The correct option is 2 and 3 only
Explanation
Biodegradable substances are organic materials that can be decomposed into simpler substances by the action of living organisms, primarily microorganisms like bacteria and fungi (saprophytes). This process is fundamental to natural waste management and nutrient recycling.
Statement-wise Analysis:
- Statement 1 is Incorrect. By definition, biodegradable substances are not resistant to breakdown. They are capable of being decomposed by biological processes. Substances that are resistant to microbial breakdown and persist in the environment for long periods are termed non-biodegradable (e.g., DDT, plastics, glass).
- Statement 2 is Correct. The decomposition process is mediated by enzymes secreted by microorganisms. Enzymes are highly specific in their action; a specific enzyme is required to catalyze the breakdown of a specific chemical bond. For instance, many synthetic polymers (plastics) are non-biodegradable because nature has not evolved specific enzymes to break their molecular bonds.
- Statement 3 is Correct. The ultimate goal of biodegradation is the mineralization of organic matter. The breakdown products-such as carbon dioxide, water, and simple mineral salts-are released back into the soil, water, and atmosphere. These nutrients re-enter ecological cycles (biogeochemical cycles) and become available for uptake by producers (plants).
Key Takeaway:
Biodegradability relies on the presence of specific microbial enzymes that can break down organic matter into simple inorganic substances, thereby facilitating the recycling of nutrients within an ecosystem.