The Living World – What is Living?: NEET MCQs with Answers

Explanation: Smaller animals have a very large surface area to volume ratio, lose heat rapidly and therefore maintain a much higher basal metabolic rate. This higher rate of energy production per unit body mass makes the extra work of running uphill relatively easier for them.

Explanation: Replication of genetic material (DNA) underlies cell division, growth, reproduction and heredity, and therefore is the most fundamental property of every living system. Many organisms are anaerobic and do not use oxygen, gamete formation is restricted to sexually reproducing forms, and only autotrophs trap solar energy — so none of these can be universal.

Explanation: Every living organism senses and interacts with its surroundings and, as a population, undergoes progressive evolution — these two properties together hold true without exception. Reproduction fails as a universal criterion because sterile individuals such as mules, worker bees and infertile human couples are still alive; growth and movement occur in non-living systems too (a growing crystal, flowing water), and responsiveness to touch is not exhibited by all organisms.

Explanation: Biological organisation starts at the sub-microscopic molecular level, where the four principal classes of biomolecules — carbohydrates, lipids, proteins and nucleic acids — are assembled into organelles. Atoms and their elements are the concern of chemistry rather than biology, while cells and organisms are higher, later levels in the hierarchy of organisation.

Explanation: Consciousness — the ability to sense what is happening in the environment, respond to it and retain a memory of it — is the defining characteristic that is exclusive to living organisms; in humans it reaches the level of self-consciousness. Isolated metabolic reactions can be made to occur in a test tube (in vitro), so they are living reactions but not 'living'. Non-living objects such as crystals or a mountain also increase in mass by surface deposition, and internal growth alone is not exclusive since dead organisms may swell.

Explanation: Metabolic rate per unit body mass is inversely proportional to body size — the smaller the animal, the higher its mass-specific metabolic rate, because a small body has a much greater surface area relative to its volume and therefore a faster rate of energy turnover. This higher metabolic rate makes more energy available per unit mass for work against gravity, so a small animal runs uphill with relative ease. Muscle efficiency and oxygen requirement per unit mass are not the deciding factors here.

Explanation: Consciousness — the capacity to sense the environment and respond to it, together with memory — is the defining property that no non-living system possesses. Metabolic reactions can be reproduced in a test tube (in vitro) and are therefore not exclusive. Growth by surface deposition occurs in non-living objects such as crystals and sand mounds, while growth by internal addition, though characteristic of living beings, is also seen in some non-living systems and is not by itself decisive.

Explanation: The hierarchy of biological organisation runs: submicroscopic molecular level → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere. Atoms are the chemical, not biological, starting point; biological properties first appear when atoms are assembled into biomolecules such as nucleic acids, proteins and lipids. Hence organisation of the living world is taken to begin at the submicroscopic molecular level.

Explanation: Self-replication of genetic material (DNA, or RNA in some viruses) is the one property common to all living systems, because it is the basis of both reproduction and continuity of life. Gamete formation occurs only in sexually reproducing organisms, oxygen-based respiration is absent in obligate anaerobes, and trapping of solar energy is restricted to photoautotrophs.

Explanation: Homeostasis is the maintenance of a relatively constant internal environment (temperature, pH, water and ions) despite external changes, achieved by feedback mechanisms. Fluctuating with the surroundings or failure of regulation is the opposite of homeostasis, and the term has nothing to do with homeopathy.

Explanation: Multicellular fungi, filamentous algae and moss protonema all multiply by fragmentation.

Explanation: Consciousness, the ability to perceive events in the environment and remember them, is the defining property of living organisms per NCERT. Isolated metabolic reactions can occur in vitro, and growth or increase in mass is not exclusive to living things.

Explanation: Biological organisation begins at the submicroscopic molecular level — molecular assemblies (like microtubules) build up organelle structure and cell membranes.

Explanation: According to NCERT, living organisms can be distinguished from non-living things by their interaction with the environment (consciousness) and their progressive evolution. Growth, reproduction and responsiveness are not exclusive defining features.

Explanation: Perception of environmental events and memory is an exclusive feature of living organisms — non-living things cannot perceive or remember events.