ecosystems

Question 1

how would you calculate biomass at each trophic level

Answer 1

biomass in each organism X N. of organisms in that level

Question 2

how would you calculate ecological efficiency

Answer 2

biomass available after transfer/ biomass available before transfer x100

Question 3

what is gross production

Answer 3

total solar energy converted into organic matter in plants

Question 4

what is net production

Answer 4

gross production- respiratory losses

Question 5

what are saprotrophs

Answer 5

obtain energy from dead organic material

digit food externally by secreting enzymes

Question 6

name the 4 features of the nitrogen cycles

Answer 6

nitrogen fixation
nitrification
denitrification
ammonification

Question 7

describe nitrogen fixation

Answer 7

nitrogen fixing bacteria contain enzyme nitrogenate
combines atmospheric nitrogen (N2) with hydrogen (H2)
produces ammonia(NH3)
this form of nitrogen can be absorbed by plants

Question 8

describe nitrification

Answer 8

ammonium compounds in soil converted into nitrogen-containg mol.s
oxidation reaction:
1- nitrifying bacteria oxidise ammonium compounds into nitrites
2- nitrobacteria oxidise nitrites into nitrates
nitrate ions are highly soluble

Question 9

describe denitrification

Answer 9

in absence of oxygen(e.g. waterlogged soils)
denitrifying bacteria convert nitrates back to nitrogen gas
bacteria use nitrates a source of energy for respiration- release nitrogen gas

Question 10

describe ammonification

Answer 10

decomposers convert nitrogen containing molecules in dead organisms and faeces into ammonium compounds