topic 5-energy and ecosystems

Question 1

What is biomass measured in terms of?

Answer 1

mass of carbon or dry mass of tissue per area.

Question 2

How can the chemical energy store in dry biomass be estimated?

Answer 2

Using calorimetry

Question 3

What is the definition of NPP

Answer 3

chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

Question 4

What is the definition for GPP

Answer 4

The chemical energy store in plant biomass in a given area or volume

Question 5

How is primary and secondary productivity measured ?

Answer 5

measured as biomass in a given area in a given time eg: KJ/ha/year ha=hector

Question 6

Give two ways that are used to increase efficiency of energy transfer

Answer 6

-simplifying food webs to reduce energy losses to non-human food chains.
-reducing respiratory losses within a human food chain

Question 7

Describe the process of calorimetry for measuring biomass

Answer 7

1. Dry sample, then burn sample
2. Heat a known volume of water
3. Measure the temp. change and calculate the chemical energy that was stored in dry biomass.

Question 8

Why is energy lost at each tropic level?

Answer 8

Some light energy is reflected or transmitted through leaves and not used up in photosynthesis. (not of the right wavelength)

some heat energy is lost to surroundings.

Energy loss in urine and faeces

Not all parts of the organism are eaten

Question 9

How are farming practices designed to increase energy transfer?

Answer 9

-Simplify food webs: reduce energy losses to non-human food chains by using pesticides.
-Reducing respiratory losses within human food chain: control conditions that livestock are kept in by eg: keeping them warm or restricting movement.