Question

Which of the following aspects is an exclusive characteristic of living beings ?

• A. Isolated metabolic reactions occur in vitro.
• B. Increase in mass by accumulation of material both on surface as well as internally.
• C. Increase in mass from inside only.
• D. Perception of events happening in the environment and their memory.

Answer 1

The correct option is D Perception of events happening in the environment and their memory.

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

Growth or an increase in mass can be observed in living things. However, non-living objects also grow. 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. In living organisms, growth is from inside. Growth, therefore, cannot be taken as a defining property of living organisms.

Perception of events happening in the environment or the being conscious of the environment, however, is an exclusive characteristic of living things. All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues.