Natural selection is the process in which organisms better adapt to their environment, so they tend to survive and produce more offspring. This theory was fully discovered by Charles Darwin, and is believed to be the main process to bring about evolution.
The Struggle to Survive!
Overproduction is the process where one species reproduces offspring. Some may survive, some may not.
Inherited variation is crucial in reproducing the population. Some mutations may be good for the species, and some may harm the species. In this case, two out of nine goldfish turned out blue. This may be an advantage to the goldfish because they live in water, and them being blue will create a better disguise to predators.
The struggle to survive is the competition in nature among organisms of a population to maintain themselves in a given environment. They must survive by reproducing with others of their kind.
Successful reproduction is the process where the species best adapted to the variant, and are likely to have lots of offspring that survive.
In conclusion, natural selection is the process in which organisms better adapt to their environment, so they tend to survive and produce more offspring.