5.3 - energy and ecosystems

How do plants use the sugars from photosynthesis?

• primarily as respiratory substrates

• Used to synthesise other biological molecules

What is biomass?

The total dried mass of tissue or mass of carbon measured over a given time in a specific area

What are the units for biomass?

• when an area is being sampled: gm-2

• When a volume is being sampled: gm-3

How can the chemical energy store in dry mass be estimated?

• calorimetry

• Energy released = specific heat capacity of water x volume of water x temperature increase in water

define gross primary production (GPP).

The total chemical energy in plant biomass within a given volume or area.

define net primary productivity (NPP)

The total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels after respiratory losses

How can the net production of consumers be calculated?

N=I - (F+R)

I: chemical energy from ingested food

F: energy lost as faeces and urine

R: respiratory losses

Define primary or secondary production

The rate of primary or secondary production

Biomass in a specific area over a given time period

Outline some common farming practices used to increase the efficiency of energy transfer.

• exclusion of predators

  • No energy lost to other organisms in food web

• Artificial heating

  • Reduce energy loss to maintain a constant body temperature

• Movement restriction

• Controlled feeding

Why is a pyramid of biomass preferable to a pyramid of numbers

The shape of a pyramid of numbers may be skewed because a small number of producers can support many consumers