can anyone?

Question

explain the concept of evolution by natural selection
thx

Answer 1

Say you have an island, about twenty miles from any other island, where there is a species of bird, say finches. In any population of birds, there is going to be a variety of beak sizes and wing sizes, (like nose and ear size, and height variation in humans). Suddenly there was a drought lasting several years and the main food source of the finches, say, sesame seed, was destroyed, and all they had to eat was wheat, which is harder to break and eat than sesame.
What characteristics would give one bird an advantage over another? Those with smaller beaks would have more difficulty cracking the wheat and feeding it to any baby birds, therefore they would have less live young. Those with larger, stronger beaks would crack and eat more wheat and have more live young. Chances are, that their offspring would have, on average, larger, stronger beaks than those of small beaked finches. The stronger your beak, the more you eat, the more children you have. Larger, stronger beaks have become more common by natural selection.
So what other characteristics? Those with stronger, larger wings could try to find other food, but if they can't make to the other island, they die, those that make it to the other island, and if it has food, will have, on average, larger wings than those that didn't make it. They will have more children, who, on average, will have larger wings. Larger wings have been become more common due to natural selection.

These are simplified examples, it is more complex than this, but the basics are there.

Answer 2

Natural selection is one of the ways evolution comes about, just like gene flow, gene drift and mutation. Natural selection simply means that animals that are worse at producing offspring that can produce more viable offspring die out in favor of animals that are more reproductively successful. Example: giraffes with longer necks could eat leaves while giraffes with shorter necks could not. Eventually, the giraffes with long necks became the common type because they were able to attain more and better food which aided in viable reproduction.