Criteria for Living Things

What is Life?
Group discussion on the defining criteria of living things

S/N	Criteria (for a living thing)	How Would You Test this Criteria	Challenges
1	Requires Oxygen	Place it in a controlled environment. Wait. Measure the composition of the air (less oxygen, more carbon dioxide/water vapour)	It could chemically react with components in the air, not due to respiration.
2	Responds to Stimuli	Introduce changes in its environment (light/dark, temperature changes, sound, other organisms)	Its response may be unnoticeable. It may not respond to such changes in environment.
3	Requires Nutrition	Observe it in its natural environment. See if it consumes food/water.	It may not need much nutrition at the time or all the time. It may not consume food but instead produce energy (plants).
4	Has Cells	Use a microscope to test if it has cells.	It might be a single-celled organism.