CHAPTER 5 - PHOTOSYNTHESIS, RESPIRATION AND NUTRIENT CYCLES Flashcards

Question

the rate of photosynthesis is partly dependent on?

Answer 1

the LIGHT INTENSITY of the ENVIRONMENT the plant is in

Answer 2

the particular level of LIGHT INTENSITY at which the rate of photosynthesis exactly MATCHES the rate of respiration

Answer 3

- to measure the rate at which OXYGEN is PRODUCED and USED by a plant at DIFFERENT LIGHT INTENSITIES - because photosynthesis PRODUCES O2 and RESPIRATION USES O2, the compensation point is the light intensity at which oxygen is being USED as quickly as it is PRODUCED - the rate of CO2 production and use could also be measured because photosynthesis USES CO2 and respiration PRODUCES it

Answer 4

the chloroplasts

Answer 5

the light dependent reaction/LDR

Answer 6

- small + flattened organelles - surrounded by a double membrane - thylakoids (fluid filled sacs) are stacked up -> forms grana - a single grana = granum - the grana are linked together by lamellae (bits of thylakoid membrane) - a single lamellae = lamella - photosystems are contained within the inner membrane of the chloroplast - stroma ( a gel like substance) surrounds the thylakoids - stroma contains enzymes, sugars and organic acids - carbohydrates that are produced by photosynthesis, but not used immediately, are stored as STARCH GRAINS in the stroma

Answer 7

- photosynthetic pigments

Answer 8

- chlorophyll a - chlorophyll b - carotene - they are coloured substances that absorb the light energy needed for photosynthesis - the pigments are found in THYLAKOID MEMBRANES - they are attached to proteins = protein and pigment is called a PHOTOSYSTEM - there are 2 photosystems used by plants to capture light energy, PSI and PSII - PSI = photosystem I - absorbs light best at a wavelength of 700 nm - PSII = photosystem II - absorbs light best at a wavelength of 680 nm

Answer 9

- reactions that involve OXIDATION and REDUCTION - they occur in photosynthesis and respiration - if something is REDUCED, it has GAINED ELECTRONS and may have GAINED HYDROGEN or LOST OXYGEN - if something is OXIDISED, it has LOST ELECTRONS and may have LOST HYDROGEN or GAINED OXYGEN - oxidation of one molecule ALWAYS involved the reduction of another molecule

Answer 10

- coenzyme = a molecule that aids the function of an enzyme - work by transferring a chemical group from one molecule to another - a coenzyme used in PHOTOSYNTHESIS = NADP - NADP transfers HYDROGEN from one molecule, to another = it can REDUCE (give H to) or OXIDISE (take H from) a molecule

Answer 11

- the light dependent reaction/LDR - the light independent reaction/LIR

Answer 12

- reaction NEEDS light energy - takes place in the thylakoid membranes of the chloroplasts - light energy is absorbed by chlorophyll, and other photosynthetic pigments, in the photosystems - the light energy excites the ELECTRONS in the chlorophyll, giving them MORE ENERGY = eventually causes the, to LEAVE the chlorophyll molecule - ^ this process is PHOTOIONISATION - chlorophyll is now a POSITIVELY CHARGED molecule - some of the energy from the RELEASED ELECTRONS is used to add a Pi to ADP, forming ATP - some of the energy from the RELEASED ELECTRONS is used to reduce NADP, forming reduced NADP/NADPH - ATP transfers energy and NADPH transfers hydrogen to the LIR - during the process, H2O is OXIDISED to O2

Answer 13

- making ATP from ADP and Pi, called photopohsphorylation (process of adding phosphate to a molecule using light) - making NADPH from NADP - splitting water into protons (H+ ions/hydrogen ions), electrons and oxygen - this is called photolysis (splitting of a molecule using light energy)

Answer 14

- ATP - NADPH/ reduced NADP - H ions - oxygen

Answer 15

- non cyclic photophosphorylation - cyclic photophosphorylation

Answer 16

basics - produces ATP, NADPH and O2 - photosystems are linked by ELECTRON CARRIERS (proteins that transfer electrons) - photosystems and electron carriers form an ELECTRON TRANSPORT CHAIN (a chain of proteins through which excited electrons flow) - multiple processes going on simultaneously in non-cyclic photophosphorylation light energy excited electrons in chlorophyll - light energy absorbed by PSII - light energy excited electrons in chlorophyll - the electrons move to a HIGHER energy level (have MORE energy) - these high energy electrons are RELEASED from the chlorophyll, they then move down the ETC to PSI photolysis of water produces protons, electrons and oxygen - because the excited electrons leave the chlorophyll (and go to PII via the ETC), they must be replaced - light energy splits water into protons (H+ ions), electrons and oxygen = PHOTOLYSIS - equation = H2O -> 2H + 1/2 O2 - the electrons from photolysis ^ here, replace the electrons lost in photoionisation energy from the excited electrons makes ATP - the excited electrons LOSE energy as they move DOWN the ETC and this energy is used to transport protons (H+ ions) into the THYLAKOID (so the thylakoid has a HIGHER CONC of PROTONS than the STROMA) - ^ this forms a proton gradient across the THYLAKOID MEMBRANE - protons move DOWN their conc gradient, into the stroma, via enzyme ATP SYNTHASE (which is embedded in the thylakoid membrane) - the energy from this movement combined ADP and Pi, forming ATP energy from the excited electrons generates NADPH - light energy is absorbed by PSI, which excites the electrons again to an even HIGHER energy level - finally, the electrons are transferred to NADP along with a proton (H+/hydrogen ion) from the STROMA to form NADPH

Answer 17

- chemoiosmosis = the process of electrons flowing DOWN the ETC and creating a PROTON GRADIENT across the membrane to drive ATP synthesis - ^ this process is described by the chemiosmotic theory

Answer 18

- produces ATP - only uses PSI - called 'cylic' because the electrons from the chlorophyll molecule aren't passed onto NADP, instead they are passed back to PSI via electron carriers - ^ this means the electrons are RECYCLED flow through PSI - this process doesn't produce any NADPH or O2 - only produces small amounts of ATP

Answer 19

by the movement of protons across the thylakoid membrane

Answer 20

- this reaction does NOT use light energy directly - it DOES rely on the products of the LDR - takes place in the stroma - the ATP and NADPH from the LDR supplies the energy and hydrgogen to make GLUCOSE from CO2

Answer 21

- takes place in the stroma - makes triose phosphate (TP), from CO2 and ribulose bisphosphate (5 carbon compound) - TP can be used to make glucose and other useful organic substances - few steps in the cycle - needs H+ ions to keep it going - RuBP is regenerated

Answer 22

formation of glycerate 3-phosphate - CO2 enters the leaf through the stomata and diffuses into the stomata of the chloroplast - it is combined with RuBP, this reaction is catalysed by rubisco (enzyme) - ^ this produces a 6 carbon compound - the unstable 6 C compound quickly breaks down into 2 molecules of a 3 C compound, called GLYCERATE PHOSPHATE (GP, has 3 C each) formation of triose phosphate - the hydrolysis of ATP (from the LDR) provides energy to reduce GP to TP, which is a different 3C compound - ^ this reaction also requires H+ ions (reduction reaction), which come from NADPH (from the LDR) - NADPH is recycled to NADP - some TP is converted into useful organic compounds, like GLUCOSE, and some continues in the calvin cycle to REGENERATE RuBP regeneration of RuBP - 5/6 molecules of TP in the cycle are used to regenerate RuBP, instead of making useful organic compounds - regenerating RuBP uses the rest of the ATP produces by the LDR

Answer 23

- simple 6 carbon sugars, like glucose - one hexose sugar is made by joining 2 MOLECULES OF TP - hexose sugars can be used to make larger carbohydrates

Answer 24

- 6 times - ^ this is because, 3 turns of the cycle produces 6 molecules of TP (2 molecules of TP are made for every 1 molecule of CO2 molecule used) - 5/6 of TP molecules are used to REGENERATE RuBP - ^ this means that for 3 turns of the cycle, only 1 TP molecule is produced that is USED TO MAKE A HEXOSE SUGAR - a HEXose sugar has 6 carbons, so 2 TP molecules are needed to form 1 hexose sugar - the cycle must turn 6 times to produce 2 molecules of TP, that can be used to make 1 hexose sugar - 6 turns of the cycle require = 18 ATP molecules and 12 NADPH molecules from the LDR - ^ this may seem inefficient, however it allows the cycle to continue and also ensures that there's always enough RuBP ready to combine with CO2, taken in from the atmosphere

Answer 25

- hexose sugars are made from 2 TP molecules - larger carbohydrates (sucrose, starch, cellulose) are made by joining hexose sugars together in different ways

Answer 26

- these are made using glycerol, which is SYNTHESISED from TP - fatty acids are SYNTHESISED from GP

Answer 27

some amino acids are made from GP

Answer 28

inputs - CO2 - ATP - NADPH outputs - organic substances (ex, glucose) - RuBP

Answer 29

- light intensity - temperature - CO2 concentration - water

Answer 30

- light is needed to provide the energy for LDR - the higher the intensity of the light, the more energy it provides - only CERTAIN wavelengths of light are used for photosynthesis - the photosynthetic pigments chlorophyll a, chlorophyll b and carotene only absorb the RED and BLUE light in sunlight

Answer 31

- photosynthesis involved enzymes, ATP synthase and rubisco - if the temp falls BELOW 10 degree cel, the enzymes may become INACTIVE - if the temp goes above 45 degrees cel, the enzymes may start to DENATURE

Answer 32

- CO2 makes up 0.04% of the gases in the atmosphere - increasing this to 0.4% gives a higher rate of photosynthesis - any higher than this rate will cause the stomata to start to close

Answer 33

- plants need a constant water supply - too little water = photosynthesis - too much water = soil becomes WATERLOGGED, which reduces the uptake of minerals like magnesium, which is needed to make chlorophyll a

Answer 34

- light - temperature - carbon dioxide - if any one of these ^ factors are too low or high, it will LIMIT photosynthesis, even if the other 2 factors are at the optimum level

Answer 35

- the right amount of everything increases growth, and therefore increases yield - growers create optimum conditions in GLASSHOUSES CO2 CONCENTRATION - carbon dioxide is added to the air - ex - by burning a small amount of PROPANE in a CO2 generator LIGHT - light can get in through the glass - at night time, lamps provide light TEMPERATURE - glasshouses trap heat energy from sunlight, which warms the air - heaters and cooling systems can also be used to keep a CONSTANT OPTIMUM TEMP - air circulation systems ensure the temp us even throughout the glasshouse

Answer 36

it is the process which allows cells to produce ATP from glucose

Answer 37

- aerobic respiration (with oxygen) - anaerobic respiration (without oxygen)

Answer 38

- respiration can be done with O2 (aerobic), and without O2 (anaerobic) - both types of respiration produce ATP, but anaerobic respiration produces LESS ATP - both start with glycolysis, however the stages after glycolysis differ

Answer 39

- the reactions in aerobic respiration take place in the mitochondria - the CRISTAE in the inner membrane (the folds) = provide a LARGE SA = MAXIMISES RESPIRATION

Answer 40

- a coenzyme = a molecule that aids the function of an enzyme, by transferring a chemical group from one molecule to another - the coenzymes in respiration = NAD, coenzyme A and FAD - NAD + FAD = can reduce or oxidise a molecule - coenzyme A = transfers ACETATE between molecules

Answer 41

- glycolysis - the link reaction - the krebs cycle - oxidative phosphorylation

Answer 42

- the first 3 stages are a SERIES OF REACTIONS - the products from these ^ reactions are used in the final stage - the first stage, glycolysis, happens in the CYTOPLASM of cells - the other 3 stages take place in the MITOCHONDRIA

Answer 43

- GLUCOSE can be used as a RESPIRATORY SUBSTRATE in BOTH aerobic and anaerobic respiration - glucose isn't the only respiratory substrate that can be used in aerobic respiration - some products resulting from the breakdown of other molecules, like fatty acids from lipids and amino acids from proteins, can be CONVERTED INTO MOLECULES WHICH CAN ENTER THE KREBS CYCLE, usually acetyl CoA

Answer 44

- doesn't involve the link reaction, krebs cycle or oxidative phosphorylation - the products of glycolysis are converted to ETHANOL or LACTATE instead

Answer 45

- glycolysis makes PYRUVATE from GLUCOSE - glycolysis involves splitting ONE molecule of GLUCOSE (6C) into TWO smaller molecules of PYRUVATE (3C) - process takes place in the cytoplasm of cells - glycolysis is the first stage of BOTH aerobic and anaerobic respiration - doesn't need O2 to take place, therefore it is an ANAEROBIC PROCESS - the 2 stages in glycolysis are phosphorylation and oxidation

Answer 46

PHOSPHORYLATION - glucose is phosphorylated using a phosphate molecule from ATP - this ^ creates 1 molecule of GLUCOSE PHOSPHATE + 1 molecule of ADP - ATP is then used to add ANOTHER Pi, forming HEXOSE BIPHOSPHATE - hexose biphosphate is then split into 2 molecules of TRIOSE PHOSPHATE OXIDATION - TP is oxidised (loses hydrogen), this forms 2 molecules of PYRUVATE - NAD collects the H+ ions, forming 2 NADH/reduced NAD - 4 ATP are produced, but 2 ATP were used in stage 1 (phosphorylation), therefore there is a NET GAIN of 2 ATP

Answer 47

- 2 NADH/reduced NAD = to OXIDATIVE PHOSPHORYLATION - 2 pyruvate = actively transported into the mitochondrial matrix for use in the link reaction - 2 ATP (net gain) = used for energy

Answer 48

- glucose cant cross the outer mitochondrial membrane - pyruvate can cross this membrane, so the rest of the aerobic respiration occur within the mitochondria

Answer 49

- in anaerobic respiration, the PYRUVATE produced in glycolysis is converted into ethanol (alcoholic fermentation) or lactate (lactate fermentation) using NADH ALCOHOLIC FERMENTATION - this occurs in PLANTS and YEAST - pyruvate is DECARBOXYLATED, which forms ETHANAL - ethanal is REDUCED by NADH, which becomes NAD, and this forms ETHANOL LACTATE FERMENTATION - this occurs in animal cells and some bacteria - pyruvate is reduced, to form lactate/lactic acid - it is reduced by NADH, so it also forms NAD - the production of lactate or ethanol regenerates oxidised NAD - this ^ means glycolysis can CONTINUE even when there isn't much oxygen around, so a small amount of ATP can still be produced to keep some biological processes going

Answer 50

- the link reaction converts the pyruvate (produced in glycolysis) to ACETYL COENZYME A - pyruvate DECARBOXYLATED, so one carbon atom is removed from the PYRUVATE in the form of CO2 - at the same time, pyruvate is OXIDISED to form ACETATE and NAD is reduced to form NADH - acetate is combined with CoA to form ACETYL COEZYME A - NO ATP IS FORMED IN THIS REACTION

Answer 51

- 2 pyruvate molecules are made per glucose molecule which enters glycolysis - link reaction and the krebs cycle happen TWICE for every glucose molecule

Answer 52

1 link reaction - 1 acetyl CoA - 1 CO2 - 1 NADH 2 link reactions, per glucose mol - 2 acetyl CoA - 2 CO2 - 2 NADH - the 2 acetyl CoA go to the KREBS CYCLE - the 2 CO2 are released as a waste product - the 2 NADH go to the oxidative phosphorylation

Answer 53

- produces reduced coenzymes and ATP - involves a series of oxidation-reduction/redox reactions, which take place in the MATRIX - cycle happens ONCE for every pyruvate molecule

Answer 54

FORMATION OF A 6C COMPOUND - acetyl coA (from the link reaction) combined with a 4C molecule (oxaloacetate) to form a 6C compound (citrate) - CoA goes back to the link reaction to be used again FORMATION OF A 5C COMPOUND - the 6C compound is converted to 5C - DECARBOXYLATION occurs, where CO2 is removed - DEHYDROGENATION also occurs, the H is used to produce NADH from NAD REGENERATION OF OXALOACETATE - the 5C molecule is converted to a 4C molecule - decarboxylation and dehydrogenation occur = this produces 1 molecule of FADH + 2 molecules of NADH - ATP is produced by the direct transfer of a phosphate group from an INTERMEDIATE COMPOUND to ADP - when a phosphate group is directly transferred from one molecule to another, its called SUBSTRATE-LEVEL PHOSPHORYLATION - citrate has now been converted to oxaloacetate

Answer 55

- 1 CoA -> reused in the next link reaction - oxaloacetate -> regenerated for use in the next krebs cycle - 2 CO2 -> released as a waste product - 1 ATP -> used for energy - 3 NADH -> to oxidative phosphorylation - 1 FADH -> to oxidative phosphorylation

Answer 56

- the process where the energy carried by electrons, from reduced coenzymes (NADH and FADH), is used to MAKE ATP - the whole point of the previous stages stages is to make NADH and FADH for the final stage - oxidative phosphorylation involves the electron transport chain and chemiosmosis

Answer 57

STEP 1 - hydrogen atoms are released from NADH and FADH as they are oxidised to NAD and FAD - the H atoms are split into protons (H+) and electrons (e-) STEP 2 - the electrons move DOWN the ETC (made of electron carriers), LOSING ENERGY at each carrier STEP 3 - this energy is used by the electron carriers to pump protons from the MITOCHONDRIAL MATRIX into the INTERMEMBRANE SPACE (the space between the inner and outer mitochondrial membranes) STEP 4 - the concentration of protons is now HIGHER in the INTERMEMBRANE space than in the MITOCHONDRIAL MATRIX - this forms an ELECTROCHEMICAL GRADIENT (a conc gradient of ions) STEP 5 - protons then move down the electrochemical gradient, back across the inner mitochondrial matrix, via ATP synthase (which is embedded in the inner mitochondrial membrane) - this movement drives the synthesis of ATP from ADP and Pi STEP 6 - this process of ATP production driven by movement of H+ ions across a membrane (due to electrons moving down an ETC) is called CHEMIOSMOSIS STEP 7 - in the mitochondrial matrix, at the end of the ETC, the protons (H+), electrons and oxygen (from the blood) combine to form WATER - oxygen is said to be the FINAL ELECTRON ACCEPTOR

Answer 58

- 2.5 ATP are made from each NADH - 1.5 ATP are made from each FADH

Answer 59

- glycolysis, 2 ATP mols produced , 2 ATP mols produced - glycolysis, 2 NADH mols produced, 5 ATP mols produced - link reaction x2, 2 NADH mols produced, 5 ATP mols produced - krebs cycle x2, 2 ATP mols produced (net) - krebs cycle x2, 6 NADH mols produced, 15 ATP mols produced - krebs cycle x2, 2 FADH mols produced, 3 ATP mols produced - total ATP produced per glucose mol = 32 ATP mols

Answer 60

- glycolysis, link reaction and the krebs cycle are basically a series of reactions which produce ATP, NADH, FADH and CO2 - the reduced coenzymes, NADH and FADH, are then used in oxidative phosphorylation, to produce more ATP

Answer 61

- ATP production can be affected by mitochondrial diseases - mitochondrial diseases affect the functioning of mitochondria - they can affect how proteins involved in oxidative phosphorylation or the krebs cycle function, reducing ATP production - this may cause anaerobic respiration to increase, to try and make up some of the ATP shortage - this results in lots of lactate being produced, which can cause muscle fatigue and weakness - some lactate will also diffuse into the bloodstream, leading to high lactate concentration in the blood

Answer 62

- an ecosystem includes all the ORGANISMS in a particular area and all the ABIOTIC (non-living) CONDITIONS - in all ecosystems, there are PRODUCERS (organisms which make their own food) - ex, in land based ecosystems, plants (like trees) produce their own food through PHOTOSYNTHESIS - during photosynthesis, plants use ENERGY, from sunlight, and CO2, from the atmosphere in land based ecosystems/dissolved in water in aquatic ecosystems, to make GLUCOSE and OTHER SUGARS - some of the sugars produced during photosynthesis are used in RESPIRATION, to release energy for growth - the rest of the glucose is used to make OTHER BIOLOGICAL MOLECULES, like CELLULOSE (a component of plant cell walls) - these biological molecules make up the plants BIOMASS (the mass of living material, can be thought of as the chemical energy stored in the plant) - energy is transferred through the living organisms of an ecosystem when organisms eat other organisms (think of this as an energy passing system) - ex, producers are eaten by PRIMARY CONSUMERS, who are eaten by SECONDARY CONSUMERS and they are consumed by TERTIARY CONSUMERS (this is a FOOD CHAIN)

Answer 63

- biomass can be measured in terms of the MASS OF CARBON than an organism contains or the dry mass of its tissue per unit area - dry mass is the mass of the organism with the WATER REMOVED - the water content of living tissue varies, so dry mass is used as a measure of biomass, instead of wet mass - to measure the dry mass, a sample of the organism is DRIED, often in an oven at a low temp - the sample if then weighed at regular intervals (everyday for ex) - once the mass becomes constant, you can be sure all the water has been removed - the mass of carbon present is usually 50% of the dry mass - once the dry mass of the sample has been measured, it can be scaled up to give the biomass/dry mass of the total population or area being investigated - typical units may be kg,m-2

Answer 64

- you can estimate the amount of CHEMICAL ENERGY stored in BIOMASS by BURNING THE BIOMASS IN A CALORIMETER - the amount of heat given off tells you how much energy is in it - energy is measured in joules or kilojoules - a sample of dry biomass is burnt and the energy released is used to heat a known volume of water - the change in temperature of the water is used to calculate the chemical energy of the dry biomass

Answer 65

- gross primary production is the TOTAL AMOUNT OF CHEMICAL ENERGY CONVERTED FROM LIGHT ENERGY BY PLANTS, IN A GIVEN AREA - around 50% of the GPP is LOST TO THE ENVIRONMENT AS HEAT, when the plants respire : RESPIRATORY LOSS (R) - the remaining chemical energy is called the NET PRIMARY PRODUCTION (NPP) FORMULA - NPP = GPP - R - often, primary production is expressed as a rate (the total amount of chemical energy/biomass in a given area, in a given time - typical units may be kJ ha-1 yr-1 (kilojoules per hectare per year) OR kj m-2 yr-1 (kilojoules per square metre per year) - when primary production is expressed as a rate, it is called PRIMARY PRODUCTIVITY - the NPP is the energy available to the plant for growth and reproduction, the energy stored in the plants biomass - it is also the energy available to the organisms at the next stage in the food chain (the next trophic level), these include herbivores and decomposers

Answer 66

- consumers also store chemical energy in their biomass - consumers get energy by INGESTING PLANT MATERIAL or ANIMALS THAT HAVE EATEN PLANT MATERIAL - however, not all the chemical energy stored in the consumers food is transferred to the next trophic level, around 90% of available energy is LOST in various ways - not all food is eaten (ex, bones) so the energy it contains is NOT taken in - for all the parts that ARE ingested, some are indigestible and egested as faeces and the chemical energy stored in these parts is lost to the environment AND some energy is lost to the env through RESPIRATION to EXCRETION OF URINE - the energy thats left after all this is stored in the consumers biomass and IS available to the next trophic level, this energy is the consumers NET PRODUCTION FORMULA - N = I - (F+R) - N = net production - I = chemical energy in ingested food - F = chemical energy lost in faeces and urine - R = energy lost through respiration - the net production of consumers can also be called SECONDARY PRODUCTION or SECONDARY PRODUCTIVITY when expressed as a RATE

Answer 67

FORMULA - % efficiency of energy transfer = (net production of trophic level / net production of previous trophic level) x100 - as you move UP a food chain (producers ->consumers_

Answer 68

- food chains and food webs show how energy is transferred through an ecosystem - food chains show SIMPLE LINES OF ENERGY TRANSFER - each stages in a food chain is called a TROPHIC LEVEL - food webs show lots of food chains in an ecosystem and how they OVERLAP - decomposers, like fungi, are also part of food webs and they break down dead or undigested material, allowing nutrients to be recycled

Answer 69

- most farming practices aim to increase the amount of energy that is available for HUMAN CONSUMPTION, this means INCREASING THE NET PRIMARY PRODUCTION (NPP) of CROPS and the NET PRODUCTION (NP) of LIVESTOCK - the energy lost to other organisms, like pests, can be REDUCED through the SIMPLIFICATION OF FOOD WEBS - the energy lost through the RESPIRATION OF LIVESTOCK can be reduced

Answer 70

- PESTS are ORGANISMS THAT REDUCE THE AMOUNT OF ENERGY AVAILABLE FOR CROP GROWTH and THEREFORE THE NPP OF CROPS, this ultimately REDUCES the amount of ENERGY available for HUMANS - by SIMPLIFYING the FOOD WEB, like getting rid of food chains that dont involve humans, energy losses will be REDUCED and the NPP of the crop will INCREASE

Answer 71

crops are plants which are grown on a LARGE SCALE for the BENEFIT OF HUMANS, like for human consumption

Answer 72

animals which are bred for their produce, like milk, or for human consumption

Answer 73

- farmers need PEST CONTROL to get rid of pests - farmers can reduce pest numbers using CHEMICAL PESTICIDES - insecticides kill insect pests that eat and damage crops - killing insect pests means LESS BIOMASS is LOST from CROPS, so they grow to be larger, which means NPP is greater - herbicides kill WEEDS - this can REMOVE DIRECT COMPETITION with the crop for energy from the sun - weeds also compete with the crop for WATER, SPACE and NUTRIENTS - it can also REMOVE the PREFERRED HABITAT or FOOD SOURCE of the insect pests, helping to FURTHER REDUCE THEIR NUMBERS and SIMPLIFY THE FOOD WEB

Answer 74

- they REDUCE the number of PESTS, so CROPS LOSE LESS ENERGY and BIOMASS and this INCREASES THE EFFICIENCY OF ENERGY TRANSFER TO HUMANS - parasites live in or lay their eggs on a pest insect - parasites either KILL THE INSECT or REDUCE ITS ABILITY TO FUNCTION, ex - some wasp species lay their eggs inside caterpillars and the eggs hatch and kill the caterpillars - pathogenic (disease causing) bacteria and viruses are used to kill pests, ex - the bacterium bacillus thuringiensis produces a toxin that kills a wide range of caterpillars

Answer 75

- the combined effect of using both can REDUCE PEST NUMBERS EVEN MORE than neither method alone, meaning NPP is increased even more

Answer 76

- one way that farmers INCREASE the NET PRODUCTION of their LIVESTOCK is by CONTROLLING THE CONDITIONS THAT THEY LIVE IN, so that MORE OF THEIR ENERGY is used for GROWTH and LESS IS LOST THROUGH RESPIRATION (and activities which increase the rate of respiration) - movement increases the rate of respiration, so animals may be kept in pens where their movement is restricted - the pens are often INDOORS and KEPT WARM, so LESS ENERGY IS WASTED BY GENERATING BODY HEAT - this means that MORE BIOMASS is produced and MORE CHEMICAL ENERGY can be stored, INCREASING NET PRODUCTION and the EFFICIENCY OF ENERGY TRANSFER to HUMANS - the benefits are that MORE FOOD CAN BE PRODUCED in a SHORTER PACE OF TIME, often at a LOWER COST - however, enhancing net production by KEEPING ANIMALS IN PENS RAISES ETHICAL ISSUES - ex, some people think that the conditions intensively reared animals are kept in cause the animals pain, distress or restrict their natural behaviour and therefor its shouldn't be done

Answer 77

- to eat the pest species, ex ladybirds eating aphids - this is useful but doesnt really simplify the food web

Answer 78

- microorganisms, like bacteria and fungi, are an important part of FOOD WEBS and ECOSYSTEMS - many are SAPROBIONTS - SAPROBIONTS FEED ON THE REMAINS OF DEAD PLANTS AND ANIMALS and on their WASTE PRODUCTS (faeces and urine), breaking them down, this makes them a TYPE OF DECOMPOSER and it allows important chemical elements in the remains and waste to be recycled - SAPROBIONTS SECRETE ENZYMES and DIGEST THEIR FOOD EXTERNALLY, then they ABSORB THE NUTRIENTS THEY NEED. this is known as EXTRACELLULAR DIGESTION and during this process, organic molecules are broken down into inorganic ions - obtaining nutrients from dead organic matter and animal waste using extracellular digestion is known as SAPROBIOTIC NUTRITION

Answer 79

- some FUNGI form SYMBIOTIC relationships (when 2 species live closely together and one or both of the species depend on the other for survival) with the ROOTS OF THE PLANT -> these relationships are known as MYCORRHIZAE - the FUNGI are made up of long, thing strands called HYPHAE, which connect to the plants roots - the HYPHAE greatly INCREASE the SURFACE AREA of the PLANTS ROOT SYSTEM, helping the plant to ABSORB IONS FROM THE SOIL WHICH ARE USUALLY SCARCE, like phosphorous - HYPHAE also INCREASE the UPTAKE OF WATER by the plant - in turn, the FUNGI OBSTAIN ORGANIC COMPOUNDS, like GLUCOSE, from the PLANT

Answer 80

BASICS - plants and animals need NITROGEN to make PROTEINS and NUCLEIC ACIDS (DNA+RNA) - the atmosphere is made up of 78% nitrogen gas, but plants and animals cant use it in that form because they need bacteria to covert it into nitrogen-containing compounds first NITROGEN FIXATION - when nitrogen gas in the atmosphere is turned into NITROGEN-CONTAINING COMPOUNDS - biological nitrogen fixation is carried out by bacteria like RHIZOBIUM, which turns NITROGEN into AMMONIA, which goes onto form ammonium ions in solution that can be used by plants - RHIZOBIUM are found inside root nodules (growths on the roots) of LEGUMINOUS plants (like peas, beans and clover) - they form a MUTUALISTIC relationship with the plants - they provide the plants with NITROGEN COMPOUNDS and the plants provide them with CARBOHYDRATES - other nitrogen fixing bacteria are found in the soil AMMONIFICATION - when NITROGEN COMPOUNDS from DEAD ORGANISMS are turned into AMMONIA by SAPROBIONTS, which goes on to form AMMONIUM IONS - ANIMAL WASTE (faeces and urine) also contain NITROGEN COMPOUNDS, these are also turned into AMMONIA by SAPROBOINTS and go on to form AMMONIUM IONS NITRIFICATION - nitrification is when AMMONIUM IONS in the SOIL are CHANGED into NITROGEN COMPOUNDS that can then be used by plants (nitrates) - first nitrifying bacteria called NITROSOMONAS change AMMONIUM IONS -> NITRITES - then other nitrifying bacteria called NITROBACTER change NITRITES -> NITRATES DENITRIFICATION - denitrification is when NITRATES IN THE SOIL ARE CONVERTED INTO NITROGEN GAS BY DENITRIFYING BACTERIA - they use nitrates in the soil to carry out respiration and produce NITROGEN GAS - this ^ happens under anaerobic conditions (where there is NO OXYGEN), like in WATERLOGGED SOILS - other ways that nitrogen gets into an ecosystem are by LIGHTNING (which fixes atmospheric nitrogen into nitrogen oxides) OR by ARTIFICIAL FERTILISERS (they are produced from atmospheric nitrogen on an INDUSTRIAL SCALE in the HARBER PROCESS)

Answer 81

- plants and animals need phosphorous to make BIOLOGICAL MOLECULES, like PHOSPHOLIPIDS (make up cell membranes), DNA and ATP - phosphorous is found in rocks and dissolved in the oceans in the form of phosphate ions - phosphate ions dissolved in water in the soil can be assimilated (absorbed and then used to make more complex molecules) by plants and other producers PROCESS - phosphate ions in rocks are released into the soil by weathering - phosphate ions are taken into the plants through roots, mycorrhizae greatly INCREASE the rate at which phosphorous can be ASSIMILATED - phosphate ions are TRANSFERRED through the food as animals eat the plants and are in turn eaten by other animals - phosphate ions are LOST from the ANIMALS in WASTE PRODUCTS - when PLANTS and ANIMALS DIE, SAPROBIONTS are involved in BREAKING DOWN the ORGANIC COMPOUNDS, releasing phosphate ins into the soil for assimilation by plants and these microorganisms also release the phosphate ions from URINE and FAECES - WEATHERING OF ROCKS also RELEASES PHOSPHATE IONS into seas, lakes and rivers. this is taken up by AQUATIC PRODUCERS, like algae and passed along the food chain to birds - the WASTE produced by the SEA BIRDS is known as GUANO and contains a HIGH PROPORTION OF PHOSPHATE IONS. guano RETURNS a SIGNIFICANT AMOUNT of PHOSPHATE IONS to SOILS (especially in coastal areas) and it is often used as a NATURAL FERTILISER

Answer 82

- they can add extra nutrients, like nitrogen and phosphorous - this could cause environmental problems because there needs to be a balance between adding to much and too little

Answer 83

- crops take in minerals from the soil as they GROW and use them to BUILD THEIR OWN TISSUES - when crops are HARVESTED, they are REMOVED from the field where they are grown instead of being allowed to die and decompose there - this means that the mineral ions that they contain, like phosphates and nitrates, are NOT returned to the soil by DECOMPOSERS in the nitrogen or phosphorous cycles - phosphates and nitrates are lost from the system when animals or animal products are removed from the land - animals eat grass and other plants, taking in their nutrients - when they are taken somewhere else for their slaughter or transferred to a different field, the nutrients aren't replaced through their remains or waste products

Answer 84

- adding fertile replaces lost minerals, so more energy from the ecosystem can be used for growth, INCREASING THE EFFICIENCY OF ENERGY TRANSFER - fertilisers can be artificial or natural - artificial fertilisers are inorganic - they contain pure chemicals, like ammonium nitrate, as powders or pellets - natural fertilisers are ORGANIC MATTER, they include manure, composted vegetables, crop residues (plants of left over after the harvest) and sewage sludge

Answer 85

- sometimes, more fertilisers is applied than the plants need or are able to use at a particular time and this can lead to the fertilisers LEACHING into waterways - leaching = is when water-soluble compounds in the soil are washed away, by rain or irrigation systems for ex and they are often washed into nearby ponds and rivers which can lead to EUTROPHICATION - inorganic ions in chemical fertilisers are relatively solouble - this means excess minerals that aren't used immediately are more likely to leach into waterways - leaching is also more likely to occur if the fertiliser is applied just BEFORE heavy rainfall - leaching is LESS LIKELY with natural fertilisers because the nitrogen and phosphorous are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants - this means that their release into the soil for UPTAKE by plants is MORE CONTROLLED - the leaching of PHOSPHATES is LESS LIKELY than the leaching if NITRATES, because PHOSPHATES ARE LESS SOLUBLE IN WATER - using fertilisers may also change the balance of nutrients in the soil and too much of a certain nutrient can cause crops and other plants to die

Answer 86

- eutrophication is caused by excess nutrients - mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers - large amounts of algae block light from reaching plants below - eventually the plants die because they are unable to photosynthesise enough - bacteria feed on the dead plant matter and the increased numbers of bacteria REDUCE 02 CONC in the WATER by carrying out AEROBIC RESPIRATION - fish and other aquatic organisms die as there isn't enough dissolved oxygen

CHAPTER 5 - PHOTOSYNTHESIS, RESPIRATION AND NUTRIENT CYCLES Flashcards

- photosynthesis, LDR and LIR - limiting factors in photosynthesis - aerobic and anaerobic respiration - energy transfer in ecosystems - farming practices - nutrient cycles - fertilisers and eutrophication