BIOL 11072:
Evolution and Biogeography
Prof. Upali
Ms. Kumudu
Evolution: 16L + 3 T
Biogeography: 8L + 1T
Practical sessions: 5 x 2h
Around us are diverse forms of life….
Jungle fowl
African elephant
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Life began on earth 3.5 byo.
Estimated – 30 million species living today
Estimated - 330 million species extinct.
Identified and named species– only 1.75
millions
• Why & How did they come to be here?
Answers??
Lazy people: That is how it has
happened.
Cunning people: Some had to die to
make way for the others
Very thoughtful people: All life forms
were created at once., and the
unwanted forms were destroyed at
several instances.
Very Intelligent people:
• They studied the fossil
records.
• Some fossils are more older,
while others are less older.
• Older fossil forms were
simple, and the more recent
fossil forms were more
complex.
• More complex life forms
were EVOLVED from more
simpler life forms.
What is Evolution?
• Change with time.
• Every thing change- evolve
• Eg. Cities evolve
new-york-skyline-evolution-since-1876
What is biological Evolution?
• Example : Industrial Malanism
Industrialization began in early
18th centuary
Coal powered industries flourished.
Coal smoke produced a lot of soot
and SO2.
SO2 is toxic to lichens.
Biston betularia - a moth
Had two morphs
1. Peppered morph
2. Dark morph
Before industrial revolution:
Peppered moths :98%
Dark moths
:2%
After industrial revolution;
Peppered moths :2%
Dark moths
:98%
Population
size of
moths
Before industrial revolution:
Eg. 1750
After industrial revolution;
Eg. 1900
Peppered moths :98%
Dark moths
:2%
Peppered moths :2%
Dark moths
:98%
What happened?
• The moth population has evolved over time.
• Body colour is controlled by genes
• Gene frequency of peppered moths has
decreased over time.
• Gene frequency of dark moths has increased over
time.
• Overall, there is a change of gene frequency of
this moth population over time/over many
generations.
• Change of gene frequency of a
population over generations is
termed as “biological evolution”.
Important notations in the above definition:
1. Biological Evolution is a property of a population.
2. Gene frequencies change over time, so that
phenotypes/ chracteristics change over time.
3. Not only major changes, as in the above example, but
also minor changes too occure during the course of
Biological evolution.
4. It has no particular goal, but provokes when there is
change in the environment.
5. As the gene frequencies change due to many reasons,
all populations evolve over time. Therefore Biological
evolution is not a theory/concept. It is a fact.