Question

What is the process of breaking down dead plant and animals and their excreta into simple compounds like carbon dioxide (CO2), water (H2O) and nutrients?

• A. Nutrient Cycling
• B. Photosynthesis
• C. Respiration
• D. Decomposition

Answer 1

Answer:

D. Decomposition

Understanding Decomposition

• Definition and Significance

  • Decomposition is the natural biological process where dead organic matter, including dead plants, animals, and their waste products (excreta), is broken down into simpler inorganic substances.
  • These simpler compounds include carbon dioxide (CO2), water (H2O), and various essential mineral nutrients (e.g., nitrates, phosphates).
  • It is a vital ecological process that prevents the accumulation of dead organic matter and ensures the continuous recycling of nutrients within ecosystems.

• Key Players: Decomposers

  • The primary organisms responsible for decomposition are known as decomposers or saprophytes.
  • The most important decomposers are bacteria and fungi.
  • Other organisms, known as detritivores (e.g., earthworms, termites, millipedes, slugs), physically break down detritus into smaller fragments, increasing the surface area for microbial action, a process called fragmentation.

• Stages of Decomposition

  Decomposition typically involves several interconnected stages:

  1. Fragmentation: Breaking down detritus into smaller particles by detritivores.
  2. Leaching: Water-soluble inorganic nutrients seep into the soil and are lost from the detritus.
  3. Catabolism: Bacterial and fungal enzymes break down complex organic matter into simpler inorganic substances.
  4. Humification: The accumulation of a dark-colored, amorphous substance called humus. Humus is highly resistant to microbial action and decomposes very slowly, serving as a reservoir of nutrients.
  5. Mineralization: Further degradation of humus by microbes, releasing inorganic nutrients back into the soil, making them available for plant uptake.

• Ecological Importance of Decomposition

  • Nutrient Cycling: It is the cornerstone of biogeochemical cycles (e.g., Carbon Cycle, Nitrogen Cycle, Phosphorus Cycle), ensuring the continuous flow of essential nutrients from dead organic matter back to the living components of the ecosystem.
  • Soil Fertility: Decomposition contributes to the formation of humus, which improves soil structure, water retention capacity, and overall fertility.
  • Waste Management: It acts as nature's recycling system, cleaning up dead organisms and waste products.
  • Carbon Release: Releases carbon dioxide into the atmosphere, which is utilized by plants for photosynthesis.

• Factors Affecting Decomposition Rate

  • Temperature: Microbial activity is optimal at moderate temperatures (e.g., 25-35°C). Extreme temperatures (too cold or too hot) slow down decomposition.
  • Moisture: Adequate moisture is essential for decomposer activity. Too little (deserts) or too much (waterlogged, anaerobic conditions) can inhibit it.
  • Aeration: Aerobic conditions (presence of oxygen) generally promote faster decomposition by most bacteria and fungi. Anaerobic conditions slow down the process significantly.
  • Chemical Composition of Detritus:
    • Lignin and chitin are complex substances that decompose very slowly.
    • Nitrogen-rich organic matter (e.g., protein-rich tissues) decomposes faster than carbon-rich matter (e.g., cellulose, wood).
  • pH: The pH of the environment can influence the types and activity of decomposers.