Ecosystem

SYNOPSIS

• Ecosystem is the relationship between a biotic community and an abiotic environment.
• Stratification is the vertical distribution of different species occupying different levels.
• Primary production is defined as 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).
• Productivity is the rate of biomass production and is expressed in terms of dry matter produced or energy captured per unit area of land per unit time.
• Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.
• Net primary productivity is the total amount of energy stored in the plant tissues after utilising some energy for their own metabolic activities through respiration.
• Secondary productivity is defined as the rate of formation of new organic matter by consumers.
• Decomposition is the process of breakdown of complex organic matter by decomposers to inorganic raw materials like carbon dioxide, water and various nutrients.
• Dead plant remains such as leaves, bark and flowers and dead remains of animals, including faecal matter, constitute detritus.
  

• Humification is the formation of a dark-coloured amorphous substance called humus.

• Mineralisation refers to the formation of minerals during the process of decomposition in the soil.

• First law of thermodynamics: Energy is neither created nor destroyed but can be transferred from one component to another or transformed from one state to another.

• Second law of thermodynamics: Every system when left to itself has the tendency towards disorderliness or entropy.

• Differences between Food Chain and Food Web

• Each step in the food chain at which the transfer of food takes place is known as a trophic level.

• Each trophic level has a certain mass of living material at a particular time called the standing crop.

• Energy flow in an ecosystem: It is unidirectional and follows the 10% law. According to this law, only 10 percent of energy is transferred from one trophic level to the other; the rest is lost to the atmosphere in the form of heat. 

• Ecological pyramids are graphic representations of certain specific parameters such as number and biomass of energy of a food chain.
  
  
  
  

• The gradual and fairly predictable change in the species composition of a given area is called ecological succession.
  
  

• Difference between Hydrarch Succession and Xerarch Succession

  Hydrarch succession	Xerarch succession
  It takes place in wetter areas and the successional series progresses from hydric to mesic conditions.	It takes place in dry areas and the successional series progresses from xeric to mesic conditions.

   

• The species which invade a bare area is called a pioneer species.

• The amount of nutrients, such as carbon, nitrogen, phosphorus, calcium etc., present in the soil at any given time is referred to as the standing state.

• The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling.
  
  

  Gaseous Cycle	Sedimentary Cycle
  Reservoir – Atmosphere	Reservoir – Earth’s crust
  Nitrogen cycle, carbon cycle	Phosphorus cycle, sulphur cycle