AQA GCSE Biology Unit 3 (including CGP revision guide page numbers)

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  • Biology Unit 3 (for CGP revision guide)
    • 3b (humans and their environment)
      • human impact on the environment (p89)
        • humans reduce the amount of land available to other plants and animals by...
          • farming
          • dumping waste
          • building
          • quarrying
        • we are producing more waste. this affects...
          • land
            • nuclear waste is buried underground and a lot of household waste is dumped in landfills
          • water
            • sewage and toxic chemicals can pollute lakes, rivers and oceans
          • air
            • smoke and gases are released into the atmosphere, polluting it
        • the population is rising due to...
          • modern farming methods
          • modern medicine
      • biofuels (p93)
        • ethanol
          • anaerobic fermentation of sugar
            • glucose broken down by yeast
        • biogas
          • anaerobic fermentation of waste material
            • plant and animal waste broken down by lots of different microorgansims
      • carbon dioxide and the greenhouse effect (p90)
        • carbon dioxide can be locked up in natural stores...
          • green plants
          • oceans, lakes and ponds
          • peat bogs
        • Untitled
        • the greenhouse effect
          • gases in the atmosphere naturally act like an insulating layer- e.g....
            • methane
            • carbon dioxide
          • the earth is gradually heating up because of the increasing levels of greenhouse gases
      • using biogas generators (p94)
        • batch generators
          • make biogas in small batches
          • manually loaded up with waste
          • by-products are cleared away after each session
        • continuous generators
          • make biogas all the time
          • waste is continually fed in
          • biogas is produced at a steady rate
          • more suited to large scale projects
        • factors to consider when designing a generator
          • cost
          • convenience
          • efficiency
          • position
        • greener alternative to fossil fuels
      • deforestation and the destruction of peat bogs (p91)
        • deforestation leads to...
          • less carbon dioxide taken in
          • more carbon dioxide in the atmosphere
          • less biodiversity
          • more methane in the atmosphere
        • deforestation is done to...
          • provide timber
          • clear land for framing
          • produce paper
        • peat bogs
          • areas of land that are acidic and water logged
          • plants that live there dont completley decay when they die because there is not enough oxygen
            • the partly rotted plants gradually build up to form peat
            • the carbon in the plants is stored in the peat instead of being released into the atmosphere
          • peat starts to decompose when bogs are drained, so carbon dioxide is released
      • managing food production (p95)
        • the efficiency of food production can be improved by...
          • restricting the energy lost by farm animals
          • reducing the number of stages in the food chain
          • developing new food sources like mycoprotein
      • climate change (p 92)
        • consequences of global warming
          • as the sea get warmer, it expands, causing sea levels to rise
          • the distribution of many wild animal and plant species may change
          • biodiversity could be reduced
          • changing weather patterns
          • changes in migration patterns
          • higher temperatures make ice melt, causing sea levels to rise
      • problems with food production and distribution (p96)
        • some people think that...
          • the conditions of the animals are cruel
        • disease
          • to try and prevent disease animals are given antibiotics which can enter humans when the animals are eaten
            • then antibiotics will become less effective in humans
          • the conditions make it easy for disease to spread
    • 3a (life processes)
      • Osmosis (p 73)
        • the movement of  water molecules across a partially permeable membrane from a region of low water concentration to a region of  high water concentration
        • a type of diffusion
        • water moves into and out of cells by osmosis
          • tissue fluid will usually have a different concentration to the fluid inside a cell
      • diffusion through cell membranes (p 76)
        • gas exchange happens in the lungs
          • lungs contain alveoli where gas exchange takes place- they have...
            • very thin walls
            • a moist lining for dissolving gases
            • a good blood suppy
            • an enormous surface area
        • digested food is diffused from the gut to the blood
          • the inside of the small intestine is covered in tiny projections called villi. they have...
            • a single layer of surface cells
            • a good blood suppy
      • gas and solute exchange (p 74)
        • substances move by diffusion, osmosis and active transport
        • exchange surfaces are adapted to maximise effectiveness
          • thin - so substances only have a short distance to diffuse
          • large surface area- so lots of the substance can diffuse across at once
          • in animals they have lots of blood vessels- to get things in and out of the blood quickly
          • in animals they are often ventilated too
      • active transport (p77)
        • absorption of substances against the concentration gradient using energy
        • used in the gut when there is a low concentration of nutrients in the gut but a high concentration of nutrients in the blood
        • root hairs take in minerals using active transport
          • the concentration of minerals is usually higher in the root hair cell than in the soil around it
      • the  breathing system (p 75)
        • ventilation
          • breathing out
            • intercostal muscles and diaphragm relax
            • thorax volume decreases
            • this increases the pressure, so air is forced out
          • breathing in
            • intercostal muscles and diaphragm contract
            • thorax volume increases
            • this decreases the pressure, drawing air in
      • water flow through plants (p78)
        • phloem tubes
          • transport food
          • made  of columns of living cells with small holes in the end to allow substances to flow through
          • the transport goes in both directions
        • xylem tubes
          • take water up
          • made of dead cells joined end to end with no walls between them and a hole down the middle
          • carry water and minerals from the roots to the stem and leaves
      • circulatory system- the heart (p79)
        • the flow of blood through the heart
      • circulatory system- blood vessels (p80)
        • arteries
          • carry blood away from the heart
          • walls are strong and elastic because of the high pressure
        • veins
          • carry blood to the heart
          • thinner walls than arteries because of lower pressure
          • have valves to keep blood flowing in the right direction
        • capillaries
          • very small
          • exchange substances with cells
          • walls only one cell thick
          • permeable walls
      • circulatory system- the blood (p81)
        • red blood cells
          • carry oxygen from the lungs to the cells
          • concave- giving it a large surface area
          • contain haemoglobin- combines with oxygen to form oxyhaemoglobin.
            • reverses in body tissues- oxyhaemoglobin splits into haemoglobinand oxygen to release oxygen to the cells
        • white blood cells
          • change shape to digest foreign microorganisms
          • have a nucleus
          • produce antibodies and antitoxins
        • platlets
          • small fragments of cells, that have no nucleus
          • help the blood to clot
        • plasma
          • carries everything in the blood
            • red and white blood cells and platlets
            • nutrients like glucose and amino acids
            • hormones
            • carbon dioxide and urea
            • antibodies and antitoxins
      • circulation aids (p82)
        • artificial blood
          • a blood substitute (e.g. saline) is used to replace the lost volume of blood
          • gives the patient enough time to produce new blood cells
        • artificial parts (for the heart)
          • artificial hearts
            • mechanical devices put into a person to pump blood if their own heart fails
            • temporary - until a donor heart is found
            • parts of it could wear out or motor could fail
          • valves
            • mechanical
            • less drastic prcedure than a whole heart transplant
        • stents
          • tubes inserted inside arteries to keep them open
          • lower the risk of a heart attack in people with coronary heart disease
      • homeostasis (p83)
        • temperature
          • too cold
            • no sweat produced
            • hairs stand up
            • blood vessels constrict
            • shiver
          • too hot
            • sweat produced
            • hairs lie flat
            • blood vessels dilate
        • water content
        • ion content
        • blood sugar level
        • carbon dioxide
        • urea
        • the maintenance of a constant internal environment
      • the kidneys and homeostasis (p84)
        • the kidneys...
          • adjust ion content
          • remove urea
          • adjust water content
      • kidney function (p85)
        • nephrons
          • (filtration units in the kidneys)
          • water, urea, ions and sugar is squeezed out of the blood and into the bowmans capsule
            • big molecules like protein and blood cells stay in the blood
            • useful substances are reabsorbed back into the blood
              • the remaining substances such as urea continue out of the nephron and into the bladder
          • useful substances are reabsorbed back into the blood
            • the remaining substances such as urea continue out of the nephron and into the bladder
      • kidney failure (p86)
        • dialysis
          • has to be done regularly
          • the persons blood flows along a selectively permeable barrier surrounded by dialysis fluid
            • only waste and excess substances diffuse across the barrier
        • transplants
          • a donor kidney could be rejected by the patient's immune system, so...
            • donor's tissue type has to closely match the patient's
            • the patient is treated with immuno-suppressants
      • controlling blood glucose (p87)
        • blood glucose levels
          • too high- insulin added
          • too low- glucagon added
        • type 1 diabetes
          • caused by a lack of insulin
          • can be controlled by...
            • avoiding carbohydrate rich foods
            • injecting insulin
  • the movement of  water molecules across a partially permeable membrane from a region of low water concentration to a region of  high water concentration

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