3. What is Evolution?
Evolution refers to the process that have changed
or transformed the life on earth from its earliest forms
to the vast vast diversity that we observe today.
It refers to any change in the heritable traits with in
a population across generation.
Evolutionary Change is based primarily on the
interactions between population of organisms and their
environment.
Ms. Bushra Fatima (Dept. of Sociology)
Shia P.G. College
4. Lamarck’s Theory of
Evolution
Organisms constantly strive to improve themselves by
Changing.
Changes are adaptations to environment acquired in
an organism’s lifetime.
By use or disuse a structure modifies or change.
The offspring inherit these modification from their
parents.
Inheritance of acquired characteristics.
Ms. Bushra Fatima (Dept. of Sociology)
Shia P.G. College
6. Darwin’s Theory of
Evolution
Darwin first formulated the theory of evolution by
natural selection in his book “On the Origin Of Species in
1859.”
In this process organisms change over time as a resu
of change in heritable physical or behavioral traits.
The theory states that all life on earth is connected an
related to each other.
This also favors some traits in an environment over
others.
Ms. Bushra Fatima (Dept. of Sociology)
Shia P.G. College
8. Theory of Natural Selection
The Struggle for Existence- Means members of
each species have to compete for necessities such as fo
shelter, etc.
Survival of the Fittest- Means only the best suited
species in the environment will sustain or survive.
Natural Selection- Means the unequal ability of
individuals to survive and reproduce leads to a gradual
change in a population, with favorable characteristics
accumulating over generations new species evolve.
Ms. Bushra Fatima (Dept. of Sociology)
Shia P.G. College
9. Spencer’s Theory of
Evolution
Herbert Spencer took Darwin’s theory and applied it
to societies that’s why we also know it by the name
Spencer’s Theory of Social Evolution.
He use the term ‘Social Analogy’ to state the similariti
between organisms and societies.
He said that societies were organisms that progress
through similar changes to that of living organisms.
Just like organisms societies begin simple and then
progress to more complex forms.
Ms. Bushra Fatima (Dept. of Sociology)
Shia P.G. College
