Energy And Ecosystems Flashcards
Can you explain how energy enters an ecosystem?
All energy in ecosystem comes from sunlight, which is conserved as chemical energy in plants
Can you explain how energy is transferred between the organisms in the ecosystem?
When biomass is consumed
Trophic level definition
Each stage in a food CHAIN
Food chain definition
Feeding relationship in which producers are eaten by primary consumers, which are eaten by secondary consumers and so on
Food web definition
Linking of food chains in a single habitat or ecosystem
Producer definition
An organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water. Generally photosynthetic.
Consumers definition
Organisms that obtain their energy by feeding on other organisms - directly on producers = primary
Decomposer/ Saprobionts definition
An organism that obtains its food from the dead or decaying remains of other organisms
Biomass definition (x2)
Total mass of living material in a specific area over specific time
Total chemical energy stored in an organism
Explain how biomass is measured using calirometer
Calirometry
Burn dry biomass in calirometer
Burning smoke heats a known value of water
Change in temperature can be used as an estimate of the chemical energy of the aamole
Biomass must always be
The dry mass/ mass of carbon (50% of dry mass sample)
When calculating biomass remember
Units may need time ie yr -1
Calculations dry mass process
Weight empty crucible
Place sample in crucible and then in oven at low temperature (to avoid burning sample)
Remove and weight at regular intervals
When mass stops decreasing, sample if fully dehydrated
Subtract this crucible mass from this mass = dry mass
Biomass calirometer limitation and solution
Heat energy lost to surroundings
Use a bomb calirometer
Limitations of calculating dry mass process
Long time to fully dehydrate
Need precise weighing scale
Why is most of suns energy not converted to organic matter by photosynthesis?
Over 90% reflected back into space or is absorbed by atmosphere
Not all wavelengths of light can be absorbed and used for photosynthesis
Light may not fall on a chlorophyll molecule
Low CO2 levels may limit rate of photosynthesis - any factor that limits photosynthesis
What is GPP/ gross primary production?
Total quantity of light energy converted into chemical energy in a given area
Why does GPP≠ NPP
GPP - gross primary production
NPP - net primary production
20-50% of chemical energy is used for respiration
NPP/ net primary production formula
NPP = GPP - R
Net primary production = gross primary production - respiratory losses
Is energy transferred to primary producers from plants more efficient then energy transferred to secondary/tertiary consumers and explain
Energy transferred to secondary and tertiary consumers is slightly more efficient because not all parts of plant can be eaten like the bark, not 100% digested.
Why is energy lost during transfer between consumers (4)
Some of organisms is not consumed
Some parts were consumed but can not be digested
Some energy lost in excretory material
Some energy losses occur due to heat from respiration; high in mammals and birds because of a high body temperature so a lot of energy is needed to maintain as heat is constantly being lost to the environment
Net primary production of consumers equation
N = I - (F+R)
Net primary production = chemical energy ingested - (faecal + respiratory losses)
Efficiency equation for sun to producer
(GPP/light energy falling on producer) x 100
Efficiency equation from producer to primary consumer
(Net consumer productivity / net primary productivity) x 100
Chemical energy of producer = net primary productivity
Chemical energy in consumer = net consumer productivity
Efficiency equation from secondary to tertiary consumers etc
(NPP of tertiary/ NPP of seocndary) x 100
How to increase yield of energy? (Abiotic and biotic factors)
Reduce energy loss from crops to other organism (abiotic like temp) or by removing pests (biotic)
Reduce loss through respiration by restricting movement
Summarise the common features of all nutrients cycles.
Nutrients are taken up by producers as simple inorganic
The producer incorporates the nutrient into complex organic molecules
When producer is eaten, the nutrients pass into consumers
It then passes along the food chain into other consumers (when eaten)
When producers and consumers die, their complex molecules are broken down by saprobionts, which release nutrients back into their original, simple form l
Why are saprobionts so necessary?
Driving force that ensures nutrients are released for reuse
Importance of nitrogen cycle?
Nitrogen is needed to make proteins and nuclei acids.
78% of atmosphere is N2 but is inaccessible to plants and animals
5 steps of nitrogen cycle (state)
Nitrogen Fixation Ammonification Nitrification Denitrification Lightening oxidation
Nitrogen fixation (4 points)
N2 is converted to NH3 or nitrogen containing compounds
Nitrogen - fixing bacteria convert N2 to NH3
NH4+ (aq) is then absorbed by plants
Free - living bacteria - use the ammonia to make amino acids and release nitrogen compounds when they die
Mutualistic nitrogen fixing bacteria - live in root nodules of leguminous plants and have a symbiotic relationship where plant gives carbohydrates and bacteria gives ammonia (NH3)
Ammonification (2)
Nitrogen compounds in urine and faeces and dead organisms are converted into ammonia by saprobionts
Forms NH4+ in soil
Nitrification
Nitrifying bacteria convert NH4+ from nitrogen fixation and ammonification into NITRITES (NO2) and then a different nitrifying bacteria converts NITRITE (NO2) into NITRATE (NO3)
NH3 to NO2
NO2 to NO3
Denitrification (2)
Denitrifying bacteria use NITRATE (NO3) in soil during ANAEROBIC respiration, which produces N2 (g), which returns to the atmosphere.
Occurs in waterlogged areas and bogs
Lightening oxidation (1)
Lightening oxidation of atmospheric nitrogen (N2(g)) to nitrogen oxides, which is then carried to the soil as nitric acid
Why is the phosphorous cycle important?
Used in phospholipid membranes
Used in nuclei acids (dna and rna)
ATP
Phosphorus cycle (5)
Phosphorous slowly released into the soil in form of phosphate ions (PO4, -3) by WEATHERING/EROSION
Phosphate ions taken up from soil by plants or absorbed from H2O by algae
Phosphate ions transferred to consumers in feeding
Phosphate ions in waster products/dead organisms are released into soil/water during decomposition by saprobionts
Phosphate ions can be taken up and used again by products or trapped in sediments and undergo sedimentation and become rock containing phosphorus
Role of mycorrhizae in nutrient cycles
Fungi act like extensions of the plants root system and vastly increase total surface area for absorption of water and nutrients.
Fungi holds nutrients and water near roots of plants allowing for a plant better resistant to drought and take up ions easily.
MUTUALSITIC RELATIONSHIP = fungi receives organic compounds like sugars and amino acids, plant receives water and ions
Explain why fertilisers are needed in agricultural ecosystems?
Crops absorb minerals and are harvested, hence minerals are not released back into soil by decomposition resulting in soil with a lack of mineral ions which prevent re-growth of crop. Extra nutrients need so that plant growth is not LIMITED by lack of nutrients.
Distinguish between natural and artificial fertilisers.
Natural = organic = dead and decaying remains of plants and animals along with animal waste
Artificial = inorganic = mined from rocks and deposits and then are converted into different forms. Almost always contains potassium, phosphorus and nitrogen
How fertilisers increase productivity?
Minerals are needed for growth. Nitrogen needed in amino acids, nuclei cells acids and ATO. Where these mineral ions are readily available, plants are likely to develop earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and improves crop productivity.
State three environmental effects of nitrogen containing fertilisers
Reduced species diversity
Leaching
Eutrophication
Reduced species diversity as an environmental effects of nitrogen containing fertilisers - explain.
Nitrogen rich soil favours growth of grasses and nettles, which grow rapidly and then outcompete other species, which die as a result.
Leaching - three environmental effects of nitrogen containing fertilisers - explain
Process by which nutrients are removed from the soil.
Rainwater dissolves soluble nutrients, which eventually run off into watercourses which can be extremely harmful if used as drinking water. Prevents efficient oxygen transport in babies and links to stomach cancer.
Eutrophication
Eutrophication- three environmental effects of nitrogen containing fertilisers - explain
Process by which nutrient concentrations increase in bodies of water
Nitrate ion concentration increases, hence no longer a limiting factor in algal growth
Mainly grows at surface
Forms a dense layer which absorbs light
Light becomes a limiting factor for plants in depths, which then die
Lack of dead plants is no longer limiting factor hence saprobionts population grows
Hence increased demand for oxygen for respiration
Oxygen becomes limiting factor for fish which die
More nitrogen released from dead matter
Anaerobic organisms release more nitrates, and hydrogen sulphides which make water putrid
Advantage of using dry mass and not fresh mass ti compare yield of plants? 2 marks
Amount of water present will cary depedning on plant and environemnt - will affect fresh mass not dry mass
Explain how farming practices increases the productivity of agricultural crops. (5 marks)
Fertilisers increase concentration of mineral ions like phosphorus or nitrogen in soil. Phosphorous need to form ATP/ nucleic acids and nitrogen needed for amino acids/nucleic acids.
Genetic modification of crops to increase speed of growth
Ploughing and aeration allows for more nitrification and decreases denitrification hence more nitrogen compounds in soil
Crop rotation -> adding leguminous (nitrogen fixing bacteria in root nodules) plants allows for an increase in NH4+ in soil hence more fertile soil
