energy transfer

Question 1

define ecosytem

Answer 1

all the living organisms and abiotic factors

Question 2

give the 2 types of producers

Answer 2

aquatic
land

Question 3

what is glucose used for in a plant

Answer 3

in respiration

to make other biological molecules (e.g: cellulose and starch) which make up a plants biomass (mass of living material, chemical energy store)

Question 4

what is biomass (2 marks)

Answer 4

• mass of living material
• chemical energy store

Question 5

what are the 2 ways of measuring biomass

Answer 5

• mass of carbon
• dry mass per given unit area (Kgm-2)

Question 6

why can you not measure the wet mass to determine biomass

Answer 6

water content of living tissue varies
so it is more accurate to measure dry mass of an organisms tissue

Question 7

what is the method to measuring the dry mass per unit area (Kgm-2) of tissue

Answer 7

• sample of an organism is dried in an oven and regularly removed, weighed, reheated
• the process is continued until mass stays constant
• mass of carbon is approximately 50% of dry mass
• scale up result to find dry mass/biomass of total population (or of area)

Question 8

give the method to find out the amount of chemical energy stored in biomass

Answer 8

CALORIMETRY
- sample of dry biomass is burnt
- energy released is used to heat a known volume of water
- change in degrees C of H2O can be used to calculate the amount of chemical energy stored in biomass (J/kJ)

Question 9

what is the equation to calculate net primary production

Answer 9

NPP = GPP - R

Question 10

define net primary production

Answer 10

remaining chemical energy after respiratory loss

this chemical energy = stored in biomass, used in growth, reproduction etc…

Question 11

define gross primary production

Answer 11

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

Question 12

define respiratory loss

Answer 12

amount of chemical energy lost as heat when plants respire

(around 50% in plants)

Question 13

what is primary production called when it is a rate

Answer 13

primary productivity
= TELLS YOU IT’S A RATE

Question 14

define primary productivity

Answer 14

total amount of chemical energy in a given area in a given time (Kjm-2Yr-1)

Question 15

grass in a school field has a gross primary productivity of 30,000 Kjm-2Yr-1 it loses 14,000 Kjm-2Yr-1 as heat from respiration

calculate net primary productivity of the grass

Answer 15

NPP = GPP - R

NPP = 30,000 - 14,000
NPP = 16,000 Kjm-2Yr-1

Question 16

why is not all chemical energy in plants or prey transferred to the next tropic level

Answer 16

10% is stored in new biomass

Question 17

give the 3 ways the chemical energy stored in “food” is lost

Answer 17

RESPIRATION - heat lost to environment

EXCRETION - urine

EGESTION - parts of plant/animal that cannot be digested are egested as faeces. so chemical energy is lost to the environment

Question 18

define net production

Answer 18

chemical energy stored in the consumers biomass that can be transferred to the next trophic level is the consumers NET PRODUCTION

Question 19

give the equation for consumers net production

Answer 19

N = I - (F + R)

Question 20

what does N stand for in the equation below

N = I - (F + R)

Answer 20

consumers net production

Question 21

what does I stand for in the equation below

N = I - (F + R)

Answer 21

chemical energy in the ingested food

Question 22

what does F stand for in the equation below

N = I - (F + R)

Answer 22

chemical energy lost in faeces and urine

Question 23

what does R stand for in the equation below

N = I - (F + R)

Answer 23

respiratory loss

Question 24

Hares ingest 30,000 Kjm-2Yr-1 of energy. They lose 18,000 Kjm-2Yr-1 of this energy as faeces/urine and a further 9,000 Kjm-2Yr-1 in respiration

Calculate net productivity of the hares

Answer 24

N = I - (F + R)

N = 30,000 - (18,000 + 9,000)

N= 3,000 Kjm-2Yr-1 net productivity

Question 25

what is the equation to calculate % efficiency of energy transfer

Answer 25

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

Question 26

hares net production was 3,000 Kjm-2Yr-1
grass production was 30,000 Kjm-2Yr-1

Answer 26

% effiency of energy transfer = (3,000/ 30,000) x 100

= 10%

Question 27

Explain how energy is lost along a food chain

Answer 27

“Plants convert approx 1% of the suns light energy into organic molecules because:
- energy is reflected back to space by clouds or absorbed by atmosphere
- not all wavelengths of light are absorbed by leaves
- light may miss the chlorophyll molecule
- other factors may limit rate of photosynthesis
Energy is lost at each stage in a food chain because:
- some parts of organisms may not be consumed
- some parts of organisms cannot be digested (lost in faeces)
- energy lost in excretory materials (urine)
- energy lost as heat to the environment from respiration - higest in mammals and birds due to maintainance of body temperature”