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AQA ALEVEL BIOLOGY P1/P2 > 5. ENERGY > Flashcards

5. ENERGY Flashcards

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1
Q

What is the source of energy for an ecosystem?

A

sunlight

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2
Q

What is the role of producers, consumers, decomposers in an ecosystem?

A

-producers = plants, perform photosynthesis, use light energy to make biological moleucles

  • Consumers = animlas cannot make their own biological molecules, need to eat plants (primary consumers) or other animals (secondary/tertiary consumers) to obtain biological molecules
  • decomposers = bacteria and fungi, perform saprobiotic decomposition, release enzyme onto dead plants/dead animals/animal waste (organic matter) breaking them down to obtain biological molecules
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3
Q

Why do producers (plants) need biological molecules?

A
  • Glucose = respiration, stored as starch, makes cellulose
  • Amino Acids = make proteins e.g. enzymes
  • Fatty Acid & Glycerol = make triglyceride as an energy store, making phospholipid for membranes
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4
Q

Why do consumers (animals) need biological molecules?

A
  • Glucose = respiration, stored as glycogen
  • Amino Acids = make proteins e.g. enzymes
  • Fatty Acid & Glycerol = make triglyceride as energy store and insulation/protection, making phospholipid for membranes
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5
Q

Why do decomposers (bacteria/fungi) need biological molecules?

A
  • Glucose = respiration
  • Amino Acids = make proteins e.g. enzymes
  • Fatty Acid & Glycerol = make phospholipids for membranes
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6
Q

How do organisms carry energy?

A
  • Main Source = Glucose
  • Stored as Starch in plants and Glycogen in animals
  • Alternative Source = Lipids/Fats/Triglycerides and Proteins
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7
Q

How does energy move through an ecosystem?

A

by the food chain, beginning with the producer and then moves on to primary consumer, then the secondary consumer, then the tertiary consumer – with decomposers occurring at each stage (trophic level)

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8
Q

Why is all the light energy not utilised by plants in photosynthesis?

A

only 2% is used in photosynthesis – of the rest, a certain part misses the chloroplast, the other parts would be reflected or the wrong wavelength

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9
Q

Why is energy lost along a food chain?

A
  • not all the glucose made by producers is stored as starch or used to build biomass, as a certain part is lost in respiration (as heat)
  • not all the stored energy in the plant is transferred to primary consumers as certain parts of the plant are inedible and indigestible (available to decomposers)
  • of the energy the primary consumer obtains, a certain amount is used in respiration, the rest is stored as glycogen and used to build biomass
  • not all this stored energy is transferred to secondary consumers due to inedible parts and indigestible parts (available to decomposers)
  • only 10% of energy is transferred from producer to primary consumer
  • only 20% of energy is transferred from consumer to consumer
  • the losses are due to respiration, inedible parts, indigestible parts
  • higher proportion is transferred from consumer to consumer because consumers are more edible and digestible, producers are made up of cellulose
  • the higher consumers have the highest respiratory losses as they have increased movement (hunt for food)
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10
Q

Effect of energy loss on a food chain?

A

places a limit on the length of a food chain, those at the higher trophic levels (just quaternary consumers) would not obtain enough energy from the food it consumes

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11
Q

What is Productivity?

A
  • Productivity = Amount of Glucose/Energy available to the organism
  • Primary Productivity = Amount of Glucose/Energy available in Plants
  • Secondary Productivity = Amount of Glucose/Energy available in Animals
  • Net Productivity = Gross Productivity – Respiratory [and Faeces] Losses
  • Gross Primary Productivity is the amount of glucose made by plant in photosynthesis,
  • Net Primary Productivity is the amount of glucose stored as starch after respiration
  • Gross Secondary Productivity is amount of glucose consumed by animal,
  • Net Secondary Productivity is amount of glucose stored as glycogen after respiration in all cases, net productivity is the glucose/energy available to organisms at the next stage of food chain
  • respiratory losses are higher in consumers then producers due to movement
  • and respiratory losses are higher in secondary/tertiary/quaternary consumers then primary consumers as they move more to hunt for food
  • and respiratory losses are higher in consumers that have to maintain a constant body temperature (endotherms)
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12
Q

What does a Pyramid of Number represent?

A
  • number of each type of organism at each trophic level – the numbers decrease as we move up trophic levels due to the loss of energy (not as many individuals can be supported)
  • can look inverted when it does not take into account mass (e.g. 1 oak tree or millions of fleas)
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13
Q

What does a Pyramid of Biomass represent?

A
  • biomass of each type of organism at each trophic level
  • biomass = mass of living tissue (based on dry mass, water excluded)
  • biomass includes biological molecules, organelles, cells, tissues, organs
  • units for biomass (g per m2 for land based animals, g per m3 for water based animals)
  • so as we move along a food chain (up trophic levels) there is a loss of energy due to respiration/inedible parts/indigestible parts, so there is less energy to build biomass, so biomass decreases
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14
Q

What does a Pyramid of Energy represent?

A
  • amount of energy found at each trophic level
  • as before, loss of energy occurs along a food chain (respiration, inedible parts, indigestible parts)
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14
Q

What are the units for energy?

A

kJ/m2 /year

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15
Q

What is photosynthesis?

A
  • using light energy to make glucose (and other biological molecules)
  • occurs in plants and algae (both have chloroplast)
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16
Q

Adaptation of plant for photosynthesis?

A
  • leaf located near top of plant = closer to light
  • leaf is thin and wide = large surface area for light, short diffusion distance for CO2
  • has many veins = connect to xylem to bring in water
  • has stomata for gas-exchange (CO2/O2)
  • has air spaces to support ease of gas-exchange
  • palisade cells located near top of leaf close to the light
  • palisade cells are large = large surface area for light
  • palisade cells have a thin cell wall = short diffusion distance for CO2
  • palisade cells contain many chloroplasts (site of photosynthesis)
  • palisade cells have a large vacuole = pushes chloroplast to edge of cell closer to light
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17
Q

Structure of chloroplast?

A
  • site of photosynthesis
  • has a double membrane (outer and inner)
  • contains discs called thylakoids (contain chlorophyll)
  • a stack of thylakoids = granum
  • thylakoids are surrounded by a fluid material called stroma
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18
Q

How does photosynthesis take place?

A
  • In 2 stages
  • light dependent stage = on thylakoids, makes ATP and reduced NADP
  • light independent stage = in stroma, uses the ATP and reduced NADP to make glucose
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19
Q

Describe the light dependent stage?

A
  • light hits chlorophyll
  • chlorophyll absorbs the light if correct wavelength
  • electrons become excited and are lost from the chlorophyll (photoionisation)
  • electrons enter an electron carrier system
  • electrons move down the system releasing energy
  • this pumps protons from stroma into thylakoid space
  • protons accumulate in thylakoid space, then diffuse back into stroma
  • they pass though ATP Synthase which joins ADP and Pi to make ATP (mechanism = chmeiosmosis, process = photophosphorylation)
  • the electron ends up by joining with NADP to form reduced NADP
  • light also hits water
  • causes photolysis (breakdown of water due to light)
  • forms: H+, e-, O2
  • the H+ joins with the reduced NADP (now carries a hydrogen atom: H+ and e-)
  • the e- replaces electrons lost from chlorophyll
  • O2 given off as waste
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20
Q

Describe the light independent stage?

A
  • involves the calvin cycle
  • RuBP (5 carbon) joins with CO2 to make 2 lots of GP (3 carbon)
  • the GP is reduced into TP (3 carbon)
  • this uses energy from ATP and hydrogen atom from reduced NADP
  • the TP can be used to reform RuBP (uses energy from ATP)
  • the TP can also be used to form glucose (carbohydrate)
  • GP can also be used to form amino acids (proteins) and fatty acids
  • TP can also be used to form glycerol
  • fatty acids and glycerol will form a lipid
  • photosynthesis/calvin cycle = produces all the main biological molecules
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21
Q

What are the limiting factors for photosynthesis?

A

factors that limit the rate of photosynthesis, when these factors are increased – the rate of photosynthesis increases, these are Light and CO2 and Temperature

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22
Q

Effect of limiting Light on the calvin cycle?

A
  • RuBP decreases – being converted into GP but not being reformed from TP (no ATP)
  • GP increases – not converted into TP (no ATP/reduced NADP) but is being formed from RuBP
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23
Q

Effect of limiting CO2 on the calvin cycle?

A
  • RuBP increases – not converted into GP (no CO2) but is being reformed from TP
  • GP decreases – not being formed from RuBP (no CO2) but being converted into TP
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24
Q

What is the compensation point in plants?

A
  • the point in the day (light intensity) when the CO2 taken in by photosynthesis equals the amount given out by respiration = no net gas exchange
  • at low light intensity: rate of respiration > rate of photosynthesis [CO2 released]
  • at high light intensity: rate of photosynthesis > rate of respiration [CO2 absorbed]
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25
Q

How to measure rate of photosynthesis?

A
  • measure amount of CO2 used or measure amount of O2 produced, in a certain time
  • one method = photosynthometer
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26
Q

How does a photosynthometer work?

A
  • measures amount of O2 produced
  • uses aquatic plants (e.g. elodea), as the O2 produced can be observed and collected
  • the plant is surrounded in sodium hydrogencarbonate solution (CO2 source)
  • the plant is kept in darkness before experiment runs (uses up all the O2 in the plant)
  • as the experiment runs, O2 will be produced, this will be collected in a capillary tube
  • the amount collected can be measured, this will be converted into a volume by multiplying length of oxygen bubble collected by πr2
  • volume of O2 collected can then be divided by time to calculate rate of photosynthesis
27
Q

Structure of ATP?

A
  • Adenosine Triphosphate
  • made from 1 adenosine and 3 phosphates
  • energy carrier molecule
  • formation: ADP + Pi (+ energy used) = ATP
  • condensation reaction using enzyme ATP Synthase
  • carries energy in its bonds
  • breakdown: ATP = ADP + Pi (+ energy released)
  • hydrolysis reaction using enzyme ATPase
  • delivers energy after breakdown
28
Q

How can ATP be formed?

A
  • photophosphorylation (light dependent stage of photosynthesis)
  • substrate-level phosphorylation (glycolysis and krebs cycle of respiration)
  • oxidative phosphorylation (electron transport chain of respiration)
29
Q

What makes ATP (from respiration) a good source of energy?

A
  • immediate source = need to only break one bond to release energy (plus bond is weak)
  • manageable source = releases small amount of energy
30
Q

Uses of ATP (made by respiration) in organisms?

A
  • protein synthesis
  • organelle synthesis
  • DNA replication
  • cell division (mitosis/meiosis)
  • active transport
  • metabolic reactions
  • movement (e.g. muscle contraction)
  • maintaining body temperature
31
Q

What is respiration?

A
  • releasing energy from glucose to make ATP
  • ATP will provide energy for life processes
  • occurs in all living organisms
  • ATP can be made by substrate-level phosphorylation (glycolysis & krebs cycle) and oxidative phosphorylation (electron transport chain)
32
Q

What are the 2 types of respiration?

A

aerobic (with oxygen) and anaerobic (without oxygen)

33
Q

Describe Aerobic Respiration?

A
  • occurs in 4 stages: Glycolysis, Link Reaction, Krebs Cycle, Electron Transport Chain
  • glycolysis takes place in cytoplasm of the cell
  • link reaction and krebs cycle take place in matrix of mitochondria
  • electron transport chain takes place on inner membrane of mitochondria (cristae)
  • the main job of the first 3 stages are to provide reduced NAD and reduced FAD for the last stage, this is where most of the ATP is made by oxidative phosohorylation
34
Q

what happens in glycolysis

A
  • glycolysis
  • uses glucose to produce 2x pyruvate, 2x ATP, 2x reduced NAD
  • pyruvate enters link reaction
  • ATP made by substrate-level phosphorylation
  • reduced NAD used in ETC
35
Q

what happens in link reaction?

A
  • link reaction
  • uses pyruvate to produce acetylcoenzyme A, reduced NAD, CO2
  • pyruvate + coenzyme A + NAD = acetylcoenzyme A + reduced NAD + CO2
  • acetylcoenzyme A used in krebs cycle
  • reduced NAD used in ETC
  • CO2 given off as waste
36
Q

what happens in kreb cycle?

A
  • krebs cycle
  • uses acetylcoenzyme A to produce 3x reduced NAD, 1x reduced FAD, 1x ATP, 2x CO2
  • reduced NAD and reduced FAD used in ETC
  • ATP made by substrate-level phosphorylation
  • CO2 given off as waste
37
Q

explain the electron transport chain?

A
  • reduced NAD and reduced FAD release the hydrogen atom (protons/electrons) they are carrying
  • the protons build up in the matrix of the mitochondria
  • the electron enter the ETC
  • the electron moves along the chain releasing energy, this pumps the protons from the matrix into the intermembranal space
  • the proton build up in the intermembranal space, then diffuse back into the matrix via a transport protein carrying ATP Synthase enzyme
  • this leads to the production of ATP = oxidative phosphorylation
  • oxygen is used as a final electron acceptor and proton acceptor
  • it removes the electron from the end of the ETC, so the ETC can continue
  • it removes the proton from the matrix, hence maintaining concentration gradient
  • it becomes water
38
Q

Describe anaerobic respiration?

A
  • no oxygen present, so no final electron acceptor and proton acceptor
  • ETC stops
  • Krebs Cycle and Link Reaction also stop as NAD amd FAD are not reformed in ETC
  • Glycolysis can continue as it reforms its own NAD
  • so Anaerobic Respiration only relies on Glycolysis (making 2x ATP by substrate-level phosphorylation
  • NAD is reformed from the reduced NAD made in glycolysis
  • the reduced NAD donates its hydrogen atom (H+/e-) to pyruvate to reform NAD
  • in animals the pyruvate becomes lactate (lactic acid)
  • in plants/yeast the pyruvate becomes ethanol and CO2
39
Q

How to measure rate of respiration?

A
  • measure amount of O2 used or measure amount of CO2 produced, in a certain time
  • one method = respirometer
40
Q

How does a respirometer work?

A
  • measures amount of gas exchange taking place between organism and the air in a test tube
  • the test tube is connected to a manometer (a U-shaped tube that contains a coloured liquid)
  • if the organism takes in more gas then it gives out (more O2 in), the amount of air in the test tube decreases, therefore there will be less pressure on the coloured liquid in the manometer, therefore the coloured liquid will move towards the test tube
  • if the organism gives out more air than it takes in (more CO2 out), the amount of air in the test tube increases, therefore there will be more pressure on the coloured liquid in the manometer, therefore the coloured liquid will move away from the test tube
  • the amount/volume by which the coloured liquid moves represents the volume of gas taken in or given out
41
Q

What are the Respiratory Substrates?

A
  • Carbohydrates, all forms of carbohydrates (starch/glycogen/lactose/sucrose) are turned into glucose
  • Proteins, excess amino acids are converted into keto acid
    [keto acid turned into pyruvate and intermediates of krebs cycle]
  • Lipids, provided fatty acids and glycerol
    [fatty acids become acetylcoenzyme A, glycerol becomes triose phosphate]
42
Q

What is the value of Nitrogen to organisms?

A

used to make amino acids & proteins and used to make nitrogenous bases in DNA

43
Q

Describe the nitrogen cycle?

A
  • nitrogen present in the atmosphere as nitrogen gas (N2)
  • N2 cannot be absorbed by plants, they can only absorb Nitrate ions (NO3-)
  • N2 converted into Ammonium Ions (NH4+) by nitrogen fixation by nitrogen-fixing bacteria
  • there are 2 types of NFB: mutualistic and free-living
  • mutualistic NFB are found in the root nodules of leguminous plants, they place the NH4+ ions directly in the roots – these plants can use this to make AA and nucleotides
  • free-living NFB are found in the soil – they place NH4+ ions in the soil
  • NH4+ ions cannot be absorbed by plants therefore is converted into NO3- by nitrification by nitrifying bacteria
  • Ammonia ions (NH4+) into Nitrite ions (NO2-) into Nitrate ions (NO3-)
  • the NO3- ions will be absorbed by plants to make AA/proteins and nucleotides/DNA
  • consumers can eat the plant to obtain the AA and nucleotides
  • organic material (dead plants, dead animals, animal waste) are broken down by saprobiotic decomposers, this releases Ammonia ions (NH4+) back into the soil by a process called ammonification
  • Nitrate ions (NO3-) can be converted back into Nitrogen gas (N2) by denitrification by denitrifying bacteria – they work in anaerobic conditions (when the field is waterlogged and all the air spaces in the soil are filled with water)
44
Q

What is the value of Phosphorous to organisms?

A

used to make Phospholipid
used to make DNA
used to make ATP

45
Q

How are crops intensively farmed for high yield?

A
  • select suitable location (sunlight, water, minerals)
  • clear area of plants and animals (deforestation – removes competition/pest)
  • selectively breed crop
  • use greenhouse to provide high levels of light, CO2, temperature
  • provide water by irrigation
  • add fertilisers (provides minerals = nitrate, phosphate, magnesium)
  • control pests
  • polyculture/crop rotation (ensures mineral levels in the soil do not become depleted)
  • ploughing (adds air spaces to soil, so bacteria involved in nutrient cycles can aerobically respire)
46
Q

Describe the phosphorous cycle?

A
  • phosphorous present in sedimentary rock as phosphate ions (PO43-)
  • when sedimentary rock erodes, leaves soil containing PO43-)
  • plants absorb PO43-) to make phospholipid/DNA/ATP
  • consumers eat plants to obtain phospholipid/DNA/ATP
  • organic material (dead plants, dead animals, animal waste) are broken down by saprobiotic decomposers, this releases Phosphate Ions (PO43-) back into the soil
  • (if soil sediments and hardens, over time, it returns to a rock state)
  • [mycorrhize are fungi in the roots of plants to support uptake of scarce minerals like phosphate ions]
46
Q

Agricultural ecosystem?

A
  • description for farming ecosystems
  • aim of farms is to grow crops and raise animals
  • grow crops to sell & feed farm animals
  • raise animals to sell meat & other resources (e.g. wool, eggs, milk, leather)
47
Q

What are pests?

A

organisms that harm plants/crops – other plants (weeds) acts as competitors, insects eat the plant, fungi cause disease

48
Q

What are pesticides?

A

chemical sprays that kill the pest,
for weeds = herbicide,
insects = insecticide, fungi = fungicide

48
Q

How can pests be controlled?

A

pesticides or biological control

49
Q

Advantages and Disadvantages of using pesticides?

A
  • advantages
  • fast acting
  • can control area covered
  • disadvantages
  • non-specific
  • non-biodegradable leading to bioaccumulation and toxicity in the higher trophic levels
  • pest may be resistant
  • needs to be reapplied
50
Q

What are biological control?

A

using predators or parasites to the pest

51
Q

Advantages and Disadvantages of using biological control?

A
  • advantages
  • specific
  • does not cause bioaccumulation
  • pests do not develop resistance
  • does not need to be reapplied
  • disadvantages
  • slow acting
  • may become a pest itself
  • cannot control area covered
52
Q

What is Bioaccumulation?

A
  • Pesticides are not biodegradeable
  • therefore, they remain stored in organism’s tissues
  • therefore, they accumulate along a food – up trophic levels
  • therefore, they are toxic to consumers at higher trophic levels
53
Q

What is an integrated pest control system and process?

A
  • makes use of both pesticides and biological control – the aim is to reduced the amount of pesticide used, as the pesticide harms food chains and ecosystems
  • process:
  • keep some native trees (will act as natural habitats to natural biological controls)
  • monitor area for pests
  • mechanically remove pests if present
  • initial dose of pesticide – fast acting
  • then apply biological control – will increase in number over time and provide long term control
  • reapply pesticides whenever there is an uncontrollable outbreak
54
Q

What minerals do fertilisers provide?

A
  • nitrate = make AA, make nitrogenous bases
  • phosphate = make ATP, DNA, phospholipids
  • magnesium = make chlorophyll
55
Q

What are the 2 types of fertilisers?

A
  • natural/organic = applying dead plants, dead animals, animal waste (decomposed leading to ammonification, followed by nitrification to provide source of NO3- nitrate)
  • artificial/chemical = spraying on concentrated solutions of the minerals
56
Q

Natural vs Artificial Fertilisers?

A
  • Natural = reduced risk of leaching/eutrophication but slower release of minerals
  • Artificial = faster release of minerals and higher concentration but risk of leaching/eutrophication and lowers water potential of soil (so plant absorbs less water by osmosis)
57
Q

What is the benefit of ploughing?

A

increases amount of air spaces in the soil, supports aerobic respiration of decomposers and bacteria involved in nitrogen cycles (nitrogen fixing bacteria & nitrifying bacteria preveting denitrifying bacteria)

58
Q

What is eutrophication?

A
  • if large amounts of chemical fertilisers are sprayed onto fields and heavy rainfall occurs, the fertiliser may leach into local water sources
  • the fertiliser will travel and build up in ponds or lakes
  • the mineral (e.g. nitrates to make AA) will be absorbed and used by Algae
  • this will lead to an increase growth of algae = algal bloom
  • the algae grows on the upper surface of the water, this prevents light reaching the plants at the bottom of the water
  • these plants cannot photosynthesise, so die
  • these provide more nutrients to saprobitoic decomposers, so these increase in number
  • the decomposers will aerobically respire, using up the oxygen in the water
  • therefore fish die as less oxygen is available
59
Q

Environmental impact of Crop Farming?

A
  • Deforestation = reduces species diversity, reduces plant species diversity, less habitats and food sources, reduces animal species diversity
  • Monoculture = one type of plant/crop grown, depletes certain nutrients in the soil (no time provided for nutrient levels to recover)
  • Selective Breeding = reduces genetic diversity of crop (reduces variation, reduces abilit to adapt to changes in the environment)
  • Pollution = bioaccumulation of pesticides, eutrophication from chemical fertilisers
60
Q

Reducing Environmental impact of Crop Farming?

A
  • keep some native trees (helps to maintain species diversity)
  • keep hedgerows (help to maintain species diversity + absorb chemical fertilisers reducing eutrophication)
  • polyculture (grow different crops at different times of the year, allows depleted nutrients to recover in the soil)
  • keep seeds of wild crop (maintain genetic diversity, use if environment changes)
  • use biological control for pests & natural fertiliser for minerals
61
Q

How are animals (domestic livestock) intensively reared in farming?

A
  • selectively bred
  • given predigested food (enzymes added), with high protein and high energy levels
  • given antibiotics and vaccinations
  • given steroid hormones
  • restricted movement and kept warm (reduce energy loss)
62
Q

Natural Ecosystem vs Agricultural Ecosystem (farms)?

A
  • natural = light energy source, agricultural = light + food for farmer + fossil fuel for machines
  • natural = high biodiversity, agricultural = low
  • natural = high species diversity, agricultural = low
  • natural = high genetic diversity, agricultural = low
  • natural = low productivity, agricultural = high
  • natural = nutrients recycled, agricultural = nutrients added (fertiliser)
  • natural = competition/predators control pests, agricultural = pesticides/biological control
  • natural = reaches climax community, agricultural = prevent climax from being reached

AQA ALEVEL BIOLOGY P1/P2 (8 decks)

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