Transfer of Biomass

What are trophic levels?

Stages in a food chain or food web representing the movement of biomass and energy

What are producers?

Organisms that make their own food

How do plants and algae act as producers?

They convert light energy into chemical energy by photosynthesis

What are primary consumers?

Herbivores that consume producers

What are secondary consumers?

Organisms that consume primary consumers

What are tertiary consumers?

Organisms that consume secondary consumers

What are saprobionts?

Decomposers that break down complex materials in dead organisms into simpler substances

What do saprobionts release into ecosystems?

Nutrients

What is a food chain?

A sequence of organisms connected by feeding

What is a food web?

A complex network of interconnected food chains

What do arrows in food chains and food webs represent?

The direction of energy flow

What is biomass?

The total mass of living material present at a particular time in a specific place or within certain organisms

What are the units for measuring biomass on land?

g m−2

What are the units for measuring biomass in aquatic environments?

g m−3

How can the chemical energy stored in dry biomass be estimated?

Using calorimetry

Why is biomass dried before calorimetry?

To obtain a constant dry mass

What is done to the dry biomass in calorimetry?

It is burned in a calorimeter

What is measured during calorimetry?

The volume and temperature change of the surrounding water

What can be calculated from calorimetry?

An estimate of the heat energy released from the biomass

What is gross primary production GPP?

The total amount of solar energy converted by plants into organic matter and stored as chemical energy

What is net primary production NPP?

The chemical energy available to the next trophic level after respiratory losses

What is the equation for NPP?

NPP = GPP − R

What does R represent in the NPP equation?

Respiratory losses

What is primary productivity?

The rate of primary production

How is primary productivity measured?

As biomass in a given area in a given time

Why does biomass and energy content decrease at higher trophic levels?

Energy is lost at each trophic level

Why is not all solar energy captured by leaves?

Some solar energy is not absorbed or is the wrong wavelength for photosynthesis

How can water availability cause energy loss between trophic levels?

It can limit photosynthesis

How is energy lost during photosynthesis?

Energy is lost during photosynthetic reactions

Why is energy lost because not all biomass is consumed?

Some parts of biomass are not edible or digestible

How is energy lost during movement and respiration?

It is released as heat

How is energy lost through excretion?

Energy is lost in materials such as urine and faeces

How can agriculture increase the transfer of biomass to humans?

By creating simpler food chains with fewer trophic levels

Why does agriculture reduce the number of trophic levels?

To maximise energy transfer into biomass that can be eaten by humans

What is ecological efficiency?

The efficiency of biomass or energy transfer from one trophic level to the next as a percentage

What is the formula for ecological efficiency?

What values should be compared to calculate energy transfer efficiency between trophic levels?

Net production or net productivity values