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5.3 energy and ecosystems - Coggle Diagram
5.3 energy and ecosystems
lesson 1: biomass production and energy transfer
photosynthesis and biomass production
in an ecosystem plants photosynthesise organic compounds from atmospheric and or aquatic carbon dioxide
most of these sugars synthesised by the plant are used as respiratory substrates
the rest are used to make other groups of biological molecules and these form the biomass of the plant
this biomass can be used by consumers as food
measuring biomass
can be measured in terms of mass of carbon pr dry mass of tissue per given area (of land/volume of soil/water)
the chemical energy store in dry biomass can be estimated using calorimetry
units --> KJ per units mass e.g KJKg^-1
biomass in producers (e.g plants)
gross primary production (GPP) is the chemical energy store in plant biomass in a given area or volume
net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
NPP = GPP - R
R = respiratory losses
this net primary production is also available for plant growth and and repodcution, it is also available to other trophic levels in the ecosystem such as herbivores and decomposers
biomass in consumers (e.g animals)
calculated as N = I - (F + R)
N = production of consumers
I = chemical energy store in ingested food
F = chemical energy lost to environment in faeces and urine
R = respiratory losses to the envrionment
rate of production (productivity)
primary and secondary productivity is the rate of primary and secondary production, respectivley
measured as biomass in a given area in a given time e.g KJha^-1year^-1
primary productivity = primary rate of production (biomass production in producers)
secondary productivity = rate of secondary production (biomass production in consumers)
by measuring productivity in energy transferred per unit/volume per unit time we can compare the different ecosystems of different sizes and over different time periods
calorimetry (bomb calorimetry)
sample of dry material is weighed and then is burnt in pure oxygen within a sealed chamber called a bomb
the bomb is surrounded by a water bath and the heat of combustion causes a small temperature rise in the water
as we know how much heat energy (specific heat capacity) is required to raise the temp of 1kg of water by 1 degree we can calculate the energy released from the burnt biomass (if we know the volume of water and how much the temperature increased by)
what Is the point of the lid/insulating jacket and the stirrir
the lid/insulating jacket prevents unwanted heat/energy loss to the environment and the stirrer ensures that heat is evenly distributed throughout the water
lesson 2: energy losses from food chains
why does not all the energy in sunlight that falls on a plan end up as a chemical energy store from photosynthesis?
not all the light energy is absorbed by the chlorophyll because it is not the right wavelength so some of the light is refelcted
photosynthesis is not 100% effectient - some will be lost to atmosphere as heat
not all the light absorbed as not all light will hit the chorophyll
why are not all the sugars made by the plant available to the consumer that eats the plant?
many of them/majority of them are used in respiration (used as respiratory substrates)
why does not all the energy in a consumers food end up as stored in its biomass?
it is used as respiratory substrates and is lost through excretory material (faeces and urine)
two farming practices that reduce energy loss from human food chains and increase secondary productivity/efficiency
redcued movement - reduced respiratory losses
warm environment - reduced respiratory losses
two farming practices that reduces energy losses to 'non-human food chains'
herbicides kill weeds- reduce competition for light
herbicides kill pests - reduce competition of crops by pests