Final answer:
An icicle is considered nonliving as its increase in size is not due to biological processes but to the physical accumulation of water molecules. Living organisms grow via anabolic processes, complex chemistry, and cellular organization, features that icicles lack.
Step-by-step explanation:
The ability to grow in size is indeed a characteristic of living organisms. However, when an icicle grows in size, it is considered nonliving because it lacks biological processes intrinsic to life. This growth in icicles is simply due to the accumulation of water molecules freezing upon contact, not the result of cellular or genetic processes. Living organisms, on the other hand, grow by means of anabolic processes where they convert nutrients into new cellular materials, leading to an increase in size. Key distinctions between living and nonliving entities include the ability of living organisms to respond to the environment, maintain homeostasis, reproduce, and have complex chemistry and cellular organization, none of which are characteristics of an icicle.
Living organisms grow through organized, controlled processes, reflecting a pattern of development. For instance, plants can acquire material from their environment and convert it into organic matter while catering to specific growth controls, unlike icicles which simply add mass based on external water supply. Moreover, biological growth in living organisms involves several complex biological mechanisms that are regulated and play a part in the organism's development, reproduction, and survival.