ENERGY TRANSFERS IN + BETWEEN ORGANISMS Flashcards
TOPIC 5
PHOTOSYTHESIS EQUATION
6CO2 + 6H2O → C6H12O6 + 6O2
ADAPTIONS OF LEAVES TO PHOTOSYNTHESIS
.Large surface area
.Thin so diffusion distances are short and to capture light as only penetrates few mm
.Transparent cuticle to let light through
.Long narrow layer of palisade mesophyll cells allows many cells packed close to surface for light absorption
.Cells packed w/chloroplasts around edge that collect light
.Stomata on lower surface for gas exchange
.Air spaces in lower mesophyll layer for diffusion of gases
.Xylem brings water and phloem carries away sugar in form of sucrose
CHLOROPLAST STRUCTURE
.Chloroplasts are transducers: convert energy of light photons into ATP chemical energy
.composed of double membrane w/ stroma inside-Stroma is site of Calvin cycle – light independent reactions of photosynthesis
.Membrane thylakoids are composed of flattened sacs called lamellae-Grana are several stacked thylakoids containing photosynthetic pigments e.g. chlorophyll-absorb light for light dependent reactions of photosynthesis
.Chloroplasts also often contain starch grains- amyloplasts and lipid droplets which are products of photosynthesis
PHOTOSYSTEMS
.Chloroplasts contain photosystems embedded in thylakoid membranes
.Photosystem I contains chlorophyll w/light absorption peak at wavelength of 700nm and Photosystem II contains chlorophyll w/light absorption peak at wavelength of 680nm
WHY DO LEAVES CONTAIN DIFFERENT TYPES OF PIGMENT
.maximise absorption of light
.absorption spectrum is graph of light absorption against wavelength of light
.action spectrum is graph of rate of photosynthesis against wavelength of light
LIGHT DEPENDANT REACTION IN THYLAKOIDS/GRANA
- Photoionisation- Light absorbed by chlorophyll in photosystems I and II-electrons of chlorophyll are excited to higher energy level
- Photosystem II Photolysis also occurs-Light used indirectly to split water to produce protons electrons and oxygen gas: H2O → H+ + OH-
- Electrons replace those previously lost by chlorophyll in Photosystem II
- Photolysis raises concentration of protons in thylakoid space
- High energy electrons released from chlorophyll are accepted by electron acceptors and are then transferred between electron carriers and used in manufacture of ATP (chemiosmosis)
- reduction of NADP is brought about by addition of electrons and H+ ions
- Electrons emitted from Photosystem II are used to replace those lost from Photosystem I
HOW CHEMIOSMOSIS PRODUCES ATP
- ATP is produced across thylakoid membranes- Hydrogen can be split into proton
and an electron - Proton pumps fuelled by high energy electrons from electron transfer chain in membrane pump protons into thylakoid space to maintain their high concentration
- membrane is impermeable to protons but they diffuse down their electrochemical gradient through enzyme ATP synthase on stalked particle from thylakoid space into stroma
- causes ADP + Pi to form ATP
PRODUCTS OF LIGHT DEPENDANT REACTION
Oxygen-used in respiration or diffuses out of leaf through stomata
ATP and reduced NADP- which are used in Light Independent Reactions
LIGHT INDEPENDANT REACTION IN STROMA
- CO2 combines RuBP using rubisco enzyme
- which produces 2 glycerate phosphate
- 2 Glycerate Phosphate are reduced to form 2 Triose phosphate using energy from ATP → ADP + Pi and reducing power and H supply of reduced NADP
- Triose Phosphate can then be converted to make 6C hexoses eg. glucose
- 5C from Triose Phosphate is used to regenerate RuBP using more energy from ATP → ADP + Pi
GROSS VS NET PHOTOSYNTHESIS
gross: total rate of CO2 uptake
net: difference between CO2 uptake and release
-gross is always bigger than net
LIMITING FACTOR MEANING
factor which if increased rate of overall reaction also increases
FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: LIGHT INTENSITY
.light intensity increases, rate of photosynthesis increases
.light saturation point now another factor is limiting photosynthesis
.high light intensities rate of photosynthesis-remains constant-limiting reagent is something else (temp or CO2)
If reduced, levels of ATP and reduced NADP would fall
LDR limited - less photolysis and photoionisation
GP cannot be reduced to triose phosphate in LIR
FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: CO2 CONCENTRATION
.increase in CO2 increases rate of photosynthesis
.at low concentration CO2 is limiting factor
.at high concentration CO2 is no longer limiting factor could be temp or CO2
If reduced, LIR inhibited
less CO2 to combine w/RuBP to form GP
less GP reduced to TP
less TP converted to hexose and RuBP regenerated
FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: TEMPERATURE
At low temperatures, there is not enough kinetic energy for successful collisions between enzyme and substrate
At too high temperature, enzymes denature, active site changes shape and enzyme- substrate complexes cannot form so limiting factor light intensity or CO2
FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: LIGHT WAVELENGTH
Provides energy for light dependent reaction
Only certain wavelengths are absorbed: red and blue
Green is reflected
COMPENSATION POINT
point at which photosynthesis and respiration are taking place at same rate
EVALUATING DATA ABOUT ARGICULTURE PRACTICES USED TO OVERCOME LIMITING FACTORS IN PHOTOSYTHESIS
.Use of glass houses to control temperature, light intensity, wavelength of light and carbon dioxide levels- increased temperature may increase rate of respiration, so no further increase in biomass of plant
.Use of pesticides removes unwanted pests: decreases biodiversity as affects feeding relationships
.Removal of hedgerows to reduce competition/shade from crops: decreases biodiversity as decreases variety of food sources and habitats
.Atrazine-herbicide is weedkiller used to reduce competition-Atrazine binds to proteins in electron transfer chain in chloroplasts of weeds reducing transfer of electrons down chain: decreases variety of food sources, habitats and therefore biodiversity
.Use of genetically modified crops which are e.g., give higher yield or resistance to herbicides-Issues
w/transferring modified genes to wild plants
RP7-USE OF CHROMATOGRAPTHY TO INVETSTIGATE PIGMENTS ISOLATED FROM LEAVES OF DIFFERENT PLANTS
- Draw line on paper using ruler and pencil
- add chlorophyll/solution to line
- Add solvent below line
- Remove before solvent reaches end
- Calculate rf value by Distance moved by
pigment/Distance moved by solvent
RP7-EXPLIAN ADVANTAGES OF CALCULATING RF VALUES
RF values can be compared to known values to identify compound
RP7-WHEN CALCULATING RF VALUE,MIDDLE OF SPOT IS USED-WHY?
Allows comparison as it standardises readings
EXPLAIN WHY STUDENT MARKED ORGIN USING PENCIL RANTHER THAN INK
Ink and leaf pigments would mix
WHY DOES SOLVENT FRONT HACE TO BE MARKED BEFORE PAPER CHROMATOGRAPHY DRIES
stood in solvent as before and left until solvent front gets close to top of paper
RP8-INVESTIGATE INTO EFFECT OF NAMED FACTOR ON RATE OF DEHYDROGENASE ACTIVITY IN EXTRACTS OF CHLOROPLASTS
- In photosystem I, during light-dependent stage of photosynthesis, NADP acts as an electron acceptor and is reduced- reaction is catalysed by dehydrogenase enzyme
- activity of enzyme can be investigated using redox indicator eg. DCPIP and adding it to extracts of chloroplasts
- DCPIP acts as an electron acceptor and becomes reduced, changing colour from blue to colourless
- End point of a colour change is subjective- absorption of solution could be measured using colorimeter every unit of time- end point could be identified by point when absorption no longer changes
RP8-WHY ARE LEAVES BLENDED
release chloroplasts by breaking open cells
RP8-WHY ARE LEAVES FILTERED
remove any large piece of cell debris
RP8-AMMONIUM HYDORXIDE IS USEF AS WEEDKILLER AS IT IS AN PROTON ACCEPTOR WHY?
Less ATP
Less reduced NADP
Less light independent reactions
Less reduction of GP to TP
Less organic products eg. glucose
Less respiration
RESPIRATION
series of enzyme-catalysed catabolic reactions which release chemical energy from organic molecules in order to synthesise ATP
TYPES OF COENZYMES
NAD: Can accept hydrogen to form reduced NAD
FAD: Can accept hydrogen to form reduced FAD
PHOSOHORYLATION
Adding an inorganic phosphate- Pi to ADP to form ATP
OXIDATION + REDUCTION
O: removing hydrogens/electrons
R: adding hydrogens/electrons
SUBSTRATE LEVEL PHOSPHORYLATION
synthesis of ATP by transfer of phosphate group from
phosphorylated intermediate to ADP
OXIDATION PHOSPHORYLATION
synthesis of ATP from reduced coenzymes and oxygen in
electron transfer chain of aerobic respiration
WHAT ARE 4 STAGES FOR AREOBIC RESPIRATION
- glycolysis
- link reaction
- Krebs cycle
- oxidation phosphorylation
GLYCOLYSIS
cytoplasm and anaerobic
- Phosphorylation of glucose using ATP
- oxidation of Triose phosphate to pyruvate
- net gain of ATP
- reduced NAD
.Net gain from 1 x glucose:
2 x ATP
2 x reduced NAD
2 x Pyruvate
LINK REACTION
.Dehydrogenation: Pyruvate is actively transported to mitochondria from cytoplasm and is oxidised as hydrogen is removed and transferred to NAD which is reduced to form reduced NAD
.It is also decarboxylated CO2 is removed to form acetate
.Acetate then combined w/CoA to form Acetyl CoA
.Net gain from 1 x glucose:
2 x reduced NAD
2 x Acetyl Coenzyme A
KREBS CYCLE
.2C Acetyl CoA enters the cycle and acetyl is accepted by 4C acid to form 6C acid regenerating CoA for link reaction
.Cycle turns twice for each original glucose molecule
.2C acetate fragment is completely broken down and 4C acid is regenerated via 6C and 5C intermediates in series of oxidation-reduction reactions
.1 x ATP is produced directly by substrate level phosphorylation of ADP
.2 x C atoms are released in 2 x CO2 molecules by decarboxylase
.3 x reduced NAD and 1 x reduced FAD are produced as 4 pairs of H atoms are removed to these hydrogen carriers by dehydrogenase
.Net gain from 1 x glucose:
6 x reduced NAD
2 x reduced FAD
4X carbon dioxide
2X ATP
OXIDATIVE PHOSPHORYLATION
.Enzymes remove hydrogen from reduced NAD/FAD and split it into H+ and high energy e-
.e- flow through electron transfer chain of carriers releasing energy at each lower energy level-This energy is used to power proton pumps
.Proton pump: H+ pumped across inner membrane to inter membrane space H+ diffuse down an electrochemical gradient back to matrix through ATP synthase synthesising ATP from ADP and Pi by chemiosmosis
.Reduced NAD powers 3 pumps, reduced FAD powers 2 pumps
.O2 acts as final H+ and e- acceptor forming H2O which maintains flow of electrons
DESCRIBE HOW ATP IS MADE IN MITOCHONDRIA
- substrate level phosphorylation
- link reaction produces reduced coenzymes
- electrons released from coenzymes
- electrons pass along carrier
- energy released
- ADP + Pi
- protons move into membrane space
- ATP synthase
HOW MANY ATP FORM EACH NAD + FAD
2.5 ATP made from each NAD
1.5 ATP made from each FAD
ANAEREOBIC RESPIRATION
.Under anaerobic conditions reduced NAD cannot be re-oxidised and so made available to pick up more hydrogen
.there is no oxygen to act as final electron acceptor at end of electron transport chain
.link reaction, Krebs cycle and oxidative phosphorylation stop
.without NAD being re-oxidised, glycolysis will stop and no ATP will be formed
.Need to re-oxidise reduced NAD back to NAD for glycolysis to continue
anaerobic respiration, much less ATP is formed compared to aerobic respiration-ATP formed is from glycolysis
OXIDATION OF NAD IN ANIMAL MUSCLE TISSUE-LACTATE FERMENTATION
.H from reduced NAD combines w/pyruvate to form lactate
.Lactate causes cramp in muscle and builds up an oxygen debt
.Lactate is eventually oxidised back to pyruvate when O2 is available by rapid breathing
Pyruvate
↓
↓ (Reduced NAD → NAD)
↓
Lactate
OXIDATION OF NAD IN YEAST-ALCOHOLIC FERMENTATION
.Pyruvate is decarboxylated to ethanal
.Carbon dioxide is produced
.Ethanal is reduced as it accepts H from reduced NAD and is converted to ethanol
Pyruvate
↓
↓ (→CO2)
↓
Ethanal
↓
↓ (Reduced NAD → NAD)
↓
Ethanol
ANAEROBIC RESPIRATION IS RELATIVELY INEFFICIENT COMPARED TO AEROBIC
.Pyruvate is used to form lactate or ethanol
.Under anaerobic conditions, link reaction/Krebs cycle/oxidative phosphorylation cannot take place so only ATP formed is from glycolysis
.Only 2 x ATP synthesised per molecule of glucose, about 2% efficiency as there is still lots of energy contained within lactate or ethanol
.More anaerobic respiration is needed to produce same amount of ATP
DESCRIBE WHAT HAPPENS TO PYRUVATE IN ANAEROBIC CONDITIONS + EXPLAIN WHY ANAEROBIC RESPIRATION IS ADVANTAGEOUS TO HUMAN SKELETAL MUSCLE
Forms lactate
Use of reduced NAD
Regenerates NAD
NAD can be re-used to oxidise more respiratory substrate
ALTERNATIVE RESPIRATORY SUBSTRATES
.carbohydrates are in short supply fats and proteins may be used as respiratory substrates
.Lipase digests fats to fatty acids and glycerol by hydrolysing ester bonds
.Glycerol is converted to 3-carbon sugar, triose phosphate, an intermediate of glycolysis
.Long fatty acid chains molecules are split into 2C fragments which enter pathways as acetyl coenzyme A- This generates lot of ATP as chains can be very long
.Endopeptidases, exopeptidase and dipeptidases digest proteins to amino acids by hydrolysing peptide bonds
.Amino acids are deaminated in liver
.amine group is converted to urea and excreted by kidneys
.rest of amino acids are converted into various organic acids which can enter respiratory pathways
RP9-INVESTIGATE TO EFFECT OF NAMED VARIABLE ON RATE OF RESPIRATION OF CULTURES OF SINGLE-CELLED ORGANISM
.Methylene blue is an artificial acceptor of H+ and changes colour from blue to colourless when reduced
.Yeast, when respiring produce H+ due to their dehydrogenase enzymes
.A: Control tube B: Experimental tube
.Measure time to go colourless at eg. range of temperatures
RP9-WHY ARE TUBES LEFT FOR __ MINUTES IN WATER BATH BEFORE ADDING METHYLENE BLUE
allows yeast mixture to equilibrate/ reach temperature of water bath
RP9-HOW WOULD TEMPERATURE BE CONSTANT
use thermostatically controlled water bath-temperature would cool using beaker of water as water bath
RP9-WHY SHOULD YOU NOT SHAKE TUBES
Oxygen would act as final electron acceptor instead of methylene blue
RP9-EXPLAIN HOW END POINT FOR THIS PRACTICAL IS STANDARDISED
Set up control to compare results to – yeast and glucose solution w/no methylene blue
RP9-SUGGEST ONE SOURCE OF ERROR
Colour change end-point is difficult to determine
USING RESPIROMETER
.Measures rate of O2 consumption by aerobic respiration
.Choose temperature normal for organism which will be optimum for enzymes
.Set up and leave for 10 minutes to reach equilibrium, allow for volume changes and respiration rate of seeds to stabilise
.CO2 given out is absorbed by KOH solution so volume in B decreases
.liquid moves as O2 is taken up by organism
.Measure distance moved by liquid in a set period of time e.g. every 10 minutes
.Calculate volume of oxygen absorbed using πr2h per unit of time where r is radius of capillary tube lumen, and h is distance moved by dye
RESPIRTOMETER-EXPLAIN WHY RESPIROMETER APPARATUS IS LEFT OPEN FOR 10 MIN
Allows apparatus to equilibrate, allows for respiration rate to stabilise following handling
RESPIRTOMETER-WHY TEMPERATURE RANGE WOULD BE SUITABLE AND WHY
20-40 ⁰C – optimum for respiratory enzymes
ECOSYSTEMS
area comprising living organisms, biotic, and non-living, abiotic, components w/which they interact, plants synthesise organic compounds from atmospheric, or aquatic CO2
Most of sugars synthesised by plants are used by plant as respiratory substrates- rest are used to make other groups of biological molecules- biological molecules form biomass of plants
BIOMASS
total mass of organisms in given area or volume formed from biological molecules
HOW TO CALCULATE BIOMASS
sample from known area is dried in a low temperature oven-mass is weighed regularly, and when this is constant, all water has been removed
Scale up answer to kg m-3
ENERGY
.chemical energy store in dry biomass can be estimated using calorimetry
.Burn plant matter in calorimeter and use energy to heat known volume of water
.amount of energy needed to raise 1cm3 water by 1°C is 4.2 joules so Energy content (J) = temperature increase of water (°C) X volume of water in cm3 X 4.2
ENERGY FLOW THROUGH ECOSYSTEMS-SUN
source of energy for ecosystem
CALORIMETER INCLUDES:
.Chamber is sealed so all heat energy produced is transferred to surrounding water
.Stirrer distributes heat energy
.Chamber is insulated to prevent heat loss to surroundings
ENERGY FLOW THROUGH ECOSYSTEMS-PRODUCERS
.Green plants trap solar energy in photosynthesis and convert it to chemical energy in sugars
.Energy hitting leaf is lost due to reflected light, light passing through leaf and energy lost as heat- Some of this heat energy evaporates water from surface of leaf
GROSS PRIMARY PRODUCTIVITY (GPP)
.biomass per area or volume
.rate at which light energy is converted into chemical energy products by photosynthesis eg glucose are formed by plants- substantial amount of gross production is respired by plant and lost as heat
NET PRIMARY PRODUCTIVITY (NPP)
which is left over and represents potential food available to primary consumers
FOOD WEB CHAIN
Shows feeding relationships-Arrow shows direction of energy flow
NPP EQUATION
NPP=GPP-respiration
TROPHIC LEVEL
Level of feeding Eg. Producer / herbivore / carnivore
ENERGY TRANSFERRED
through trophic levels from plants to animals when eaten, animals to animals and plants and animals to decomposers through food webs
ENERGY LOST
transfer from one trophic level to next due to heat loss in respiration, egestion of non-digestible parts, excretion of waste products, and not eating all parts- loss limits food chain to 4 or 5 steps
HERBIVORES (PRIMARY CONSUMERS)
receive about 10% of energy-Eg. Some parts of plants are not eaten/are egested so are passed to decomposers instead
CARNIVORS (SECONDARY/TERTIARY CONSUMERS)
more efficient at energy conversion because they are able to digest their high protein diets more efficiently so less egestion
NET PRODUCTION OF CONSUMERS EQUATION
N = I – (F + R)
I represents chemical energy store in ingested food
F represents chemical energy lost to environment in faeces and urine and
R represents respiratory losses to environment
DECOMPOSERS
feed as saprobionts gaining energy from organic compounds in dead producers and consumers
ENERGY FROM RESPIRATION IN CONSUMERS IOS USED THEN LOST AS HEAT
eg. Movement, active transport, maintaining body temperature, anabolic/catabolic reactions
EXCREATION
Consumers lose energy excreting eg. Urea Energy in faeces/urine is passed to decomposers
FARMING PRACTICES INCREASE EFFICIENCY OF ENERGY TRANSFER BY:
.Simplifying food webs to reduce energy losses to non-human food chains
Eg. Reducing pests w/chemical pesticides, eg weeds that compete for light/water/minerals w/herbicides, greenfly that eat crops w/ insecticides- increase crop NPP
.Reducing respiratory losses within human food chain
.Restrict movement of animals as this uses energy
.Keep animals warm indoors to reduce energy lost maintaining body temperature
CALCULATE EFFICIENCY OF ENERGY TRANSFER
net productivity/ energy supplied x 100
RABBITS INGEST 20,000 KJ M-2 OF ENERGY. THEY LOSE 12,000 KJ M-2YR-1 IN FEACES AND URINE AND USE 6000 KJ M-2YR-1 FOR RESPIRATION CALCULATE EFFICIENCY % FOR ENERGY TRANSFER
N = I – (F + R)
20,000-12,000 + 6000=2000
2000/20,000 x100= 10%
SAPROBIONTS FEED ON DEAD ORGANISMS AND THIER WASTE PRODUCTS
.Extracellular digestion: secrete enzymes and digest their food externally-they absorb products of digestion
.During this process, organic molecules are broken down to inorganic ones
MYCORRHIZAE
.Some fungi form symbiotic relationships w/ plants
.long, thin hyphae of fungi connect to plant roots
.increase surface area enabling plant to obtain more water and inorganic ions
.fungi get useful organic compounds from plants eg. Sugars
NITROGEN CYCLE
- Ammonification/Putrefaction
.Saprobionts convert proteins from dead or decaying matter into ammonium compounds - Nitrogen Fixation
.Nitrogen gas (N2) ‘fixed’ to ammonium (NH4+) and then amino acids/other compounds .Symbiotic nitrogen fixing bacteria in root nodules of leguminous plants-which pass on compounds to plant-plant can then grow in low fertility soils-plant provides anaerobic conditions for bacterium and passes on carbohydrates - Nitrification
.Requires aerobic conditions as is oxidation
.Nitrifying bacteria convert ammonia/ammonium (NH4+) to nitrite (NO2-) then- to nitrate (NO3-) -require O2 to oxidise NH4+ ions - Conversion to Organic Nitrogen
. Plants absorb nitrate ions by taking them up via their roots from soil by active transport and use nitrogen to produce amino acids then proteins eg enzymes and nucleic acids, ATP
.Animals eat plants, digest proteins to amino acids make more proteins-Proteins are eventually deaminated and urea excreted - Denitrification
.Requires anaerobic conditions so often problem in waterlogged soil
.Denitrifying bacteria convert nitrate to atmospheric nitrogen gas - Ammonification
.Organic nitrogen in dead organisms, faeces, nitrogenous excretory products eg. urea decayed by decomposers
.Proteins hydrolysed to amino acids. Surplus amino acids converted to ammonia which dissolves as ammonium ions (NH4+)
AFTER HARVESTING REMAINS OF CROP PLANTS ARE OFTEN PLOUGHED INTO SOIL. EXPLAIN HOW MICRO-ORGANISMS IN SOIL PRODUCES SOURCE OF NITRATES FROM THESES REMAINS
- Protein into ammonium compounds
- By saprobionts
- Ammonium into nitrite
- Nitrite into nitrate
- By nitrifying bacteria
ROLE OF SAPROBIONTS IN NITROGEN CYCLE
- use enzymes to decompose proteins
- releasing ammonium ions
PHOSPHOROUS CYCLE
- PO43- in soil through weathering rocks
- plants absorb inorganic phosphate and use it to form inorganic compounds eg.ATP
- animals digest organic matter and form animal compounds
- saprobionts digest organic matter eg.DNA and release inorganic phosphates in soil
- PO43- in rocks
weathering of rocks also releases PO43- into seas, lakes,rivers to aquatic food chains
FERTILISERS
.Nutrients are lost from soils on agricultural land
.Plants absorb nutrients then are harvested and taken away
.Animals eat plants, then are taken away and slaughtered
.Fertilisers replace these nutrients, so that more energy can be used for growth
.Artificial fertilisers are inorganic eg. Ammonium nitrate- more soluble in water than organic fertilisers
.Natural fertilisers are organic eg. Manure, composted vegetables
NATURAL FERTILISER ADVANTAGE + DISADVANTAGE
ADVANTAGES
.Cheaper than artificial fertilisers
.often free if farmer has own
animals - recycle manure organic molecules have to be broken down first by saprobionts so leaching less likely
DISADVATAGES
Exact minerals and proportions cannot be controlled
ARTIFICIAL FERTILISER ADVANTAGE + DISADVANTAGE
ADVANTAGES
.Contain pure chemicals in exact proportions
more water-soluble, so more ions dissolve in water surrounding soil
.higher absorption
DISADVATAGES
.High solubility means larger quantities can leach away w/rain
.risking eutrophication reduce species diversity as favour plants w/higher growth rates e.g., nettles
LEACHING
When water-soluble compounds are washed away into rivers for nitrogen fertilisers, this can lead to eutrophication
EUTROPHICATION CAUSE ALGAL BLOOMS IN RIVERS/LAKES
.Mineral ions e.g nitrate and phosphate are soluble and leach into rivers after rainfall on agricultural land
.Algal bloom: single celled plants rapidly grow due to high nutrients
.General decrease in diversity as light cannot reach larger submerged plants which die
.Algae are short lived and are decomposed by saprobiotic bacteria which respire aerobically and create high biological oxygen demand so fish die due to lack of oxygen
.Anaerobic bacteria may then reduce nitrates to nitrites
NITRATE FROM FERTILISER APPLIED TO CROPS MAY ENTER PONDS AND LAKES. EXPLAIN HOW NITRATE MAY CAUSE DEATH OF FISH IN FRESH WATER
- Growth of algae blocks light
- Reduced / no photosynthesis so plants die
- Saprobiotic bacteria
- Aerobically respire
- Less oxygen for fish to respire
