MECHANISMS

6.FOUR STEPS OF NATURAL SELECTION

7.WEALTH OF EVIDENCES

8.PATTERNS OF EVOLUTION

9.REFERENCES

DEFINITION

“Evolution: The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years." -Oxford Concise Science Dictionary

EVOLUTION

The last shore-dwelling ancestor of modern whales was Sinonyx, top left, a hyena-like animal. Over 60 million years, several transitional forms evolved: from top to bottom, Indohyus, Ambulocetus, Rodhocetus, Basilosaurus, Dorudon, and finally, the modern humpback whale.

EVOLUTION BY NATURAL SELECTION

The theory of evolution by natural selection, first formulated in Darwin's book “The Origin of Species" in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits.

Darwin wrote, "…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps."

PREVALENT IDEAS AT DARWIN’S TIME

NEW IDEAS PROPOSED

• Fossils indicated the earth was very old.

• Lyell, a Geologist argued that land forms changed constantly.

• Lamarck proposed that organisms changed and these changes were passed to progeny.

Species are fixed.

Earth is about 6,000 years old.

DARWIN’S IDEA OF EVOLUTION

In 1831,Darwin went on a round the world voyage while he made observations of organisms in South America and the Galapagos Islands.

"I can see no difficulty in a race of bears being rendered, by natural selection, more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale," he speculated.

The idea didn't go over very well with the public. Fig. Coverpage of Darwin's Book.

Mediumground finch

Cactusground finch

Smalltree finch

Largeground finch

Smallground finch

Large cactusground finch

Sharp-beakedground finch

Vegetarianfinch

Seedeaters

Ground finches

Cactus flowereaters

Budeaters

Tree finches

Insecteaters

Mediumtree finch

Largetree finch

Mangrovefinch

Woodpeckerfinch

Greenwarbler finch

Greywarbler finch

Warbler finches

Common ancestor fromSouth America mainland

DARWIN’S FINCHES

CHANGE MECHANISMS

Mutation Migration Genetic drift Natural selection

FOUR STEPS OF NATURAL SELECTION

1. Overproduction2. Variation3. Competition4. Selection

“I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.”

—Charles Darwin from "The Origin of Species“, 1859

WEALTH OF EVIDENCES

Embryology Vestigial and Homologous structures Biogeography The Fossil Record Biochemical Evidence

Snake Chicken Possum Cat Bat Human

Embryology & Homologous Structures

Fossil Record & Biochemical evidence

HOMINID SKULL & AMMONITE CASTE DNA-BIOCHEMICAL EVIDENCE

PATTERNS OF EVOLUTION

1. Macroevolution-

Large scale changes taking place over long periods of time.

Lead to new species formation.

2. Microevolution-

Small scale changes within a species.

Produce new varieties or species in a relatively short amount of time.

Macroevolution v/s Microevolution

REFERENCES

• Biology Book – Class 12th NCERT• Class lectures• http://evolution.berkeley.edu/evolibrary/article/