5B - Energy Transfer and Nutrient Cycles

Question 1

What is an ecosystem?

Answer 1

• entire number of organisms in an area and all the abiotic conditions

Question 2

What must ecosystems contain?

Answer 2

• producers that make their own food which start the food webs

Question 3

How is biomass measured?

Answer 3

• by the carbon or dry mass of an organism

Question 4

How can we measure carbon or dry mass of an organism?

Answer 4

• removing the water through heating or calorimetry.

Question 5

How do we use the sample of an organism to measure dry mass?

Answer 5

• sample is dried in an oven at low temperature
• measured at regular intervals
• when mass is constant, all water has been removed

Question 6

What is calorimetry?

Answer 6

• measures the amount of chemical energy an organism contains
• the organism is burnt which releases the energy as heat, heating a known volume of water
• temperature change of the water can be used to calculate the chemical energy of the biomass.

Question 7

What is Gross Primary Production (GPP)?

Answer 7

• the amount of chemical energy converted from light energy by plants in a given area or time

Question 8

What is respiratory loss?

Answer 8

• the loss of GPP lost to the environment as the plant respires, usually about 50%

Question 9

What is the remaining energy known as?

Answer 9

• Net primary production (NPP)

Question 10

What is the equation of primary production?

Answer 10

• NPP= GPP-R

Question 11

What is the net production in consumers?

Answer 11

• the energy left after a consumer has digested and used what energy they can / the energy for the next trophic level

Question 12

What is the equation for this?

Answer 12

• N=I-(F+R)

Question 13

What is I?

Answer 13

• chemical energy in ingested food

Question 14

What is F?

Answer 14

• chemical energy lost in urine and faeces

Question 15

What is R?

Answer 15

• respiratory losses

Question 16

How would you calculate efficiency of energy transfer?

Answer 16

• (net production of trophic level / net production of previous level ) x 100

Question 17

How could you increase efficiency?

Answer 17

• simplify food webs by having fewer organisms in the web means more energy for crops/livestock

Question 18

How would reducing respiratory loss increase efficiency?

Answer 18

• controlling the conditions livestock live in so more energy is used for growth and less is lost through respiration e.g restricting animals movements by keeping them in pens.
• this raises ethical issues about animal welfare

Question 19

What does mycorrhizae do?

Answer 19

• forms a symbiotic relationship with the roots of plants.

- connect to the roots which increases the SA and helps plant absorb minerals which are scarce such as phosphorus

Question 20

How does this benefit the fungi?

Answer 20

• in return they obtain organic compounds from the plant, e.g. glucose

Question 21

What is nitrogen fixation?

Answer 21

• when nitrogen gas in the atmosphere is turned into nitrogen containing compounds e.g ammonia which can then be used in the plants to make proteins

Question 22

What is ammonification?

Answer 22

• nitrogen compounds in dead organisms are converted into ammonia/ ammonium ions by saprobionts

Question 23

What is a saprobiont?

Answer 23

• saprobionts are organisms that digest their food externally and then absorb the products
• fungi are examples of saprobiontic organisms also known as decomposers

Question 24

What is nitrification?

Answer 24

• ammonia and ammonium ions in the soil are changed into nitrogen compounds that can be used by the plant

Question 25

What is denitrification?

Answer 25

• nitrates in the soil are converted into nitrogen gas by denitrifying bacteria
• use nitrates in the soil to respire, producing nitrogen gas
• happens in anaerobic conditions e.g waterlogged soil

Question 26

What is the 1st stage of the phosphorus cycle?

Answer 26

• rocks are weathered which release Phosphate ions into the soil as well as leeching

Question 27

What is the 2nd stage of the phosphorus cycle?

Answer 27

• Plants absorb the phosphate ions from their roots in the soil
• mycorrhizae increase the rate at which phosphates can be absorbed

Question 28

What is the 3rd stage of the phosphorus cycle?

Answer 28

• phosphate ions are transferred through the food chains as animals eat other animals

Question 29

What is the 4th stage of the phosphorus cycle?

Answer 29

• phosphate ions are lost through animal waste

Question 30

What is the 5th stage of the phosphorus cycle?

Answer 30

• animals die and saprobionts break down the organic compounds releasing
• phosphate ions into the soil and back to sedimentary rock

Question 31

What is the 1st stage of Eutrophication?

Answer 31

• mineral ions leached from the fertilized fields stimulate the rapid growth of algae in a pond

Question 32

What is the 2nd stage of Eutrophication?

Answer 32

• the mass of algae blocks sunlight from penetrating the water

Question 33

What is the 3rd stage of Eutrophication?

Answer 33

• plants die at the bottom of the water as they have no sunlight to photosynthesise with

Question 34

What is the 4th stage of Eutrophication?

Answer 34

• bacteria feed on the dead organisms, increasing the number of bacteria

Question 35

What is the 5th stage of Eutrophication?

Answer 35

• mass of bacteria reduced the oxygen content of the water by aerobically respiring

Question 36

What is the 6th stage of Eutrophication?

Answer 36

• fish and other aquatic organisms die due to lack of oxygen

Question 37

What effect does the respiring bacteria have?

Answer 37

• makes the water toxic with the CO2 from aerobic respiration