Energy And Ecosystems

Question 1

biomass

Answer 1

all the biological molecules made by the plant and are not immediately use for respiration

Question 2

How is biomass measured?

Answer 2

•As mass of carbon
•As dry mass
•As an energy value

Question 3

practical estimation of dry mass

Answer 3

1. Heat in a low temperature open to evaporate water in the tissues.
2. Until there’s no further change in mass
3. Calculate dry biomass in kgm-2y-1
4. Carbon content estimated is 50% of dry mass

Question 4

why use dry biomass rather than wet biomass?

Answer 4

Water is not made by the plant in photosynthesis so it is not biomass

Question 5

Energy in dry biomass

Answer 5

1. Dried biomass from a known area is placed in a calorimeter
2. The dry biomass is then burnt (combustion)
3. The energy released is used to heat water.
4. The change in water temperature is used to calculate the energy released.
5. Energy per square metre per year is calculated.(kJm-2y-1)

Question 6

Gross primary production (GPP)

Answer 6

The total amount of light energy captured in photosynthesis and stored in molecules as chemical potential energy

Question 7

Respiration (R)

Answer 7

The amount of energy lost from the plant in respiration.
This returns to the environment as waste heat.

Question 8

Net primary production (NPP)

Answer 8

This is the remaining amount of chemical potential energy stored in the biomass of the plant.
This can be used for growth and reproduction.

Question 9

NPP equation

Answer 9

NPP=GPP-R

Question 10

untrapped light energy causes

Answer 10

•Some light is reflected from the surface of the leaf
•Only certain wavelength of light are absorbed by chlorophyll
•Light may not strike a chloroplast and pass straight through the leaf
•Some other factor may be limiting e.g.CO2
•Some may be absorbed but transferred into thermal energy

Question 11

net production in consumers

Answer 11

•Consumers get their energy by ingesting biomass
•Some of this is used for respiration by the consumer and is lost eventually as heat to the atmosphere
•Some is indigestible so is lost as faeces or excreted as urine
•The rest is used to make consumer biomass e.g. growth
•only the energy the net production can be passed onto the next consumer

Question 12

Net production equation

Answer 12

N= I-(F+R)

Question 13

Trophic levels

Answer 13

A trophic level is the feeding position of an organism in a food web.

A pyramid of energy represents the amount of energy stored in by a mass at each trophic level

Question 14

Why do the layers narrower as food moves up through the trophic levels?

Answer 14

Energy is lost to the decomposes as faeces, urine and uneaten material and energy is lost due to respiration by the consumer

Question 15

Farming: maximising efficiency in food production

Answer 15

•Keep food chains short
•Reduce energy losses by animals in the food chain
•Reducing respiration
•Reducing loss to faeces
•Simplifying food webs