A food chain is a _________________________
Strand of a foodweb
What is a biomass?
Reservoir of energy
How is energy transferred through food chains?
Through one trophic level to the next
What are the 2 kinds of food chains?
- Plant-driven 2. Ditritus-driven
What’s about the detritus food chain?
It is not about photosynthesis, it is the ecosystem’s stream that is supported by detritus
What’s determining a web of interaction?
It is based on who feeds who
What are the two reasons why food chains are usually short?
- Longer chains tend to be unstable
- Increasingly less energy reaches higher trophic levels when the chains are too long, there are more energy loss among the way (2nd law of thermodynamics)
Why does energy always dissipate as it moves from one trophic level to the next?
Not all energy consumed by an animal is retained, some is excreted and some is respired, energy balance equation : What goes in (i) = what goes out (o, output + d, dying + r, respired + e, excreted)
What is the amount of energy reaching each trophic level, depending on ?
1- the net primary production
2- the energy transfer efficiency
How do you find the energy transfer efficiency?
It is: consumption (at trophic level n)/production (at trophic level n-1)
How would you explain the net primary production?
It is the amount of primary producers - respiration: you know what’s available in the transfer and what is lost
What do biomass tend to do up the food chain?
It tends to decrease, it is consumed rapidly and replaced rapidly, it = not production, the pyramid can be inverted (when consumed and replaced rapidly), a smaller box can support a bigger one
What’s production?
The creation of new organic matter, it is the change in biomass per unit time and the change in energy per unit area per unit time
True or false: energy pyramid can be inverted?
False, energy pyramid can NEVER be inverted
What paradox is this: How can the energetic demands of consumers exceed available production, there’s not enough energy for the demand
It is Allen’s paradox
The amount of CO2 fixed by the plant through photosynthesis is
The gross primary production (GPP)
The amount of CO2 lost through metabolic activity is
Respiration
The rate of accumulation of plant biomass or what is available from the next level of food chain (food chain fuel) is
Net primary production (NPP) calculated : NPP=GPP-R
How is the net ecosystem production calculated?
NEP= GPP - (Respiration by plants - Respiration by heterotrophs)
What does it mean when NEP > 0?
That the ecosystem is a sink for C
What does it mean when NEP < 0?
That the ecosystem is a source for C
What does it mean when NEP = 0?
C is transferred to the ecosystem and the atmosphere at equal rates
What are the effects of deforestation on the carbon cycling?
- We remove a CO2 sink when we remove a forest
- If we burn the forests, the stored carbon is released as carbon dioxide
- It increases the rate of decomposition of soil organic matter (which release more CO2)
- The land use change will replace a carbon sink by a carbon source
