Requirements of life

What do living creatures need to live? Energy, water, protection and an appropriate habitat. Most of them also need oxygen, food and nutrients and temperatures they feel comfortable with.


Without energy (see Big Idea 4) living things could not grow. For example plants get energy from the sunlight (solar radiation) that they absorb and convert into nutrients. Animals cannot use the solar radiation directly. But you can eat plants or other animals with their nutrients (which they got from the sun) instead.


All living things need water. On the one hand, their cells mostly consist of them and on the other hand, the water helps to transport substances into or out of the cells. Some organisms need only few water: the animals and plants of the deserts like e.g. camels and cactuses. Fish and other living things need a lot of water, because they spend their whole life there.


Most animals are take shelter somewhere in their lives. They do that, for example to avoid predators or bad weather, to sleep in safety or give birth to their offspring, who would not survive without protection. Plants cannot take shelter because they are not able to move. They have found other ways to defy themselves, the weather and predators.


All living creatures need space to live and grow. Some need very little: bacteria e.g. can grow in tiny cavities. Other creatures need a lot: A Siberian tiger needs a territory in which he can walk around, which must be larger than Kiel or Stuttgart. If there is only little space, the organisms are have not enough food or water and diseases can also spread more easily.


Emperor penguins live in the Antarctic at -60 degrees and breed their eggs there for months. Fennecs (desert foxes) and camels live near the equator, where it is up to 60 degrees. Life also thrives under these extreme conditions. However, not every organism can survive in all temperature ranges. For emperor penguins, the temperatures in Germany are much too warm but for camels, it is much too cold.

Food and Nutrients

All living creatures need food and nutrients. They are helping the organisms to build up and preserve their bodies. In addition, they enable the organisms having good life functions and producing energy. Animals get their nutrients through food. Instead of this, plants receive them from the ground or the air by their roots and leaves. Bacteria absorb the nutrients directly through the cell membrane. A lack of nutrients leads to problems. However, usually we get hungry before, so we can get the missing nutrients by food.


All living creatures need oxygen. Only a few bacteria can survive in an oxygen-free habitat. Plants produce almost all of our world’s oxygen. They generate nutrients and oxygen from water and carbon dioxide using solar energy (solar radiation). Without oxygen, a human being can live only a few minutes.