What are the reasons for the diversity of the modern animal world on our planet?

Such a wide variety of types of organisms of different kingdoms that we have now is associated with their adaptive abilities. In the process of evolution, many adaptations arose that allowed organisms to survive and fix these traits as necessary in their genetic material. Living in different conditions, occupying different ecological niches, they have developed a number of properties that are characteristic only of them and help them in their struggle for existence.