An organism is a living thing. Many organisms have organs and systems. We will examine how organisms begin to interact with their environment. Each living thing or organism has been classified into a genus and species. The genus and species are the two smallest divisions of living things.
Classification helps show if living things are closely related.
The more similar two living things are, the more groups they share. For example leopards and house cats have the same classification in kingdom, phylum, class, order, and family. When you reach the genus and species they are very different. So when we define a species we are speaking of related individuals that resemble one another, are able to breed among themselves but are not able to breed with other members of another species. If you were asked what a population is, you might think of the human population.