Ch13 Nutrient cycles

Question 1

4 main stages of nitrogen cycle

Answer 1

1. ammonification
2. nitrification
3. nitrogen fixation
4. denitrification

Question 2

ammonification

Answer 2

1. saprobionts feed on dead matter
2. break down nitrogen-containing substances
3. extracellular digestion
4. release ammonia
5. form ammonium ions in the soil

Question 3

Nitrification

Answer 3

1. Nitrifying bacteria
2. oxidation reaction
3. ammonium ions to nitrite ions NO2- by nitrosomonas
4. nitrite ions to nitrate ions NO3- by nitrobacter
5. Plants absorb NO3- by active transport

Question 4

Oxygen in soil

Answer 4

1. needs air spaces
2. structure is light and well aerated by ploughing
3. good drainage to prevent filled air spaces

Question 5

Nitrogen fixation

Answer 5

Nitrogen gas is converted into nitrogen-containing compounds

Question 6

Free-living nitrogen-fixing bacteria

Answer 6

1. reduce gaseous nitrogen to ammonia
2. manufacture amino acids
3. released when they die and decay

Question 7

Mutalistic nitrogen-fixing bacteria

Answer 7

1. Rhizobium live on nodules of roots of plants
2. obtain carbohydrates from plant
3. plant receives amino acids from bacteria

Question 8

Denitrification

Answer 8

1. Poor O2 supply in soil
2. Anaerobic denitfifying bacteria
3. convert soil nitrate ions into gaseous nitrogen
4. reduce availability of N-containing compounds for plants

Question 9

Nitrogen- containing compounds

Answer 9

DNA
amino acids
proteins
urea

Question 10

Basic nutrient cycle

Answer 10

1. taken up by producers as simple inorganic molecules
2. producers incorporate into complex organic molecules
3. passes into consumer when producer is eaten
4. passed along food chain
5. producers and consumers die
6. complex molecules broken down by saprobionts into simple form

Question 11

Phosphorous cycle

Answer 11

1. Phosphate ions (PO4^3-) in rock
2. weather and erosion
3. phosphate ions dissolve
4. plants absorb
5. plants incorporate into ATP/ DNA
6. pass into animals after consumption
7. excretion and death
   8 saprobionts break down, releasing ions back into water/soil

Question 12

Guano

Answer 12

excrement of seabirds
excess phosphate ions
used as fertiliser

Question 13

Mycorrhizae

Answer 13

1. extensions of fungi on plant root
2. increase SA for mineral and water absorption
3. holds water and minerals in roots
4. plant can resist drought
5. receive organic compounds from plant- mutalistic

Question 14

Natural fertilisers examples

Answer 14

1. dead/decaying remains of plants/animals
2. manure
3. slurry
4. bone meal

Question 15

Artificial (inorganic) fertilisers

Answer 15

1. mined from rocks/deposits
2. converted and blended
3. contains nitrogen, phosphorous and potassium

Question 16

Fertilisers productivity increase

Answer 16

1. plants absorb nutritents
2. convert nitrogen/phosphate into DNA, amino acids and ATP
3. grow faster, taller and greater SA
4. increased rate of photosynthesis

Question 17

Atmospheric fixation

Answer 17

1. lightning breaks nitrogen into atoms
2. bond with O2 to form nitrogen oxides
3. dissolved in moisture to form nitrate

Question 18

Leaching

Answer 18

1. removal of nutrients from soil
2. carried deep into soil away from plants
3. enter watercourses to lakes or rivers

Question 19

High N concentration in drinking water

Answer 19

prevent efficient O2 transport in babies
stomach cancer

Question 20

eutrophication

Answer 20

1. nutrient concentration increases due to leaching
2. plants and algae grow
3. dense layer of algae absorbs light on top of water(algal bloom)
4. lack of light and lower depth cause plants and algae to die
5. saprobiontic bacteria grow due to increase of dead organisms
6. O2 concentration decreases and nitrate concentration increases