ECOSYSTEMS

 

Hydrarch (succession in aquatic environment)

• In primary succession in water, the pioneer species are phytoplankton.
• Zooplanktons.
• Sub merged plant stage. (rooted hydrophytes)
• Sub merged and free-floating plant stage.
• Reed-swamp stage.
• Marsh-meadow stage.
• Shrub stage
• Trees
• The climax again would be the forest
• All the succession whether taking place in water or on land, proceeds to a similar climax community – the mesic.

NUTRIENT CYCLING:

• Organism needs constant supply of nutrients to grow, reproduce, and regulate various body functions.
• Standing state: the amount nutrients such as carbon, nitrogen, phosphorus, calcium etc. present in soil at any given time.
• Nutrient cycling: The movement of nutrient elements through the various component of an ecosystem is called nutrient cycling.
• Another name of nutrient cycling is biogeochemical cycle.
• Nutrient cycles are of two types:
  • Gaseous cycle
  • Sedimentary cycle.
  
  
• The reservoir for gaseous type of nutrient cycle (nitrogen, carbon) exists in the atmosphere.
• The reservoir for sedimentary cycle (sulphur, phosphorus) is Earth’s crust.
• Environmental factors like soil, moisture, pH temperature regulate the rate of release of nutrient into the atmosphere.
• The function of the reservoir is to meet the deficit which occurs due to imbalance in the rate of influx and efflux.

Ecosystem – Carbon cycle:

• Carbon constitutes 49 percent of dry weight of organism.
•  Out of total global carbon:
  • 71 percent carbon found dissolved in ocean.
  • About 1 percent in the atmosphere.
  
  
• 4 X 10¹³ kg of carbon is fixed in the biosphere by photosynthesis, annually.
• Large amount of carbon returned to the atmosphere as CO₂ through respiration of producers and consumers.
• Decomposers also return CO₂ to reservoir during decomposition process.
• Some amount of Carbon is lost to sediments and removed from circulation.
• Burning wood, forest fire, combustion of organic matter, fossil fuel, volcanic activities are additional sources for releasing CO₂ to atmosphere.

Influence of human activity on Carbon cycling.

• Rapid deforestation.
• Massive burning of fossil fuel for energy and transport
• Increased the rate of release of CO₂ into the atmosphere.

Ecosystem Phosphorus cycle:

• Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer system(ATP)
• Animals need phosphorus to make shell, bones and teeth.
• Reservoir pool of phosphorus is the rock, which contain phosphorus in the form of phosphates.
• During weathering of rock small amount of phosphates dissolved in soil solution and are absorbed by the roots of the plants.
• Herbivore and other animals obtain organic form of phosphorus from plants.
• The waste product and dead organisms are decomposed by phosphate-solubilising bacteria releasing phosphorus.

How phosphorus cycle differs from carbon cycle?

• There is no respiratory release of phosphorus into atmosphere.
• Atmospheric inputs of phosphorus through rainfall are much smaller.
• Gaseous exchange of phosphorus between organism and environment are negligible.

ECOSYSTEM SERVICES:

• The products of ecosystem processes are named as ecosystem services.
• Healthy forest ecosystems purify air and water.
• Mitigate droughts and flood.
• Cycle nutrients.
• Generates fertile soil.
• Provide wildlife habitat.
• Maintain biodiversity.
• Pollinate crops.
• Provide storage site for carbon
• Provides aesthetic, cultural and spiritual values

PAR:        Photosynthetically Active Radiation
GAP:        Gross Primary Productivity
NPP:        Net Primary Productivity
DFC:        Detritus Food Chain
GFC:        Grazing Food chain

 

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