Although living things can be found on all continents, in every sea, and from pole to pole, biodiversity is not spread equally around the globe.
Some areas possess a richer variety of species than others.
At low elevations, for instance, species diversity is greater than at high elevations, where temperatures are cooler and the growing season shorter. Areas in which a generous supply of rain encourages the growth of lush vegetation are more diverse than arid locations. Notice how biodiversity also increases as you move from the poles to the equator. The sun shines more in the tropics than it does farther north and south, boosting the productivity of equatorial ecosystems. Tropical climates also tend to be more stable, which decreases the chance of weather-related extinction there.