paper 2: Energy and Ecosystems Flashcards
define an ecosystem
the community and the abiotic components of its environement
how does energy enter an ecosystem?
during photosynthesis, plants synthesise organic compounds e.g. glucose from carbon dioxide, using light energy.
give the names of the different biological molecules formed from the sugars produced in photosynthesis and their uses
- amino acid: protein synthesis
- lipids: phospholipid bilayer
- starch (alpha glucose): storage
- beta glucose: form cell wall
DNA/ RNA: replication
what is biomass
mass of organic molecules
what 2 ways can biomass be represented as
- dry biomass
- mass of carbon
units of biomass
kgm^-1year^-1
how would you measure the dry biomass of some grass
- heat grass in oven to evaporate the water
- measure mass of grass
- reheat and find mass again
- repeat until contant mass is rached
describe the process of calorimetry
- the sample of living tissue is burned in a combustion chamber
- the heat energy released is transfered to a known volume of water surrounding the tissue
- the increase temperature of the water is measured and used to calculate chemical energy in the biomass
give the equation for calculating the energy released from a sample when when it is burnt during calorimetry
energy released (J) = volume of water (cm^3) X temp increase (C) X specific heat capicity (4.2J)
why does simple calorimety apparatus cause an inaccurate measurement for the energy content of the combusted biomass
- heat energy can escape to the surroundings and does not enter the water
- heat energy can escape from the water due to the calorimeter not being insulated
explain why the features of the enclosed calorimeter which allow it to accurately measure the total heat energy released fromthe combusted biomass
- container is insulated preventing loss of heat by conduction
- the stirer ensures heat is evenly distributed
- water has a high specific heat capacity
what is GPP
the chemical energy store in plant biomass in a given area or volume in a given time
how does GPP diectly relate to rate of photsynthesis
the greater the rate of photosynthesis the greater the GPP as more organic molecules formed
what are the units for GPP
KJ m^-2 year^-1
only about 2% of the light energy is converted to bioass in photosynthesis. why so low?
- some light missed by chlorophyll
- some light reflected from leaf
- some light is wrong wavelength for photosynthesis
what is NPP
the chemical energy store in plant biomass after respiratory losses to the environment
give the equation for calculating NPP
NPP = GPP - R
r= respiratory losses
in what ways is energy lost between trophic levels
- energy lost as heat dur to repiration of rganic molecules
- some organic molecules are not absorbed and are lost in faeces
- some organic molecules are excreted in urine
- not all the organism is eaten e.g. bones
why is there less energy transferred between producer and primary consumer than primary and secondary consumer
- producers contain lots of cellulose which is difficult to digest so less is absorbed and more energy is lost in egestion/ faeces
what is N
the chemical energy stored as biomass in a consumer which is available to the next trophic level
give the equation for calculating N
N = I - (F + R)
I = energy ingested from food
F = energy lost in faeces/ urine
R = energy lost in repspiration
give the eqaution for calculating the % efficiency of energy transfer between trophic levels in a food chain
% energy transfer = net production fo trophic level
__________________________________
net production of previous trophic level
X100
explain how farmers can increase productivity in livestock
- movement can be restricted so less respiration occurs for muscle contraction
- animals can be kept indoors or in heated rooms so less respiration to maintain body temp
- animals fed high calorie controlled diet designed for maximum absorption and minimum faeces production
describe methods farmers can use to simplify food webs to increase productivity and explain how this increases energy transfer to humans
- use chemical control ( insecticide to kill pests directly or herbicide to kill weeds which removes interspecific competition)
- use biological control e.g. adding a predator of pests to ecosystem
