When we think of deserts, we often think
of hot deserts with sand dunes. While it is true that some parts of deserts have
dunes, desert landscapes vary widely. This picture shows a part of Monument Valley,
which is an arid area. You can see sand in the foreground, but behind the sand there
are some desert plants: probably rabbit brush. Notice that these plants are not close
to each other -- there is not enough moisture in the soil to support more plants.
However, there is something here for animals to eat. There are probably some little
rodents in this desert -- mice or kangaroo rats, and some lizards. There will be
a few snakes to eat the lizards and rodents. There will be insects, too. During the
summer many of the animals will seek shelter from the heat by hiding in burrows underground.
They will come out at night to hunt for food.
Deserts are described as areas that
get an average of less than ten inches of rain a year. In the summer, temperatures
may soar to over 120 degrees during the days, but will drop as soon as the sun sets.
Winters may be cold. The dry desert air and clear skies do not hold onto the heat
at night. The heat just radiates out into space.
Plants and animals make special adaptations to the desert environment.
are annuals. Their seeds wait in the ground for years until there is a rainy winter:
then they sprout rapidly and grow as fast as they can. They race the sun to make
seeds before the water evaporates and the heat dries them up. Some of these plants
are so tiny that the whole plant could be hidden under a dime. Others spread colorful
blossoms over the sand and rocks for a few brief days.
Some plants develop water-storing strategies. Cacti have chlorophyll
in their fleshy stems, and they store the water that they gather in those stems.
They defend themselves with sharp spines. They have large networks of roots that
lie under the ground near the surface of the soil. If it does happen to rain, these
roots can soak up the water quickly. Many cacti have corrugated stems which can expand
quickly if water becomes available.
If you cut
across one of these stems, you would see shapes like this. The first shape shows
the cactus stem when the plant has plenty of water, and you can see that it is pretty
full. The second shape shows how the sides fold in when the plant is dry.
Some parts of deserts are covered with stones. Sometimes the stones
are huge and jumbled. Sometimes these areas are flat, with the stones set close together.
Flat, stone-covered areas are called desert pavement. In the wet springs, tiny flowers
may appear between the stones.
Animals in the hot desert also make special adaptations. Most of
these animals are small, because food and water are scarce. Some are reptiles, lizards
and snakes, animals who are cold-blooded ectotherms. These animals do not need as
much food as warm-blooded animals, and can go weeks between meals if they have to.
The sun provides heat for them, and they can find little niches in the rocks to hide
in during the heat of the day and during the cold nights.
Warm-blooded rodents are also small, and can survive by eating
seeds and nibbling on plants where there is enough plant growth. They have evolved
to be able to live with very little water. They are preyed upon by snakes, and perhaps
by desert foxes or coyotes or hawks if there is enough vegetation to support a good-sized
colony of these plant eaters.
Photographa from Corel CD-ROMs: for viewing only, not for downloading. More Information.
Copyright © 1999. Elizabeth Anne Viau and her licensors. All
rights reserved. This material may be used by individuals for instructional purposes
but not sold. Please inform the author if you use it at firstname.lastname@example.org