Energy And Ecosystem Flashcards
The grass in an ecosystem has a gross primary productivity of 20,000 kJ m² per year
it loses 8000 KJ m² per year as heat from respiration
calculate the net primary productivity of the grass in this ecosystem
NPP = GPP - R
20,000 - 8000
NPP = 12,000 kJ m² per year
The net primary productivity in an area of tundra is 2800 kJ metres squared per year
it loses 1250 kJ metres squared per year through respiration
calculate the gross primary product productivity of the area of tundra
GPP = NPP + R
2800 + 1250 = 4050 kJ m² per year
Net production in consumers
Equation
N = I - (F + R)
I is chemical energy thats ingested
F is chemical energy thats lost in faeces and urine
R is energy thas lost thru respiration
The rabbits in an ecosystem ingest 20,000 kJ m² per year of energy
But lose 12,000 kJ m² per year of it in faeces and urine
they lose a further 6000 kJ m² per year using energy for respiration
calculate the net productivity of the rabbits:
NPP = 20,000 - (12,000+6000)
Efficiency of energy transfer
% efficiency of energy transfer = net production of trophic level / net production of previous trophic level x 100
The rabbits receive 20,000 kJ m² per year and the net productivity is 2000 kJ m² squared per yer so the percentage efficiency of energy transfer is:
2000/20000 x 100
= 10%
The scientist wanted to measure the biomass of a crop of wheat
to do so he took a sample of the wheat and measured its dry mass
describe how the scientist could have measured the dry mass of the wheat
once the scientist has a sample of dry mass decides to burn it in a colorimeter what will the results from this procedure tell him about the wheat
Dry in a oven at low temperature
Check weight everyday until it becomes constant
Weight constant means all water has been removed so this would b the dry sample
It will give him an estimate of the chemical energy stored in the wheat
The mussels in an ecosystem ingest 57,153 kJ m² squared per year
34,292 kJ metres squared per year is ingestible lost through urine and 17,000 kJ m² squared per year is lost through respiration
calculate the net productivity of the mussels
the mussels provide food for crayfish which have a net productivity of 627 kJ m² squared per year
Calculate the energy transfer between the mussels and the crayfish
N = I (F+R) N = 57,153 (34,292 +17,000) N= 5861 KJ m² per yr
New / previous x 100
(627 / 5861) x 100 = 10.7%
Two reasons why the net productivity of the large fish is less than the net productivity of the small fish
Because some of the energy is lost to the environment through respiration or excretion of urine
Some parts of the small fish are indigestible and so are egested as faeces
What is a plants biomass?
The chemical energy stored in the plant
What is gross primary production?
The total amount of chemical energy converted from light energy by plants in a given area
What is meant by respiratory loss?
The energy lost to environment as heat when organisms respire
What is net production?
The energy is stored in the consumers biomass it’s also the energy available to organisms at the next trophic level
The equation for net production
Net production = I - (F + R)
A pig Farmer wants to maximise production on his farm
he collects data on three different breeds of pig as shown in the table on the right and in the graph below
Meat yield (% of total body weight) Breed 1. 64 Breed 2. 73 Breed 3. 66
Calculate the rate at which breed 3 gained weight between 18 and 22 weeks
Which breed of pig would produce the most meat at 22 weeks?
Antibiotics can be used to treat bacterial diseases in a pigs
Suggest how using antibiotics may increase the net production of the pigs
Suggest and explain one other way the farmer could increase the net production of the pigs
Rate = change y / change in x
Meat yield / 100 x weight at 22 weeks
Breed 1 : 64 / 100 x 82 = 52 kg
Breed 2 : 73 / 100 x 76 = 55 kg
Breed 3 : 66 / 100 x 57 = 38 kg
Using antibiotics may mean that the pigs use less energy fighting the disease so they can use more energy to grow increasing their net production
Keep the pigs in pens to restrict the movement this will reduce the energy lost through respiration
keep the pigs indoors so that they are kept warm this will reduce the energy lost through generating body heat
What does a food change show
Simple lines of energy transfer through an ecosystem
Explain how simplifying a food web could increase the efficiency of energy transfer to humans
Simplifying the food web gets rid of food chains that don’t involve humans or pests this means that less energy is transferred to the pests increasing the efficiency of energy transfer to humans
Give two examples of methods of pest control
Pesticides herbicides
The table on the right shows the rate of nitrogen fixation by various sources in the early 1990s
Source of nitrogen fixation : rate of fixation (Tg N yr-1)
Lightning : 5.4
Bacteria in uncultivated land : 107
Bacteria in cultivated land : 31.5
Fertiliser manufacture : 86
What percentage of the total amount of nitrogen fixed by all sources was fixed by bacteria
1860, 120 Tf N per year was fixed by bacteria on uncultivated land.calculate the overall percentage decrease in the mass of nitrogen fixed per year by bacteria on uncultivated land between 1860 and the early 1990s
Suggest why the mass of nitrogen fixed in uncultivated land decreased between 1860 and the early 1990s
Using the table suggest one way in which the nitrogen cycle may have been altered by the action of humans
Percentage decrease = change / original x 100
(120-107) / 120 x 100 = 11%
More land was being cultivated in the 1990s than in 1860 so there was less uncultivated land
Thru the Manufacture of fertilisers
Heavy rain combined with poor drainage can lead to soils becoming waterlogged.suggest and explain what might happen to the amount of nitrogen assimilated by a plant in waterlogged soils
It might decrease because waterlogged soils create anaerobic conditions this means that denitrifying bacteria convert nitrates in the soil back into nitrogen gas which the plants constant assimilate without nitrogen fixation
Figure A and B below show simplified versions of the nitrogen and phosphorus cycles
In what form is phosphorus Assimilated by plants?
Name the process labelled x in figure A
(Living organism to soil)
Explain whats happening at the part labelled y in figure b
Give two ways in which phosphate ions r returned from living organisms to the soul
As phosphate ions dissolved in water
Ammonification (when n compounds turn into ammonia (saprobionts do this)
Phosphate ions dissolved in the oceans are assimilated by aquatic producers such as algae
Thru the death And decomposition of organisms and through the breakdown of compounds and faeces and urine
Name two types of saprobiont
bacteria fungi
How do saprobionts digest their food
The secrete Enzymes and digest food externally then absorb the nutrients they need
What are mycorrhizae?
Mycorrhizae are symbiotic relationships between fungi and the roots of plants
Explain how mycorrhizae increase water and mineral ion uptake by plants
The fungi have long thin strands called hyphae which connect to the plants roots.
the hyphae greatly increase the surface area of the plants roots system allowing the plants to absorb more water and mineral ions
Name 4 processes in the nitrogen cycle
Nitrogen fixation
nitrification
denitrification and ammonification
Describe the role of saprobionts in the phosphorus cycle
Saprobionts are involved in breaking down the organic compounds when plants and animals die releasing phosphate ions into the soil for assimilation by plants they also release the phosphate ions from urine and faeces
What is guano
The waste produced by seabirds
Why is guano important in the phosphorus cycle
Because it returns a significant amount of phosphate ions to the soil from the oceans
Suggest an explanation for the increase in peak nitrate concentration between the first and second farm along the river
The second form uses a higher concentration of nitrate fertiliser on its land
What are the results of the control river show
The nitrate concentration and algal content of the control river remain constant at 7 mgl-1 and 10,000 cells cm-3
this indicates that the nitrates concentration and Algal growth on rivers a and B were affected by the two farms and not due to any other environmental variable
Describe and explain the possible consequences of the peaks in the algal content of river a at 200 m and 900 m
Large amounts of algae block lights from reaching the plants below
eventually the plants might die because they’re unable to photosynthesise enough bacteria would then feed on the dead plants matter
the increased number of bacteria reduces the oxygen concentration in the water by carrying out aerobic respiration this could reduce the number of fish and other aquatic organisms of the locations because there isn’t enough dissolved oxygen in the water
Explain how mineral ions are lost from crop fields
Crops take in mineral ions from the soil as they grow
When crops are harvested they r removed from the fields where they’re grown rather than being allowed to die and decompose
this means the mineral ions that they contain for example phosphate and nitrates arent returned to the soil by decomposers in the nitrogen or phosphorus cycles
Give an example of a natural fertiliser
Manure
Crop residue
By what process do fertilisers get into waterways
Leaching
Name the process that can occur as a result of excess fertilisers in waterways
Eutrophication
Suggest environmental conditions under which the seedlings were grown which should have been controlled by the scientists
That should have controlled the temperature that the group of seedlings were kept at and the light intensity that the two groups of seedlings were exposed to
Suggest an explanation for the differences between the mycorrhizae group and the control group shown in figure 2
The fungi are used to inoculate the mycorrhizae cultural group increase the surface area of the seedlings’ root systems compared to those in the control group
this increases the mycorrhizae group seedlings’ uptake of water and important mineral ions compared to the seedlings’ in the control group
this increases the growth of the seedlings in the mycorrhizae group
When fertilisers are applied to fields next to a lake nitrogen-containing substances from the fertilisers get in to the lake
describe how the nitrogen-containing substances get into the lake
dissolve in soil water(leaching)
It takes longer for the nitrogen-containing substances to get into the lake when an organic fertiliser is used than when an inorganic fertiliser is used explain why it takes longer when an organic fertiliser is used
Less soluble
Molecules require breaking down
Describe how the presence of nitrates in a lake may eventually lead to the death of fish
Algal bloom Blocks light Less photosynthesis Plants die Increase in decomposers Bacteria respire Less oxygen
Scientists investigatedthe effect of mycorrhizal fungus on the growth of pea plants with a nitrate fertiliser or ammonium fertiliser
the fertilisers were identical except for nitrate or ammonia
The scientists took pea seeds and sterilised their surfaces they planted the seeds in soil that had been heated to 85°C for two days
the soil was sand that contained no mineral ions useful to the plants
explain why the scientists sterilised the surfaces of the seeds and group them into soil but had it had been heated to 85°C for two days
Explain why it was important that the soil contained no mineral ions useful to the plants
To kill any fungus on surface of seeds
So only the added fungus has any effect
So that only nitrate or ammonium affects growth
Describe the role of microorganisms in producing nitrates from the remains of dead organisms
Saprobionts break down remains into ammonia or ammonium
Ammonia ions to nitrite to Nitrate
By nitrifying bacteria/nitrification
Nitrification
Ammonium ions to nitrates
The diagram above include one process in which microorganisms add ammonium ions to soil describe another process carried out by micro organisms which adds ammonium ions to soil
Protein broken down into ammonia by Saprobionts
Denitrification requires anaerobic conditions
ploughing aerates the soil
explain how ploughing would affect the fertility of the soil
Fertility is increased as more nitrate is produced
Less denitrification
One farming practice used to maintain high crop yields is crop rotation
this involves growing a different crop each year in the same field
suggest two ways in which crop rotation may lead to high crop yields
Grow crops with nitrogen fixing bacteria
Different crops use different nutrient from the soil
