Most living organisms cannot thrive in extreme environments. Sometimes, extreme habitats are very hot or cold. Others might be too acidic.

For many years, scientists thought that living things could not survive in extreme environments. Most organisms cannot live in these places. But special organisms called extremophiles do well in these extreme conditions.

How Does Acid Affect Environments?

Some environments are very acidic. Acidity is measured on something called a pH scale. The scale ranges from 1 to 14. A level of 1 is very acidic. A level of 14 is very basic. A level of 7 is neutral. It is important for humans to have a pH that is close to neutral.

An environment is extremely acidic when conditions are less than 5 on the pH scale. These acidic habitats are found around the world. They can be natural or human-made. For example, areas near volcanoes have large amounts of sulfuric acid, a dangerous chemical. It produces low pH ecosystems. Another example of an acidic environment is the red-tinted Rio Tinto, a river in Spain.

Creatures that survive in pH levels between 1 and 5 are called acidophiles. One acidophile is a type of red algae called Cyanidium caldarium. For most animals, high acid levels destroy or damage their cells. This is not the case for acidophiles. Inside their cells, the pH stays neutral.

Basic Environments

The opposite of an acidic environment is a basic environment. It is also known as an alkaline environment. These natural habitats have a pH level higher than 9. They are also found in areas with high volcanic activity. Some are found in geothermal areas, such as hot springs. The United States' Yellowstone National Park's hot springs are home to some extremely basic environments.

Another example of an habitat">extreme habitat is a bitter cold, dry environment. Some of these habitats continuously reach temperatures below 5 degrees Celsius (41 degrees Fahrenheit). Studies have discovered that some microbes—very tiny organisms—live well in cold regions. In 2013, scientists discovered bacteria under the ice in Antarctica. These bacteria are a type of psychrophile. A psychrophile is a microbe that grows best at temperatures of 15 degrees Celsius (55 degrees Fahrenheit) and below.

Superhot Environments

Other extreme habitats reach temperatures of more than 40 degrees Celsius (104 degrees Fahrenheit). This is too hot for many living things. Some of these habitats are driven by geothermic heat—or heat that comes from deep in the planet. This includes deep-sea vents and hot springs.

Thomas Brock was an American microbiologist. He found microbes growing in Yellowstone's scalding hot springs in 1966. Organisms that require hot water to live are called thermophiles. They have been found all over the world in hot springs and geysers.

Deserts are also considered to be extreme, hot environments. The sidewinder snake has learned to survive in this environment. It developed a way to slither across the hot sand. They do not move lengthwise like most snakes. Instead, they move their bodies so that only parts of it touch the hot sand at once. This limits the amount of body exposed to the burning sand.

What Can We Learn from Extreme Environments on Earth?

Scientists can learn a lot from the animals that thrive in extreme places. Take wood frogs (Lithobates sylvaticus), for example. They freeze when winter arrives in far northwestern U.S. state of Alaska. When spring appears many months later, the frogs thaw, or defrost. Then, they carry on with their lives.

How can this be? The frogs produce chemicals that prevent ice crystals from forming in their bodies. Ice crystals would normally pierce the frogs' cells and organs. By studying the frogs, scientists hope to discover a way to successfully store human organs for long periods of time. This would allow them to save the organs for people who might need them in the future. Currently, organs cannot last longer than a few hours when refrigerated. They are destroyed when frozen.

Another extremophile is the tardigrade or water bear. It is very tiny. It can survive many kinds of extreme environments. It has survived high up on the tallest mountains where there isn't as much air. It has also survived deep in the ocean where there is a lot of pressure. Tardigrades could help scientists to understand how to live on Mars. These extremophiles have traveled and survived a 10-day journey to space.