Snails can have a long life. The life span for snails depends on their habitat and the species. Some of them only live for about 5 years. However, others in the wild are believed to be up to 25 years old in unusual occasions. 3.
Facultative means optional or discretionary (antonym obligate), used mainly in biology in phrases such as: 1  Facultative anaerobe, an organism that can use oxygen but also has anaerobic methods of energy production. It can survive in either environment. Facultative biped, an animal that is capable of walking or running on two legs as well as walking or running on four limbs or more, as appropriate.
A facultative anaerobe is, simply speaking, an organism which possesses the ability to survive in an environment containing oxygen while growing even more efficiently in an environment without oxygen. Facultative anaerobes can optionally function without oxygen by two main mechanisms; fermentation and alternate terminal electron acceptors. In fermentation, glycolysis is performed and pyruvate is converted to a fermentation product, reducing NAD+ back to NADH. (Note that there are likely many variations on this).