Aerobic Any organism, environmental condition, or cellular process that requires atmospheric oxygen. Aerobic microorganisms, called aerobes, require the presence of oxygen for growth. An aerobe is capable of using oxygen as a terminal electron acceptor and can tolerate oxygen levels higher than that present in the air (21 percent oxygen). They have a respiratory type […]
Allantois During the embryonic stage of mammals, birds, and reptiles, the allantois, a small sac, is one of four extra-embryonic membranes (along with amnion, yolk sac, chorion) and serves several functions, such as a repository for the embryo’s nitrogenous waste (chiefly uric acid) in reptiles and birds (in the egg). The allan-tois provides oxygen to […]