Energy and ecoystems

Question 1

define autotroph and state the two

Answer 1

• producers
• photoautotrophs use light energy to synthesis their own food
• chemoautotrophs use inorganic molecules

Question 2

explain how a plant forms its biomass

Answer 2

Most of the sugars synthesised by plants are used by the plant as respiratory substrates.
The rest are used to make other groups of biological molecules. These biological molecules form the biomass of the plants.

Question 3

define heterotroph

Answer 3

• cannot synthesise their own energy
• must obtain it from other heterotrophs or autotrophs
• consumers

Question 4

how can biomass be measured

Answer 4

• mass of carbon

- dry mass of tissue per given area

Question 5

Describe how to measure the dry mass of tissue per given area, and why it is used instead of wet mass.

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Answer 5

• sample of organism dried in oven set at a temperature
• sample reweighed at regular intervals
• mass remains consistent= all of water removed
• mass of carbon = 50% of dry mass

Question 6

why is dry mass used instead of wet mass

Answer 6

dry mass more representative

water sample varies

Question 7

describe how to estimate the chemical energy stored in the dry mass

Answer 7

• calorimetry
• sample burnt
• energy released used to heat known volume of water
• change in temp of water used to calculate chemical energy

Question 8

explain GPP

Answer 8

• chemical energy stored in plant biomass in a given area

Question 9

explain NPP

Answer 9

• GPP -R
• chemical energy stored in plant after respiratory losses
• plant growth + reproduction
• available to other trophic levels

Question 10

how to calculate net primary production of consumers

Answer 10

N= I - (F+R)

Question 11

units for rate of productivity

Answer 11

Kjm-1year-1

Question 12

why is energy transfer from the sun to producers inefficient

Answer 12

• wrong wavelength of light
• light strikes non-photosynthetic region
• light reflected
• lost as heat

Question 13

explain why energy transfer between trophic levels in inefficient

Answer 13

• respiratory lossses
• lost as heat
• not all ingested
• some food not digested

Question 14

how can crop farming practices increase energy transfer efficiency in crops

Answer 14

herbicides = more energy to create biomass
fungicides = more energy to create biomass
pesticides = more energy to create biomass
fertilisers

Question 15

explain how livestock farming practices can increase energy transfer efficiency in livestock

Answer 15

• restrict movement
• keep warm
• slaughter animals young when most of energy used for growth
• selective breeding
• antibiotics