Final answer:
Biologists consider an organism alive if it can undergo metabolism and has cellular organization. Metabolism includes all chemical processes of life, while cellular organization relates to the basic structure of cells. Non-living examples include viruses (lacking independent metabolism) and crystals (lacking cells).
Step-by-step explanation:
Biologists agree that for an organism to be considered alive, it must exhibit certain characteristics. Two items that are necessary are ability to undergo metabolism and presence of cellular organization. Metabolism refers to the chemical processes that occur within a living organism to maintain life. Every living thing, from the smallest bacterium to the largest whale, engages in some form of metabolism. On the other hand, cellular organization means that an entity is structured into one or more cells, which are the basic units of life. For example, a virus does not undergo metabolism on its own, thus despite its complex structure, it's not considered alive outside a host. Similarly, a crystal may have an organized structure, but it lacks cells and cannot metabolize, placing it firmly within the non-living category.
In order for biologists to consider an organism "alive," it must possess certain characteristics. These characteristics include:Ability to undergo metabolism: Living organisms engage in chemical reactions that allow them to obtain and use energy. A nonliving example that fits this definition is a fire, which undergoes a chemical reaction to release energy.Presence of cellular organization: Living organisms are made up of one or more cells, which carry out the functions necessary for life. An example of a nonliving object that has cellular organization is a virus.