Question

Which organisms are identified as the major decomposers in an ecosystem?

• A. Producers and consumers
• B. Bacteria and fungi
• C. Plants and animals
• D. Algae and protozoa

Answer 1

Answer:

B. Bacteria and fungi

Decomposers in an Ecosystem: The Role of Bacteria and Fungi

• What are Decomposers?

  Decomposers are organisms, primarily bacteria and fungi, that break down dead organic matter (dead plants and animals) and waste products. They play a crucial role in recycling nutrients within an ecosystem.

• Why are Bacteria and Fungi Major Decomposers?

  • Microscopic Size and Abundance: Both bacteria and fungi are microscopic and extremely abundant in various habitats, allowing them to colonize and break down organic matter efficiently.
  • Enzymatic Digestion: They secrete powerful extracellular enzymes that break down complex organic molecules into simpler inorganic substances. These simpler substances are then absorbed by the decomposers and released into the environment.
  • Nutrient Cycling: Their decomposition process releases essential nutrients (like nitrogen, phosphorus, and carbon) back into the soil and atmosphere, making them available for producers (plants) to absorb. This continuous cycle is vital for the sustainability of life on Earth.

• Key Facts about Decomposition:

  • Saprophytes: Fungi and some bacteria are often referred to as saprophytes because they obtain their nutrition from dead or decaying organic matter.
  • Aerobic and Anaerobic Decomposition: Decomposition can occur in the presence of oxygen (aerobic) or in its absence (anaerobic). Different types of bacteria are involved in each process.
  • Role in Carbon Cycle: Decomposers are fundamental to the global carbon cycle, releasing carbon dioxide (CO2) back into the atmosphere through cellular respiration during the breakdown of organic matter.
  • Role in Nitrogen Cycle: They are also critical for the nitrogen cycle, converting organic nitrogen into inorganic forms (ammonia, nitrates) that plants can utilize.
  • Detritivores vs. Decomposers: It's important to distinguish decomposers from detritivores. Detritivores (e.g., earthworms, millipedes, slugs) are consumers that physically ingest and break down dead organic matter into smaller fragments, increasing the surface area for decomposers to act upon. Decomposers, on the other hand, perform chemical breakdown.
  • Ecological Niche: Decomposers occupy the trophic level known as the 'reducers' or 'recyclers' in a food web, connecting all other trophic levels by breaking down their waste and remains.

• Examples:

  • Fungi: Mushrooms, molds, and yeasts are common examples of fungi that act as decomposers.
  • Bacteria: Various soil bacteria, such as those belonging to genera like Pseudomonas, Bacillus, and Clostridium, are significant decomposers.