Why are some animals already extinct?

Animals have become extinct for various reasons ever since thr first life forms evolved in the seas.The habitat that they were adapted to changed because of climate change or because extra terrestrial events impacted the earth. The Cambrian-Ordovician extinction 488 million years ago resulted in the death of millions of species.The Cretaceous-Paleogene extinction 66 million years ago killed off all the non avian dinosaurs totally. In modern times humans have had a drastic effect on animal populations. Humans have killed or exploited animals and their habitats so ruthlessly that thousands of species have been driven to near extinction.Big game animals, lions tigers elephants rhinos, whales and river dolphins are major examples.

Numerous factors, including habitat loss, pollution, climate change, hunting, and the introduction of invasive species, have led to the extinction of some animals.