energy and ecosystems

Question 1

how is biomass formed in plants

Answer 1

during photosynthesis plants make organic compounds from atmospheric or aquatic co2
most sugars synthesised used by plant as respiratory substrates
rest used to make other groups of biological compounds to form biomass

Question 2

how can biomass be measured

Answer 2

mass of carbon
dry mass of tissue per given area

Question 3

how can dry mass of tissue be measured

Answer 3

sample dried in oven at 100 to avoid combustion
sample regweighed and heated at regular intervals until mass remains constant

Question 4

why is dry mass more representative than fresh wet mass

Answer 4

water content in samples will vary but won’t affect dry mass

Question 5

how can chemical energy stored in biomass be estimated

Answer 5

colorimeter
known mass of dry biomass fully combusted
heat energy released heats know volume of water
increase in temp of water used to calculate chemical energy of biomass

Question 6

features of calorimeter enabling valid measurement of heat energy released

Answer 6

stirrer to evenly distribute heat energy
insulation to reduce heat loss and gains from surroundings
water - has high specific heat capacity

Question 7

GPP

Answer 7

CE store in plant biomass in given area volume and time
total energy transferred into chemical energy from light energy during photosynthesis

Question 8

NPP

Answer 8

CE store in plant biomass after respiratory losses to envi taken into account

Question 9

importance of NPP in ecosystem

Answer 9

NPP - available for plant growth and reproduction
available to other trophic levels in ecosystem like herbivore and decomposers

Question 10

units for primary and secondary productivity and why

Answer 10

KJha-1year-1
per unit area takes into account Dif envi vary in size standardises result enabling comparison
per year - seasonal variation on biomass
Representative and enables comparison between environments

Question 11

why is most light falling on producers not used in photosynthesis

Answer 11

light reflected - wrong wavelength
light misses chlorphyll
co2 conc or temp is a limiting factor

Question 12

net production of consumers formula

Answer 12

n= I- (f+r)
I is the CE store in ingested food
F CE lost to envi in faeces or urine

Question 13

efficiency of energy transfer formula

Answer 13

energy or biomass after transfer divided by energy or biomass before trnasfer
times a 100 if percentage

Question 14

why is energy transfer between trophic levels inefficient

Answer 14

heat energy lost via respiration
energy lost via parts of organisms not eaten like bonds
energy lost via food not digested lot as faeces
energy lost via excretion like urea in urien

Question 15

crop farming practice to increase efficiency of energy transfer

Answer 15

simplify food webs to reduce energy losses to non human food chains
herbicides kill weeds less comp so more energy to create biomass
pesticides kill insects reducing loss of biomass from croops
fungicides reduce fungal infections so more energy to create biomass
Fertilisers to prevent poor growth due to lacking nutrients

Question 16

livestock farming practices increase efficiency of energy transfer

Answer 16

reduce resp losses within human food chain
restrict movement keep warm less energy lost as heat from respiration
slaughter animals while still growing and young when most energy is used for growth
treat with antibiotics prevent energy loss due to pathogens
selective breeding produce breeds with higher growth rates