Explain the process of natural of natural selection as proposed by Darwin with the help of a suitable example . what are the roles of swim bladder in aquatic aquatic adaptation of rohu fish?
Answers
According to Darwin's theory of Natural Selection,
only the fittest would survive.Darwin believed that organisms reproduced in order to produce more of their progeny as every organism has the innate desire to do so.As generations pass by there is a change in the environment which causes variations due to which even the offsprings of the same parents do not look alike in some respects.The individual having better adaptations will survive in the struggle for life while those which are not adapted will perish.Therefore we can say that Darwin's theory was based on the fundamental principle of THE SURVIVAL OF THE FITTEST.
The swim bladder is located in the body cavity and is derived from an outpocketing of the digestive tube. It contains gas (usually oxygen) and functions as a hydrostatic, or ballast, organ, enabling the fish to maintain its depth without floating upward or sinking.Therefore it allows the rohu fish to survive.
Natural selection is the process whereby organisms better adapted to their
environment tend to survive and produce more offspring, whereas other less
favourable traits tend to become eliminated. Continuous competition between
individuals for environmental resources creates a ‘struggle for existence and this
struggle makes sure that certain organisms fail to survive or reproduce’.
Examples include
i. Galapagos finches all have different types of beaks. During drought, the finches
with the larger beaks survived better than those with the smaller beaks. During
rainy times, more small seeds were produced and the finches with smaller
beaks fared better.
ii. A habitat has red bugs and green bugs. Birds prefer the taste of red bugs, so
soon there are many green bugs and few red bugs. Green bugs reproduce and
make more green bugs and eventually there are no more red bugs.
iii. In one ecosystem, lizards which had long legs could climb better to avoid floods
and reach the food.