3.5.3 Energy And Ecosystems

Question 1

What do plants use to synthesis organic compounds

Answer 1

Atmospheric/ aquatic carbon dioxide

Question 2

What are most of the sugars synthesised by a plant used for

Answer 2

Respiratory substrates

Question 3

What’s biomass

Answer 3

The total mass of living material in a specific area at a given time

Question 4

How can biomass be measured

Answer 4

dry mass of tissue per given area
Mass of carbon in tissue per given area (dry mass x 0.5)

Question 5

How to measure the chemical energy store in dry biomass

Answer 5

Calorimetry

Question 6

What’s GPP (gross primary production)

Answer 6

Chemical energy store in plant biomass in a given area/volume

Question 7

What’s NPP (net primary production)

Answer 7

Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

Question 8

Equation to calculate NPP

Answer 8

NPP= GPP - R

GPP, gross production
R, respiratory losses to the environment

Question 9

What’s NPP used for

Answer 9

Available for plant growth and reproduction
If the plant is consumed it can be available to herbivores/decomposes

Question 10

Equation to calculate the net production of consumers (N)

Answer 10

N= I - (F+R)
I, chemical energy store of ingested food
F, chemical energy lost to environment in faeces
R, respiratory losses to the environment

Question 11

How much energy is transfered from the sun to a producer and how is energy lost

Answer 11

1-3%
Incorrect wavelength of light, not all can be absorbed and used for photosynthesis (always use this in exam)

Reflected back into space

Light may be transmitted through the leaf without making contact with chlorophyll

Question 12

How much energy is transferred from producers to primary consumers and reasons for energy loss

Answer 12

5-10%
Not all of the plant is eaten such as roots, so primary consumers energy isn’t the NPP
Egestion, much of plant contains cellulose and is indigestible, lost in faeces
Excretion of urine and respiration cause heat loss
Energy is used for metabolic processes eg active transport, muscle contraction

Question 13

How much energy is transferred from primary consumer to secondary consumer and explain losses

Answer 13

20%
Not all of animal is eaten eg bones/fur so energy consumed by the secondary consumer is not NPP
Animal tissue is digestible however some energy is lost in faeces through egestion
Respiration and excretion of urine loses heat
Energy is used for metabolic processes eg active transport, muscle contraction, cell division

Question 14

Units for the rate of productivity

Answer 14

Kj/ha/year

Kj- unit of energy
ha- unit for area, allows for comparison from different size environments
Year- accounts for impact of different seasons, provides an annual average

PEAT
Productivity, energy, area, time

Question 15

Example of a farming practice which increases the efficiency of energy transfer

Answer 15

Factory farming
Animals kept in small confined spaces, movement is restricted less energy used for muscle contraction, warm environment reduced heat loss, predators are excluded so no loss to other organisms in food web

Question 16

How can energy losses to non human food chains be reduced

Answer 16

Simplifying food webs, mono culture of crops (grow lots of the same crop)
Use insecticides, kills insects, they can’t eat crop, increases yield
Herbicides, kills weeds, reduces interspecific competition for nitrates, light intensity

Question 17

Additional practises to increase the efficiency of energy transfer (not on spec)

Answer 17

Hormones, increase growth rate
Selective breeding, higher growth rates
Antibiotics, stop disease spreading in confined areas