Biol4 - Energy Transfer

Question 0

Explain why all the light energy reaching the producers cannot be passed to the next trophic level (7)

Answer 0

~not all wavelengths of light can be used in photosynthesis, green/yellow light is reflected
~some light misses chlorophyll
~some energy dissipated as heat in the reactions of photosynthesis
~some used as respiration by the plant
~some of the plant may not be eaten e.g. roots, bark
~some biomass is indigestable (e.g. Humans unable to digest cellulose)
~lost through excretion

Question 1

Energy Transfer overview? (3)

Answer 1

~to each trophic level energy is lost
~most energy given is the transfer from the sun to the primary consumer - plants
~At each level energy is lost through respiration, heat loss and excretion (i.e. Faeces and urine)

Question 2

Transfer of energy between trophic levels (7)

Answer 2

~some light energy is reflected/not of appropriate wavelength
~efficiency of photosynthesis in plants is low
~respiratory loss/excretion/faeces/not eaten
~loss as heat
~efficiency of transfer to consumers greater than transfer to producers
~efficiency lower in older animals/warm blooded animals
~efficiency lower in herbivores because plant material has low digestibility

Question 3

Why a food chain rarely consists of more than four trophic levels (5)

Answer 3

~energy losses at each trophic level
~in excretion/movement respiration
~energy is lost as heat
~so not all the energy level at each trophic level can be passed on
~there is too little left to sustain higher trophic levels

Question 4

Ways in whichintensive rearing of domestic livestock affects productivity by increasing the efficiency of energy conversion (5)

Answer 4

~slaughtered before maturity/ while young so more energy transferred to biomass
~fed on controlled diet so higher proportion of food absorbed/lower proportion lost in faeces
~movement restricted so less respiratory loss/energy used
~sheltered/heating so less heat loss
~genetically selected for high productivity

Question 5

Suggest an explanation why the efficiency of conversion for food to biomass is lower at 0°C than 20°C for pigs? (3)

Answer 5

~pigs will lose heat
~resulting from respiration
~more food used in respiration

Question 6

If organisms in an energy transfer test relating to temperature are allowed to eat as much as they want, how could this decrease the reliability of the investigation? (2)

Answer 6

~different growth rate/gain different biomass
~not due to independant variable temperature

Basically keep other variable the same other than one you are testing like to, this case temperature

Question 7

How can increase the yield/ productivity of crops in agricultural farming (7)

Answer 7

~addition of (nitrogenous) fertilisers
~(addition of/containing) nitrates in soil which crops use for forming proteins (and therefore growth)
~pesticides, destroy weeds so less/remove (interspecific) competition
~put under growth lamps, so light is not a limiting factors
~Irrigate the soil, so water is not a limiting factor on photosynthesis
~selective breeding
~aerating soil so nitrifying bacteria can work more efficiently (aerobically respire)

Question 8

Birds with feather mites use more energy to maintain body temp, have less energy available for other processes. suggest how feather mites could affect breeding of these birds (2)

Answer 8

~breeding less successful
~less energy for breeding/reproduction
even ~feathers in poor condition, less attractive to mates