ecosystem

• Ecosystem

  A self-sustainable model consisting of the functional interaction between the biotic and abiotic components
• Types of Ecosystems

  • Terrestrial
  • Aquatic
• Terrestrial Ecosystems

  • Forest
  • Grassland
  • Deserts
• Aquatic Ecosystems

  • Freshwater (River, pond, lakes)
  • Marine (Sea, Ocean, Lagoon)
• Artificial Ecosystem

  Man-made, e.g. Crop field, Aquarium
• Natural Ecosystem

  • High species diversity
  • Complex food chain
  • Efficient cycling of nutrients
  • Lower productivity
• Artificial Ecosystem

  • Low species diversity
  • Simple food chain
  • Little cycling of nutrients
  • High productivity
• Abiotic Factors

  • Climatic (air currents, temperature, humidity)
  • Edaphic (soil structure and composition)
  • Topographic (mountain, valley, plains, desert, slope)
  • Light
• Biotic Components

  • Producers (Autotrophs - Terrestrial: Herbaceous & woody plants, Aquatic: Phytoplankton, algae, submerged/floating plants)
  • Consumers (Heterotrophs - Herbivores, Primary Consumers, Secondary Consumers, Top Carnivores)
  • Decomposers (Saprophytic micro-organisms, fungi, flagellates, bacteria)
• Ecosystem Structure

  • Species composition
  • Stratification (Top layer: Trees, Middle layer: Shrubs, Bottom layer: Grasses & herbs)
• Productivity


  Rate of production of biomass
• Productivity Levels


  • Most Productive: Coral Reef, Tropical Rain Forest, Sugar Cane Field
  • Least Productive: Desert, Deep Sea
• Primary Productivity

  Rate of production of organic matter by plants per unit time and area
• Gross Primary Productivity (GPP)


  Rate of production of organic matter by producers during photosynthesis per unit time and area
• Net Primary Productivity (NPP)

  GPP - Respiration loss
• Factors affecting Primary Productivity

  • Abiotic: Temperature, Availability of nutrients, Moisture of soil, Solar radiation
  • Biotic: Pollinators, Photosynthetic capacity
• Aquatic Ecosystems contribute less to NPP compared to Terrestrial Ecosystems due to less light penetration in water
• Secondary Productivity

  Rate of production of new biomass by consumers
• Decomposition


  Breakdown of complex organic matter into various inorganic raw materials
• Decomposition Processes

  • Fragmentation
  • Leaching
  • Catabolism
  • Humification
  • Mineralization
• Factors affecting Decomposition

  • Chemical Nature (C/N ratio, water solubility, lignin/tannin content)
  • Temperature
  • Moisture
  • Aeration
• Trophic Level

  The position of an organism in a food chain
• Law of Energy Transfer: Only 10% of energy is transferred from one trophic level to the next
• Types of Food Chains

  • Grazing Food Chain
  • Detritus Food Chain
• Food Web

  All food chains interconnected with each other
• Standing State

  Amount of inorganic substances present per unit time and area
• Standing Crop

  Amount of biomass present in an ecosystem per unit time and area
• Ecological Pyramids

  • Pyramid of Number
  • Pyramid of Biomass
  • Pyramid of Energy
• Pyramid of Energy is always upright, energy flow is unidirectional
• pyramid of biomass - organic matter

  • upright - tree and grassland
  • inverted - aquatic ecosystem
• Limitations of Ecological Pyramids:

  • They are based on food chains, but in nature we have food webs
  • doesn't include decomposers, saprophytes
  • species can have different tropical level position in different food chain
• pyramid of number:

  1. upright shaped : grassland and pond ecosystem
  2. Inverted shaped : aquatic and tree ecosystem
  3. spindle shaped : birds on a tree
• trophic level : it's a position of an organism in a food chain
• detritus food chain :

  • starts from dead
  • mainly fungi and bacteria
• grazing food chain : grassland

  • primary producer : phytoplanktons , grasses and tress
  • 1° consumer : zooplanktons , grasshopper ans crow
  • 2° consumer or 1° carnivore : birds, fish, wolf
  • 3° consumer or 2° carnivore: man, lion
• parasite food chain :

  • lives on host
  • trees - birds- lice and bugs
• source of energy :

  sun - solar radiation - plant - producers- organic matter
• energy flow :

  incident solar radiatin

  • PAR : less than 50% , photosynthic (active radiation) , 400-700nm ( visible spectrum)
  • more than 50% , absorbed by gases, water, vapour, dust particles
• fragmentation :

  earthworm (detrivorous) break large fragments into smaller fragments because it increases surface area so that bacterial and fungal Enzyme can be degrade
• leaching :

  part of water soluble substances present in the fragmented detritus go down into soil and get precipitated as unavailable salt