Topic 5B - Energy Transfer And Nutrient Cycles Flashcards
How do plants use the sugars from photosynthesis
As respiratory substitutes
To synthesise other biological molecules
What is biomass
Total dry mass of tissue or mass of carbon measured over a given time in a specific area
How can the chemical energy store in dry biomass be estimated
Using calorimetery
What is Gross Primary Production
Total chemical energy in a plant biomass within a given volume or area
What is Net Primary Productivity
Total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels after respiratory losses
How can the net production of consumers be calculated
N = I - (F + R)
What do the letters N, I, F and R stand for
N - net production
I - chemical energy from ingested food
F - energy lost as faeces or urine
R - respiratory losses
Why does biomass decrease along the food chain
Energy lost in urine or faeces
Energy lost as heat to the surroundings
Some of the animal can’t be consumed
Respiratory losses
Outline some common farming practices used to increase the efficiency of energy transfer
Exclusion of predators - no energy lost to other organisms in the food web
Artificial heating - reduce energy lost to maintain constant body temperature
Restriction of movement
Feeding is controlled at the optimum
Why is the length of food chains limited
Energy is lost at each trophic level
So there is insufficient energy to support a higher trophic level
Name the general stages in the phosphoprous cycle
- Weathering
- Runoff
- Assimilation
- Decomposition
- Uplift
Why is the phosphorous cycle a slow process
Phosphorous has no gas phase, so there is no atmospheric cycle
Most phosphorous is stored as PO43- in rocks
What happens during weathering and runoff
Phosphate compounds from rocks leach into surface water and soil
Why is phosphorous important to living organisms
Plants convert inorganic phosphate into biological molecules e.g. DNA, ATP, NADP
Phosphorous is passed to consumers via feeding
What happens during uplift
Sedimentary layers from oceans are brought up to land over many years
How does mining affect the phosphorous cycle
Speeds up uplift
Name the 4 main stages in the nitrogen cycle
Nitrogen fixation
Ammonification
Nitrification
Denitrification
What happens during atmospheric fixation of nitrogen⚡️
High energy of lightning breaks N2 to form N
N reacts with oxygen to form NO2-
NO2- dissolves in water to form NO3-
What’s the role of bacteria in nitrogen fixation
Turns nitrogen into ammonia, which forms into ammonium ions in solutions that can be used by plants
Outline the role of bacteria in ammonification
Saprobiants feed on and decompose organic waste containing nitrogen
Nitrogen released and dissolved in water to in soil to form NH4+.
Outline the role of bacteria in nitrification
2 types of bacteria in nitrification
Nitrosomonas - changes ammonium ions into nitrites
Nitrobacter - changes nitrites into nitrates
Outline the role of bacteria in denitrification
Denitrifying bacteria convert nitrates in the soil back into nitrogen gas
Outline the role of mycorrhizae
Form a symbiotic relationship between plant and fungus which increases the surface area of root system - increases uptake of water and mineral ions.
Give 3 benefits of planting a different crop on the same field each year
Nitrogen fixing crops
Different crops have different pathogens
Different crops use different proportions of certain ions
Name the 2 types of fertiliser and the purpose for using fertiliser
Organic - decaying organic matter and animal waste
Inorganic - minerals from rocks
Increase the gross productivity for a higher yield
Outline 2 main environmental issues caused by the use of fertilisers
- Leaching: nitrates dissolve in rainwater and ‘runoff’ into water sources
- Eutrophication: water source becomes progressively enriched with minerals and nutrients.
What happens during eutrophication
- Mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers
- Large amounts of algae block light from reaching the plants below
- Eventually the plant dies as they cant photosynthesise enough.
- Bacteria feed on dead plant matter. Increased number of bacteria reduce the O2 concentration in the water by carrying out aerobic respiration.
- Fish and other animals die as there isn’t enough dissolved oxygen.
How can the risk of eutrophication be reduced
Sewage treatment marshes on farms
Pumping nutrient-enriched sediment out of water
Using phosphate-free detergent
