AQA GCSE Core Biology [Higher]


Diet and Metabolic Rate (Pg. 13)

A Balanced Diet

  • Provide the energy you need.
  • Balance of the right foods:
    • Carbohydrates (release energy); Fats (keep warn and release energy); Proteins (cell repair, replacement, and repair); Fibre (keep everything moving in the digestive system); Vitamins & Minerals (healthy skin, bones, and blood)

Diet Dependence

  • Depends on your metabolism
    • Metabolism is "the chemical processes that occur within a living organism in order to maintain life."
  • Metabolism varies, depending on the person: little exercise = less energy = less fats and carbohydrates.
    • High muscle:fat ratio = higher metabolism
    • Bigger people = higher metabolism
    • Men tend to have a higher metabolism
    • Regular exercise increases metabolic rates.
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Factors Affecting Health (Pg. 14)

  • Malnourished = unbalanced diet (either too fat or thin, or unhealthy in other ways)
  • Excess carbohydrates or fat leads to obesity:Excess saturated fat = increase in blood cholestrol levels
    • 20% or more over the recommended body mass.
    • Hormonal problems; bad diet; overeating; and lack of exercise all cause obesity.
    • Can cause arthritis (inflammation of joints); type 2 diabetes (inability to control sugar levels); high bloody pressure and heart disease.
  • Excess salt = high blood pressure; heart problems
  • Eating too little = slow of growth; fatigue; poor resistance to infection; irregular periods
  • Deficiency diseases = lack of vitamins or minerals (i.e. lack of Vitamin C = scurvy)
  • Exercise increases amount of energy used; decreases amount of stored fat.
  • You can be fit and unhelathy - physically fit but malnourished.
  • Inherited factors:
    • Underactive thyroid gland = lower metabolic rates; can cause obesity.
    • Blood Cholestrol level = fatty substances in blood (essential); too much increases heart disease chance.
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Evaluating Food, Lifestyle and Diet (Pg. 15)

  • In the exam, you may have to evaluate information about how food affects health.
  • You may get asked to evaluate lifestyle choices (what you eat and do).
    • You must use your own knowledge to answer these questions in the exam.

Watch out for slimming claims that aren't scientifically proven

  • Lots of slimming products (e.g. diet pills) and slimming programmes (e.g. the Atkins Diet) claim they'll help you lose weight.
  • Look out for:
    • Scientific study evidence; qualified author; sample range; other study comparison.
    • There has to be a large survey for it to be assured.
  • To lose weight, you have to take in less energy than you use:Some claims may also be true, but misleading (i.e. low in fat cereal bars, but no overall effect on health).
    • Eat less fat or carbohydrate.
    • Do more exercise.
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Fighting Disease (Pg. 16)

  • Bacteria are very small living cells
    • Small cells (1/100th of you body cell)
    • Make you feel ill by: damaging your cells; producing toxins (poisons)
  • Viruses are not cells - they're much smallerSkin, hairs, and mucus stop a lot of pathogen.
    • 1/100th of a Bacterium
    • Replicate themselves by invading your cells to make copies; cells burst releasing virus.
    • Cell damage makes you feel ill.
  • Skin, hairs, mucus stop pathogen getting in your body.
  • Platelets help blood clots appear when you cut yourself, stopping pathogen entry.
  • White Blood Cells [WBCs] (part of the Immune System) can:
    • Consume them (engulf and digest foreign cells)
    • Produce AntibodiesProducing Antitoxins (counteracts toxins produced by invading bacteria).
      • WBCs produce proteins [antibodies] to lock on and kill invading cells; only designed for one cell type; antibodies are produced rapidly and kill similar bacterium or viruses; WBCs will recreate these antibodies if person becomes reinfected.
    • Produce Antitoxins (counteract toxins from invading bacteria)
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Fighting Disease - Vaccination (Pg. 17)

  • Vaccinations - small amounts of dead/inactive microorganisms.
    • Carry antigens, body produces antibodies to attack them; WBCs remember the type of antigen and will produce antibodies to rapidly kill invading microorganisms (i.e. MMR vaccination).
  • Some vaccinations wear off over time, boosters may be needed.
  • Pros of vaccinations:
    • Controls a lot of infectious diseases (i.e. Smallpox); prevents epidemics
  • Cons of vaccinations:
    • Don't always work (don't give you immunity); may have a bad reaction (though this is very rare)
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Fighting Disease - Drugs (Pg. 18)

  • Some relieve symptoms, others cure problems.
    • Painkillers (i.e. Aspirin) relieves symptoms; antibiotics (i.e. Penicillin) kill bacteria, doesn't stop a virus
  • Bacteria can become resistant to Antibiotics (Antibiotic Resistance)
    • Bacteria mutate; infection becmes rantibiotic resistant; non-resistant bacteria killed; resistant survive and reproduce; mutations cause serious infections; slow mutations by not over-prescribing antibiotics.
  • Investigate Antibiotics by Growing Microorganisms in the Lab
    • Grow them in "culture medium" (usually agar jelly) containing carbohydrates, minerals, proteins, and vitamins.
    • Hot agar jelly poured into Petri Dishes; when cooled use an inoculating loop to put microorganism in jelly.
    • Paper discs soaked in antibiotics and placed on jelly; resistant bacteria survive.
    • All equipment must be steralised before use - pass through a flame; lid is used to stop other microorganisms.
    • Microorganisms are usually stored at 25C at school - harmful pathogens cannot grow; temperature much higher in industrial conditions.
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Fighting Disease - Past and Future (Pg. 19)

  • Semmelweis - observed women dying from puerperal feer after childbirth; doctors spreading diseases through unwashed hands. He told doctors to wash hands - death rates to 2% from 12%. Antiseptic kill bacteria, but there was no evidence of this; nowadays basic hygiene is essential (though MRSA has started spreading)
  • More Common Antibiotic Resistance - death rates fallen; overuse of antibiotics means resistance; can't easily treat; big problem in modern world; suberbugs (bacteria resistant to most antibiotics) are more common.
  • Bacteria
    • Mutate to new strains; antibiotic resistant; can cause epidemic
  • Virus
    • Mutate often (hard to develop vaccines); huge problem in regard to deadly and infectious virus evolution; vaccines and antiviral drugs could be developed; potential pandemic.
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The Nervous System (Pg. 20)

  • Sense organs detect stimuli (change in the environment) - eyes (light receptiors), ears (sound receptors), nose (smell receptior), tongue (taste receptor), skin (touch, pressure, pain receptor); they change stimulus energy to electrical impulses.
  • Do not get sense organs (eyes, ears, etc.) mixed up with receptors (light receptor, sound receptor, etc).
  • The Central Nervous System (CNS) coordinates the response.
    • Organises where information from sense organ is sent, and where reflexes are coordinated (brain and spinal cord only). 
    • Sensory Neurones carry electrical impulses from receptor to the CNS.
    • Relay Neurones carry signals from the sensory neurones to the motor neurone.
    • Motor Neurones carry impulses from CNS to the effector.
    • Effectors are muscles or glands that contract in response to  nervous impulse, or secrete hormones.
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Synapses and Reflexes (Pg. 21)

  • Synapses connect neurones; nerve signals transfer by checmicls which diffuse across the gap.
  • Reflexes help prevent injury; automatic responses; passage of information in reflex (receptor - effector) is a reflex arc.
  • Reflex Arc goes through the CNS - neurones go through spinal cord or unconscious part of the brain.
  • Stimulus - Sensory Neurone - Synapse - Relay Neurone - Synapse - Motor Neurone - Effector
  • Quicker than a normal response because you don't have to think about it.
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Hormones (Pg. 22)

  • Hormones are chemical messages sent in the blood; carried in blood plasma; affects target cells; hormones control things in organs and cells that need constant adjustment; produced and secreted in various glands.
  • Pituitary Gland - produces many important hormones such as FSH and LH for the menstrual cycle.
  • Ovaries (females only) produce oestrogen, used in the menstrual cycle.
  • Nerves:
    • Very fast; act for a short time; target one area.
  • Hormones:
    • Slower; act for a long time; general area.
  • If response is quick, it is probably nervous; if a response is long lasting, it's probably hormonal (i.e. adrenaline)
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The Menstrual Cycle (Pg. 23)

  • Four Stages
    • Day 1 - Bleeding Starts; Day 4-14 - Uterus Lining builds up; Day 14 - Egg Released; Day 14-28 - Wall is maintained, and will break down if no fertilised egg is present.
  • FSH (Follicle-Stimulation Hormone) - Produced in Pituitary Gland; causes egg to mature in ovaries; stimulates ovaries to produce oestrogen.
  • Oestrogen - Produced in obaries; causes pituitary to produce LH; inhibits further release of FSH.
  • LH (Luteinising Hormone): Produced by Pituitary Gland; stimulates release of an egg in middle of cycle
  • Progesterone is another hormone involved in the cycle - produced by ovaries.
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Controlling Fertility (Pg. 24)

  • Oestrogen can prevent egg release - keeping levels high inhibits FSH production, stopping egg development.
  • Progesterone reduces fertility - stimulates thich cervical mucus to prevent gamete fusion.
  • The Pill (oral contraceptive) - lower dose of Oestrogen than in 1950s, fewer side effects.
    • Pros - 99% Effective; reduces cancer risk.
    • Cons - Not 100%; side effects (headaches, nausea, irregular menstrual bleeding); doesn't stop STDs
    • There's a progesterone-only pill - fewer side effects; not as effective.
  • FSH/LH can inject, up levels to produce eggs; Pros - helps women get pregnant; Cons - not 100%; too many eggs.
  • In vitro fertilisation (sperm and egg mixed in labs), planted in Uterus once cells grow; FSH/LH given.
    • Pros: Infertile couples can have children; Cons: strong reactions, increased cancer risk, multiple births.
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Plant Hormones (Pg. 25)

  • Auxin (plant hormone) in shoot/root tips; controls growth to light (phototropism), gravity (geotropism) and moisture.
  • Moves backwards to promote cell elongation, occurs just behind the tip. Extra auxin = shoot grow, not roots.
  • Shoots grow towards the light (auxin accumulates on shady side)
  • Shoots grow away from gravity (unequal distribution of auxins to the lower side)
  • Roots grow towards gravity (extra auxin inhibits the growth, so root bends down)
  • Plant hormones are used in agriculture (i.e. Weed Killers don't affect crops)
  • Rooting powder will allow plant cuttings to grow in soil - good to clone really good plant quickly
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Homeostasis (Pg. 26)

  • Ion content, water content, sugar content, and temperature need to be monitored and constant.
  • Ions regulated in kidney; taken in by food, absorbed in blood, excess ions removed; lost in sweat or urine.
  • Water taken in by food/water; lost through sweat (skin), breath (lungs), and urine (kidneys)
    • Cold days = more urine (less concentrated), less sweat; hor days = less urine (more concentrated), more sweat
  • Body temperature controlled by brain (enzymes work best at 37C) - own personal thermostat.
  • Carbyhydrates put glycose into blood from gut; more exercise = more removed; insulin maintains glucose levels.
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Drugs (Pg. 27)

  • Drugs - change body chemistry; leads to addiction; can cause withdrawal symptoms if stopped.
  • Medical Drugs (medically useful); Recreational Drugs (fun - legal or illegal); Performance-enhancing Drugs (sport).
  • Performance-enhancing drugs include anabolic steroids (increase muscle size), stimulants (increase heart rate); negative effects (high blood pressure); some are illegal, all are banned by sporting bodies.
  • Against Drugs: Unfair for an advantage; athletes may be misinformed of risks.
  • For Drugs: Athletes have the right to their own decision; drug-free sport isn't always "fair".
  • Statins: Prescribed drugs; lower risk of heart/circulatory disease; lower cholesterol; original research by Government (6000 patients); two groups of pateints (statin users and non-statin users).
  • Cannabis: illegal drug; varied results into mental health problems; no definite evidence.
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Testing Medicinal Drugs (Pg. 28)

  • Stage One: testing on human cells/tissues in labs; cannot test drugs that affect whole body.
  • Stage Two: live animal testing (best dosage and toxicity of drug); two mammal restriction for testing (cruel ethically).
  • Stage Three: healthy human volunteers; low dose increased over trial; then tested on ill patients; tested in two groups (drug users and placebo - see effects - blind tests).
  • Thalidomide (1950s) intended to be sleeping pill but could cure morning sickness; wasn't tested in advance; caused abnormal limb development (could affect the fetus and penetrated the placenta); 10,000 babies affected by thalidomide, half survived; drug banned and more rigorous testing introduced.
  • Thalidomide used in treatment of leprosy and other diseases.
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Recreational Drugs (Pg. 29)

  • Recreational Drugs - legal or illegal; hard (more addictive/harmful) and soft; all can cause heart/circulatory problems.
  • Reasons for use: enjoyment; relaxation; stress relief; sometimes influenced by background.
  • Canabis classification: desire to try hard drugs; contact drug dealers; genetic influence.
  • Some legal drugs have more impact than illegal.
  • Smoking: can cause heart, blood vessel, and lung disease; tobacco smoke causes cancers; nicotine is addictive.
  • Alcohol: slows down body's reactions; impairs judgement; can cause liver and brain damage.
  • Tobacco and alcohol has bigger impacts in UK; NHS overrun by lung diseases and alcohol crime.
  • Sorrow and anguish for people affected directly and indirectly.
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Adaptations (Pg. 31)

  • Desert Animals to save water and keep cool: Large SA to Volume Ratio (lose body heat); Water Efficient (concentrated urine, little sweat); Good in Hot Conditions (thin body fat/coat); Camouflage (avoid predators, sneak up on prey).
  • Artic Animals to reduce heat loss: Small SA to Volume Ratio (round shape, minimise SA); Well Insulated (thick layer of blubber, energy store); Camouflage (avoid predators, sneak up on prey).
  • Desert Plants adapt to little water: Small SA to Volume Ratio (spines instead of leaves reduce water loss); Water Storage Tissues (i.e. cactus stores in thick stem); Maximising Water Absorption (shallow/extensive roots).
  • Deter Predators: Armour (thorns/sharp spines/shells); Poisons (i.e. bees and poison ivy); Warning Colours.
  • Microorganisms: Some are known as extremophiles (adapted to live in extreme conditions - i.e. volcanic vents, salty lakes, high pressure)
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Competition and Environmental Change (Pg. 32)

  • Organisms compete for resources to survive: Plants - light/space/water/minerals; Animals - territory/food/water/mates
  • Compete with other/like species (i.e. Red/Grey Squirrels: Grey win the food, therefore Reds are in decline).
  • Environmental Change by Different Factors: Living Factors - infectious diseases/predators/prey/food availability/competitors; Non-Living Factors - temperature/rainfall/air or water pollution.
  • Change affects populations differently: Population increase (prey increase = predator increase); Population decrease (pesticides/less food/more disease); Population distribution (i.e. temperature)
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Measuring Environmental Change (Pg. 33)

  • Measured using living indicators: Litchen (sulfur dioxide sensitive for air pollution); Mayfly Larvae (dissolved oxygen sensitive for water cleanliness);.
  • Other invertebrate species adapt to their conditions (i.e. MAggots and Sludgeworms living in high water polution levels).
  • Measured using non-living indicators: Satellites (temperature/snow or ice cover); Automatic Weather Stations (atmospheric temperatures/rainfall - use dissolved oxygen meters to measure water pollution).
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Pyramids of Biomass (Pg. 34)

  • USUALLY as you move up the pyramid, less organisms are feeding - consider biomass and not numbers)
  • Represent food chain: mass of the living animal (practically always pyramid-shaped).
  • Bottom bar = producer; next bar = primary consumer, next bar = secondary consumer, etc.
  • Need to explain (i.e. Thousands of aphids feed on a tree, then a lot of ladybirds eat aphids, few patridges eat ladybirds).
  • Biomass always decreases as you go up.
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Energy Transfer and Decay (Pg. 35)

  • Sun energy = energy for all life; Green plants and algae use energy for photosynthesis; respiration produces heat energy - lost into surroundings; food and energy lost through waste.
  • Explains why biomass pyramids decrease as you go up (rarely more than five trophic levels).
  • Elements are cycled to start of food chain by decay: living things are made up of what they take in (i.e. plants - Carbon, Oxygen, Hydrogen, and Nitrogen); elements returned through waste products/death (become broken down by microorganisms - work best in warm/moist/oxygenated conditions); important elements recycled by decay (constant in a sable community).
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The Carbon Cycle (Pg. 36)

  • Carbon Dioxide removed from atmosphere by photosynthesis.
  • Some returned to atmosphere by plant respiration; some becomes part of pats and proteins in animals.
  • Some returned to atmosphere by animal respiration.
  • Plants/algae/animals die (or produce waste), detritus feeders and microorganisms feed on the remains/waste, and return Carbon Dioxide to atmosphere through respiration.
  • Some products are burnt (combustion) and releases Carbon Dioxide into the atmosphere.
  • Carbon is constantly being cycles, from air, through food chains, and eventually back to the air.
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Variation (Pg. 37)

  • Same Species have Differences - different hair/noses/heights etc (variation in species - genetic or environmental).
  • Different Genes = variation; parents' characteristics (inherited genes passed on through sex cells (gametes)); mix of genes from both parents (genetic variation, with the exception of identical twins).
  • Some characteristics dependent only on genes (i.e. eye colour, blood group, inherited diseases).
  • Environmental Variation (environmental influence) - losing toes in piranha attack, suntan, yellow leaves, etc.
  • Most factors are a mix of both (i.e. weight, height, skin colour, etc.) - example is that maximum height is determined by genes, but real height is dependent on its environment (i.e. how much food).
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Genes, Chromosomes and DNA (Pg. 38)

  • Most cells have a nucleus (genetic material in the form of a chromosome - 23 pairs to carry genes (characteristics)).
  • Gene = short length of a chromosome = long length of DNA (coiled up to form the arms of the chromosome)
  • Different versions of the same gene (called alleles).
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Reproduction (Pg. 39)

  • Sexual Reproduction (genetically different cells) - two different organisms combine genetic information for offspring.
  • Produced through gametes; 23 chromosomes from each parent (46 overall/23 pairs); egg and sperm cell fuse.
  • Mixture of genetic material inherited from both parents.
  • Asexual Reproduction (genetically identical cells) - divind into two; exactly the same genetic information as parent.
  • Each chromosome is split down the middle, a membrane forms around each set of half chromosomes, and replicates.
  • How all plants and animal grow replacement cells; offspring production (i.e. bacteria and certain plants)
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Cloning (Pg. 40)

  • Plants cloned from cuttings (plant good cuttings them to produce genetically identical plants - quick and cheap) and Tissue Culture (few plants cells put in growth medium with hormones; grow to be new plants (clones of parents) - quick, little space, grown all year).
  • Animal clones from Embryo Transplant (sperm from prize bull and egg from prize cow; artificially fertilise to split; implanted in other cows to grow into baby calves (genetically identical to parents); hundreds of "ideal" offspring) and Adult Cell Cloning (remove genetic material from unfertilised egg and replace with a complete set of chromosomes from an adult body cell (e.g. skin cell); cell stimulated with electric shock to form ball fo cells; implanted into adult female (surrogate mother) to grow the clone - used to create Dolly the Sheep).
  • Issues - reduced genetic pool (no different alleles, vulnerable to disease); may affect health; unsuccessful rates.
  • Advantages - greater understanding of embryo development and age related diseases; preserve endangered species).
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Genetic Engineering (Pg. 41)

  • Enzymes to cut and paste Genes - cut useful gene from one organism's chromosome using enzymes; cut out of another organism's chromosome and insert the useful gene; used to cut human insulin gene to be inserted into bacteria to produce human insulin.
  • Genes transferred into animals and plants - Genetically Modified (GM) Crops have genes modified (i.e. disease/insect/herbicide resistance); sheep modified to produce substances (like drugs) in milk to treat human diseases; Cystic Fibrosis (genetic disorder) caused by faulty genes - gene therapy by scientists trying to stop this.
  • Genetic Engineering Controversy - can solve many problems; not overly popular; may cause unplanned problems.
  • GM Crops Cons: affect number of weeds/flowers (and insect population), reducing biodiversity; may not be safe; transplanted genes may get into the environment (i.e. superweed which is resistant).
  • GM Crops Pros: increase product yield; improve nutience in plants; grown often without problem.
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Evolution (Pg. 42)

  • Everything is related in groups: plants make their own food (photosynthesis) and are fixed in one place; animals move but cannot make their own food; microorganisms are different to plants and aminals (i.e. single-cell bacteria)
  • Studying all organisms shows evolutionary relationships (similar characteristscs (common ancestor); look alike; evolutionary trees show common ancestors and relationships) and ecological relationships (similar characteristics may mean competition (i.e. for same food source); difference between organisms in the same environment can show predator-prey relationships (i.e. Dolphins (swim in small groups) hunt Herring (swim in giant sholas).
  • Natural Selection explains evolution - Darwin's Theory: Differences in genes; better adapted characteristics for environment meant better survival chance = more breeding; advantageous genes passed on to next generation.
  • Evolution occurs due to mutations - mutation = change in an organism's DNA; can be beneficial by producing a useful characteristic (better chance of survival and reproduction); passed on by natural selection; accumulate in population (i.e. bacteria and antibiotic resistance).
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More About Evolution (Pg. 43)

  • Not everyone agreed with Darwin: against creationism (religion); couldn't give a good explanation (didn't know about genes or mutations until 50 years after the theory publication); wasn't enough evidence to convince scientists.
  • Lamarck had different ideas - more use of a characteristic = more developed during lifetime; aquired characteristics would be passed onto the next generation (i.e. rabbit offspring would have longer legs to escape predators).
  • Scientists can develop different hypotheses from similar observations - different beliefs (i.e. religious) or influence (i.e. other scientists) or they just think differently.
  • Have to find evidence to either support or disprove each hypothesis (i.e. Lamarck and Darwin had different hypotheses)
  • Lamarck's hypotheses eventually rejected (no experimental support) - dying a hamster's fur bright pink will not affect offspring fur colour; genetics supported Darwin's idea (provided an explanation of how organisms born with beneficial characteristics can pass them on).
  • Darwin's theory is now accepted because there's so much evidence for it.
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