Part 2: The Classification of Animals. There are many different types of animals. They all vary internally and externally. Other distinguishing factors include: habits. dwelling places. type of nutrition. physiology. Earth's biodiversity is huge and is believed to be comprised of over 40 million species of organisms. However, only about 1.7 million have been classified. Many of these organisms have differences as well as similarities but have to be classified into groups to allow a better...