Charles Darwin believed that every species must be fertile enough in order to reproduce and extend the population of its own kind.

However, when asked about the origin of species, he declares that the true indication for this measurement is to first under natural selection and the survival rate of the organism could last.

In a natural selection process, newly-formed organisms have to attest their endurance for the recurring struggle to exist.

Darwin found that in ancient Egypt, plants and animals were nurtured in order to produce selective breeding of only the best lots.

For example, pigeons were bred with careful selection of the strongest groups, and the strongest nestlings were retained. This was remarked that the diversity of species was incredible but they were all bred from the same group, the Rock Pigeon.

According to medieval Greek scholar, Genesis, an organism is one of the many creations of nature, which does not have a specific physical form because it will interbreed with others, and a fusion of new categories is born.

The uncontrollable and diverse factors of nature intricate the process of identifying a static and fixed species.

However, a scientist called John Ray stated in his taxonomy that organisms are classified in accuracy and the difference that may occur between the same classifications are due to environmental conditioning.

In 1735, Carlos Linnaeus designed a biological classification that comprises strata, families, and other significant details of the organism which is still applied in modern-day biology.

In a journal written by Alfred Russel Wallace in 1885, he mentioned that a close look at newly discovered organisms can reveal the similarity of the new-found species with an existing one.

The latest form of the organism is far more improved than the previous after re-adjusting its ability to survive better.