1. Presented by
MD NURUDDIN
SUMIT KUMAR
SHARDA UNIVERSITY
2. EVOLUTION
• Evolution is the change in
the inherited characteristics of biologica
l populations over..successive generatio
ns.
• Evolutionary processes give rise to
diversity at every level of biological
organisation,including species, individua
l organisms and molecules such
as DNA and proteins.
3. Evolution
Descent with Modification
Evolution means change over time
Evolution can also be defined more narrowly as a change in the genetic
composition of a population from generation to generation.
4. Evolution on earth
• Formation of Amino Acids – Miller's
Experiment
Process of Evolution
5.
6. Genes and Chromosomes
• Complex, double-stranded
helical molecules
– of deoxyribonucleic acid (DNA)
• called chromosomes
– are found in cells of organisms
• Specific segments of DNA
– are the basic units of heredity
(genes)
• The number of chromosomes
– varies from one species to
another
– fruit flies 8; humans 46; horses 64
7. Theories of Organic Evolution
Historically three theories
1. Lamarck’s Theory of Evolution, 2. Darwin’s Theory
of Evolution, 3. De Vries Mutation Theory of
Evolution.
The views of most modern biologists combine the
second and third
No evidence of the first theory, that of Lamarck’s Use
and disuse theory.
8. Jean Baptiste Lamarck, 1744-1829
• French geologist and naturalist
• published Philosophie
Zoologique in 1809
• Speculated about mechanisms
of biological evolution, offered
no evidence
9. In 1809 Jean-Baptiste Lamarke hypothesized that “simple”
organisms emerge spontaneously and evolve to greater
“complexity”.
Principles to his theory
1. Organisms constantly strive to improve
themselves.
2. Most used body structures develop and
unused waste away. (Use and Disuse)
3. A structure is modified by use or disuse, the
modification is inherited to the offspring.
(Inheritance of acquired characteristics).
10. • Structural variations are due to
functional needs – “to use or
disuse”
• Use of a structure increases its size.
• Failure to use it decreases its size
• These variations (now referred to as
“acquired characteristics” are
inherited.
• There is no supporting evidence in
modern biology to support
Lamarck’s idea
11. Lamarck’s Giraffes
• According to Lamarck’s theory of inheritance
of acquired characteristics
– ancestral
short-necked
giraffes
– stretched
their necks
– to reach
leaves high on
trees.
– Their offspring
were born
– with longer
necks
12. Charles Darwin: The Theory of Natural Selection
• His theory was effectively
presented to the world in
1859 when his book “The
Origin of Species” was
published.
• Darwin’s Theory rests on 5
principles:
13. 5 principles of Darwin’s Theory
1. Overproduction
- All species have a tendency and the potential to
increase at a geometric rate.
All organisms produce more organisms but only a few
survive.
2. Competition
- Due to environmental pressures, the organisms
within a population must compete with each other to
survive.
14. 3. Variation
- Individuals in a population vary greatly in their
characteristics.
4. Adaptation
- individuals who best adapt to the environment are the
ones who will most likely survive
5. Natural Selection
- Individuals having favorable traits will produce more
offspring, and those with unfavorable traits will produce
fewer offspring.
• Speciation
-The process in which new genetically
distinct species evolve usually as a result of genetic
isolation from the main population.
15. DE VRIES MUTATION THEORY
• His experiment was on evening primose.
• Mutation form raw material for evolution.
• It suddenly appears.
• Single mutation may produce new species.
16. Modern Synthesis Theory
Important points of Modern Evolutionary Theory
All evolutionary phenomena can be explained in a way
consistent with known genetic mechanisms.
Evolution is gradual: small genetic changes regulated by natural
selection accumulate over long periods. Discontinuities amongst
species are explained as originating gradually through
geographical separation and extinction.
Natural selection is by far the main mechanism of change.
Thinking in terms of populations rather than individuals, is
primary: the genetic diversity existing in natural populations is a
key factor in evolution
