nutrient cycles

Question 1

why is phosphorus important for plant growth

Answer 1

creation of nucleotides for DNA - required for protein production / cell division

make phospholipids - required for membrane integrity in cells

Question 2

outline two important roles of nitrogen for all organisms

Answer 2

make NADP / RuBP - required for fixation of Co2

manufacture of proteins / amino acids - creation of nitrogenous bases for DNA, RNA

Question 3

two processes in which plants directly receive nitrogen

Answer 3

absorption - absorbing nitrate ions through the soil via active transport

nitrogen fixation - through conversion of nitrogen into nitrogen containing compounds via nitrogen fixing bacteria

Question 4

nitrogen fixation

Answer 4

nitrogen converted into ammonia

which allows nitrogen uptake into organisms on all trophic levels

for DNA / protein synthesis

Question 5

mycorrhizae

Answer 5

associations between roots of particular plants and fungi

mutualistic / symbiotic relationship

plant benefits form an improved water and inorganic ion intake

fungi receive sugars and amino acids in return

Question 6

saprobionts - phosphorus

Answer 6

plants and animals which once held phosphate are broken down by saprobionts

saprobionts carry out extracellular digestion of plants and animal waste

this releases phosphate ions which end up in sediment

rocks undergo weathering - re-releasing phosphate allowing the cycle to continue

Question 7

explain the different ways microbial decomposers and detritivores obtain their nutrients

Answer 7

decomposers secrete enzymes on organic matter - break down larger pieces of dead organic matter

detritivores invest food - providing more surface area for microbial activity

Question 8

explain two ways how the presence of detritivores may cause the activity of microbial decomposers to increase

Answer 8

add products of excretion - more nutrients

aeration by tunnelling increases oxygen content for respiration of microorganisms