Why are so many animals found only in Africa?

Lions, Rhinos, Hippos, etc. are found only in Africa. Why?

because of aforestation

It's a result of evolution. Due to varying resources and the weather from one part of the earth to the other, some animals were able to evolve into forms that the environment would not allow elsewhere. Species able to survive on the types of available food, live in that climate and protect themselves from other predators would survive and reproduce, amplifying the characteristics that enabled their survival. The others didn't make it. With the land being separated by water and temperature extremes they were unable to migrate to other parts of the earth so the species is only seen in that area.

The effect is equally visible in areas that are more isolated like Australia and the Galapagos Islands.

Africa is the land of wild animals, can find different of animals. It is very difficult to say which is more in number of animals but I think tiger.
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