Energy and Ecosystems

Question 1

What is a saprobiont and what does it do?

Answer 1

A decomposer, break down the complex mineral ions in dead organisms into simple ones.

Question 2

What is each stage in the food chain called?

Answer 2

A trophic level

Question 3

What is biomass and what is it measured in?

Answer 3

he total mass of living material in a specific area in a given time. Measured in grams per square meter.

Question 4

What is the Gross primary production?

Answer 4

The total quantity of chemical energy stored in plant biomass in a given area/volume in a given time.

Question 5

What is the calculation for net primary production?

Answer 5

NPP = GPP - respiratory losses

Question 6

Name 4 reasons why there is only a low % of energy transferred at each stage in the food chain.

Answer 6

• Some of the organism is not consumed,
• Some parts of the organism cannot be digested,
• Some energy is lost in excretory materials,
• Some energy is lost as heat to the environment.

Question 7

What is the calculation for net production?

Answer 7

NP = Ingested - (lost in waste + lost in respiration)

Question 8

Why do most food chains only have 4-5 trophic levels?

Answer 8

Because there insufficient energy to sustain a breeding population at a higher trophic level than these.

Question 9

In what form do plants take up nitrogen and how?

Answer 9

Nitrate ions (NO3-) by active transport in the roots.

Question 10

What are the four stages in the nitrogen cycle?

Answer 10

Ammonification, nitrification, nitrogen fixation and denitrification.

Question 11

What happens in ammonification?

Answer 11

Organic nitrogen containing compounds are broken down by saprobionts into ammonium ions.

Question 12

What happens in nitrification?

Answer 12

Ammonium ions are oxidised to nitrite ions and then oxidised to nitrate ions by free-living nitrifying bacteria.

Question 13

What is nitrogen fixation?

Answer 13

Nitrogen gas is converted into nitrogen containing compounds by free-living nitrogen fixing bacteria or mutualistic nitrogen fixing bacteria.

Question 14

What is denitrification?

Answer 14

Denitrifying bacteria convert soil nitrates into gaseous nitrates as they respire anaerobically.

Question 15

What are mycorrhizae?

Answer 15

Form symbiotic relationships with the roots of plants by increasing their surface area in exchange for organic compounds like glucose.

Question 16

Where is phosphorus mainly found?

Answer 16

As phosphate ions in the form of sedimentary rock deposits.

Question 17

What do natural fertilisers consist of?

Answer 17

Mainly dead and decaying remains of plants and animal as well as animal wastes.

Question 18

What do artificial fertilisers contain?

Answer 18

Mined from rocks and deposits, converted into different forms and blended together to give the appropriate balance of minerals for that specific crop.

Question 19

Name three negatives of using nitrogen-containing fertilisers.

Answer 19

• Reduced species diversity,
• Leaching,
• Eutrophication.