Question

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

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

Answer 1

The Correct Option is C

- Metabolism is the process by which all living things assimilate energy and use it for various purposes such as growth, movement, locomotion etc. This mechanism of metabolism is not shown by nonliving objects. However, some of the metabolic reactions can be carried out in a cell-free system or outside the cells. Isolated metabolic reactions in vitro are not living things but are living reactions. Hence, statement A is incorrect. - All living organisms show growth either by multiplication or by an increase in size. It is an irreversible increase in the mass of individual from inside. Two types of substances are produced by the cells, apoplastic and protoplastic. Apoplastic substances are nonliving materials formed by the cells which become components of tissues. For example, cell wall, the matrix of bone etc. Protoplastic substances are the components of living matter like cytoplasm and nucleus. - Although some nonliving things like mountains, sand mounds, crystals also grow, their growth is due to the addition of matter from outside. Hence, statements B and D are incorrect. - All organisms respond to external stimuli which can be physical, chemical or biological. This is called irritability. Stimuli are perceived by sense organs in animals but plants can respond to external factors like water, temperature, light etc. All organisms from prokaryote to the most complex eukaryotes can sense and respond to environmental events.