13.3

Question 1

basic nutrient cycle

Answer 1

1. take up by producers as simple inorganic molecules
2. producers incorporate it into complex organic molecules
3. nutrient passes into consumer when producer is eaten
4. passed along food chain
5. producers and consumers die- complex molecules broken down by saprobiontic micro-organisms into simple form

Question 2

4 main stages of nitrogen cycle

Answer 2

ammonification
nitrification
nitrogen fixation
denitrification

Question 3

ammonification

Answer 3

production of ammonia form organic nitrogen-containing compounds

saprobiontic microorganisms feed on faeces and dead organisms, releasing ammonia
forms ammonia ions in the soil

Question 4

organic nitrogen-containing compounds

Answer 4

urea
proteins
nucleic acids
vitamins

Question 5

nitrification

Answer 5

nitrifying bacteria release energy through chemical reactions
- use oxygen
1. oxidation of ammonia ions to nitrite ions(NO2-) by nitrosomonas
2. oxidation of nitrite ions to nitrate ions (NO3-) by nitrobacter

Question 6

Oxygen in soil

Answer 6

• need air spaces
• structure is light and well aerated by ploughing
• good drainage to prevent filled air spaces

Question 7

nitrogen fixation

Answer 7

nitrogen gas is converted into nitrogen-containing compounds

Question 8

free-living nitrogen fixing bacteria

Answer 8

reduce gaseous nitrogen to ammonia
manufacture amino acids

Question 9

mutualistic nitrogen fixing bacteria

Answer 9

Rhizobium
live on nodules on roots of plants(e.g. peas and beans)

obtain carbs from plant
plant gets amino acids from bacteria

Question 10

denitrification

Answer 10

• poor oxygen supply in soil
  -anaerobic denitrifying bacteria
• convert soil nitrates into gaseous nitrogen
• reduces availability of nitrogen-containing compounds for plants

Question 11

atmospheric fixation

Answer 11

energy of lighting break nitrogen molecules into atoms
they bond with oxygen to form nitrogen oxides
dissolve in moisture to form nitrates

Question 12

Haber process

Answer 12

industrial using pressure temp and iron catalyst
converts atmospheric nitrogen and hydrogen to ammonia

Question 13

Phosphorous use

Answer 13

ATP
phospholipids
nucleic acids

Question 14

Sedimentary rock

Answer 14

exist as phosphate ions PO4^3-
weathering and erosion helps phosphate ions dissolve
absorbed by plants
converted into biomass
pass into animals
excretion and death
saprobients break down releasing into water or soil
phosphate ions can stay in bones or shells

Question 15

mycorrhizae

Answer 15

extensions of fungi on plant root system
increase SA for absorption of water and minerals
holds water and minerals in roots so plants can resist drought and take up nutrients ore readily
fungi receive organic compounds from plant(mutalistic)