Energy and ecosystems

Question 1

Where do plants synthesise their organic compounds from?

Answer 1

• atmospheric or aquatic carbon dioxide
• plants fix carbon during photosynthesis and transfer light energy to chemical energy
• The chemical energy is stored in C-C and C-H bonds

Question 2

What are organic compounds used for?

Answer 2

• most are used for respiratory substances and others are converted to the biomasss of a plant

Question 3

What is a trophic level?

Answer 3

• A stage in a food chain

Question 4

What is biomass?

Answer 4

• The mass of carbon or dry mass at a given time per given area

Question 5

What is GPP

Answer 5

• Gross primary production
• This is the chemical store of energy in the living biomass of a producer in a given area or volume

Question 6

What is NPP

Answer 6

• Net primary production
• The chemical energy store in a plants biomass after respiratory losses having been taken into account
• This is avaliable for plant growth and reproduction, and also other trophic levels

Question 7

How do you calculate NPP?

Answer 7

NPP = GPP - R

Question 8

Why is only a bit of NPP avaliable to consumers?

Answer 8

• some of the organism is not consumed
• some parts are not consumed
• some lost in excretion
• energy loss in respiration and to environment

Question 9

How do you calculate the net production of consumers

Answer 9

N = I - (F+R)
N = net production
I = ingested
F = faeces and urine
R = respiration

Question 10

What is primary and secondary production and how do we measure it?

Answer 10

• the rate of secondary and primary production
• secondary productivity decreases at each trophic level, therefore a gievn area of land supports few predators
• KJ ha-1 year-1