13.2 Energy transfer and productivity

Question 1

How much of the suns energy available to them is transferred into organic matter

Answer 1

1-3%

Question 2

Why is most of the suns energy not converted to organic material

Answer 2

1. Over 90% of the suns energy is reflected back into space by clouds and dust or absorbed by the atmosphere
2. Not all wavelengths of light can be absorbed and used for photosynthesis
3. Light may not fall on a chlorophyll molecule
4. A factor, like co2, may limit photosynthesis

Question 3

What is the gross primary production (GPP)

Answer 3

The total quantity of the chemical energy store in plant biomass, in a given area, in a given time

Question 4

What is net primary production (NPP)

Answer 4

GPP - respiratory energy losses

Question 5

How much of NPP in plants can be used by primary consumers for grwoth

Answer 5

Less than 10%

Question 6

Why is the percentage of energy transferred at each stage so low

Answer 6

1. Some of the organism isnt consumed
2. Some parts are consumed but not digested so are lost in faeces
3. Some of the energy is lost in excretory materials, like urine
4. Some energy losses occur as heat from respiration and lost to the environment. These losses are high in mammals and birds due to temperature regulation

Question 7

What does the inefficiency of energy transfer between trophic levels explain

Answer 7

1. Why most food chains only have four or five trophic levels because insufficient energy is available to support more than these
2. Why the biomass is less at higher trophic levels
3. Why the total amount of energy available is less at each level as one moves up a food chain