3.5.3 Energy and Ecosystems

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

What is GPP?

Answer 6

Gross Primary Productivity: The rate at which chemical energy is incorporated into organic molecules by an ecosystem

Question 7

What is NPP?

Answer 7

Net Primary Productivity: The rate at which chemical energy is incorporated into organic molecules that make up the new plant biomass

Question 8

What is primary productivity?

Answer 8

The rate at which energy is incorporated into organic molecules

Question 9

What is secondary productivity?

Answer 9

The amount of energy from the organism that passes on to it’s consumers or decomposers

Question 10

State the equation that links NPP/GPP/R (respiration)

Answer 10

NPP= GPP-R

Question 11

Define efficiency in relation to food chains

Answer 11

Energy available after transfer/energy available before transfer) x 100

Question 12

Answer 12

Question 13

Answer 13

Question 14

Why isn’t the transfer of energy from producers to primary consumers very efficient ?

Answer 14

Not all of the available food is eaten (roots, bones twigs),some undigested food remains in faeces (cellulose in cell walls), much of the food absorbed by the consumers is used in respiration

Question 15

What is net productivity?

Answer 15

The energy that is used for biomass and is available to the next trophic level

Question 16

What is gross productivity ?

Answer 16

the available energy that is taken in

Question 17

What don’t plants take in all of the available energy?

Answer 17

some light energy is reflected, transmitted through the leaf, is the wrong wavelength or hits parts of the plant that cannot photosynthesis (bark of a tree)

Question 18

What is a primary consumer?

Answer 18

Organisms that eats plant material

Question 19

What is a secondary consumer?

Answer 19

An organisms that eats primary consumers

Question 20

Define ‘trophic level’

Answer 20

Position a species occupies in a food chain. energy is transferred from one trophic level to the next by consumers

Question 21

Answer 21

Question 22

Define detritivore

Answer 22

Primary consumer that feeds on dead organic material

Question 23

Define decomposer

Answer 23

Bacteria and fungi that feed on the dead remains of organisms and animal faeces

Question 24

Define biomass

Answer 24

The mass of an organism without water (organic material only)

Question 25

Answer 25

Question 26

Answer 26

Question 27

Draw the nitrogen cycle

Answer 27

Check - ammonium - nitrites, nitrates. Denitrification, nitrification, ammonification

Question 28

Define ‘denitrification’ and state why it happens

Answer 28

when nitrate ions in the soil are converted into nitrogen gas (by anaerobic denitrifying bacteria) - happens in waterlogged soils

Question 29

Describe the process of ammonification

Answer 29

When organic compounds (e.g. urea) are converted into ammonia by saprobiontic microorganisms (fungi and bacteria)

Question 30

Define ‘nitrification’

Answer 30

When ammonium is oxidised into nitrites, then nitrates by nitrifying bacteria

Question 31

State two ways in which nitrogen fixation can take place

Answer 31

Free living nitrogen fixing bacteria can convert N2 gas into ammonia, which they use to make ammino acids. OR mutualistic nitrogen fixing bacteria in root nodules use N2 gas into amino acids whilst they obtain carbohydrates from the plants

Question 32

(bit post spec)

Answer 32

(dont need names for AQA)

Question 33

Define mycorrhizae

Answer 33

An association between plant roots and fungi which increase the surface area for plant roots to absorb water and minerals. The fungus receives sugars and amino acids from the plant.

Question 34

Answer 34

Question 35

Describe the process of eutrophication

Answer 35

Fertilisers are leached into water, algal bloom occurs on upper layers of water so light does not reach deeper water. Plants and algae at lower depths die and saprobiontic bacteria increase. As they respire, O2 concentrations decrease and aerobic organisms die. Anaerobic conditions continue and anaerobic organisms release more nitrates and toxic wastes.

Question 36

Draw the phosphate cycle

Answer 36