This common misconceptions covers Common Misconceptions within Decomposition for GCSE Biology. Topic 4: Decomposition It is section 8 of 12 in this topic. Use this common misconceptions to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 8 of 12
Practice
15 questions
Recall
20 flashcards
Common Misconceptions
Misconception: "Only bacteria cause decomposition."
Reality: Both bacteria AND fungi are major decomposers. Fungi are particularly important decomposers of tough materials containing lignin (in wood) and cellulose (in plant cell walls), which most bacteria cannot break down efficiently. In forest soils, fungal networks (mycelia) are responsible for much of the decomposition of leaf litter and fallen wood. Detritivores such as earthworms also assist by physically breaking material into smaller pieces, increasing surface area for microbial decomposers.
Misconception: "Decomposition only happens underground or in soil."
Reality: Decomposition occurs wherever decomposer organisms are present — in soil, in water (aquatic decomposers break down dead organisms in lakes, rivers, and oceans), on the surface of dead wood, in compost heaps, in sewage treatment plants, and even inside organisms (the decomposition of food by gut bacteria). The same factors — temperature, oxygen, moisture, pH — affect rate of decomposition in all these environments.
Misconception: "Hot conditions always speed up decomposition."
Reality: Temperature increases decomposition rate only up to the optimum temperature for the decomposers' enzymes (approximately 37 degrees C for most mesophilic bacteria). Above this temperature, enzymes are denatured — the active site shape is permanently altered and they can no longer function. At very high temperatures (above 60-70 degrees C), decomposition slows dramatically as enzymes are destroyed. This is why sterilisation (high-temperature treatment) kills decomposer bacteria and prevents food from spoiling.
Misconception: "Biogas is pure methane."
Reality: Biogas is a mixture of gases. The exact composition varies, but it typically contains approximately 60-70% methane (CH4) and 30-40% carbon dioxide (CO2), with traces of hydrogen sulphide and other gases. Biogas must be purified before use as vehicle fuel. Even without purification, biogas can be burned directly for heating or electricity generation.