What is a biome? Scientists
divide the planet into climate regions called biomes. Earth has six main
biomes: deserts, grasslands, temperate deciduous forests, rainforests, taiga,
and tundras. These biomes generally differ in their latitude, weather and
relative humidity, amount of sunlight, and topography. Each biome has a unique
set of plants and animals that thrive in its climate.
Latitude and humidity
Relative humidity is a measure of
how much water vapor an air mass contains . Humidity is related to plant and
animal diversity. From the poles to the equator, humidity and the diversity of
plants and animals increases.
Sunlight at the equator vs high latitudes
Earth is hottest near the equator
where the Sun is closest to being directly overhead year round. At the north
and south poles, temperatures are much colder. This effect is related to the
fact that light travels in straight parallel lines. To demonstrate what is happening,
imagine shining a flashlight on a sheet of paper. The light makes a bright,
small spot. By tilting the paper, you can make the light spot bigger and less
intense. At the equator, sunlight is direct and intense. Earth’s north and south
poles are tilted away from or toward the Sun depending on the time of year. The
locations of the poles relative to the Sun and Earth’s spherical surface mean
that sunlight reaching these areas is spread out and less intense. As a result,
the average yearly temperature at the equator is 27 °C (80 °F), while at the
North Pole it is -18 °C (0 °F). Generally, as latitude (or distance from the
equator) increases, the amount of incoming solar radiation decreases.