Q.Distinguish between primary productivity and secondary productivity.

Ecological pyramids graphically depict how the number, biomass, or energy of organisms changes from producers at the base to top consumers at the apex — pyramids of numbers and biomass can each be upright or inverted depending on the ecosystem.

Ecological pyramid — definition:

An ecological pyramid is a graphical representation of the trophic (feeding) structure and function of an ecosystem, starting with producers at the base and successive trophic levels (herbivores, primary carnivores, secondary carnivores, etc.) stacked above, ending with the top carnivores at the apex. The width of each bar/level represents the value of the parameter being measured (number, biomass, or energy) at that trophic level.

1. Pyramid of Numbers:

This represents the number of individual organisms present at each trophic level.

• Upright example (grassland ecosystem): Numerous grass plants (producers) support a smaller number of herbivores (e.g., grasshoppers, rabbits), which in turn support a still smaller number of primary carnivores (e.g., frogs, snakes), and an even smaller number of top/secondary carnivores (e.g., hawks) — the pyramid narrows steadily upward.
• Inverted example (tree ecosystem/parasitic food chain): A single large tree (one producer) can support a much larger number of herbivorous insects feeding on it, which in turn may support a smaller number of birds, and so on — here the base is narrow (few producers) while herbivore numbers are large, giving an inverted shape.

2. Pyramid of Biomass:

This represents the total dry weight (biomass) of organisms at each trophic level, usually measured per unit area. …