Define decomposition and describe the processes and products of decomposition.
Decomposition refers to the process by which organic substances are broken down into simpler organic or inorganic matter. This process is primarily carried out by microorganisms such as bacteria and fungi. Decomposition is a vital ecological process as it allows the recycling of nutrients that can be used by plants and other organisms.
Processes of Decomposition:
1. Fragmentation: The breakdown of detritus (dead plant and animal tissues) into smaller pieces by detritivores (like earthworms).
2. Leaching: The process by which water-soluble substances are washed out from organic materials or soil.
3. Catabolism: The metabolic breakdown of complex molecules into simpler ones by organisms. Enzymes released by bacteria, fungi, and other decomposers break down these molecules.
4. Humification: The process of transforming organic material into humic substances, which are dark, organic compounds that remain after the major decomposition processes have finished. This is the formation of humus, which is a stable, long-lasting component of soils.
5. Mineralization: The final step in decomposition in which the humus or organic matter is converted into inorganic substances such as carbon dioxide, water, and nutrients.
Products of Decomposition:
1. Carbon dioxide (CO2): Produced during the breakdown of organic carbon compounds.
2. Water (H2O): Released during the decomposition of organic substances.
3. Inorganic Nutrients: Such as nitrates (NO3-), phosphates (PO4^3-), and sulfates (SO4^2-). These nutrients are essential for the growth and development of plants and other organisms.
4. Humus: A stable, dark, organic component of the soil formed from decomposed organic matter. Humus increases the soil’s water retention, cation exchange capacity, and overall soil fertility.
5. Heat: Decomposition is an exothermic process, meaning it releases heat. This is why compost piles can become warm or even hot.
6. Simple organic molecules: Such as sugars or amino acids that are more easily assimilated by plants and microorganisms.
In ecological terms, decomposition is essential for nutrient cycling. It releases nutrients stored in dead organisms, making them available again for uptake by plants and subsequent incorporation into new organic matter. Without decomposition, the world would quickly become cluttered with dead material, and the cycle of life would be disrupted.