GCSE AQA Biology Higher Tier Paper 2h Questions & Answers

Name two types of microorganism that cause decay. (2) - ANSWERSbacteria fungi Cows' milk is pH 6.6. As milk decays, lipids in the milk are broken down. One of the products of the breakdown of lipids causes the pH of milk to decrease. Name the product that causes the pH to decrease. (1) - ANSWERSfatty acid(s) A student investigated the effect of temperature on the time taken for different types of milk to decay. This is the method used. 1. Put cows milk in six test tubes 2. Keep each test tube at a different temperature. 3. Measure the pH of the milk in each tube every day for 12 days. 4. Record the number of days taken to reach pH 5. 5. Repeat steps 1 to 4 with goats' milk and with almond milk. Give one way the pH can be measured. (1) - ANSWERSany one from: • universal indicator (paper /solution) • pH meter Give two control variables the student should have used in this investigation. (2) - ANSWERSany two from: • volume of milk • exposure to air / oxygen • sterilise test tubes • treatment of milk before investigation • freshness / age of milk (at start) • time of day pH was measured The time taken for cows milk to reach pH 5 at 10*C is less than the time taken for cows milk to reach pH 5 at 5*C. Suggest one reason why. (1) - ANSWERSany one from: bacteria / microbes / microorganisms / fungi dividing faster (when warmer) reactions (in the bacteria) are happening faster (to decay milk) (because there is) more (kinetic) energy enzyme activity is higher (at 10 °C than at 5 °C) The increasing human population has caused a decline in fish stocks. Describe how fishing quotas can help to return fish stocks to a sustainable level. (2) - ANSWERSfewer fish caught or limit the number of fish caught (remaining fish) can reproduce Farming techniques have changed in recent years. Describe: - why more land is being used for farming - how increased farming has decreased biodiversity (6) - ANSWERSIndicative content human land use • increasing population requires more food • crops / livestock for food • farming crops for biofuels • peat use as compost • peat use as fuel • increased use of pesticide / insecticide / herbicide / fertilisers • use of free-range / organic methods increases land use (for same yield) link to biodiversity • deforestation • monocultures • loss of hedgerows (to make fields larger) • loss of habitat • consequence of loss of habitat eg (change in) migration • fertiliser run off polluting water • use of pesticide / insecticide / herbicide reduces insects / plants which damages food chains • more soil erosion link to atmospheric pollution • more carbon dioxide (from farm animals / machinery) • more methane (from cows) • climate change or global warming • example of impact on biodiversity • acid rain • desertification Genetic modification of crop plants can help meet the demands of the increasing human population. Golden rice is a genetically modified crop. What is the advantage of golden rice compared with non GM rice? (1) - ANSWERSgolden rice has improved nutritional value Suggest one reason why some people are concerned about the use of golden rice. (1) - ANSWERSany one from: gene may contaminate / enter other breeds / species reduction / extinction of population of wild / traditional rice reduction / extinction of population of flowers / insects high cost of seeds may have too much vitamin A (in diet) Farmers can spray seeds with gibberellins to start germination. What are two other uses of gibberelliins? (2) - ANSWERSto increase fruit size to promote flower production Bananas are often stored separately from other fruits because bananas release a plant hormone. Why does storing bananas with other fruits cause the other fruits to ripen faster? (1) - ANSWERSethene is released from bananas Why is DNA described as a polymer? (1) - ANSWERSmany (joined) nucleotides or monomers Describe the structure of a nucleotide. (4) - ANSWERSphosphate (phosphate attached to a) sugar (which has 1 of 4) base(s) (attached to sugar) (bases) are A, C, G and T Some parts of DNA do not code for proteins. Describe how non-coding parts of DNA can affect the expression of genes. (1) - ANSWERS(non-coding parts) can switch genes on / off Describe three differences between the processes of mitosis and meiosis. (3) - ANSWERSany three from: mitosis produces two (daughter) cells but meiosis produces four (daughter) cells one cell division in mitosis but two cell divisions in meiosis mitosis produces cells with two of each chromosome, but meiosis produces cells with one of each chromosome mitosis produces genetically identical cells, but meiosis produced genetically different cells Describe one similarity between the processes of mitosis and meiosis. (1) - ANSWERSany one from: • DNA doubles / copies / replicates (once) • increase in the number of mitochondria / ribosomes / sub-cellular structures Name the part of the brain that is responsible for making a decision. (1) - ANSWERScerebral cortex In most MRI scanners the person being scanned needs to stay completely still. A functional MRI (fMRI) scanner allows a person to move while the scanner makes images of the person's brain activity.