Biodiversity describes the variety of living things in an area. It includes plants, animals, and microorganisms. Some places have more biodiversity than others.

Tropical rainforests and coral reefs are known for having many different species. In contrast, deserts or polar regions usually have fewer species. Scientists estimate that millions of species live on Earth, many still not fully studied. Biodiversity is often measured by counting species in a region.

Biodiversity is studied in ecosystems around the world. It is part of how living systems are described and compared.