5.4 nutrient cycles

Question 1

saprobionts role in recycling chem elements

Answer 1

decompose organic compounds eg protein dna
by secreting enzymes for extracellular digestion
absorb soluble needed nutrients and release mineral ions

Question 2

mycorrhizae

Answer 2

symbiotic association between fungi and plant roots
fungi act as an extension of plant roots to increase the surface area of the root system
to increase the uptake of water and inorganic ions
in return fungi receive organic compounds

Question 3

examples of biological molecules containing nitrogen

Answer 3

amino acids proteins dna rna ATP

Question 4

what is the role of bacteria in nitrogen fixation

Answer 4

nitrogen gas converted to ammonia which is converted to ammonium ions by nitrogen fixing bacteria

Question 5

role of bacteria in ammonifcation

Answer 5

nitrogen containing compounds from dead organisms broken down
converted to ammonia which form ammonium ions in soil
by saprobionts which secrete enzymes for extracellular digestion

Question 6

bacteria in nitrification

Answer 6

Ammonium ions in soil converted to nitrites
then nitrates
via two step oxidation for uptake by plant root hair cells by active transport
by nitrifying bacteria in aerobic conditions

Question 7

bacteria in dentrification

Answer 7

nitrates in soil converted to nitrogen gas
by gentrifying bacteria in anaerobic conditions

Question 8

ploughing soil increases fertility???

Answer 8

more ammonium converted to nitrite
then nitrate so more nitrification
less dentrification

Question 9

examples of biological molecules containing phosphate

Answer 9

phospholipids
dna rna
atp
nada
rubp

Question 10

describe phosphorus cycle

Answer 10

phosphate ions in rocks released by erosion
taken up by producers plants algae
incorporated into their biomass
rate of absorption increased by mycorrhizae
phosphate ions transferred through the food chain
some phosphate ions lost from animals as waste products
saprobionts decompose organic compounds releasing phosphate ions

Question 11

why are fertilisers used

Answer 11

replace nitrates or phosphates lost when plants harvested and livestock removed
improves efficiency of energy transfer increasing productivity and yield

Question 12

natural fertiliser

Answer 12

organic like manure compost and sewage
ions released during decomposition by saprobionts

Question 13

artificial fertilsier

Answer 13

contain inorganic compounds of nitrogen phosphorus and potassium

Question 14

envi issues with fertilisers

Answer 14

phosphates and nitrates dissolve into water
leads to leaching of nutrients into lakes rivers and oceans
leading to eutrophication
rapid growth of algae in pond so light blocked
so submerged plants die as cant photosynthesise
so saprobionts decompose dead plant matters using oxygen in aerobic respiration
so less oxygen for fish to aerobically respire leads to their death

Question 15

advantage of natural fertiliser over artifical

Answer 15

less water soluble so less leaching so less likely eutrophication
Organic molecules require breaking down by saprobionts → slow release of nitrate / phosphates