Which one of the following statements refers to Reductionist Biology?

The correct answer is: Physico‑chemical approach to study and understand living organisms.

Reductionist biology seeks to explain biological phenomena by breaking them down into their most fundamental physical and chemical components. It assumes that the behavior of a whole organism can be understood by analyzing the underlying physico‑chemical processes such as molecular interactions, biochemical pathways, and physical forces.

Let's examine each option and see why only the physico‑chemical approach matches this definition:

1. Physiological approach focuses on the functions and activities of whole organs or systems without necessarily reducing them to molecular or atomic level mechanisms. While useful, it does not emphasize the reduction to physical and chemical fundamentals.

2. Chemical approach examines chemical reactions in organisms, but it omits the physical aspects (e.g., forces, energy transfer) that are integral to a full reductionist perspective.

3. Behavioural approach studies observable actions and responses of organisms, which is a higher‑level description and does not involve breaking the system down to physical‑chemical constituents.

4. Physico‑chemical approach combines both physical (e.g., thermodynamics, mechanics) and chemical (e.g., molecular chemistry, biochemistry) analyses. This aligns perfectly with reductionist biology, as it attempts to explain life by studying the most basic physical and chemical laws governing biological systems.

Therefore, among the given statements, the one that refers to reductionist biology is the physico‑chemical approach.