Which of the following is not listed as a necessary life function?

• A. Maintain boundaries
• B. Movement
• C. Digestion
• D. Photosynthesis

Answer: (D)

Necessary life functions describe activities that keep an organism alive and healthy. For humans, maintaining boundaries, movement, and digestion are classic examples. Maintaining boundaries means keeping internal conditions separate from the outside, like the skin and cell membranes regulating what enters and leaves. Movement covers both the ability to move the body and the internal movement of substances. Digestion is the breakdown of food into absorbable nutrients to fuel body processes. Photosynthesis, by contrast, is the process plants use to convert light energy into chemical energy. Humans don’t perform photosynthesis, so it isn’t listed as a necessary life function for our bodies. That’s why Photosynthesis is the correct choice.