Adenine, guanine, thymine and cytosine are the four nitrogenous bases that are attached to a sugar molecule<span> on each </span>side of the ladder<span>. When a phosphate, a sugar and a base form an attachment, they create a sub-unit of </span>DNA<span> called a nucleotide. Each nitrogenous base is held together by a hydrogen bond.</span>
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I think u right. it's what I woulda picked
The climate? That would fit I suppose.
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The process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as be the main process that brings about evolution.
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.