energy flow

Question 1

what can productivity mean?

Answer 1

• the creation of new organic matter
• change in biomass per unit time
• change in energy per unit area per unit time

Question 2

why are food chains usually pretty short?

Answer 2

• longer chains tend to be unstable
• increasingly less energy reaches higher trophic levels

Question 3

why does energy dissipate as it moves from one trophic level to the next?

Answer 3

• some energy is excreted
• some energy is respired as waste heat
• not all the available food is consumed

Question 4

what is secondary production?

Answer 4

the rate of transformation (through consumption) of one’s food into your own biomass

Question 5

what is production efficiency?

Answer 5

fraction of energy stored in food that is used for secondary production

Question 6

why do birds and mammals have a production efficiency of 1-3%?

Answer 6

because they spend all their food energy to heat themselves

Question 7

what does the amount of energy reaching every level depend on?

Answer 7

• net primary production
• energy transfer efficiency

Question 8

what is the equation of energy transfer efficiency?

Answer 8

energy transfer efficiency = consumption (at trophic level n)/ production (at trophic level n-1)

Question 9

how can consumers biomass be larger than producer biomass?

Answer 9

when biomass of producers is consumed rapidly and replaced rapidly (common in marine food webs because phytoplankton is very easy to eat)

Question 10

What is Allen’s Paradox?

Answer 10

• how can the energetic demands of consumers exceed available production?
  -> Allen only measured the prey that was present at the time of sampling. The population reproduced many times during the year
  -> Allen is only considering the marine ecosystem, not the terrestrial ecosystem that could be bringing in food for fish to eat

Question 11

what is the gross primary production (GPP)?

Answer 11

• the amount of CO2 fixed by the plant through photosynthesis
• rate that the plant is taking in energy and turning it into glucose

Question 12

what is respiration?

Answer 12

the amount of CO2 lost through metabolic activity

Question 13

what is net primary production (NPP)?

Answer 13

• the net amount of primary production after the cost of plant respiration (NPP=GPP-Rp)
• the rate of accumulation of plant biomass
• what energy is available consumers to eat

Question 14

what is the equation for net ecosystem production?

Answer 14

NEP = GPP- (Rp+Rh+Rc+Rd)
or
NEP= NPP- Rhet

Question 15

what is net ecosystem production?

Answer 15

net carbon storage in the ecosystem
- > is a sink is NEP > 0, is a source is NEP < 0

Question 16

what is the equation for residence time of energy?

Answer 16

Rt= energy in biomass/NPP

Question 17

what is disturbance of an ecosystem?

Answer 17

any discrete removal of biomass
- ecosystems are used to their natural disturbance regime (mix of large infrequent events and small frequent events)

Question 18

what are the consequences of a fire in a deciduous forest?

Answer 18

• loss of principal habitat structure
• loss of understory diversity
• release of stored nutrients
• conversion of forest to grassland