Question

Question- the mass of living material at a trophic level at a particular time is called
A.Net primary productivity
B.Standing crop
C.Gross primary productivity
D.Standing state

Answer 1

Hint:Standing crop can be expressed as biomass or equivalent to it in terms of energy. It can vary at different times of the year. For example, standing crops will be different for a population of deciduous trees in winter and summer.

Complete answer:
Standing crop is the total dried up biomass present at a trophic level of an organism at a particular time. The amount of inorganic nutrients present in the soil or water ecosystem at any given time is called standing state. The total organic matter produced by producers during photosynthesis per unit time and area is called gross primary productivity. Net primary productivity is the weight of the organic matter stored in unit area/volume per unit time.
Among the options given:
a.Net primary productivity is gross primary productivity minus the rate of energy loss during metabolism and maintenance. It’s the rate at which energy is stored as biomass by plants and other primary producers and is made available to the consumers in the ecosystem.
b.The standing crop is part of the life cycle phase after death of an organism when the biomass of the organism which is totally dried up remains present only at the trophic level.
c.Gross primary productivity is the rate at which solar energy is captured in sugar molecules during photosynthesis. Producers such as plants use some of this energy for metabolism/cellular respiration and some for growth.
d.Standing state is the amount of inorganic nutrients found in an ecosystem. It represents part of non-living matter. It circulates between living and non-living and gets continuously depleted and replenished. It is the amount of biomass present in an ecosystem.

Hence the correct answer is option B.

Additional Information:
Ten percent law- according to this law, during the transfer of organic food energy from one trophic level to the next higher level, only about ten percent of the transferred energy is stored as flesh.

Note:
The highest net primary productivity in terrestrial environments occurs in swamps and marshes and tropical rainforests; the lowest occurs in deserts.