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Decomposition is an important process in an ecosystem. It will keep the ecosystem clean and make our soil fertile. The decomposition process is done by the organisms called decomposers and it is a five-stage process in which dead organisms or substances are broken down into simpler organic or inorganic matter. It maintains the balance of an ecosystem.
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Keyterms: Ecosystem, Soil, Organisms, Decomposers, Bacteria, Fungi, Enzymes, Nutrients, Carbon dioxide, Water, Decomposition, organic substances, Fallen leaves, Animal wastes
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Decomposition Definition
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The process of breaking down the complex organic substances (eg, fallen leaves or animal wastes) into small organic or inorganic substances like nutrients, water and carbon dioxide is known as Decomposition. Bacteria and Fungi are the organisms mainly involved in the decomposition process, where they secrete enzymes which help in digestion of the dead organic matter. It can later be used by the plants as a source of nutrients. The rate of the decomposition process increases when the temperature and moisture is high.
Decomposition Terminologies
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The organisms(bacteria or microbes) which break down complex organic matters into small substances are called Decomposers.
Some Organisms fed on the organic matters of dead animals and plants, that organisms are known as Detritivores.
Dead remains of plants such as fallen leaves, barks, flowers and animal wastes including faecal matters are known as Detritus.
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Types of Decomposition
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There are two types of decomposition, they are:
Biotic Decomposition
In this type, the degradation is done by physical or chemical substances, eg. hydrolysis.
Abiotic Decomposition
In this type, the degradation of substances is done by living organisms eg. Rotting of fruits and vegetables.
Stages of Decomposition
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There are five stages in decomposition which are explained below:
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Decomposition Process
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Fragmentation
Fragmentation is the first stage of the decomposition process. In this process, the invertebrates (Detitivoes) feed on the dead remains of plants and animals(Detritus). The complex organic matter passes through the digestive tract of detritivores and is degraded into small particles.
Leaching
Leaching is the second stage of the decomposition process. In this process, the water-soluble organic particles are transferred to the soil horizon and it gets precipitated as unavailable salt.
Catabolism
Catabolism is the third stage of the decomposition process. After breaking down the complex organic matters and removing water-soluble nutrients, the detritus is converted into small inorganic compounds. This process is done by various bacteria and fungi(Decomposers)
Humification
The above three stages are simultaneous. After that, the detritus is converted into humus. The process of formation of humus is known as humification and it is a rich fertilizer for the soil. It is highly resistant to microbial actions so it decomposes at an extremely slow rate. This stage of decomposition takes more time than other stages.
Mineralization
This is the last stage of the decomposition process. In this, the humus (colloidal nature) is converted into inorganic nutrients by some microbes. The inorganic nutrients are again used by plants and again the food chain begins.
Factors influencing Decomposition
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Many factors are affecting the decomposition of dead plants and animals. In this section, we are going to see about factors influencing decomposition in detail:
- Oxygen level
- Temperature
- The pH of soil
- Soil Texture
- Moisture
Oxygen level
Decomposers need oxygen to respire. If the oxygen level of the atmosphere increases, the speed of decomposition will also increase. But if the oxygen level of the atmosphere decreases, the decomposition speed will decrease respectively.
Soil Texture
In loose texture soil, oxygen will easily penetrate and make microbes grow and decompose the dead plant and animal quickly. But in composite soils like clay, the air penetration is less, so the decomposition is slow
Moisture
Moisture has direct and indirect effects on decomposition. If moisture in the soil increases, it slows down the breakdown of organic matters because water fills the air bubbles in the soil. It results in less microbe respiration. All organisms need water, if the soil is dry, microorganisms cannot survive which directly results in slow decomposition.
The pH of Soil
The pH of the soil determines the acidic or alkaline nature of the soil. Fungi and bacteria are the major microbes that help in the decomposition process. Fungi lives in mildly acidic environments whereas some bacteria cannot survive in an acidic environment. Bacteria will survive in soil that has above pH 6. So pH of soil directly affect the microbes growth and the decomposition of organisms.
Temperature
Soil bacteria growth depends on the temperature of the atmosphere. For every 10 degrees increase in Fahrenheit the growth of bacteria doubles. It results in high organic matter breakdown. So decomposition occurs fast in warm weather than in cold weathers.
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Points to Remember
- Decomposition is a part of the Ecosystem, containing 3 to 4 marks.
- The process of breaking down complex organic matter into simple inorganic matter is known as decomposition. The organisms which decompose the dead plants and animals are known as decomposers
- The dead animal or plant remains are known as detritus and organisms that fed on detritus are detritivores.
- The decomposition process comprises 5 stages, they are fragmentation, leaching, catabolism, humification and mineralization where the first three stages occur simultaneously.
- Some factors affecting or slowing down the decomposition process are oxygen level, soil texture, moisture, pH of soil and temperature.
- Decomposition is the five-stage of death followed by skeletonization and fossilisation.
- The decomposition rate not only depends on climatic conditions it also depends on the quality and quantity of dead animal or plant.
Previous Year Questions
- An ecosystem which can be easily damaged but can….[NEET 2004]
- The biomass available for consumption by the herbivores...[NEET 2010]
- Both hydrarch and xerarch successions lead to...[NEET 2011]
- During ecological succession...[NEET 2015]
- In a biotic community, the primary consumers are...[NEET 1995]
- In an ecosystem, which one shows one-way passage...[NEET 1988]
- Upper part of sea/aquatic ecosystem contains...[NEET 1988]
- Vertical distribution of different species occupying different...[NEET 2015]
- What is true of ecosystem?...[NEET 1988]
- Which ecosystem has the maximum biomass ?...[NEET 2017]
- Which of the following aquatic plant does not show pollination by water? … (KCET 2021)
- Aquatic reptiles are … (NEET 1999)
- Upper part of sea/aquatic ecosystem contains … (NEET 1988)
- An ecosystem which can be easily damaged but can recover … (NEET 2004)
- Energy transfer from one trophic level to other...[NEET 1999]
Sample Questions
Ques 1. Name some decomposer bacteria? (1 mark)
Ans. There are many decomposer bacteria, some of them are Bacillus Subtitles, Pseudomonas Fluorescens.
Ques 2. What factor affects the rate of decay? (1 mark)
Ans. The factors affecting the rate of decay are temperature, moisture, oxygen, the quantity and quality of dead organisms.
Ques 3. Difference between decomposers and detritivores. (2 marks)
Ans.
| Decomposers | Detritivores |
|---|---|
| Decomposers are some bacterias that break down the complex organic matter into simple inorganic substances | Detritivores are some small organisms that fed on the dead remains of plants and animals |
| Eg. Bacteria | Eg. Worms and some insects |
Ques 4. Explain the process of decomposition in short. (4 marks)
Ans. The decomposition process comprises 5 stages, they are fragmentation, leaching, catabolism, humification and mineralization.
First, in fragmentation, the detritus is degraded into small pieces
Second, in Leaching the water-soluble organic nutrients are absorbed by the soil and the inorganic substances left behind
Third, in Catabolism the complex inorganic substances are breakdown into small pieces
Fourth, in the Humification process, the humus is formed which is a fertile reserve
Next, in mineralisation, the humus is converted into inorganic nutrients by microbes.
Ques 5. What are Detritivores and Detritus? (2 marks)
Ans. Some Organisms feed on the organic matter of dead animals and plants, that organisms are known as Detritivores.
Dead remains of plants such as fallen leaves, barks, flowers and animal wastes including faecal matters are known as Detritus.
Ques 6. What are the types of decomposition? (2 marks)
Ans. The two types of decomposition are:
- Biotic Decomposition:
In this type, the degradation is done by physical or chemical substances, eg. hydrolysis.
- Abiotic Decomposition:
In this type, the degradation of substances is done by living organisms eg. Rotting of fruits and vegetables.
Ques 7. How does the texture and pH level of the soil affect decomposition? (3 marks)
Ans. When the texture of the soil is loose, oxygen will easily penetrate and make microbes grow and decompose the dead plant and animal quickly. But in composite soils like clay, the air penetration is less, so the decomposition is slow
The pH of the soil determines the acidic or alkaline nature of the soil. Fungi and bacteria are the major microbes that help in the decomposition process. Fungi lives in mildly acidic environments whereas some bacteria cannot survive in an acidic environment. Bacteria will survive in soil that has above pH 6. So pH of soil directly affect the microbes growth and the decomposition of organisms
Ques 8. Differentiate between a detritivore and a decomposer giving an example of each. (2 marks)
Ans. The differences are:
| Detritivore | Decomposer |
|---|---|
| Detritivore is an organism that helps in the breakdown of detritus into little fragments. | Decomposer is an organism which uses enzymes to break down detritus into inorganic substances. |
| Example: Earthworm | Example: Certain types of bacteria and fungi. |
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