transfers in ecosystems

Question 1

How can you show change in the number of organisms throughout several trophic levels? [2]

Answer 1

pyramid of number
pyramid of biomass

Question 2

Biomass

Answer 2

Total mass of living material in a specific area at a given time (g/cm2/day)

Question 3

Dry Mass [2]

Answer 3

• Dry mass often measured due to varying water content but to measure will kill the organism
• Gives more accurate results

Question 4

How to measure dry mass [4]

Answer 4

• Take the mass of the sample.
• Heat for 1 hour at temperature that will evaporate water, but
  not burn the sample
• Take the mass of the sample
• Repeat heating and taking mass until mass remains constant

Question 5

Calorimetry [5]

Answer 5

• Take the mass of the sample
• Burn in pure oxygen in a sealed container surrounded by water
• Measure the increase in temperature
• Use specific heat capacity of water (amount of energy to increase 1kg of water by 1°C)
• Energy released can be measure (kJkg-1)

Question 6

What is the aim of intensive farming? + 4 examples

Answer 6

Intensive farming practices aim to reduce energy loss through food chains:
- restrict movement
- keep environment warm
- control feeding and type of food
- ensure predators are excluded

Question 7

What is the main source of energy in the food chain?

Answer 7

The Sun

Question 8

Energy Transfer from source to producers [4]

Answer 8

Plants only convert about 1% of Sun’s energy into organic matter due to:
- Reflection of light by atmosphere/leaf
- Not all wavelengths of light absorbed (e.g. green)
- Light may miss/pass through leaf
- Light might not fall on a chlorophyll molecule

Question 9

Energy Transfer between trophic levels [4]

Answer 9

Only about 10% of energy passes from one trophic level to the next due to:
- Not all the organism is eaten
- Some parts are not digested
- Excretion e.g. urine
- Energy losses due to heat from respiration

Question 10

Equation relating to energy stores in producers (plants)

Answer 10

NPP = GPP - R

NPP = Net primary production - chemical energy store available for growth and reproduction
GPP = Gross primary production - quantity of chemical energy stored in plant biomass but between 20 - 50% used in respiration (R)
R - respiration

Question 11

Equation relating to energy stores in consumers (animals)

Answer 11

N = I - (F+R)

N - net production of energy
I - chemical store of ingested food
F - energy lost in faeces and urine
R - energy lost in respiration

Question 12

Efficiency of energy transfer equation

Answer 12

Percentage efficiency = Energy available after the transfer / Energy available before the transfer x 100

Question 13

Primary Productivity

Answer 13

When producers make new organic matter

Question 14

Secondary Productivity

Answer 14

when consumers create matter

Question 15

Compare Primary and Secondary productivity

Answer 15

Primary
- Process of production is faster
- Productivity is higher

Secondary
- Process of production is slower
- Productivity is lower