3.5.3 - ENERGY + ECOSYSTEMS

Question 1

freshwater marshes have one of the highest rates of gross primary production (GPP) and net primary production (NPP) of all ecosystems.

carbon use efficiency (CUE) is the ratio of NPP:GPP. freshwater marshes have a high CUE.

use your knowledge of NPP to explain why freshwater marshes have high CUE and the advantage of this (2)

Answer 1

1. low respiration (less energy lost in respiration)
2. more growth/biomass

Question 2

suggest one reason for conserving woodlands (1)

Answer 2

1. conserving habitats
2. protecting endangered species
3. reduces greenhouse effect/global warming

Question 3

explain why a increase in shoot biomass can be taken as a measurement of net primary productivity (2)

Answer 3

1. represents dry mass/mass of carbon
2. represents GPP - R

Question 4

farming cattle for humans to eat is less efficient than farming crops because of energy transfer.

explain why (2)

Answer 4

1. energy lost between trophic levels
2. energy lost via respiration/excretion/faeces

Question 5

give three reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem (3)

Answer 5

1. not all eaten OR food not digested
2. heat loss from respiration
3. excretion