Primary Productivity and Biomass

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Questions and Answers

What is the unit of measurement for standing crop or biomass?

g/m2

lb/acre

kg/ha

all of the above (correct)

What contributes to primary productivity, although of small significance?

Bacterial photosynthesis

Chemosynthesis

Algal photosynthesis

All of the above (correct)

What is the difference between gross primary productivity and net primary productivity?

Gross primary productivity is the energy available for harvest, while net primary productivity is the energy stored in plants

Gross primary productivity is the energy stored in plants, while net primary productivity is the energy available for harvest

Gross primary productivity is the total energy trapped, while net primary productivity is the energy left after respiration (correct)

Gross primary productivity is the energy left after respiration, while net primary productivity is the total energy trapped

What is the term for the rate at which heterotrophic organisms resynthesize energy-yielding substances?

Secondary productivity Signup and view all the answers

What is the term for the amount of energy stored in the tissues of consumers or heterotrophs?

Net secondary production Signup and view all the answers

What is the formula for net productivity of energy?

Net productivity = Gross productivity - Energy lost in respiration Signup and view all the answers

What is the term for the total plant material ingested by herbivores?

Grass secondary production Signup and view all the answers

What is the relationship between Ingested Secondary Production and Total Plant Material ingested by herbivores?

Ingested Secondary Production is equal to Total Plant Material ingested by herbivores minus the materials lost as faeces Signup and view all the answers

What is the direction of energy flow in an ecosystem?

Unidirectional Signup and view all the answers

What is ecological efficiency?

The ratio of output of energy to input of energy Signup and view all the answers

What is assimilation in the context of ecological efficiency?

The amount of food absorbed and fixed into energy-rich organic substances Signup and view all the answers

What is respiration in the context of ecological efficiency?

The energy lost in metabolism Signup and view all the answers

What is primary productivity?

The rate of energy accumulation in green plants per unit area of earth's surface per unit time Signup and view all the answers

What is the unit of measurement for primary productivity?

Energy in calories/cm²/yr Signup and view all the answers

What is ingestion in the context of ecological efficiency?

The quantity of food or energy taken by a trophic level Signup and view all the answers

What happens to the energy captured by autotrophs?

It is passed on to the next trophic level Signup and view all the answers

What does the pyramid of biomass of organisms indicate?

Decrease of biomass in each tropic level from base to apex Signup and view all the answers

What happens to energy and material in each successive link of the food chain?

They are lost Signup and view all the answers

What is true about the pyramid of biomass in a pond ecosystem?

It is inverted Signup and view all the answers

What does the pyramid of energy depict?

The amount of total energy utilized by organisms at each trophic level Signup and view all the answers

What happens to energy during energy transfer from one trophic level to the next?

It decreases Signup and view all the answers

Why are higher trophic levels more efficient in energy utilization?

Because they have lower energy loss by respiration Signup and view all the answers

Where does energy come from in an ecosystem?

From an outside source, i.e. the sun Signup and view all the answers

What is the direction of energy flow in an ecosystem?

Unidirectional Signup and view all the answers

Study Notes

Primary Productivity

Primary productivity is the rate at which energy is bound or organic material is created by photosynthesis per unit area of earth's surface per unit time.
It is the result of photosynthesis by green plants, including algae of different colors, and bacterial photosynthesis or chemosynthesis.
Gross primary productivity (GPP) is the total solar energy trapped in the food material by photosynthesis.
Net primary production (NPP) or plant growth is the amount of energy bound in organic matter per unit area and time that is left after respiration in plants.

Secondary Productivity

Secondary productivity is the rate at which heterotrophic organisms resynthesize the energy-yielding substances.
It is the productivity of animals and saprobes in communities.
Net secondary production is the amount of energy stored in the tissues of consumers or heterotrophs.

Energy Flow

The energy captured by autotrophs does not go back to the sun, and the energy that passes from autotrophs to herbivores does not revert back.
There is a progressive decrease in energy level at each trophic level, which is accounted for by the energy dissipated as heat in metabolic activities.
The ratio of output of energy to input of energy is referred to as ecological efficiency.

Pyramid of Biomass

The living weights or biomass of the members of the food chain present at any one time form the pyramid of biomass of organisms.
The pyramid of biomass indicates the decrease of biomass in each trophic level from base to apex.

Pyramid of Energy

The pyramid of energy depicts not only the amount of total energy utilized by the organisms at each trophic level of food chain but also the actual role of various organisms in transfer of energy.
The total energy at the producer level is much greater than the energy at the successive higher trophic level.
Higher trophic levels are more efficient in energy utilization, but much heat is lost in energy transfer.