Evolution is a term derived from word "evolve" which means "to unroll" or a process of development where organism reached a final destination. In scientific terminology, evolution also means almost similar, the process in which living organisms adapt themselves with respect to the environmental fluctuations by bringing some changes in their genetic makeup.
Though this is an inevitable process which is not in control of a certain living organism, therefore it has both positive and negative effects on species.
Beneficial aspects:
Evolution is the process which helps the organisms to survive when there are detrimental environmental hazards. In this process some organisms of a specie die while the others go through some genetic modification in such a way that they are better able to bear those environmental constraints and survive. This fittest and survived specie then reproduce superior offspring that are better able to withstand that environmental fluctuation in future. In simple terms we can say that evolution is a key process which makes specie more fit.
Harmful aspects:
Since evolution is just a hit and trial mechanism in which DNA undergoes some modifications in organism so the results are not always certain goal oriented. One devastating effect of evolution is parasitism which causes deadly effects for humans. There are some viruses and bacteria which are disease causing and when we are able to kill them with antibiotics they undergo evolution and form stronger parasites which are more difficult to combat the next time. This process has created a resistance for multiple strains of bacteria and the medical world is worried with the troublesome effects of this evolution in diseases like tuberculosis and AIDS.
Therefore, evolution is both beneficial and harmful for species.
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