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A look at how organisms survive in places with very little water and high heat.
Imagine being in a place where it is so hot you could cook an egg on a rock, and there is no water fountain for miles! How do plants and animals stay alive without a fridge or a faucet?
A desert is a very dry place that gets very little rain. In fact, most deserts get less than inches of rain in an entire year! Because there is so little water, the ground is often sandy or rocky. During the day, the sun shines brightly, making the air very hot. However, without clouds to trap the heat, deserts can actually get quite chilly at night. To survive here, living things must have special adaptations. An adaptation is a 'superpower' or a special body part that helps a plant or animal live in its environment.
Quick Check
What is the main reason it is hard for plants and animals to live in the desert?
Answer
The main reason is the lack of water and the extreme heat.
Plants like the cactus are masters of saving water. Instead of thin leaves like an oak tree, a cactus has a thick, fleshy stem. This stem acts like a giant sponge that stores water for a long time. On the outside, the cactus has a waxy skin. This wax acts like a seal to keep moisture from escaping into the hot air. Most cacti also have spines instead of leaves. These sharp spines protect the plant from thirsty animals and even provide a tiny bit of shade to the plant's skin!
Let's look at the three steps a cactus takes to stay hydrated: 1. Collection: When it rains, the cactus uses wide roots to soak up water quickly. 2. Storage: The water moves into the thick, green stem which expands like a balloon. 3. Protection: The waxy skin and sharp spines make sure the water stays inside and isn't stolen by animals.
Quick Check
How does the waxy skin help a cactus survive?
Answer
The waxy skin keeps water from escaping the plant into the dry air.
Animals cannot store water as easily as plants, so they have to be smart. Many desert animals are nocturnal. This means they sleep during the hot day and come out at night when it is much cooler. Some animals, like the Fennec fox, have extra-large ears. These ears aren't just for hearing; they work like radiators to let heat out of the fox's body! Other animals, like the desert tortoise, spend their days in underground burrows. The soil stays much cooler than the air, acting like a natural basement.
Imagine a Fennec fox trying to stay cool. It uses a combination of tricks: 1. It digs a hole to feet deep to find cool soil. 2. It waits until the sun sets to look for food. 3. Its -inch long ears help pump heat away from its blood and into the air.
Quick Check
Why would an animal choose to be nocturnal in the desert?
Answer
To avoid the extreme heat of the daytime sun and stay cool.
Survival in the desert is about balance. Plants must protect their water, and animals must protect their bodies from the sun. Some animals, like the camel, can go for a long time without drinking because they can store fat in their humps and lose very little water when they breathe. Every living thing in the desert has a unique way of solving the problem of scarcity, which means there isn't enough of something (like water) to go around.
If you were to design a new desert animal, it would need: 1. A way to stay cool (like large ears or light-colored fur). 2. A way to find or store water (like eating juicy cactus fruit). 3. A way to avoid the sun (like being nocturnal or living in a cave).
What is an adaptation?
Which part of a cactus stores most of its water?
Nocturnal animals are active during the hottest part of the day.
Review Tomorrow
In 24 hours, try to remember the three main parts of a cactus that help it save water.
Practice Activity
Draw a picture of a desert animal and label two adaptations it uses to stay cool!