Test

Question 1

DESCRIBE THE ROLE OF BACTERIA IN MAKING THE NITROGEN IN DEAD LEAVES AVAILABLE TO GROWING PLANTS 5marks

Answer 1

• Saprobionts digest nitrogen containing substances.
• release of enzymes causes ammonium to be produced.
• ammonia is converted to nitrite.
• Nitrification
• oxidation to produce nitrate.

Question 2

Clearing the forests and burning the vegetation affects the CO2 concentration in the atmosphere. Describe how and explain why/ 4 marks

Answer 2

CO2 concentration increases (1)

Less vegetation so less photosynthesis (1)

Less CO2 removed from atmosphere (1)

Burning releases CO2 (1)

Question 3

Microorganisms make the carbon in polymer in a dead worm available to cells in a leaf. Describe how 5 marks

Answer 3

mircoorganiss are saprobionts (1)

They secrete enzymes onto dead tissue (1)

They absorb products of digestion (1)

respiration by microorganisms produces CO2 (1)

CO2 taken into leaves (1)

Question 4

Explain how including leguminous plants in a crop rotation reduces the need to use artificial fertilizers 2 marks

Answer 4

Contains nitrogen fixing bacteria in roots, so they dont need fertiliser (1)

nitrogen containing compounds added to the soil when plants die (1)

Question 5

Explain how soil microorganisms contribute to the cycling of carbon 3 marks

Answer 5

Microoganims are decomposers (1)

CO2 is produced (1)

CO2 is used by plants in photosynthesis

Question 6

Nodules on the roots of some plants enable them to survive in soils with a low concentration of nitrate ions.. Explain how.

Answer 6

nodules contain nitrogen fixing bacteria (1)

Atmospheric nitrogen into ammonia (1)

Question 7

Waterlogged soil may have a low concentration of nitrate ions. Explain why

Answer 7

Anaerobic conditions (1)

Favor the growth of denitrifying bacteria (1)

Bacteria convert nitrates to atmospheric nitrogen (1)

Question 8

Anabaena can produce ammonia from nitrogen. takes place only in anaerobic conditions found in heterocyst’s cells. which do not contain chlorophyll. What features of Heterocyst improve the efficiency of the process of nitrogen fixation 3 marks

Answer 8

Thick walls exclude oxygen (1)

Produced by photosynthetic cells of fern (1)

contain no chlorophyll so dont photosynthesise (1)

Question 9

Explain how ploughing the fern plants into the soil results in an improvement in the growth of the rice crop grown in these fields 5 marks

Answer 9

Decomposers in fields (1)

convert organic nitrogen in cells of fern into ammonia (1)

Ammonia converted to nitrite (1)

Nitrite converted to nitrate (1)

by nitrifying bacteria (1)

extra
Nitrate form amino acids in rice.

Decomposers respire and release CO2 which is used in photosynthesis by rice.

Question 10

Describe how microorganisms produce nitrates (3 marks) and nitrogen gas (2 marks)

Answer 10

1. Oxidation of ammonium via nitrate through nitrifying bacteria
2. reduction of nitrate to nitrogen gas by denitrifying bacteria

Question 11

Give two ways in which ammonium ions can be produced 2marks

Answer 11

Decomposition (1)

Nitrogen fixation (1)