i) Pyramid of number:
• It is an ecological pyramid which represents the number of individual organisms at each trophic level in an ecosystem.
• Pyramid of numbers can be either upright or inverted.
ii)Pyramid of biomass:
• It is an ecological pyramid which represents the amount of organic matter present at each trophic level in an ecosystem.
• It can be either upright or inverted pyramid.
The inverted pyramid signifies that the number of consumers is more than the producers. In the case of the marine ecosystem, the food chain in the marine ecosystem is generally depicted as Phytoplankton → zooplankton → predatory fish. Now, the total biomass of zooplankton is greater than that of phytoplankton because the life span of zooplanktons are longer and phytoplankton multiply at a much faster rate but they have a shorter lifespan. Therefore, a single generation of zooplankton can consume a number of generations of phytoplankton. Also, the biomass of the fish is larger because the fishes are larger in size and they have a longer lifespan and thus they can consume a generation of zooplankton.
Therefore increases from Phytoplankton → zooplankton → predatory fish and we obtain an inverted pyramid.
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