Energy and ecosystems (13)

Question 1

What are 2 ways plants use sugars from photosynthesis?

Answer 1

• primarily used as respiratory substances
• to synthesise other biological molecules e.g. cellulose

Question 2

What is biomass?

Answer 2

total dry mass of a tissue (or twice the mass of carbon) measured over a given time in a specific area

Question 3

What are the units of biomass when area is being sampled?

Answer 3

gm-2

Question 4

What are the units of biomass when volume is being sampled?

Answer 4

gm-3

Question 5

What is the equation for how the chemical energy store in dry biomass is estimated using calorimetry?

Answer 5

energy released = specific heat capacity of water x water volume x temperature increase of water

Question 6

What type of calorimetry is preferable to simple calorimetry and why?

Answer 6

bomb calorimetry because it reduces heat loss to surroundings

Question 7

How can you ensure all water is removed from a sample?

Answer 7

heat sample and reweigh until mass reading is constant

Question 8

What is the equation for NPP?

Answer 8

NPP = GPP - R

Question 9

What does the R stand for in NPP = GPP - R?

Answer 9

respiratory losses

Question 10

What does GPP stand for?

Answer 10

gross primary production

Question 11

What is meant by gross primary production?

Answer 11

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

Question 12

What does NPP stand for?

Answer 12

net primary production

Question 13

What is meant by net primary production?

Answer 13

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

Question 14

What is a pyramid of biomass?

Answer 14

diagram showing biomass at each trophic level

Question 15

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

Answer 15

the shape of a pyramid of numbers may be skewed since a small number of producers can support many consumers

Question 16

What are 4 reasons why most of the suns energy is not converted to organic matter?

Answer 16

1) most solar energy is absorbed by atmosphere or reflected by clouds
2) photosynthetic pigments cannot absorb some light wavelengths
3) not all light falls directly on chlorophyll molecule
4) energy lost as heat during respiration/photosynthesis

Question 17

What is the equation for net production of consumers?

Answer 17

N = chemical energy from ingested food (I) - (energy lost as faeces and urine (F) + respiratory losses)

N = I - (F+R)

Question 18

What are 3 reasons why biomass decreases along a food chain?

Answer 18

1) energy lost in urine and faeces
2) some of the organism is not consumed
3) energy lost to surroundings as heat

Question 19

What is the equation for rate of primary/secondary production?

Answer 19

biomass in specific area
_________________________
given time period

Question 20

What are 4 farming practices used to increase efficiency of energy transfer?

Answer 20

1) exclusion of predators so no energy is lost to other organisms in the food web
2) artificial heating to reduce energy lost to maintain constant body temperature
3) restriction of movement
4) feeding is controlled at the optimum

Question 21

What is the equation for % efficiency?

Answer 21

(energy converted to a useful form x 100)
________________________
total energy supplied

Question 22

Why is a food chains length limited?

Answer 22

energy is lost at each trophic level so there’s insufficient energy to support a higher trophic level