Fauna refers to all the animal life in a particular place or time period. When scientists study the fauna of the Amazon rainforest, they're investigating every creature living there: the jaguars prowling through the undergrowth, the colorful parrots in the canopy, the tiny poison dart frogs on the forest floor, and even the insects crawling beneath logs.

The word pairs naturally with flora, which means plant life. Together, flora and fauna describe all the living things in an ecosystem. A marine biologist studying coral reefs examines both the plants and algae growing there (flora) and the fish, sea turtles, and octopuses swimming around them (fauna).

You might read about the “fauna of prehistoric Earth” in a book about dinosaurs, or hear that scientists discovered new fauna in a deep ocean trench. National parks often work to protect both the flora and fauna within their boundaries, preserving entire ecosystems.