Question

Evolution by natural selection, initially described by Charles Darwin, is the theory that explains how a population’s inherited traits change over time and describe why organisms must adapt to their environments. Evolutionary theory can explain how specialized features develop in different species.

Answer 1

Natural selection is a process of adapting an organism to new environment though selectively inheriting the advantageous traits among generations.

The genetic variation exists among every organism through random mutations, these variations are transfered to the offspring. Generally, every individual interacts with external (outside of cell, abiotic factors) and internal environment (internal to cell) regularly. If there is any particular change in the environment, some of the traits will make specific individual to get adapted to new environment, which improve their life span and reproductive ability. Those particular traits which have advantage towards surviving in the environment will be further favored and inherited. If population cannot adapt to new environment, survival of individuals will gradually decline and leading to extinction. This lead to the concept of "survival of fittest", the organisms which have more survival rate and reproductive advantage are termed as fit and their gene pool will become more common through generations.

In addition, if gene pool of population becomes homogenous, they may not survive towards new external forces and become extinct. So, it is necessary for every population to maintain variations in gene pool to make them resistant to new environments. In this particular case, natural selection helps for selecting advantageous traits which improve fitness.

Natural selection acts on phenotype of organism interacting with particular environment. However genetic basis of phenotypic traits which possess adaptation will be inherited and become common among the population, leading to evolution of new specialized structures or new species.        

The best example is peppered moth adaptation to industrial revolution, initially peppered moths exist as light color and reside on bark of trees to camouflage themselves from predators. During industrial revolution, all trees were covered with soot and made them exposed for predators. Simultaneously, dark colored moths evolved at same time and they have been naturally selected thus making their population to flourish. Later, by improving environmental conditions, populations of light colored moths increased. This a typical example of species adaptation towards industrial pollutants.#

Darwin finches are one more example of development of specialized features. One common ancestor developed 15 different species having different beak shapes. these different beak shapes made them to adapt to new foods like fruits, insects etc. They developed new ecological niches for sharing food availability in Galapogos islands.