 In this video we are going to discover what the word species means and how our new species created. 18th century naturalist Carl Linnaeus used the term species to describe a group of very similar organisms. Linnaeus was interested in classifying all living things and he came up with a system for grouping organisms and identifying the relationships between them based on their physical features. His system placed organisms with the most similar characteristics together in a group he called the species. This species group was then incorporated into ever large groups based on shared physical features right up to the level of kingdom, domain, kingdom, phylum, class, order, family, genus, species. A species is defined as all organisms that are able to breed with one another and most importantly are able to produce fertile offspring. Horses are an example of such a group, all breeds of horse including ponies can mate and produce fertile offspring. However, although horses may mate with donkeys, their offspring will not be fertile. This means that horses and donkeys are placed in separate species groups even though they are very closely related to one another. The species group is accepted as the smallest unit of biological classification and is always given a Greek or Latin name. In horses, this name is ferrous, whilst in donkeys, the species name is chian. Both species belong in the larger group or genus known as equus. These two species both evolved through process of natural selection from a common ancestor called equusimplicidens or hageman horse. The emergence of a new species from an existing one happens as a result of natural selection. This process is called speciation. Some scientists believe that speciation occurs continuously over a long period of time, whilst others believe that speciation occurs only rarely and in relatively short bursts, sometimes as a result of a dramatic environmental event. An example of speciation event happened in North America in the 19th century. At that time, hawthorn flies traditionally laid their eggs on hawthorn fruit, which were then eaten by the newly hatched maggots. Some time after the introduction of non-native apple trees, a new hawthorn fly was recorded. It laid its eggs on apples. Over time, this new hawthorn fly stopped laying eggs on hawthorn in favor of apples. This new fly is now called the apple maggot fly. Human beings can directly influence or even potentially cause speciation. A program of selective breeding of livestock over several years led to the creation of now domestic sheep, Orvis eris, which is unable to produce fertile offspring when mated with Orvis orientalis, the species from which it is descended. So from this video, you should now know that a species is a group of organisms that can produce fertile offspring. In some cases, such as donkeys and horses, different species can mate, but their offspring are not fertile, hence donkeys and horses are different species. You should also know that new species can emerge for different reasons, such as a change in habitat and also through humans' selectively breeding. See if you can find other examples of speciation.