DESCENT WITH MODIFICATION BY NATURAL SELECTION This theory was first formulated by Charles Darwin, and is actually another name for today's modern theory of evolution. The theory itself refers to how in nature, there are more offspring produced and born than can survive and reproduce again. As a result, the struggle for survival its his among the amounts of offspring because of this overabundance. Since every population contains variations of all traits and types, the offspring with variations that help them to survive and adapt better in their environment have a higher chance of surviving. This is called "Survival of the Fittest." As time passes, the offspring who survived will reproduce and mate with others who survived and have the same favourable traits, passing these characteristics on to future generations. This is known as natural selection, and is the mechanism of evolution.
While Darwin proposed a strong, correct theory, there were two problems with it. The first was that Darwin could not explain to others how variations in a population could happen or appear. However, this answer was found by Gregor Mendel, who studied pea genetics and found that variations truly could appear in a gene pool and/ or population, Mendel concluded that changing the genotype- the genes of an organism- also causes the phenotype- what we see- to change. The second problem Darwin had was that he could not show any evidence or examples of evolution occurring in the future/ today. One of the biggest examples he missed of evolution occurring was the Peppered Moths, located in the Manchester Forest. (Diagram shown below). In this forest, the trees were lightly coloured, and the two variations of light moths and dark moths affected how natural selection occurred. Since the light moths blended in with the trees, they could hide from predators and reproduce, while the dark moths were eaten by birds and other animals looking for prey. This caused a decrease in the population of dark moths and an increase of light ones. However, this process flipped when the Industrial Revolution occurred. The loose dust, ash, and smoke in the air turned the light trees a darker shade. As a result, the dark moths could now stay hidden and reproduce while the white moths were eaten. Over time, there was a decrease in the population of light moths and an increase of the dark moths. This displayed natural selection was occurring, as the dark moths were more fit for the environment and were able to survive better than the light moths.