The environment is everything that is around us. It can be living (biotic) or non-living (abiotic) things. It includes physical, chemical and other natural forces. Living things live in their environment. They interact with it constantly and adapt themselves according to the circumstances in their environment. In the environment, there are different interactions between animals, plants, soil, water and other living and non-living things. Some people call themselves environmentalists. They think we must protect the natural environment, to keep it safe. Things in the natural environment that we value are called natural resources. For example; fish, insects, and forests. These are renewable resources because they come back naturally when we use them. Non-renewable resources are important things in the environment that are limited, for example, ores and fossil fuels. Some things in the natural environment can kill people, such as lightning. Ecological units which are natural systems without much human interference. These include all vegetation, microorganisms, soil, rocks, atmosphere, and natural events. Universal natural resources and physical phenomenon which lack clear-cut boundaries. These include climate, air, water, energy, radiation, electric charge, and magnetism.