As we move up in trophic levels, biomass decreases drastically. We lose 90 to 99 percent of biomass at each level. This is known as Reasons for the decrease of biomass as we move up trophic levels are:

(i) Only fraction of the food taken in by a consumer is converted into body tissue. Remaining is stored as energy to be used by the consumer when needed.

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(ii) Much of the biomass, especially at the producer level, is never eaten and goes directly to the decomposers.

Solved Examples:

Example 1

Why the mass of water is not usually included in biomass?

Solution this is because the water content is variable and contains no useable energy.

Example 2

What is net primary production?

Solution Total amount of energy captured by producers is termed as Gross Primary Production (GPP).

When energy lost due to respiration is subtracted from GPP we get Net Primary Production (NPP).

NPP = GPP – respiration

Net primary production is the amount of energy stored by the producers and potentially available to the consumers and decomposers.

Example 3

What is secondary productivity?

Solution it is the rate at which consumers convert organic material into new biomass of consumers.

Example 4

“The pyramid of total biomass produced must resemble the pyramid of energy flow”. Comment

Solution The above statement is TRUE.

This is because biomass can be equated to energy.

Example 5

Why the pyramids of energy and yearly biomass production can never be invested?

Solution because this would violate the laws of thermodynamics