Energy Transfers

Question 1

What is a tropic level

Answer 1

The position of an organism occurs within an energy transfer

Question 2

What does autotrophic mean and an example of autotrophic

Answer 2

Producers are autotrophic
It means they are self nourishing

Question 3

What do saprobionts do and give an example

Answer 3

They break down complex organic compounds in dead organisms. Bacteria and fungi are saprobionts/ decomposers.

Question 4

What does biomass mean

Answer 4

The total mass of organic material (carbon) in a specific area at a given time.

Question 5

What is wrong with using dry mass of carbon

Answer 5

Has to be dead
difficult to assess
small same size so not representative
unreliable as it is unethical to collect large samples
It is situational (only valid at that moment in time) as standing crop may fluctuate

Question 6

The energy stored in biomass can be estimated using

Answer 6

….calorimetry Q=MC🔼T

Question 7

What happens to energy through the trophic level

Answer 7

Energy is lost at each trophic level

Question 8

Why is only 1-3% of sunlight energy ——> producer (photosynthesis)

Answer 8

Some of the light energy is reflected
Some light energy may be absorbed by gases/water vapour in the atmosphere
Some light energy is the wrong wavelength
Some light energy does not hit the chlorophyll

Question 9

The light energy converted to organic molecules (glucose/cellulose/starch/amino acids) is called

Answer 9

Gross Primary Production (GPP)

Question 10

The remaining energy stored is called ………. And give the equation

Answer 10

Net primary Production (NPP)

NPP= GPP - R

Question 11

How is energy lost from the producer to the primary consumer

Answer 11

Large amounts of plants are indigestible and lost from the animal as faeces
Not all of the plant may be eaten (root, bark)
Some energy is lost in excretion such as energy lost is urine
Energy lost in respiration and as heat to the environment

Question 12

How is energy lost from the primary consumer to secondary consumer

Answer 12

Large amounts of the animal may be indigestible
Not all of the animal may be eaten (bones and organs)
Some energy is lost in excretion such as energy lost in urine
Energy lost in respiration and as heat to the environment

Question 13

The net production of consumers can be calculated as

Answer 13

N = I -F - R

Question 14

How to calculate percentage efficiency

Answer 14

Energy available after transfer
—————————————— x 100
Energy available before transfer

Question 15

Explain why an increase in shoot biomass can be taken as a measurement of net primary production

Answer 15

Represents mass of carbon
Represents gross production minus respiratory losses
NPP = GPP - R

Question 16

What is the advantage of using dry mass and not fresh mass to compare the yield of plants

Answer 16

Water content is variable
Water will affect the fresh mass

Question 17

Suggest how you could determine the dry mass of a sample of plant material

Answer 17

Heat at 100 degrees to evaporate the water
Weigh and heat until no further change in mass

Question 18

Define Biomass

Answer 18

• Mass of carbon (organic compounds)
• Dry mass of tissue per given area

Question 19

Suggest what you should do to ensure all water is removed from a tissue / sample.

Answer 19

• Regularly weigh and Heat (less than 100 °C)
• Until mass is constant

Question 20

Explain how the intensive rearing of domestic livestock increases net productivity

Answer 20

• Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production;
• Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition;
• Movement restricted so less respiratory loss / less energy used;
• Kept inside/heating/shelter / confined so less heat loss / no predators;
• Genetically selected for high productivity;

Question 21

Describe the need for plants to both photosynthesise AND respire

Answer 21

• In the dark no ATP production in photosynthesis;
• Some tissues unable to photosynthesise/produce ATP;
• ATP cannot be moved from cell to cell/stored;
• Plant uses more ATP than produced in photosynthesis;
• ATP for active transport;
• ATP for synthesis (of named substance);

Question 22

The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur.

Answer 22

• High concentration of carbon dioxide linked with night/darkness;
• No photosynthesis in dark/night / light required for photosynthesis/light-dependent reaction;
• (In dark) plants (and other organisms) respire;
• In light net uptake of carbon dioxide by plants/plants use more carbon dioxide than they produce/ rate of photosynthesis greater than rate of respiration;
• Decrease in carbon dioxide concentration with height;
• At ground level fewer leaves/less photosynthesising tissue/more animals/less light;