1) Evolution is defined as gradual change over time. Charles Darwin proposed the theory of evolution by natural selection, where heritable traits that increase an organism's chances of survival are passed on to offspring. 2) Darwin observed variations among species on the Galapagos Islands that supported his theory of evolution from common ancestry. 3) Darwin's theory combined Mendel's principles of heredity with Malthus' population principles to explain evolution through natural selection acting upon inherited variation.

1. EVOLUTION
Biology 1 / SY 2006-2007

2. Evolution
 Definition
- gradual change over time
- L. e-, out + volvere, to roll
 Types
GEOLOGIC EVOLUTION
BIOLOGICAL or ORGANIC EVOLUTION
 The foundation of modern evolutionary thought was
described by Charles Darwin

3. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
Greek Philosophers
• Plato’s Idealism
• Aristotle’s scala naturae (scale of
nature)
 special creation of each species
 organisms were created in their current
form
 the earth was only a few thousand years
old

4. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
CARL Von LINNE
• Swedish botanist
• worked on the classification of
plants
• published Species Plantarum
(~7,300 plants)
• ordered classification of plants
based on their similarities
 showed the natural
relationships of plants

5. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
THOMAS MALTHUS
• economist & clergyman
• published
An Essay on the Principle of
Population
 Populations had an inherent tendency to increase geometrically,
while the resources needed to support this growth increase slowly or
not at all.
 Because of the continued growth of a species would outstrip
needed resources, growth would be limited.

6. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
JEAN-BAPTISTE de LAMARCK
• French biologist
• proposed that modern species
descended from other species
• Lamarckism based on two theories:
1. Inheritance of Acquired Characteristics
- traits acquired by an individual during its life are passed to its
offspring
2. Use and Disuse
- organs of the body that were used extensively to cope with the
environment became larger and stronger, while organs that
were not used deteriorated

7. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
Example:
The Evolution of the Giraffe
Giraffes obtained their long necks from
previous giraffes who stretched to eat the
leaves of high tree branches.
Stretching increased the length of their
necks, and this acquired characteristic
was passed to the next generation.

8. THE ROAD TO EVOLUTIONARY THEORY
Evolution Before Darwin
Lamarckism
• first to present a unified theory that attempted to explain the
changes in organisms from one generation to the next
• although mechanisms proposed for change was wrong, since
acquired characteristics are not heritable!!!
 origin of species from preexisting species
 ability of organisms to adapt

9. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
GEORGES CUVIER
• French anatomist and
naturalist and writer
• paleontologist
• strongly opposed the
concept of evolution
 history of living organisms recorded in layers of rock
containing a succession of fossil species in chronological
order
 fossils were organisms that had died in a series of
catastrophes, after which extinct plants and animals were
replaced by the immigration of distant species to the
devastated region  Catastrophism

10. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
JAMES HUTTON
• Scottish geologist
• took up law, medicine
and agriculture
• published
Theory of the Earth
 geological change occurred slowly but continuously by the
process of Gradualism
 sedimentary rock that encased fossils formed by the gradual
accumulation of sediments in bodies of water

11. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
CHARLES LYELL
• Scottish lawyer
turned geologist
• published
Principles of Geology
 Uniformitarianism - the processes that alter the Earth are
uniform through time
 believed Hutton’s evidence for gradualism indicated that
the earth was millions of years old
 believed that even the slow and subtle processes could
cause substantial change over time

12. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
GEORGES CUVIER
JAMES HUTTON
CHARLES LYELL
Geological evolution
 the earth is very old and constantly changing
 life existed millions of years ago
• geologists were convinced of an ancient earth, but were at
odds over how to explain the appearance and disappearance
of species in the fossil record
• believed in in special creation

13. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
GREGOR MENDEL
• Austrian biologist
• discovered the basic principles of
heredity
• father of Classical Genetics
 Individual characteristics determined by
inherited factors transmitted from
parent to offspring.

14. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
CHARLES DARWIN
• voyage on the H.M.S.
Beagle (1836)
• published (1859)
The Origin of Species
• first person who proposed a
mechanistic approach to
evolutionary thought
• the father of synthetic
evolution

15. The Voyage of the Beagle

16. On the Galapagos
Islands...
 Galapagos tortoise
Darwin’s finches
Most organisms on the islands
were endemic.

17.  species not specially created in their
present forms, but had evolved from
ancestral species
 proposed a mechanism for evolution:
Natural Selection
A population of organisms can change
over time as a result of individuals with
certain heritable characteristics
leaving more offspring than other
individuals.

18. THE ROAD TO EVOLUTIONARY THEORY
Darwin’s Time (1800s)
ALFRED RUSSELL WALLACE
• English naturalist
• studied the Malay
archipelago and Amazon
• proposed a theory of
evolution similar to Darwin’s
“Then I saw at once that the ever-present variability of all living
things would furnish the material from which, by the mere
weeding out of those less adapted to the actual conditions, the
fittest alone would continue the race.”

19. Darwinism in Historical Context

20. THE ROAD TO EVOLUTIONARY THEORY
Neo-Darwinian/Contemporary Times
HUGO CARL ERICH VON
DE VRIES CORRENS TSCHERMAK
• rediscovered Mendel’s laws of heredity
• the start of rediscovering evolution in terms of Mendel’s
ideas

21. THE ROAD TO EVOLUTIONARY THEORY
Neo-Darwinian/Contemporary Times
JAMES WATSON
FRANCIS CRICK
• elucidated the structure of
DNA (genetic material)
• DNA contains coded
information which acts as a
blueprint for the transfer of
hereditary information from
generation to generation
• mutation as the raw material
for evolution