Energy and Ecosystems Flashcards
what are producers?
Plants and algae make there own food through photosynthesis. this means that they can synthesise glucose from water and carbon dioxide. Light energy is needed to make this reaction happen. The light energy is ultimately stored in the bonds of the glucose molecules as chemical potential energy
what is biomass?
Biomass is all the biological molecules made by the plant and are not immediately used for respiration. This will include cellulose, starch, proteins, lipids etc.
It represents the growth of the plant
how is biomass measured?
- as mass of carbon
- as dry mass (kgm^-2yr^-1)
- as an energy value (kJm^-2yr^-1)
what is the process of estimating dry mass?
1) heat in a low temperature oven to evaporate water in the tissues
2) until there is no further change in mass
3) calculate dry biomass (kilograms per metre squared per year)
4) carbon content estimated as 50% of dry mass
why use dry biomass rather then wet biomass?
water in not made by the plant in photosynthesis so is not biomass
what is the method for finding amount of chemical potential energy in biological molecules?
- dried biomass from a known area is placed in a calorimeter
- the dry biomass is then burnt (combustion)
- the energy released is used to heat water
- the change in water temperature is used to calculatr the ernergy released
- energy per square metre per year is calculated
what is gross primary production (GPP)?
the total amount of light energy captured in photosynthesis and stored in molecukes as chemical potential energy
what is respiration (R) ?
the amount of energy lost from the plant in respiration. This returns to the environment as waste heat
what is net primary production (NPP)?
this is the remaining amount of chemical potential energy stored in the biomass of the plant. This can be used for growth and respiration
what is the equation for
i) NPP
ii) GPP
i) NPP = GPP - R
ii) GPP = NPP + R
What is untrapped light energy?
Why does it happen?
(may not be on spec)
only about 1-5% of light energy falling on a leaf is captured in photosynthesis, the rest in untrapped
this is for several reasons:
- some light is refelcted from the surface of the leaf
- only certain wavelengthsof light are absorbed by chlorophyll
light may not strike a chloroplast/chrolophyll and pass staright through the leaf
- some other factor may be limiting eg carbon dioxide, meaning the light energy cant be used
- some may be absorbed but transferred into thermal energy i.e. it simply warms the plant
why is NPP important?
- can eb used to make new cells and tissues for growth and reproduction eg seeds
- part of the light energy captured by the plant that can be transferred to consumers
what happens to NPP with producers?
- consumed by animals
- lost to decomposers eg fallen leaves
what happens to NPP in consumers?
- consumers get their energy by ingesting biomass
- some of this is used for respiration by the consumer and is lost eventually as heat to the atmosphere
- some is indigestible so is lost as faeces and some is excreted as urine
- the rest is used to make consumer biomass ie growth
- only the energy in the net production can be passed on to the next consumer
what is the net production equation?
N = I - (F+R)
N= net production
I= chemical energy in ingested food
F= chemical energy lost to the environment as faeces and urine
R= respiratory losses
why do the layers become narrower as food moves up through the trophic levels?
energy is lost to decomposers as faeces, urine and uneaten material + energy is lost due to respiration by the consumer
how do you calculate the % efficiency of energy transfer?
