Biodiversity refers to the variety of species, genetic diversity, and ecosystems on Earth. There are estimated to be 10-15 million species but only 1.4 million have been identified. Major extinction events have occurred throughout history, with the most recent one 65 million years ago wiping out 75% of species including dinosaurs. Today, 20% of vertebrates are threatened with extinction due to human impacts like habitat destruction, invasive species, pollution, overconsumption, and population growth. Island species are especially vulnerable. Conservation efforts aim to preserve biodiversity through protecting endangered species and their habitats.