By intruding mutations, which are the ultimate source of biological diversity. I think this is it.
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Sixty-five million years ago, more than three-fourths of all plant and animal species living on Earth becameextinct<span>. This event is known as the </span>K-T<span> mass </span>extinctionbecause it occurred at the boundary between theCretaceous<span> (K) and Tertiary (T) time periods. The most famous group of animals to perish was the dinosaurs.
Hope this helps :)</span>
Answer:
No, mutations do not all result in negative effects. Sometimes they can be beneficial, as they are completely random. It is our general tendency to think of the word "mutation" in negative terms; however, do not get confused. Mutations are the root/ultimate source of genetic variation; they are one of the main factors that allow populations to evolve.