1. Presented By -
(Enrollment no :
CENTER FOR BIOLOGICAL SCIENCES
CENTRAL UNIVERSITY OF SOUTH BIHAR, PATNA
2.EVOLUTION BY NATURAL SELECTION
3.PREVALENT IDEAS AT DARWIN’S TIME
4.DARWIN’S IDEA OF EVOLUTION
6.FOUR STEPS OF NATURAL SELECTION
7.WEALTH OF EVIDENCES
8.PATTERNS OF EVOLUTION
“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
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.
5. EVOLUTION BY NATURAL
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
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."
6. PREVALENT IDEAS AT
NEW IDEAS PROPOSED
Fossils indicated the earth was very old.
Lyell, a Geologist argued that land forms changed
Lamarck proposed that organisms changed and these
changes were passed to progeny.
Species are fixed.
Earth is about 6,000 years old.
7. DARWIN’S IDEA OF
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.
Common ancestor from
South America mainland
10. FOUR STEPS OF NATURAL
“I have called this principle, by which each slight
variation, if useful, is preserved, by the term Natural
—Charles Darwin from "The Origin of Species“, 1859
11. WEALTH OF EVIDENCES
Vestigial and Homologous structures
The Fossil Record
13. Fossil Record & Biochemical evidence
HOMINID SKULL & AMMONITE CASTE DNA-BIOCHEMICAL EVIDENCE
14. PATTERNS OF EVOLUTION
Large scale changes taking place over
long periods of time.
Lead to new species formation.
Small scale changes within a species.
Produce new varieties or species in a
relatively short amount of time.