The tropics are regions of Earth that lie roughly in the middle of the globe. The tropics between the latitude lines of the Tropic of Cancer and the Tropic of Capricorn. The tropics include the Equator and parts of North America, South America, Africa, Asia, and Australia. The tropics account for 36 percent of Earth's landmass and are home to about a third of the world's people.

The tropics are warm all year, averaging 25 to 28 degrees Celsius (77 to 82 degrees Fahrenheit). This is because the tropics get more exposure to the sun. Because of all that sun, the tropics don't experience the kind of seasons the rest of Earth does. The tropical seasons are broken up into just two: the wet season and the dry season.

The amount of rain can vary greatly from one area of the tropics to another. Some areas, like parts of the Amazon Basin in South America, get almost three meters (nine feet) of rain per year. Other areas in the tropics have a drier climate. The Sahara Desert in northern Africa only gets two to 10 centimeters (0.79 to 3.9 inches) of rain per year.

The amount of rain a region gets in the tropics directly affects which plant and animal species live there. The baobab tree thrives in the arid tropics of Africa, for instance. The baobab stores water in its huge trunk. On the other extreme is the rainy island of Sri Lanka in the Indian Ocean. Sri Lanka gets enough precipitation to support 250 species of frogs.