2.3 Flows of energy

Question 1

On average, how much of the available energy in a trophic level is taken up by the level after it?

Answer 1

On average only 10% of energy is passed on through, every trophic level 90% is lost as heat

Question 2

What is chemical energy used for?

Answer 2

• Growth
• Respiration
• Transferred to decomposers (bacteria and fungi)
• Reproduction

Question 3

What are the units of a pyramid of energy/ productivity?

Answer 3

Energy = kJ
area of habitat occupied = m2
period of time sampled = yt
–> kJ/m2/yr

Question 4

Why is only around 1% of the suns energy absorbed by the plants?

Answer 4

99% of the sun’s energy is reflected/ wrong colour/ transmitted through leaves

Question 5

How is energy lost during respiration?

Answer 5

• -> movement
• -> urine and faeces
• -> decomposition

Question 6

What is the equation for ecological efficiency?

Answer 6

(Energy used for growth/ energy supplied) x 100

–> same as the energy that is transferred from 1 trophic level to the next

Question 7

What is gross primary productivity (GPP)?

Answer 7

The quantity of organic matter produced, or solar energy fixed, by photosynthesis in green plants per unit area per unit time.

Question 8

What is gross productivity (GP)?

Answer 8

the total gain in energy or biomass per unit time, which could be through photosynthesis in primary producers OR absorption in consumers

Question 9

How do you calculate (GP)?

Answer 9

(GP = food eaten - faecal losses)

Question 10

What is net productivity (NP)?

Answer 10

The gain in energy or biomass per unit time remaining after allowing for respiratory losses (R)

Question 11

What is net primary productivity (NPP)?

Answer 11

The amount of energy left over by the autotrophs after they have met their own energy needs

Question 12

How do you calculate (NPP)?

Answer 12

NPP = GPP - R

Question 13

How could you calculate gross secondary productivity (GSP) and net secondary productivity (NSP)?

Answer 13

NSP (Net secondary productivity) can be calculated by measuring the increase in biomass (of species) over a specific amount of time.

• NSP = mass of x at the end of experiment - mass of x at beginning of experiment
  - -> Calculates the INCREASE

GSP (Gross secondary productivity) can be calculated using the following equation:
- GSP = food eaten - faecal loss

This can also be used to calculate respiration:
- R = GSP - NSP

Question 14

What are the 6 elements that make up 95% of living matter?

Answer 14

• Carbon
• Hydrogen
• Nitrogen
• Oxygen
• Phosphorus
• Sulfur

(CHONPS)

Question 15

What must happen to the 6 CHONPS elements?

Answer 15

They must be recycled or they would become locked up in dead bodies and life would no longer exist. Decomposers play a VITAL role in carrying out nutrient recycling.

Question 16

How is carbon released back into the atmosphere?

Answer 16

As CO2

• Photosynthesis takes in CO2 –> transforms into carbohydrates
• Respiration and Burning/Combustion release CO2

Question 17

What are the flows in the carbon cycle?

Answer 17

• Respiration and photosynthesis move carbon into and out of the atmospheric store.
• Decay by decomposers and detritivores releases the nutrients locked up in dead organic matter along with CO2 in atmosphere
• Combustion breaks the long chain hydrocarbons found in fossil fuels and wood and releases CO2 into the atmosphere

Question 18

What must happen to nitrogen before it can be used?

Answer 18

It must be converted into absorbable nitrogen compounds.

Question 19

What are the 4 types of transforming nitrogen into absorbable nitrogen compounds?

Answer 19

• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification

Question 20

What is nitrogen fixation?

Answer 20

Nitrogen fixing organisms, are able to reduce nitrogen gas to ammonia. The reaction occurs in anaerobic conditions within the bacterial cells and is catalysed by the enzyme nitrogenase.

Question 21

Give an example of a nitrogen fixing bacteria and what it does

Answer 21

Rhizobium lives inside the root cells of leguminous plants (such as peas, beans and clover), where it forms root nodules.
The relationship of Rhizobium with the legume is mutualistic as both organisms contribute and benefit. The ammonia is available for use by the plant to synthesize amino acids, without having to absorb nitrates, which are often in short supply. The bacteria get protection and obtain sugars from the plant, which are used as a source of energy.

Question 22

What is ammonification?

Answer 22

Ammonification involves the breakdown of organic nitrogen compounds (eg. protein and urea into ammonia). The process is carried out by saprotrophic bacteria and fungi. These remove the nitrogen containing amino groups and combine them to form amino acids.

Question 23

What is nitrification?

Answer 23

During nitrification, ammonium compounds are oxidised by nitrifying bacteria into nitrates. The process takes place in two stages involving different species of bacteria.

• Nitrosomonas - converts ammonium ions to nitrites
• Nitrobacter - converts nitrites to nitrates

Question 24

What does “nitrobacter” convert?

Answer 24

Converts nitrites to nitrates

Question 25

What does “nitrosomonas” convert?

Answer 25

Converts ammonium ions to nitrites

Question 26

What is denitrification?

Answer 26

This is a process that occurs under anaerobic conditions, for example when soils are waterlogged in bogs and marshes. It is carried out by dentrifying bacteria (like Pseudomonas denitrificans and Thiobacillus denitrificans).

These can use nitrate ions as an electron acceptor, instead of oxygen, in respiration.

The nitrates are converted to nitrogen gas and returned to the atmosphere.

Question 27

What are some human impacts on the carbon cycle?

Answer 27

• Deforestation
• Urbanisation
• Agriculture
• Combustion of fossil fuels

Question 28

What are some human impacts on the nitrogen cycle?

Answer 28

• Fertilisers
• Human population growth
• Deforestation
• Agriculture
• Nitrogen oxides from burning fossil fuels