intro to energy transfers

give the eqn for the efficiency of biomass transfers between trophic levels by %:

% efficiency = (energy after transfer/energy before transfer) x 100

describe and explain how leaves are adapted for photosynthesis:

• large SA - max light absorption

• thin - reduces diffusion distance for gases

• lots of chloroplasts in palisade cells - captures light efficiently

• stomata - allows gas exchange

• air spaces in spongy mesophyll - facilitates gas diffusion

• vascular bundles (xylem/phloem) - transports water and sugars

• transparent cuticle/epidermis - allows light through and reduces water loss

• leaf arrangement - minimises overlapping to capture more light

what is biomass?

measure of mass of carbon/dry mass of tissue per given area

what substance do plants used to synthesise organic compounds?

atmospheric/aquatic CO₂

what are sugars used for in plants?

• most used as respiratory substrates

• rest used to make other biological molecules which form the plant’s biomass

what can a calorimeter be used for?

to estimate the energy store in dry biomass

give 4 aspects of the setup of a calorimeter and explain their roles:

• water - high known SHC so chemical energy can be calculated from temp change

• stirrer - distributes heat energy evenly

• thermometer - measures temp changes

• insulated jacket - reduces heat loss/gain

what is gross primary production (GPP)?

total chemical energy store or biomass produced by plants/producers through photosynthesis in a given area/volume

what is net primary production (NPP)?

energy/biomass that remains after plants have used some for respiration

what is the eqn for net primary production?

NPP = GPP - R (where R = respiratory losses)

what is the net primary production available for?

• plant growth

• reproduction

• other trophic level consumers e.g. herbivores and decomposers

what are the units for biomass measurement?

kg / m²

which process increases gross primary production?

photosynthesis

what is the net production of consumers?

the energy/biomass available to consumers after accounting for energy losses due to respiration, excretion and egestion

give the eqn for the net production of consumers:

N = I - (F + R), where:

• I = chemical energy store in ingested food

• F = chemical energy lost to environment in faeces and urine

• R = respiratory losses to the environment

how can the yield of a plant be measured? how would this occur in practice:

calculate dry mass of plant:

• heat at 100^oC as this would evaporate water and not burn the material

• weigh and heat until there is no further change in mass

what is productivity?

the measure of biomass in a given area in a given time e.g. kJ ha^-1 year^-1

name and define the two types of productivity:

• primary productivity - rate of primary production by green plants

• secondary productivity - rate of secondary production by consumers

give 3 reasons why not all the light energy falling on producers is used in photosynthesis:

• reflected

• misses chlorophyll

• wrong wavelength

give 3 reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem:

• heat loss from respiration

• faeces

• excretion i.e. urine

what is the difference between egestion and excretion?

• egestion involves the removal of undigested food from the body i.e. faeces

• excretion involves the removal of waste products e.g. CO₂, urea, sweat i.e. urine