Trophic Level, Energy Flow, Food Chain YouTube Lecture Handouts

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Ecosystem: Energy Flow, Food Chain, Pyramids of Number, Energy & Biomass

Trophic Level

  • Guild

Food Chain

Types

  • Parasitic Food Chain
  • Detritus Food Chain
  • Grazing Food Chain

Food Web

Energy Flow

  • 1st law of thermodynamics - Energy can neither be created nor destroyed
  • 2nd law of thermodynamics – every activity involving energy transformation is accompanied by dissipation of energy
  • 50% energy from sun to Par (photosynthetically active radiation)

Unidirectional

  • Decrease in content & flow of energy
  • 10% energy is passed (Lindeman՚s law, 1942)
  • This means tiger requires an area of 240 km2 to support itself

Ecological Pyramids (By Charles Elton)

Also called Eltonian pyramid

Represent

  • Biomass – amount of living organic matter both dry and wet (maximum in producers and reduces with hierarchy – 10 - 20% is transferred to the next level)
    • Inverted – aquatic ecosystem
    • Upright – terrestrial ecosystem
  • Energy – energy trapped at different trophic levels – kcal/m2/yr (maximum in producers) – always upright
  • Number – number of individuals per unit area (top carnivores are few but grass is lot)
    • Upright – terrestrial or pond
    • Inverted – parasitic food chain
    • Spindle shaped – tree birds hawk

Ecological Efficiency

Ratio between energy assimilated over the energy available between two trophic levels – also called progressive efficiency

Ecological Succession

Natural development of series of biotic communities at same site one after another till climax community develops which does not change further because it is in perfect harmony with environment

Pioneer community – 1st community on bare land – little diversity – longest time to change

Climax community – stable, self-perpetuating & final biotic community that develops at end – maximum diversity and niche specialization

Seral or transitional community – biotic communities that develop during biotic succession

Sere – series from pioneer to climax community

Lithosere – on land (Lichens Moss Annual Grass Perennial Grass Shrub Climax)

Psammosere – on sand

Hydrosere – on water (Planktons Submerged Floating Reed Swamp Marsh Meadow Woodland Climax)

Psammosere – on sand

Changes in Biotic Succession

Increase in respiratory consumption and decrease in productivity until two become equal, P = R

Types

Primary Succession – biotic succession that occurs on a previously sterile bare area (no soil, no humus) – newly exposed sea floor, igneous rocks & sand dunes

Secondary Succession – Occurs in area which became secondarily bared due to destruction of community previously there (fugitive species – species adapted to colonize newly disturbed habitats)

✍ Manishika