Variability is necessary for evolutionary change to occur via natural selection. This is because natural selection acts upon the variation that exists within a population and favors individuals with traits that provide an advantage in their specific environment. Without variability, there would be no differences among individuals for natural selection to act upon, and evolutionary change would be limited or nonexistent.

Here are a few reasons why variability is necessary for natural selection and where it comes from:

In summary, variability is essential for natural selection to operate and drive evolutionary change. Genetic variability arises through genetic mutations, genetic recombination during sexual reproduction, and gene flow between populations. The presence of variability allows natural selection to act on different traits, promoting the survival and reproduction of individuals with advantageous traits and leading to evolutionary change over time.

Dear Susanta Roy thank you for your contribution to the discussion

Genetic Variation is Essential for Evolution by Natural Selection. For natural selection to occur, a population must have a wide variety of individuals with different traits. As natural selection would not influence fish body color if all individuals in a population were exactly the same color? Genetic variation is essential for natural selection because natural selection can only increase or decrease frequency of alleles that already exist in the population. Genetic variation is caused by: mutation and random mating between organisms. Variability is essential for natural selection to work. If all individuals are the same on a given trait, there will be no relative difference in their reproductive success because everyone will be equally adapted to their environments on that trait. Natural selection itself does not create new traits; it only changes the proportion of variation that is already present in the population. The repeated two-step interaction of these processes is what leads to the evolution of novel adaptive features. Genetic variation is the raw material of evolution. Without genetic variation, a population cannot evolve in response to changing environmental variables and, as a result, may face an increased risk of extinction. Genetic diversity is important because it gives species a better chance of survival. However, genetic diversity can be lost when populations get smaller and isolated, which decreases a species' ability to adapt and survive.