ECOSYSTEMS

 

ECOSYSTEMS

• The interaction between the living organism and the non-living environment is called ecosystem.

ECOSYSTEM – STUCTURE AND FUNCTION:

• Interaction of biotic and abiotic components results in a physical structure that is characteristic of each type of ecosystem.
• Identification and description of plant and animal species of an ecosystem gives its species composition.
• Vertical distribution of different species occupying different levels is called stratification.
• The components of the ecosystem are seen to function as a unit:
  • Productivity.
  • Decomposition.
  • Energy flow and
  • Nutrient cycle.
  
  
• Description of pond as an ecosystem:
  • The abiotic components include all dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond.
  • The solar input, cycle of temperature, day length, regulates the rater of function of the entire pond.
  • The producer (autotrophic) includes phytoplankton, some algae and the floating, submerged and marginal plants found in edge of pond.
  •  The consumers are represented by zooplankton, free swimming and bottom dwelling animals.
  • The decomposers are the fungi, bacteria especially abundant at the bottom of the pond.
  
  
• Basic events (in terms of function) in an ecosystem:
  • Conversion of inorganic into organic material (photosynthesis) by producers.
  • Consumption of the autotrophs by heterotrophs.
  • Decomposition and mineralization of the dead organic matter to release them back for reuse by the autotrophs
  • There is unidirectional flow of energy towards the higher trophic levels and its dissipation and loss as heat to the environment.

PRODUCTIVITY:

• Primary productivity:
  • The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.
  • It is expressed in terms of weight (g-2) or energy (kcal m-2)
  • The rate of biomass production is called productivity.
  
  
• Gross primary productivity: (GPP) is the rate of production of organic matter during photosynthesis.
• Net primary productivity:
  • A considerable amount of energy is utilized by plants in respiration.
  • Gross primary productivity minus respiration losses (R) is the net primary productivity.
  • GPP – R = NPP.
  
  
• Net primary productivity is the available biomass for the consumption to heterotrophs (herbivore and decomposers.
• Secondary productivity: is defined as the rate of formation of new organic matter by the consumer.

DECOMPOSITION:

• Earthworm is said to be ‘friends’ of farmer:
  • Breakdown the complex organic matter.
  • Loosening of the soil helps in aeration and entry of root.
  
  
• The decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients, called decomposition.
• Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute the detritus.
• The process of decomposition completed in following steps:
  • Fragmentation  :  Break  down  of  detritus  into  smaller  particles  by  detritivore  (earthworm).
  • Leaching: Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
  • Catabolism  :  Bacterial  and  fungal  enzymes  degrade  detritus  into  simple  inorganic  substances.
  • Humification: Accumulation of dark coloured amorphous substances called humus.

  Importance of humus:

  • Highly resistance to microbial action.
  • Undergo decomposition at an extremely slow rate.
  • Being colloidal in nature, it serves as reservoir for nutrients.
  • Mineralization: The  humus  is  further  degraded  by  some  microbes  and  release of  inorganic nutrients  occur.

Factor affects rate of decomposition:

• Decomposition is largely an oxygen-requiring process.
• Detritus rich in chitin and lignin has slow rate of decomposition.
• Detritus rich in nitrogen and water-soluble substance like sugar has faster decomposition.
• Temperature and soil moisture are most important climatic factor that regulate decomposition
• Warm and moist environment favor decomposition.

Low temperature, dryness and anerobiosis inhibit decomposition.

 

CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : [email protected]