Energy transfers

Question 1

What are the 7 life processes?

Answer 1

Movement, Reproduce, Sensitive, Growth, Respiration, Excretion, Nutrition

Question 2

What is a trophic level?

Answer 2

The position an organism occurs within an energy transfer/feeing relationship

Question 3

What does autotrophic mean?

Answer 3

Building up organic compounds from simple molecules needed for growth

Question 4

Example of autotropic organisms

Answer 4

Photosynthetic organisms build up complex organic compounds in the process of photosynthesis. Most of the sugars synthesised are used to make respiratory substrates

Question 5

What does heterotrophic mean?

Answer 5

Rely on external source of organic compounds

Question 6

What does saprotrophic mean?

Answer 6

Break down complex organic compounds in dead organisms
Bacteria and fungi are Saprobionts
Digest externally and excrete cellular enzymes to digest

Question 7

What is biomass?

Answer 7

mass of living material of the organism or tissue

Question 8

Advantages of fresh mass (wet)

Answer 8

Easy to assess

Question 9

Disadvantages of fresh mass (wet)

Answer 9

Living
variable water content
unreliable due to varying water content
variable food indigested

Question 10

Advantages of dry mass (mass of carbon)

Answer 10

Dead

Question 11

Disadvantages of dry mass (mass of carbon)

Answer 11

Difficult to assess
Small sample size (may not be representative)
Unreliable (unethical to collect large sample)
Situational - only valid at that moment in time standing crop - may fluctuate

Question 12

How can the chemical energy stored in biomass be measured?

Answer 12

Calorimetry

Question 13

What is bomb calorimetry?

Answer 13

A sample of dry biomass is combusted (burnt in pure oxygen) within a sealed chamber (called a bomb)
The chamber is surrounded by a water bath and the heat energy released causes a temperature rise in the water
Using the known specific heat capacity of water and the volume of the water and temperature rise, we can calculate the energy released from the mass of burnt biomass in kJ kg-1

Question 14

How much light energy is trapped in photosynthesis and converted to chemical energy in the form of organic molecule?

Answer 14

about 1-3%

Question 15

What are the 4 ways in which light energy is lost (from the sun to the producer)

Answer 15

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

Question 16

What is gross primary production (GPP)?

Answer 16

The chemical energy store in plant biomass, in a given area or volume (rate of photosynthesis)

Question 17

What is net primary production (NPP)?

Answer 17

GPP - R
(Energy which is stored or forms new biomass)

Question 18

How much energy is transferred from producers to primary consumers?

Answer 18

around 10%

Question 19

What are the 4 ways in which light energy is lost from the producer to primary consumer?

Answer 19

Large amounts of the plant may be indigestible and lost from the animal a faeces
Not all of the plant may be eaten
Some energy is lost in excretion such as energy lost in urine
Energy is lost in respiration and as heat to the environment

Question 20

What are the 4 ways in which light energy is lost from the primary consumer to secondary consumer?

Answer 20

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

Question 21

How is the net production of consumers calculated (N)

Answer 21

chemical energy store of ingested food - (energy lost in excretion + energy lost in respiration )
I - (F + R)

Question 22

How to calculate efficiency of energy transfer?

Answer 22

percentage efficiency = (energy available after transfer / energy available before transfer) x 100

Question 23

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 23

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

Question 24

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

Answer 24

Water content is variable
Will not affect dry mass/water will affect fresh mass

Question 25

What is the aim of rearing domestic livestock?

Answer 25

To increase productivity (net productivity) by reducing the energy losses at each stage in the food chain so that more energy is converted into new tissue/animal biomass

Question 26

NPP = GPP - R
How to increase NPP?

Answer 26

Increase GPP and keep R the same
GPP stays the same and R reduces

Question 27

NPP = GPP - R
How to decrease NPP?

Answer 27

GPP stays the same and R increases

Question 28

How can energy conversion rates be increased?

Answer 28

Restrict movement so less respiratory loss due to less muscle contraction
Keep animals indoors and warm to reduce heat loss from body
Feed which is of the optimum type for growth
Food source which is easier to absorb to reduce the amount of energy lost in egestion
Exclude predators so that energy is not lost to another consumer
Slaughtered before reaching adulthood so more energy transferred to biomass

Question 29

Explain how the intensive rearing of domestic livestock increases net productivity

Answer 29

Slaughtered when still growing so more energy transferred to biomass
Fed on concentrate/controlled diet so higher proportion of food absorbed
Movement restricted so less respiratory loss
Kept warm/inside so less respiratory loss
Selective breeding for high productivity