Question

Which of the following is an exclusive characteristic of living things?

• A. Isolated metabolic reactions in vitro
• B. Perception of events happening in the environment
• C. Increase in mass
• D. All of these

Answer 1

The correct option is B:

Explanation of the correct option:

1. Perception of events happening in the environment or the being conscious of the environment is an exclusive characteristic of living things.
2. All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues.
3. For example, on touching the hot pot by a man, his hand is pulled back due to reflex action.
4. Similarly, on sensing the light the unicellular organism Euglena turns towards it by the action of its flagella.

Explanation of the incorrect options:

Option A:

1. Living cells and organisms exhibit metabolism.
2. However, metabolic reactions can be demonstrated outside the body in cell-free systems.
3. An isolated metabolic reaction outside the body of an organism, performed in a test tube (i.e., in vitro reaction) is neither living nor non-living.
4. Hence, while metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things, but are rather just living reactions.

Option C:

1. Growth or an increase in mass can be observed in living things.
2. However, non-living objects also grow if we take an increase in body mass as a criterion for growth.
3. Mountains, boulders and sand mounds grow, although this kind of growth exhibited by non-living objects is through an accumulation of material on the surface.
4. In living organisms, growth is from inside.
5. Growth, therefore, cannot be taken as a defining property of living organisms.

Option D:

1. Since, isolated metabolic reactions in vitro and increase in mass can not be considered exclusive properties of the living beings.
2. Hence, all of the above is not the correct option.

Final answer: Perception of events happening in the environment is an exclusive characteristic of living things.