1. Energy Transfer in Ecosystems

Ecosystem

All the organisms living in a particular area and all the abiotic conditions.

biomass

the mass of living material/ the chemical energy stored in the plant.

Dry mass

The mass of the organism with the water removed.

How can be biomass be measured? (2)

1. The mass of carbon that an organism contains.

2. The dry mass of its tissue per unit.

How to measure dry mass?: 2

• sample of the organism is dried, often in an oven set to low temperature.

• the sample is then weighed at regular intervals. Once the mass becomes constant, you know all the water is removed.

How to weigh the mass of carbon

• Generally taken to be 50% of the dry mass.

How to estimate the amount of chemical energy stored in biomass.: 3

using a calorimeter

• burn the biomass in a calorimeter.

• The amount of heat given off tells you how much energy is in it.

• The change in temperature of the water is what is used to calculate the chemical energy present.

GPP

Gross primary production

what is GPP

The total amount of chemical energy converted from light energy by plants, in a given area.

R

respiratory lloss

what is R

When approximately 50% of the GPP is lost to the environment as heat when the plants respire.

NPP

Net primary production

what is NPP

definition of NPP

The remaining chemical energy left in the plant after respiratory loss.

NPP - the energy available to the plant for growth and reproduction. It is also the energy available to organisms at the next stage in the food chain/ next trophic level.

Formula for the relationship between NPP, GPP and R

NPP = GRPP - R

kJ ha-1yr-1

kilojoules per hectare per year.

what is it called when primary production is expressed as a rate

primary productivity

Why doesn’t all the chemical left in the organism go to the next organism?

What are the statistics?

• Not all parts of the organism are ingested.

• The parts that are taken in, the parts that are indigestible are excreted as faces, causing this chemical energy to be lost in the environment.

• Respiration

• Urine

consumer’s net production

The energy that is left after all the chemical energy is stored in the consumer’s biomass and is available to the next trophic level.

Equation for consumer’s net production.

N = I - (F+R)

N = Net production

I = Chemical energy ingested in food

F = Chemical energy lost in faeces and urine.

R = Energy lost through respiration.

Equation for calculating the efficiency of energy transfer

%efficiency of energy transfer = net production of trophic level/ net production of previous trophic level x 100.