5.3: Energy & Ecosystems Flashcards
What happens to most of the sugars synthesised by plants
used as a respiratory substrate
What is biomass
The total mass of organic material
What units are used to measure biomass
dry mass of tissue per unit area
Describe a method you could use to find the dry mass of a plant
Burn a sample (oven), heat and reweigh until the mass is constant
Why might it be useful to measure the dry mass of a sample rather than the fresh mass
fresh mass includes water content which fluctuates a lot
Name the technique used to estimate the chemical energy stored in dry biomass
calorimetry
What is GPP
The total quantity of chemical energy store in plant biomass in a given area/volume at a given time
What is NPP
Net primary production
GPP - energy lost in respiration
What is the equation linking GPP and NPP
NPP = GPP - R
What is net primary production available for
the next trophic level
Write the equation for calculating the net production of consumers and state what each variable is
N = I - (F+R)
where N = net production of consumers
I = chemical energy store of ingested food
F = energy lost in faeces and urine
R = energy lost in respiration
Who passes on more energy out of mammals and invertebrates and why?
Invertebrates as they are not endotherms and so they don’t have as high of a rate of respiration and so less energy is lost as heat and so more chemical energy is put down as biomass
Who is more efficient at energy conversion out of carnivores and herbivores and why?
Carnivores as they can digest and absorb protein and convert to glucose whereas Herbivores take in cellulose which is indigestible
What is meant by photosynthetic efficiency
How well a plant is able to capture light energy and convert it into chemical energy
Give four reasons as to why plants may have low photosynthetic efficiency
1 - light is reflected (Waxy, shiny surface of leaves)
2 - Light is not absorbed as it is the wrong wavelength (green light)
3 - Light is transmitted (doesn’t strike chlorophyll molecules
4 - Low concentration of carbon dioxide limits rate of photosynthesis -> limits absorption of light energy
Name the 2 ways biomass can be measured
1- mass of carbon in a given area/volume
2- dry mass of tissue in a given area/volume
What is primary and secondary productivity and describe how they are measured
the rate of primary or secondary production
measure the biomass in a given area/volume at a given time
what do the arrows in a food web diagram represent
the direction of energy transfer
what is the general term used for fungi and bacteria that break down DOM
saprobionts
Define ‘trophic level’
the feeding position organisms occupy in a food web
