Fijista theory: the first responses were always related to those beliefs rather than to the observations. It was easier to accept the creation of each species independently. This belief is known as fixism-creationism. In the eighteenth century, Linnaeus, the most representative, proposed a system of natural classification of organisms, intended to reflect the plan of divine creation. I group organisms according to their similarities and differences so you can find out what kind it was. I group organisms into species identical to the similar in genera, genera into families alike ... each of these groups is called a taxon. The taxonomic groups are from lowest to highest: species, genus, family, order, class, or type filium kingdom. He created the binomial nomenclature to name the species.
Natural selection among individuals within a population there are heritable variations. Most living things are born than can survive, there is a fight for survival. Hereditary variations provide benefits to individuals, only the best adapted survive. The best adapted are those that reproduce, so the offspring inherits characters. This is how the town is changing.
As critical as there not knowing the characters are inherited.