Biology GCSE B2


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Just the notes I made for one of my Biology GCSE exams...a lot of diagrams and sich are taken from GCSE BBC Bitesize, which is a very awesome site and recommended.

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  • it should be 6c02+6h20--->c6h1206+602
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  • the balanced symbol equeation for photosynthesis is wrong
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Biology GCSE B2

  1. 1. Biology Revision<br />Same genes on for four days now<br />Inheritance and Variation<br />We resemble our parents because characteristics are inherited from them. This is the process of genetic information being passed on to offspring in the sex cells/gametes which they develop from.<br /> <br />Genetic information is stored in thread-like structures called chromosomes, which are made up of a chemical called DNA (deoxyribose nucleic acid). DNA molecules are double helix. <br />Humans have 46 chromosomes, 23 from the mother and 23 from the father. Every normal body cell has these 23 pairs. Each chromosome contains thousands of genes joined together. Each gene is a small section of the long DNA molecule. Different versions of the same gene are called alleles. <br />Common in the smallest animals, plants and in the human body – cells dividing to grow and replace worn-out tissue.<br />Asexual ReproductionSexual reproduction<br /><ul><li>Involves one parent
  2. 2. Offspring identical to itself
  3. 3. No variety = clones
  4. 4. Male and female sex cells join
  5. 5. Genetic information inherited
  6. 6. Mix of characteristics = variety</li></ul>Biology Revision<br />4450715234315Wtf they’re the same!?<br />Cloning<br />Plants: cuttings & tissue culture<br /><ul><li>Taking cuttings from the stem/leaf. Cuttings are genetically identical to the parent plant. This is quick and cheap.
  7. 7. Tissue culture: using a mixture of plant hormones to make a small group of cells from the parent plant to produce a big mass of identical plant cells, which are stimulated to each form a new plant. This is more expensive, but means the plants are guaranteed to have the characteristics you want. </li></ul>Embryonic cloning works because the cells of the embryo have not yet become specialized. <br />Animals: embryonic cloning<br /><ul><li>Fertility hormones given to top-quality female to make her produce a lot of eggs
  8. 8. Sperm taken from top-quality male to fertilise the eggs (inside the womb or in the lab)
  9. 9. Each embryo is divided into individual cells, and each grow into an identical embryo
  10. 10. Embryos are transferred to host mothers who have been hormone’d up for pregnancy
  11. 11. Identical cloned offspring are born – they are not biologically related to their mothers</li></ul>Animals: fusion cell cloning or adult cell cloning<br />The most complicated form of asexual reproduction, fusion cell cloning is complete cloning of animals without sexual reproduction involved at all.<br /><ul><li>Take the adult cell of the animal to clone and an egg cell from another of the same species
  12. 12. Remove the nucleus from both cells
  13. 13. Place the nucleus from the original adult in the empty egg and give it a mild electric shock
  14. 14. The new cell has been fused together and starts the process of cell division
  15. 15. -54610158750An embryo develops which is genetically identical to the original adult animal</li></ul>This technique could be used to clone animals which have been genetically engineered to be medically useful. Species could be saved; pets or prized animals could be cloned.One big problem is that modern cloning reduces variety in a population, meaning they are less able to survive changes in their environment in the future. future..(because none of them have a useful mutation).<br />Biology Revision<br />Fresh genes<br />Genetic Engineering<br />Genetic engineering involves changing the genetic material of an organism. You cut a gene from one organism using enzymes, and then transfer it to the cell of a completely different organism.<br />Genetic engineering produces a unique set of genes which can be swapped across species.<br />22860132080<br />493649039370317436539370225996539370<br />Gene for making insulin Restriction enzyme cuts out geneInsulin gene is inserted into (from a human cell)and plasmid of bacterial DNAthe plasmid<br />317436514160527104141605<br /> Plasmid is put back into the bacteriumExactly the right kind of insulin which then multiples many times at a constant, harvestable supply<br />Advantages: <br /><ul><li>Genetically engineered bacteria can make exactly the right type and amounts of proteins to be harvested as a constant supply.
  16. 16. Engineered food can have improved growth rates, food value, reduced fat levels and also last longer in supermarkets.
  17. 17. Engineered plants which make their own pesticide chemicals can be produced, as can plants which can grow well in rough parts of the world.
  18. 18. Animals which produce life-saving human proteins in their milk.
  19. 19. “Correcting” genetic material in humans to treat genetic diseases.</li></ul>Disadvantages: <br /><ul><li>No one can be completely sure what all the long-term effects might be.
  20. 20. GM food could have some effect on human health.
  21. 21. Insects could become pesticide-resistant if they eat a constant diet of GM plants.
  22. 22. Genes from GM plants/animals or bacteria/viruses might spread into the environment.
  23. 23. Designer babies – people may want to manipulate the genes of their future children to be good-looking, clever, sporty etc.</li></ul>Biology Revision<br />Photosynthesis<br />CARBON DIOXIDE + WATER -> GLUCOSE + OXYGEN<br />6CO2H2O6C6H2O6O2<br />Leaf Structure<br />Leaf cells have many chloroplasts which contain chlorophyll. Chlorophyll absorbs light energy to convert carbon dioxide and water into a sugar called glucose.<br />Upper epidermis:waxy cuticle; waterproof layer stops water loss<br />Palisade layer:palisade cells at the top of the leaf are close to the light, tightly packed together and full of chloroplasts<br />Spongy layer:cell not tightly packed, so there are air spaces<br />large surface area available for gas exchange<br />Lower epidermis:guard cells open and close the stomata to control <br />water loss/gases coming in and out<br /><ul><li>Carbon dioxide is delivered to the chloroplasts by diffusion.
  24. 24. Photosynthesis is slowed down by the waxy cuticle adapted to prevent water loss</li></ul>How Plants Affect The Atmosphere<br />During the day, plants both respire and photosynthesise. This means that there is a two-way traffic of oxygen and carbon dioxide both into and out of the plant.<br />During the night, plants do not photosynthesise, but they always respire. This means when it is dark, oxygen is being taken in but not given out. Carbon dioxide is given out but not being taken in.<br />PhotosynthesisRespirationTakes CO2 from the air and puts oxygen into the air.Takes oxygen from the air and puts CO2 into the air.DayActiveActiveNightNo photosynthesisActive<br /> <br />Plants use more carbon dioxide in photosynthesis than they produce in respiration. <br />They produce more oxygen by photosynthesis than they use in respiration.<br />The overall result is that plants put oxygen into the atmosphere. This makes it possible for animals to breathe. <br />Limiting Factors<br />2159094615Light intensity<br /> As the light intensity increases, the rate of oxygen also increases to the point where the graph levels out and stays at the same rate of reaction. At this point, something else must be the limiting factor. <br />Wavelength also makes a difference – blue and red lights are the best but NEVER green.<br />2886075206375<br />Temperature<br /> Photosynthesis involves enzymes which are temperature sensitive, so once the temperature gets too high, and the rate of photosynthesis falls as enzymes are denatured.<br />The peak of the graph is the optimum temperature.<br />Carbon dioxide<br /> Carbon dioxide levels are higher at night because plants are respiring but not photosynthesising. So on a sunny day, carbon dioxide is very likely the limiting factor. <br />Biology Revision<br />Glucose<br />Plants respire 24 hours a day to release energyGlucose is soluble in water, starch is insolubleUses of Glucose<br />Oxygen is taken in -> glucose breaks down and provides energy for cells<br />-> carbon dioxide and water are the waste products <br />Minerals and salts are taken in through active transportGlucose can be used to:<br /><ul><li>make long chains of starch for storage
  25. 25. make cellulose for cell walls
  26. 26. combined with nitrates to make proteins for growth
  27. 27. be converted into lipids (fats or oils) to store in seeds
  28. 28. combined with nutrients from the soil to make amino acids
  29. 29. make genetic material (DNA) to replicate dividing cells</li></ul>Nitrates are used to make proteins and the lack of it leads to a small plant.<br />Magnesium is the principle molecule in chlorophyll and the lack of it leads to yellow leaves.<br />Transport and Storage<br /><ul><li>Phloem transports sugars from leaves to the rest of the plant for growth and storage. The phloem is made of living tissue.
  30. 30. Xylem carries water and mineral ions from the soil. Xylem vessels are not living.</li></ul>Glucose is stored as starch (insoluble) so the soluble glucose doesn’t have an effect on the water balance of the plant. Starch is an energy store for when light levels are low. Starch is stored in tubers/bulbs. We eat some of these – potatoes, carrots and onions. <br />Biology Revision<br />Cell your soul to science<br />Animal and Plant Cells<br />2971165106045<br /><ul><li>Nucleus: controls all activities of the cell and contains instructions for making new cells or organisms
  31. 31. Cytoplasm is where the chemical reactions take place – importantly, respiration
  32. 32. Cell membrane controls the passage of substances in and out of the cell
  33. 33. Mitochondria, where most of the energy is released during respiration
  34. 34. Ribosomes, where proteins are made</li></ul>Specialized Cells<br />1517015113030<br />Cells<br />Tissues<br />Organs<br />Organ systems<br />Whole body<br />Biology Revision<br />In, our, in, our, shake it all about<br />Diffusion Confusion<br />Diffusion is the passive movement of molecules from the region of high concentration to a region of lower concentration. Therefore it moves down a concentration gradient.<br />If there is no concentration gradient then you get even distribution and no net movement – but particles still have random movement from kinetic energy.<br />Examples of diffusion include:Gases in leavesOxygen in the lungsFood in the gut<br />For most efficient diffusion, you need:<br /><ul><li>Large surface area
  35. 35. Short distance
  36. 36. Steep concentration gradient</li></ul>Diffusion is faster with:<br /><ul><li>Higher temperatures
  37. 37. Lighter molecular mass
  38. 38. 254571588265Gases -> liquids -> solids</li></ul>Osmosis...can’t think of a rhyme<br />Osmosis is the passive movement of water molecules through a partially permeable membrane from a region of high water potential to a region of lower water potential.<br />High water potential = dilute solution <br />Low water potential = more concentrated solution <br /><ul><li>337439057785Cells full of water become turgid. The vacuole swells up and everything is pushedagainst the cell wall.
  39. 39. Cells in concentrated salt solutions lose waterand become flaccid.The vacuole shrinks and the cytoplasm pulls away from the cell wall. This is plasmolysis. The spaces between the clinging cytoplasm and the cell wall are full of the outside solution. </li></ul>Not so much in plant cells<br />Biology Revision<br />Energy and Eating<br />Food Chains/Webs<br /><ul><li>Food chains show the feeding relationships in a habitat.
  40. 40. Energy is lost as you move up a food chain, and this limits the length of the chain Some energy goes into growth in biomass and the production of offspring, but most is used up in other ways:
  41. 41. Sunlight is reflected off leaves instead of being used for photosynthesis
  42. 42. Energy is lost through respiration as heat
  43. 43. Energy is lost because of excretion and defecation
  44. 44. Energy is used for movement and transport
  45. 45. 3231515274955
  46. 46. Food chains always start with producers, which are almost always green plants
  47. 47. The other organisms in the food chain are consumers – they all get their energy and biomass by consuming other organisms</li></ul>Efficiency of food production and organic farming<br />Meat-eating and energy efficiency<br />It is far more efficient for humans to eat cereals such as wheat and barley themselves, rather than to use the cereals to feed cattle and then to slaughter the cattle for beef.<br />This is because the energy in the beef has already passed through two steps by the time it gets to humans, and at each step the amount of available energy is reduced. <br />When we eat cereals (or vegetables or fruit) the energy has only passed through one step, and there has only been one set of energy losses instead of two.<br />Biology Revision<br />Biomass<br />Pyramids of Biomass<br /><ul><li>Pyramids of biomass are charts that show the mass of living material at each step in food chain
  48. 48. Most food chains are quite short because a lot of energy is lost at each step. After about three steps, very little energy is still available for use by living organisms. This also explains why there are few organisms at the top of food chains, compared with those lower down.</li></ul>37077657366077406573660 <br />A pyramid of biomass looks like pyramid 2. Note the large biomass of the one oak tree, compared with the small biomass of lots of caterpillars, indicated by the shape of the pyramid.<br />The wider the bar, the more biomass there is. <br />Pyramids of biomass always have this shape (but pyramids of numbers can be any shape).<br />Biomass Fuels<br />Biomass fuels are wood (by burning), alcohol (by fermentation) and biogas (from decay). Biomass fuels are renewable, produce less pollution and are energy self-reliant.<br />Biology Revision<br />Intensive and Organic Farming<br />Organic farming<br />Organic farming involves producing food without the need for artificial fertilisers and pesticides - this may be better for people's general health, but it may also mean crop yields are smaller. Organic food is often more expensive compared to food produced by normal 'intensive' farming methods because:<br />More labour is needed<br />The crop yields may be smaller<br />Organic produce may be more difficult to transport without being spoiled<br />Intensive Farming<br /><ul><li> Intensive farming improves the efficiency of energy transfer in food chains.
  49. 49. Intensive farming uses pesticides to kill pests, and herbicides to kill weeds.
  50. 50. More food is produced
  51. 51. Causes problems such as pesticides accumulation in food chains
  52. 52. There are ethical issues with the treatment of intensively farmed animals</li></ul>Minerals, Fertiliser and Cannabis Farms<br />Farmers put fertiliser on crops to replace minerals lost from the soil. This is necessary because the crops are harvested as opposed to being left to decay naturally (which would then return minerals to the soil). This may mean chemical fertilisers or organic ones like bones/food waste/manure which release minerals slowly because they have to decay.<br />Hydroponics is controlling the growth of plants by growing them in water and then manipulating the light, temperature, carbon dioxide and mineral levels to make plants grow as fast and as big as possible. You are also able to control diseases easier. There can be huge hydroponic farms with no limiting factors of photosynthesis.<br />There are also hydroponic farms set up to grow cannabis. This is not relevant but it makes a flashy title. <br />Biology Revision<br />Carbon cycle<br />Carbon Cycle<br />Most of the chemicals that make up living tissue contain carbon. When organisms die, the carbon is recycled so that it can be used by future generations. This process is called the carbon cycle.<br />33743901276352540127635<br />Carbon enters the atmosphere as carbon dioxideCarbon dioxide is absorbed by producers to make from respiration and combustion.carbohydrates in photosynthesis.<br />33743901327154445132715<br />Animals feed on the plant passing the carbonThe dead organisms are eaten by decomposers &compounds along the food chain. Most of thethe carbon in their bodies is returned to the carbon they consume is exhaled as carbon dioxideatmosphere as carbon dioxide. In some conditionsformed during respiration. The animals and plantsdecomposition is blocked. The plant and animaleventually die.material may then be available as fossil fuel in the<br />future for combustion.<br />1659890375285<br />Biology Revision<br />Revision of Cell Division<br />Mitosis<br />1526540799465Mitosis is a type of cell division that is used for growth and repair in all cells, and produces diploid cells (two of each chromosome, the normal number) which are identical to each other and the parent cell. This means the human body’s 46 chromosomes are copied exactly.<br /><ul><li>Chromosomes in the nucleus are copied
  53. 53. Each chromosome has 2 chromatids
  54. 54. The chromosomes align themselves and move towards the poles
  55. 55. The chromatids are pulled apart
  56. 56. There are now double the number of chromosomes as there was before. These also separate
  57. 57. The cell divides</li></ul>Constant cell division ensures that cells never get too large. The larger the cell becomes, the smaller its surface area to volume ratio. Objects with a small surface area to volume ratio find it difficult to maintain exchange of materials with their environment. Large cells could run out of oxygen, and accumulate too much waste, such as carbon dioxide. For this reason it's more efficient for large organisms to be multicellular, rather than single-celled<br />Biology Revision<br />Revision of Cell Division<br />Meiosis<br />In sexual reproduction, cells from each parents with half the normal number of chromosomes join together to make a new cell containing both parents’ genetic material. The human gametes (egg and sperm) have 23 chromosomes which join together during fertilisation.<br />Meiosis is the type of cell division used in sexual reproduction. It occurs only in the testes and ovaries and produces cells that are haploid, which means they are different to each other, and to the parent cell. The cells produced have half the normal number of chromosomes.<br />Meiosis therefore causes genetic variation.<br />888365103505<br />Biology Revision<br />Crap things no one ever remembers<br />Variables<br />Categoric: best described by a label, usually a word. (e.g. colours)<br />Discrete: described in whole numbers. (e.g. number of leaves on different plants)<br />Ordered: able to order the data but not give it an actual number. (e.g. different heights) <br />Continuous: measured, so its value can be any number. (e.g. temperature)<br />An independent variable is one that we change ourselves.<br />A dependent variable is one that we measure. <br />A control variable is one kept constant so it is a fair test. <br />A conclusion is making links between variables. <br />Graphs<br />Bar charts: <br />-> Independent variable is categoric or ordered<br />-> Dependent variable is continuous<br />Line graphs: <br />-> Independent variable is continuous<br />-> Dependent variable is continuous <br />Scatter graphs: <br />-> like line graph, but for when you are not expecting a clear line of best fit<br />Reliability, Validity, Stupidity<br />Reliability: <br /><ul><li>When results are the same or similar every time
  58. 58. Necessary to control as many other variables as possible
  59. 59. Repeating, discarding anomalies and calculating an average</li></ul>Precision: <br /><ul><li>When REPEATED results are closely grouped together
  60. 60. Precise results are not necessarily accurate</li></ul>Accuracy: <br /><ul><li>When results are very close to the TRUE VALUE
  61. 61. Using higher quality instruments and/or being more careful
  62. 62. Repeat results for accuracy of the mean</li></ul>Validity: <br /><ul><li>Must be reliable and also answer the original question