Question

What criteria do we use to decide whether something is alive?

Answer 1

Any visible movement such as walking, breathing, or growth is generally a good indicator which helps us to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of life processes is the fundamental criterion which is used to decide whether something is alive or not. There are 7 major life processes that are classified under this criteria:
i. Nutrition
ii. Respiration
iii. Transportation
iv. Locomotion
v. Excretion
vi. Reproduction
vii. Sensitivity
Thus, presence of these processes can be used to decide whether something is alive or not.