Write in brief about 'Natural Selection' in the context of evolution of vision.
Darwin’s theory of Natural Selection also
known as ‘Descent of Man’ in 1871 – propounded by – Charles Darwin. Charles
Darwin was a great British Naturalist and is considered as father if evolution.
Darwin’s theory based on following 5
principles, that are as follows as –
1.
Overproduction
2.
Struggle of existence
3.
Variations and heredity
4.
Survival of fittest
5.
Natural selection and origin of
new species
Each of them is explained below in a
simpler way
1.
Overproduction – reproduction
is a rule of nature and by the process if reproduction new individuals or
species are formed from their pre existing or old individuals or species. Thus
reproduction continues the life of living organisms on earth and play important
role in evolution.
But overproduction means
every living organisms on earth reproduces and produce more progeny i.e., every
living organisms has great potential for reproduction of more young ones than
those which can survive upto the maturity. Due to overproduction population of
that species tends to multiply geometrically.
2.
Struggle of existence – due to
overproduction the population of any species increases but the basic needs like
food space and mating partner are constant. Thus for getting these basic needs
struggle are seen between the living organisms to survive on earth.
According to Darwin those
individuals become success in struggle for getting basic needs survived on
earth and those become unsuccessful in struggle become extinct on earth
3.
Variations and heredity –
variations are the differences among the individuals from same species. These
variations play an important role in the
process of evolution. According to the
Darwin’s theory there are three types of variations are found.
a.
Useful variations – increases the
efficiency of the individuals to survive in changing environment ex – different
colours of wings in birds
b.
Non useful variations –
decreases the efficiency of the individuals to survive in changing environment
ex – colour blindness
c.
Neutral variations – neither
increases or decreases the efficiency of the individuals to survive in changing
environment ex – attached and lobed ear lobes in human
a/c to Darwin’s
theory Nature selects useful variations because they are useful for the species
survival while nature avoid non useful variations.
Genes responsible
for useful variations transmit the characters from generation after generation
more speedily than the genes responsible for harmful variation.
4.
Survival of fittest – a/c to
Darwin those individuals which become success in struggle every time in getting
basic needs are with more and more useful variations to survive on earth in
changing environment are selected by nature and survive on earth.
This process of selection
of well adapted organisms with changing environment is called as natural
selection or survival of fittest.
5.
Origin of new species – a/c to
Darwin those individuals become success in struggle for existence preserved or
survived by nature. Such individuals preserved by nature shows more and more
useful variations. Genes responsible for useful variations transmit the
characters from generations to generation through heredity. After many
generation such individuals become completely differ from their own ancestors.
Darwin considered such individuala as new species on earth.
Darwin’s theory of Natural Selection also known as ‘Descent of Man’ in 1871 – propounded by – Charles Darwin. Charles Darwin was a great British Naturalist and is considered as father if evolution.
Darwin’s theory based on following 5 principles, that are as follows as –
1. Overproduction
2. Struggle of existence
3. Variations and heredity
4. Survival of fittest
5. Natural selection and origin of new species
Each of them is explained below in a simpler way
1. Overproduction – reproduction is a rule of nature and by the process if reproduction new individuals or species are formed from their pre existing or old individuals or species. Thus reproduction continues the life of living organisms on earth and play important role in evolution.
But overproduction means every living organisms on earth reproduces and produce more progeny i.e., every living organisms has great potential for reproduction of more young ones than those which can survive upto the maturity. Due to overproduction population of that species tends to multiply geometrically.
2. Struggle of existence – due to overproduction the population of any species increases but the basic needs like food space and mating partner are constant. Thus for getting these basic needs struggle are seen between the living organisms to survive on earth.
According to Darwin those individuals become success in struggle for getting basic needs survived on earth and those become unsuccessful in struggle become extinct on earth
3. Variations and heredity – variations are the differences among the individuals from same species. These variations play an important role in the process of evolution. According to the Darwin’s theory there are three types of variations are found.
a. Useful variations – increases the efficiency of the individuals to survive in changing environment ex – different colours of wings in birds
b. Non useful variations – decreases the efficiency of the individuals to survive in changing environment ex – colour blindness
c. Neutral variations – neither increases or decreases the efficiency of the individuals to survive in changing environment ex – attached and lobed ear lobes in human
a/c to Darwin’s theory Nature selects useful variations because they are useful for the species survival while nature avoid non useful variations.
Genes responsible for useful variations transmit the characters from generation after generation more speedily than the genes responsible for harmful variation.
4. Survival of fittest – a/c to Darwin those individuals which become success in struggle every time in getting basic needs are with more and more useful variations to survive on earth in changing environment are selected by nature and survive on earth.
This process of selection of well adapted organisms with changing environment is called as natural selection or survival of fittest.
5. Origin of new species – a/c to Darwin those individuals become success in struggle for existence preserved or survived by nature. Such individuals preserved by nature shows more and more useful variations. Genes responsible for useful variations transmit the characters from generations to generation through heredity. After many generation such individuals become completely differ from their own ancestors. Darwin considered such individuala as new species on earth.
