Home | Ecosystem : Decomposition and Nutrient cycling

Chapter: 11 th 12th std standard Bio Botany plant tree Biology Higher secondary school College Notes

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Ecosystem : Decomposition and Nutrient cycling

Decomposition refers to the break down of complex organic matter by bacteria and fungi into inorganic substances like CO2, water and nutrients. Decomposition takes place mostly in the upper layer of the soil.

Ecosystem : Decomposition

 

Decomposition refers to the break down of complex organic matter by bacteria and fungi into inorganic substances like CO2, water and nutrients. Decomposition takes place mostly in the upper layer of the soil. The dead plants and animal parts are formed as detritus. The process of decomposition involves 3 major steps. They are 1. Fragmentation of detritus. 2. Leaching. 3. Catabolism.

 

1. Fragmentation of Detritus

 

The invertebrates feeding on detritus breaks it into small pieces and as a result the number of particles increases.


2. Leaching

 

A leaching action is done mainly by water, which percolates the soil and remove the soluble substances.

 

3. Catabolism

 

Various enzymes secreted by microbes convert the complex substances into simpler inorganic ones. As a result of above three processes, a dark coloured amorphous substance, called humus is formed.

 

Various climatic factors affect the process of decomposition. Soil moisture and temperature, latitude and altitude also influence the rate of decomposition.

 

Ecosystem : Nutrient cycling

 

In an ecosystem, minerals and energy move through biotic and abiotic components. The cyclic movements of chemical elements of biosphere between the organism and their environment are referred to as bio-geo chemical cycles. There are two types of bio-geo chemical cycles. i.e. the gaseous and the sedimentary.

 

In gaseous cycles, the reservoir of nutrients is the atmosphere and the ocean. In the sedimentary cycle the reservoir is earth's crust.

 

Hydrological cycle

 

The circulation of water and moisture between atmosphere and living organisms is known as water cycle or hydrological cycle.

 

Water forms a significant factor of environment and without water bio-geo chemical cycle could not exist. Water from the atmosphere reaches the earth through precipitation and then it reaches the atmosphere through evaporation and transpiration.

 

Carbon cycle

 

Carbon is a basic constituent of all organic compounds. The source of carbon found in living organisms is carbon-dioxide of atmosphere. The green plants use CO2 through photosynthesis in the presence of sunlight to form carbohydrates. Carnivores feed on herbivores and the carbon compounds are converted into other forms. Carbon is released directly into the atmosphere by the process of respiration of plants and animals.

 

The decomposition of complex organic compounds by bacteria and fungi release carbon in the form of carbon-dioxide.


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