Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli and reproduction.^[34] Life may also be said to be simply the characteristic state of organisms.

Properties common to terrestrial organisms (plants, animals, fungi, protists, archaea and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made analogs of life may also be considered to be life.

Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several gradually migrating tectonic plates, which have changed relatively quickly several times. The interior remains active, with a thick layer of molten mantle and an iron-filled core that generates a magnetic field.

The atmospheric conditions have been significantly altered from the original conditions by the presence of lifeforms,^[12] which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods,^[13] and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth

Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. “Nature” refers to the phenomena of the physical world, and also to life in general. Manufactured objects and human interaction generally are not considered part of nature unless qualified in ways such as “human nature” or “the whole of nature”. Nature is generally distinguished from the supernatural. It ranges in scale from the subatomic to the galactic.