An 'atmosphere (from Greek τμός (atmos), meaning "vapour", and σφα ρα (sphaira), meaning "sphere" [1][2] ) is a layer of gases surrounding a planet or other material body of sufficient mass [3] that is held in place by the gravity of the body. An atmosphere is more likely to be retained if the gravity is high and the atmosphere's temperature is low.
The atmosphere of Earth is mostly composed of nitrogen. It also contains oxygen used by most organisms for respiration and carbon dioxide used by plants, algae and cyanobacteria for photosynthesis. It protects living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.
The term stellar atmosphere describes the outer region of a star, and typically includes the portion starting from the opaque photosphere outwards. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere.
The Earth's atmosphere is kept close to Earth by gravity. Just as the Earth's gravity keeps you firmly on the ground, it also acts on the gases of the Earth's atmosphere, holding it in place and allowing us to breathe.
The genetic material is identical in asexual reproduction- in order for organisms to be strong they need variety so if a disease comes, some of the species may be able to fight it off because of their varied genetics
