Energy Transfer

Question 1

Why are green plants referred to as photoautotrophs

Answer 1

They use energy from the sun in photosynthesis to synthesise organic molecules such as glucose

Question 2

What is a basic food chain?

Answer 2

Producer –> Primary Consumer –> Secondary Consumer –> Tertiary Consumer –> Predator

Question 3

State ways in which energy is lost at each tropic level

Answer 3

• Heat
• Excretion (urine)
• Egestion (faeces)
• Movement
• Respiratory losses

Question 4

How is energy transferred throughout a food chain?

Answer 4

It is transferred through trophic levels and passes through in the form of food through one level to the next

Question 5

What is biomass?

Answer 5

Mass of living material measured over a particular area

Question 6

How do you work out dry mass for plants?

Answer 6

Use an oven to remove all the water form plant material before weighing to determine biomass

1. Find mass before putting in oven
2. Turn oven on at 95-100*C
3. Heat + reweigh
4. Repeat and reweigh until mass is constant for 3 consecutive readings

Question 7

Why is dry mass calculated as dry mass of tissue?

Answer 7

Percentage of water varies from species to species

Question 8

Why is biomass recorded per unit area?

Answer 8

To compare biomass in different locations

Question 9

Units for biomass?

Answer 9

• g/m2
• kg/hectare
• lb/ft2

Question 10

How do you convert biomass into mass of carbon?

Answer 10

Multiply biomass by 0.5

Question 11

Why can’t all the energy at the leaf surface be absorbed?

Answer 11

• Reflected at the leaf surface
• Incorrect wavelength
• Transmitted through leaf without coming into contact with a chloroplast

Question 12

What is Gross Primary Production (GPP)?

Answer 12

Chemical energy store in plant biomass in a given area or volume

Question 13

What is Net Primary production (NPP)?

Answer 13

Chemical energy store in plant biomass after respiratory losses (R) to the environment have been taken into account

Question 14

How do you calculate Net Primary Production (NPP)?

Answer 14

NPP = GPP – R

Question 15

What can NPP be used for?

Answer 15

• Plant growth + reproduction

* Other trophic levels (herbivores + decomposers)

Question 16

Why doesn’t energy consumed equate to NPP between producer and primary consumer?

Answer 16

This is because some of the plant may not have been eaten i.e roots

Question 17

What is the typical energy transfer % from producer to primary consumer?

Answer 17

5 – 10%

Question 18

Of the food consumed, not all energy is used for biomass, state 4 ways energy is lost

Answer 18

• Lost in urine during excretion
• Lost as heat during respiration
• Used for metabolic processes
• Most of plant is indigestible so mostly lost as faeces

Question 19

Why is energy transfer for secondary consumer more efficient?

Answer 19

This is because animal tissue is more digestible

Question 20

What is the energy transfer % between consumers?

Answer 20

20%

Question 21

How do you calculate net production for consumers?

Answer 21

N = I – (F + R)
I = Chemical energy store in ingested food
F = Chemical energy lost in faeces + urine
R = Respiratory losses to the environment

Question 22

What are endotherms?

Answer 22

Animals that maintain a constant body temp for e.g birds have high rates of respiration which generate heat as less of the food is converted into biomass

Question 23

Why do herbivores convert less food into biomass?

Answer 23

This is because there is lots of cellulose in plant food which is indigestible so its lost in faeces

Question 24

State a few practices used by farmers to minimise energy losses from animals?

Answer 24

• Keep animals in confined spaces to reduce energy lost in movement (Intensive Rearing of livestock)
• Environment kept warm so less energy used to maintain constant body temp
• Controlled feeding so little is lost through faeces
• Slaughtered young, when growing, as most energy is being used to produce biomass

Question 25

What is the monoculture of crop plants?

Answer 25

When one crop is grown on a large scale to achieve the greatest yield. This can involve simplifying food webs so energy is not lost to non-human food chains

Question 26

Why are insecticides used?

Answer 26

They will stop insects eating the crops as they reduce yields

Question 27

Why are herbicides used (weedkillers)?

Answer 27

They will kill other plants and will reduce competition for nitrates, water etc.

Question 28

Why are hedges removed?

Answer 28

Makes it easier to remove combine harvesters and hedges will compete for nitrates and water and they could contain insects that eat crops  lower yields