13.4 Energy transfers

Question 1

Biomass definition

Answer 1

The man of carbon or dry mass of tissue per given area

Question 2

Name some advantages of wet mass

Answer 2

Living
Easy to access
Variable water content
Unreliable
Variable food ingested

Question 3

Name some advantages of dry mass

Answer 3

Dead
Difficult to assess
Sample size may not be representative
Unreliable
Situational

Question 4

What happens to energy at each trophic level of the food chain?

Answer 4

It gets lost
Only about 1-3% of the sun light energy available is trapped in photosynthesis and converted into chemical energy

Question 5

What happens between the sun and the producer?

Answer 5

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

Question 6

What is the equation for net primary production?

Answer 6

NPP = GPP - R
GPP = gross primary production
R = respiratory losses

Question 7

What is NPP available for?

Answer 7

Plant growth
Plant reproduction
Other trophic levels

Question 8

Equation for the net production of consumers

Answer 8

N = I - (F+R)
I = Chemical energy store of ingested food
F = Energy lost in faeces and urine
R = Energy lost in respiration

Question 9

What are the 4 reasons energy may be lost between trophic levels?

Answer 9

• Energy may be lost in excretion
• Large amounts of the animal may be indigestible
• Energy lost in respiration and as heat to the environment
• Not all the animal may be eaten

Question 10

Percentage efficiency equation

Answer 10

Energy available after transfer/ energy available before transfer x100

Question 11

Yield can be determined by measuring the dry mass of plants
Suggest how you could determine the dry mass of a sample of plant material

Answer 11

Heat at 100C
Weigh and heat until no further change in mass

Question 12

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

Answer 12

Water content is variable
Will not affect the dry mass

Question 13

What is the aim when rearing domestic livestock?

Answer 13

Increase productivity by reducing the energy losses at each stage of the food chain

Question 14

What are the 6 ways energy conversion rate can be increased by?

Answer 14

Restricting movement so less respiratory loss due to less muscle contraction
Keeping animals indoors and keep the animal warm to reduce heat loss
Feeding which is the optimum type for growth
Selective breeding
Slaughtered before they reach adulthood so more energy is transferred to biomass