3.5.3 energy and ecosystems Flashcards
how do you use a calorimeter?
- an oxygen supply is connected to the apparatus
- a copper spiral is attached to the top of the combustion chamber
- the water jacket contains a large volume of water. the total rise of temperature when the heather is burned is only small
what is the equation for the net production of consumers?
N = I - ( F + R )
I = chemical energy stored in digested food
F = chemical energy lost to the environment in faeces + urine
R = respiratory losses
how is energy lost at the primary and secondary consumer trophic levels?
- some of organism is not eaten
- some part are eaten but cannot be digested so lost in faeces
- some is lost in excretory materials such as urine
- some energy lost in heat from respiration
why can not all energy be passed on?
10% of food stored in plants used by primary consumers for growth
secondary and tertairy consumers consumes transfer about 20% of energy availaible
describe NPP + GPP
NPP: rate at which plants store energy is called the net primary production
net primary production = gross primary production - respiratory losses
NPP = GPP - R
what is net primary production (npp)?
chemical energy store in plant biomass after respiratory losses to the environment has been taken into account
availiable for plant growth and reproduction
npp available to to other trophic levels such as herbivores + decomposers
what is gross primary production (gpp)?
gpp = chemical energy store in plant biomass in a given area or volume in a given time
plants use 20-50% of this energy in respiration
plants leave little energy stored
what are the uses of light for photosynthesis?
sugars synthesised by plants for respiratory substrates
rest are biological molecules, form biomass
why do producers only absorb some of the suns energy?
90% of suns energy is reflected back into space
not all wavelengths can be absorbed and used for photosynthesis
light may not fall on a chlorophyll molecule
limiting factors (such as low carbon dioxide levels) may limit the rate of photosynthesis
energy source and energy transfer
main energy source = sunlight (conserved as chemical energy in plants)
plants use this sun light in making organic compounds from carbon dioxide and water
organic compounds contain sugars
remainder is used to make biological compounds which forms biomass of plants
5 trophic levels in a food web… why?
energy is transferred as it moves up through a food chain
only a small amount of chemical potential energy is transferred from one trophic level to the next (20%)
cannot be a higher level than trophic level 5 as there would be not enough energy to sustain a breeding population of organisms
important terms:
herbivore = an animal that eats plants (producers) and is therefore a primary consumer
carnivore = an animal that eats animals and may therefore be a secondary or a tertiary consumer
omnivore = an animal that eats both plants and animals and is therefore a primary consumer and also a secondary or a tertiary consumer
how is biomass measured?
sample of grass such as 10cm3
collect all parts including roots
clean off soil
weigh sample and place in oven at 100c for several hours
weigh again, repeat to ensure mass remains same so all water has evaporated
repeat with other samples and collect mean dry biomass per m2 , then calculate mean total biomass in meadow
check diagram on notes
what is an agricultural ecosystem?
made up of largely domensticed animals
plants used to produce food for mankind
only a tiny proportion of energy from the sun is available to humans
channel energy flowing through a food web into the human food chain and away from other food chains
what is productivity?
productivity = rate at which something is produced
rate at which plants assimilate chemical energy is called productivity
measured in kj m-2 year-1
20% of this is used by the plant for respiration, rest is NPP
