Life exists all over the Earth in air, water, and soil, with many ecosystems forming the biosphere. Some of these are harsh environments occupied only by extremophiles. The life in a particular ecosystem is called its biota.
Life-forms present on Earth today have evolved from ancient common ancestors through the generation of hereditary variation and natural selection.
Life is a concept in biology. It is about what separates a living thing from dead matter. Most life on Earth is powered by solar energy: the only known exceptions are the chemo-synthetic bacteria living around the hydrothermal vents on the ocean floor.The existence of diverse definitions of life, as detailed in the previous section, surely means that life is complex and difficult to briefly define. A scientific understanding of living systems has existed since the second half of the 19th century.