Decomposers and Decomposition

Carbon Cycle and Decomposers

  • Carbon Release into the Atmosphere:

    • Respiration

    • Combustion

    • Decomposition

  • Carbon Removal from the Atmosphere:

    • Photosynthesis

Decomposers

  • Definition: Microorganisms that break down dead organisms and waste material.

  • Examples: Bacteria, fungi, some snails, and insects.

Detritivores vs. Decomposers

  • Detritivores:

    • Examples: Dung beetles, maggots, some worms, and beetles.

    • Mechanism: Break down organic waste into smaller pieces, increasing the surface area for decomposers.

    • Role: Start the decay process by eating dead animals and plants and producing waste material.

  • Decomposers:

    • Examples: Bacteria and fungi.

    • Mechanism: Secrete digestive enzymes to break down the cells of dead organisms, plants, and detritivore waste.

    • Role: Feed on waste left by detritivores, completing the decay process and returning nutrients to the soil.

Decomposition Process

  • Decomposers cause decay by releasing enzymes onto dead animals or plants.

  • These enzymes break down complex compounds into simple, soluble ones that can be absorbed.

  • Decomposers use some nutrients from the waste material to grow and reproduce.

  • Materials such as carbon dioxide, water, and mineral ions (e.g., nitrates) are released back into the environment.

  • Plants absorb these mineral ions through their roots to build chemicals such as proteins.

Recycling of Materials

  • Detritivores and decomposers are crucial for recycling materials in the ecosystem.

  • Detritivores start the process by consuming dead organisms and waste.

  • Decomposers complete the process by breaking down the remaining material and releasing nutrients back into the soil.

Environmental Factors Affecting Decomposition Rate

  • Optimal conditions for microorganisms to decompose materials efficiently:

    • Warm temperatures

    • Aerobic conditions (presence of oxygen)

    • Moist environments

Impact of Temperature on Decomposition

  • High Temperatures: Enzymes used by microorganisms are denatured, preventing decomposition. Denature means the active site on the enzyme will change shape and will no longer bind to the substrate.

  • Low Temperatures: The rate of decomposition is slow as the rates of enzyme-controlled reactions are reduced.

Impact of Oxygen on Decomposition

  • Oxygen is needed for microorganisms to respire.

  • Aerobic Conditions: With oxygen.

  • Anaerobic Conditions: Without oxygen; prevent most forms of decomposition as microorganisms cannot survive.

Impact of Moisture on Decomposition

  • If there is not enough water available, reactions within the microorganisms will slow down or be prevented, reducing or stopping decomposition.

Practical Application: Increasing Decomposition Rate

  • To increase the rate of decomposition on a wide scale (e.g., in composting): maintain warm temperatures, moist environments, and aerobic conditions.

Evaluation and Higher-Level Thinking

  • Evaluation involves looking at multiple pieces of information and making an independent decision about which is best and why.

  • Six-mark questions on exams may require evaluation skills to gain marks.

Role of Detritivores in Speeding Up Decay

  • Detritivores like woodlice and earthworms speed up decay by breaking down organic material into smaller pieces.

Compost Heap Factors

  • Factors affecting the rate of decay in a compost heap include:

    • Temperature

    • Moisture

    • Oxygen availability