Species are one of the more specific classifications used by scientists to describe animals. Scientists use a binomial nomenclature system to describe animals without confusing common names.

This system uses the genus name as the first name, always in uppercase, and the species name as the second, always in lowercase. Therefore, some animals such as the red fox, Vulpes vulpes, all belong to the Vulpes genus and their specific name is vulpes.

Note the difference in capital letters to distinguish genus and species. Other foxes such as the fast fox, Vulpes velox, are also of the Vulpes genus, but there are barriers that prevent them from mating with the red fox.

In this way, they are always separate species. Since the time of Charles Linnaeus, the creator of binomial nomenclature, animals have been continually classified and reclassified into different groups, genera, species and subspecies.

Linnaeus, a taxonomy of organisms in the 1700s, limited its classification to the physical attributes of various organisms. Surprisingly, most of the organisms identified were related to each other. Others, however, could not have been more wrong.

Genetic engineering today has given us a much better chance of historical relationships between animals. For example, when Linnaeus first classified elephants in the early 1700s, he saw only one specimen. The specimen was an Asian elephant fetus, the smallest of all elephant species known today.

Without a better understanding, Linnaeus called the species Elephants maximus. Scientists today have been forced to reclassify the elephant over and over again. The first distinction is between Asian and African elephants, which vary greatly in size.

Scientists therefore had to distinguish between elephants that live in the grasslands and elephants that live in forests in Africa. Genetics show that populations do not intersect and are separated by a reproductive barrier.

In the following century, Charles Darwin and Alfred Wallace tailor-made the mechanism to generate multiple species from a single species. This process of natural selection applies the various adversities that organisms must overcome in order to reproduce.

Organisms better adapted to the environment can reproduce more and their offspring can also increase in number. In this way, different lines of the same species can be better or worse, depending on their genetics.

Eventually, the two successful lines can diverge, creating a reproductive barrier between the two populations. According to Darwin and Wallace, these populations are now considered separate species.

Since the dawn of time, this process has occurred and has divided organisms along a number of successful lineages. This theory has been confirmed by a lot of evidence. Fossil evidence provides clues that animal species have continuously changed over time, in response to changing environments.

When Linnaeus considered animals to be static and immutable entities, it is now widely accepted that species exist in a spectrum, with some species being closer to certain species than others. Therefore, animals can often interbreed or interbreed between species.