Define biodegradable and non-biodegradable substances with examples.

Biodegradable substances are materials that can be broken down into simpler, harmless substances by natural agents such as microorganisms (bacteria and fungi). These substances decompose relatively quickly and do not persist in the environment. Examples include food waste, paper, leaves, cotton, and wood.

Non-biodegradable substances are materials that cannot be decomposed easily by natural processes or microorganisms. They remain in the environment for a long time and may cause pollution. Examples include plastics, glass, metals, and synthetic chemicals.

The key difference lies in their ability to decompose naturally. Biodegradable substances support ecological balance by participating in nutrient cycling, whereas non-biodegradable substances tend to accumulate and harm the environment.