Biology Regents Practice Exam 2025 - Free Practice Questions and Study Guide

The statement that rocks are not composed of cells, while living organisms are, is the best reason for classifying rock formations as non-living. This distinction is fundamental to the definition of living organisms, which are characterized by the presence of cells — the basic units of life. Cells carry out essential functions such as metabolism, growth, and reproduction, which are hallmarks of living systems. Rocks, on the other hand, are aggregates of minerals and do not exhibit cellular structures or life processes.

While it is true that rocks can be affected by environmental changes and can remain stable in various physical conditions, these characteristics alone do not classify something as living or non-living. The absence of cells and cellular organization sets a clear boundary between living organisms and non-living entities like rocks. The notion that rocks perform complex metabolic processes but cannot grow is misleading, as it implies some form of life activity that rocks do not exhibit at all. Therefore, the lack of cellular composition is a defining factor in classifying rocks as non-living.