49 Extreme Environments-Mid

Extreme Environments FOCUS Question How do organisms survive in extreme environments?

Beyond the Ordinary Rainforests, grasslands, oceans, and deserts are just some of Earth's key ecosystems. Each one is unique and is home to many kinds of organisms. But some environments are so extreme? that only certain organisms can live there. What makes an environment extreme It may be boiling hot or freezing cold. It may be filled with salt or be completely dark. It may be waterlogged or arid. The plants and animals that live in these extreme environments have special adaptations that help them survive. These amazing creatures are called extremophiles.

Severely Salty The Dead Sea is located on the border between Jordan and Israel. The water is too salty for most organisms to survive. A few kinds of bacteria are the only organisms that can live there. Earth's oceans are salty (but not as salty as the Dead Sea!). Marine iguanas live on the Galapagos Islands, off the coast of Ecuador. They feed on algae growing in the ocean. As these iguanas eat, they swallow salt. Too much salt in their bodies would kill them. These lizards have special glands that filter salt from their blood. Then they sneeze the salty liquid out through their nostrils!

Too Cold or Too Hot Some creatures have to adapt to living in an extremely cold or hot environment. The wood frog has adapted to chilly conditions. When the temperature dips below freezing. so does most of the water inside the frog's body. In this state, the frog doesn't breathe. It doesn't even have a heartbeat! When the weather warms up, so does the frog. At the other extreme, fennec foxes live in the scorching Sahara Desert in North Africa. Their oversized ears release body heat and help keep the foxes cool.

Too Wet or Too Dry Too much water can be hard on plants and animals. But mangrove trees have adapted to live in waterlogged soil. Special roots grow in the air and act like snorkels. They get the oxygen the tree needs, even when the tide is high. Too little moisture can also be a problem for most living things. However, the tiny tardigrade can survive with no water at all! During dry times, it curls up into a ball called a tun (rhymes with "sun"). The water in its body is replaced with a special sugar that keeps it alive. When water is available again, the tardigrade uncurls and swims away.

Complete Darkness Most caves are completely dark. With no sunlight, there is no need for animals to have vision or be colorful. Over many generations, some creatures that live in caves have lost their eyesight and body color. Mexican cave fish have no color and no eyes. They don't need to see in order to catch their food. These fish have a strong sense of smell. They can also sense tiny pressure changes in the water. These abilities help cave fish find food and survive in complete darkness. Do You Know? It takes energy for an organism to produce body color, or pigment. In total darkness, animals save this energy because they don't need color for protection or camouflage.