Natural Selection In Biology

Natural selection is the process by which individuals with characteristics that are advantageous to reproduction in a particular environment leave more offspring in the next generation, thereby increasing the proportion of their genes in the population gene pool over time. An example of modern natural selection that is frequently observed is the insecticide resistance in pest insects. Prior to the use of pesticides in the 1940s, crop insect populations only contained a limited amount of genetic variability for resistance to these chemicals. When a pest insect population is sprayed for the first time with a chemical insecticide allowing some insects to be more resistant, the population will be composed of individuals that vary in their susceptibility to the insecticide. The susceptibility and resistance to pesticides are established by a single gene locus with two alleles. The occurrence of the resistant allele within the population is initially quite small. Once the crop has been sprayed, the frequency of the resistant allele is higher allowing survivors to mate, creating a second generation of the …show more content…
However, their intelligence was shown when they discovered the internal nitrogen base structure of the DNA. Watson had proposed many models including one based around identical base pairing. However, none of these theories survived scrutiny of the public. However, using Chargaff’s rule (the rule is based on the number of adenine bases being equal to the number of thymine bases as well as the number of guanines being equal to the number of cytosine bases.) When the answer occurred to Watson that the adenine base was internally linked to the thymine and the guanine to the cytosine. He realised that this would mean that the A-T bond would be exactly the same size as the G-C bond (they already had the knowledge of hydrogen bonds connecting the bases). Thus, became the double-helix structure of