nutrient cycle

Question 1

what are the 4 processes of the nitrogen cycle?

Answer 1

nitrogen fixation
ammonification
nitrification
denitrification

Question 2

why cant most organisms use the nitrogen as it comes from the atmosphere?

Answer 2

it is generally unreactive due to the triple bonds in the molecules

Question 3

what happens in nitrogen fixation?

Answer 3

atmospheric nitrogen gas is converted into nitrogen containing compounds like ammonia

Question 4

what are saprobionts?

Answer 4

a type of decomposer that externally digest their food and feed on the remains of dead plants/animals and their waste

Question 5

what is ammonification?

Answer 5

converting organic nitrogen compounds (like ammonia (NH4)) into ammonium (NH3)

Question 6

what is nitrification?

Answer 6

converting ammonium into nitrate ions

Question 7

what is required for nitrification?

Answer 7

oxygen

Question 8

what is denitrification?

Answer 8

when denitrifying bacteria reduce the nitrates in the soil to nitrogen gas

Question 9

what are mychorrhizae?

Answer 9

a type of fungi that can form a symbiotic relationship

Question 10

what is a symbiotic relationship?

Answer 10

a relationship where at least one species benefits

Question 11

describe the symbiotic relationship between mychorrhizae and a plant

Answer 11

fungi have hyphae that connect to the plant roots , they increase the surface area for ion+water uptake (benefit for the plant)
fungi obtain organic compounds (glucose) from the plant (benefit for the fungi)

Question 12

what do nitrogen fixing bacteria do?

Answer 12

convert nitrogen gas to ammonium ions

Question 13

what do saprobionts do?

Answer 13

convert organic material into ammonia/ammonium ions

Question 14

what do nitrifying bacteria do?

Answer 14

convert ammonium ions to nitrates

Question 15

what do denitrifying bacteria do?

Answer 15

convert nitrates in the soil to atmospheric gas

Question 16

what does the phosphorus cycle start with?

Answer 16

wind and rain eroding phosphate rich rocks

Question 17

what are the key steps of the biological part of the phosphorus cycle?

Answer 17

1/ rainfall - erodes rocks
2/ phosphates enter the soil
3/ plants - get their sources of phosphorus as phosphate ions from the soil
4/ consumption - primary and secondary consumers - phosphorus passed through the food chain
5/ phosphates become part of the organism in atp/rna/dna
6/ saprobionts - feed off the dead organisms/their waste
7/ saprobionts excrete their waste, releasing phosphate ions , some small sediment form larger rocks or are released to the soil/water

Question 18

what is leaching?

Answer 18

some phosphorous is washed away and end up in rivers or lakes
the phosphates become incorporated in sediment

Question 19

why are fertilisers used by farmers?

Answer 19

the amount of phosphates in the soil are quite low so it can be a limiting factor for plant growth

Question 20

what are the ethical issues of fertilisers?

Answer 20

artificial fertilisers are readily soluble so can quickly leach
natural fertilisers make leaching less likely as organic matter is decomposed first so the release is slower

Question 21

what can leaching lead to?

Answer 21

eutrophication

Question 22

what are the two main strategies that a farmer can use to increase efficiency?

Answer 22

1/ reducing the loss of energy to other organisms (eg pests) by the simplification of the food chain
2/ reducing the energy lost through the respiration of livestock

Question 23

how can farmers reduce the loss of energy to other organisms by the simplification of the food chain?

Answer 23

eliminate pests by the use of pesticides, as pests reduce the amount of energy available for a crop to grow

Question 24

what are the two types of inorganic pesticides?

Answer 24

herbicides
insecticides

Question 25

what do herbicides kill?

Answer 25

weeds that are pestswhat

Question 26

what do insecticides kill?

Answer 26

insects that are pests

Question 27

what are organic methods of pesticides?

Answer 27

introducing a predator
pathogenic bacteria/virus ( produce toxins )
parasites ( lay eggs on pests )

Question 28

how do farmers reduce the energy lost through the respiration of livestock?

Answer 28

intensive farming - reducing the energy lost by limiting space or increasing temperature

eg - intensive fishing uses cages to limit the space the fish have to move

Question 29

what are the ethical issues of intensive/battery farming?

Answer 29

ethical issues
lots of chemicals used to fight pathogens passed within the livestock

Question 30

what are the types of fertilisers and examples?

Answer 30

organic - manure
inorganic - npk fertilisers

Question 31

what is the nitrogen for in an NPK fertiliser?

Answer 31

plants need nitrate ions to make amino acids, protein and nucleic acidsw

Question 32

what is the phosphate for in NPK fertilisers?

Answer 32

the manufacture of ATP in a plant

Question 33

what is the potassium for in NPK fertilisers?

Answer 33

K+ ions are needed by the plant
they are used for the efficient functioning of certain enzymes for photosynthesis and respiration

Question 34

why does the crop yield decrease when the amount of fertiliser is too high?

Answer 34

the curve drops off due to root damage and this affects the osmotic withdrawal of water

Question 35

what causes algal bloom?

Answer 35

the mineral ions from excess fertiliser being leached from farmland to waterways, causing a rapid growth of algae

Question 36

how does algal bloom lead to eutrophication?

Answer 36

1/ algal bloom blocks sunlight so aquating plants below the water surface begin to die as they cant photosynthesise
2/ algae start to die when competition for nutrients becomes too intense
3/ saprobiotic bacteria feed on the dead organic matter and increase in number
4/ use up the dissolved oxygen in the water to respire aerobically
5/ amount of dissolved oxygen in the water decreases, so aquatic organisms like fish and insects may be unable to survive