Energy and ecosytems 3.5.3 (Energy transfers in and between organisms 3.5) Flashcards
(18 cards)
Describe how biomass is formed in plants
• During photosynthesis , plants make organic compounds from atmospheric CO2
• Most sugars synthesised are used by the plant as respiratory substrates
• Rest used to make other groups of biological molecules
how can biomass be measured
Mass or carbon or dry mass of tissue per given area
Describe how dry mass of tissue can be measured
1) sample dried in an oven e.g. at 100 degrees
2) sample weighed and reheated at regular intervals
3) until mass remains constant
Explain why dry mass is more representative than fresh ( wet ) mass
Water volume in wet samples will very but will not affect dry mass
Describe how the chemical energy stored in dry biomass can be estimated
Using calorimetry :
1) known mass of dry biomass is fully combusted
2) heat energy released heats a known volume of water
3) increase in temperature of water is used to calculate chemical energy of biomass
explain how features of a calorimeter enable valid measurement of heat energy released
• stirrer => evenly distributes heat energy
• Air / insulation => reduces heat loss and gain to and from surroundings
• water => has a high specific heat capacity
Explain the importance of NPP in ecosystems
• NPP is available for plant growth and reproduction
• NPP is also available to other trophic levels in the ecosystem, such as herbivores and decomposers
What is primary or secondary productivity
The rate of primary or secondary production
State the formula for efficiency of energy transfer
Energy or biomass available after transfer / Energy or biomass available before transfer x100
Explain why energy transfer between trophic levels is inefficient
• Heat energy is lost via respiration
• Energy lost via parts of an organism that aren’t eaten
• Energy lost via food not digested => lost as faeces
• Energy lost via excretion
Explain how crop farming practices increase energy transfer efficiency
- Simplifying food webs to reduce energy / biomass losses to non human food chains e.g.
• Herbicides kill weeds => less competition
• Pesticides kill insects => reduce loss of biomass from crops
• Fungicides reduce fungal infections => more energy to create biomass - Fertilisers to prevent poor growth due to lack of nutrients
Explain how livestock farming practices increase energy transfer efficiency
• Reducing respiratory losses within a human food chain :
- Restrict movement and keep warm => less energy lost as heat from respiration
- Slaughter animal while still growing / young , when most of their energy is used for growth
- Treated with antibiotics => prevent loss of energy due to pathogens
- Selective breeding to produce breeds with higher growth rates
What is net primary production (NPP)
Chemical energy store in plant biomass after respiratory losses to environment taken into account
state the formula for NPP
NPP = GPP- R
( R = respiratory losses to environment )
State the units used for primary or secondary productivity
kJha-1year-1
what is gross primary production (GPP)
- chemical energy store in plant biomass , in a given area of volume in a given time
- total energy transferred into chemical energy from light energy during photosynthesis
Explain why these units for primary and secondary productivity are used
- per unit area => takes into account that different environments vary in size
• standardising results to enable comparisons between environments - Per year ==> takes into account effect of seasonal variation
• more representative and enables comparison between environments
State the formula for net production of consumers (N)
N = I -(F + R )
I = chemical energy store in ingested food
F = the chemical energy lost to the environment in faeces and urine
