B13 - Energy and ecosystems

Question 1

What is biomass?

Answer 1

The biomass of an organism is:
- The mass of living material of the organism or tissue
- The chemical energy that is stored within the organism or tissue

Question 2

How is biomass measured?

Answer 2

It can be measured in terms of the dry mass of an organism or tissue which is the mass of the organisms or tissues after all the water has been removed. Or the mass of carbon that an organism or tissue contains which can be measured through calorimetry which is used to estimate the chemical energy stored in dry biomass

Question 3

What is gross primary production?

Answer 3

Gross primary production (GPP) is the amount of chemical energy stored in carbohydrates within plants

Question 4

What is gross primary productivity?

Answer 4

Gross primary productivity (GPP) is the rate at which plants are able to store chemical energy via photosynthesis

Question 5

What is net primary production and how is it calculated?

Answer 5

Net primary production (NPP) refers to the amount of energy available to herbivores in the plant’s biomass after plant respiratory losses.

NPP = GPP (gross primary production) - R (respiratory losses)

Question 6

How is the net production for consumers calculated?

Answer 6

Net production for consumers = I - (F + R)

I is the chemical energy store in ingested food
F is the chemical energy lost to the environment in faeces and urine
R is the respiratory losses to the environment

Question 7

What farming practices can increase the efficiency of energy transfer in order to increase the total amount of energy available for human consumption?

Answer 7

• Reducing the energy lost by crops to other organisms (e.g. pest species that feed on crops)
• Reducing the energy lost by livestock (e.g. cattle) through respiration
• Chemical pesticides (Insecticides & herbicides)
• Biological agents (e.g., ladybugs, which eat aphids…)

Question 8

How can energy loss from respiration be reduced?

Answer 8

• They can be kept livestock in pens → movement is restricted → less energy lost through respiration
• Keep livestock indoors and in heated pens → reduces respiration rate needed to maintain a body temperature
• These practice ensure more chemical energy is stored as biomass and not lost to respiration which increases the net production. However there are ethical concerns