nutrient cycles

Question 1

where is nitrogen found

Answer 1

in amino acids, protiens, nucleic acids, ADP and ATP

Question 2

how can most plants only absorb nitrogen

Answer 2

as nitrates from the soil ( NO-3)

Question 3

describe the nitrogen cycle

Answer 3

1) plants take up nitrate ions which are absorbed by active transport through the root hair cells
2) the plants use the nitrogen to build up protiens and other N containing compounds
3) consumers then eat the plants and hydrolyse protiens to amino acids, these are absorbed and assimilated into the new tissue in the consumer
4) primary consumers may be eaten by secondary consumers and N containing compounds are passed along trophic levels
5) both plants and animals die and biomass is hydrolysed by saprobionts
6) animals also excrete nitrogenous waste

Question 4

describe ammonification

Answer 4

1) sabrobiants hydrolyse N containing compounds by extracellular digestion
2) sabrobionts secrete hydrolytic enzymes that hydrolyse large insoluble molcules into smaller ones that are uptaken by active trasnport
3) these are then further broken down and release ammonia into the soil

Question 5

describe nitrification

Answer 5

1) ammonia is oxidised to nitrates then further oxidised to nitrates by nitrifying bacteria
2) nitrates can then be absorbed by the root hair cells and assimilated into new biomass

Question 6

describe nitrogen fixation

Answer 6

1) nitrogen fixing bacteria found in the soil and the root nodules of some leguminous plants can reduce N2 gas to ammonium compounds which plants can then use
2) electrical fixation of N2 gas in atmospherer to nitrates in the soil can occur due to lightning

Question 7

describe denitrification

Answer 7

1) under anaerobic conditions nitrates can be converted to N2 gas by denitrifying bacteria in a process called denitrification

Question 8

where does phospherous mostly exist

Answer 8

in sedimetry rock

Question 9

describe the phosphorus cycle

Answer 9

1) phospholipids, Rna, DNA etc from dead organisms are decomposed by sapriobionts into phosphate ions
2) these ions are transported by streams, rivers etc
3) these form sedimentry rock
4) weathering and erosion of these rocks releases phosphate ions
5) plants uptake and incorporate them into their biomass
6) sapriobants decompose plants returning phosphate ions back into the soil.

Question 10

what is the role of mycorrhizae

Answer 10

mycorrhizae are symbiotic relationships that form betwen fungi and plants.
the fungi colonise the root system of a host plant, increasing the water and inorganic ion.
the plant provides the fungus with amino acids and carbohydrates formed from photosynthesi.
enables the plant to better resist draught and absorb inorganic ions more readily.

Question 11

what is the use of fertilisers

Answer 11

replace the nitrates and phospahtes lost by harvesting plants and removing livestock

Question 12

what are the two types of fertilisers

Answer 12

• organic = waste materials such as manure
• inorganic = manufactured powders or pellets produced in factories containing nitrogen, phosphorus and potassium

Question 13

what is leeching

Answer 13

inorganic fertilsers result in more ions applied to the soil than are actually taken up by the plants. This leads to leaching, the highly soluble ions dissolve in soil water and are washed from the soil into streams, rivers and lakes.

Question 14

what is eutrophication

Answer 14

1) excess soluble ions which washed away into lakes or rivers build up
2 )high concentration of ions causes rapid growth of algae
3) algae block light and less light penetrates the water
4) plants die as they cant photosynthesise
5) large increase in population of sapriobiants decompose dead plants
6) bacteria respire aerobically and reduce oxygen concentration of the water
7) oxygen levels decrease resulting in death of other aerobic organisms