AQA GCSE Biology Paper Two with correct answers to every question

AQA GCSE Biology Paper Two. "Sampling is also used to... - CORRECT ANSWER ...measure changes in the distribution of organisms over time. Repeat measurements at regular time intervals and calculate mean. Finding the range of distribution and the median and mode of your data can also be useful." "What factors could you investigate in an experiment about the distribution of species? (3) - CORRECT ANSWER 1. Trampled/untrampled grass 2. Light levels 3. Soil pH ENSURE YOU DECIDE ON YOUR SPECIES BEFORE DOING THE INVESTIGATION. (e.g. dandelions)" "Quantitative sampling - CORRECT ANSWER Records the number of organisms rather than just the type" "Mean - CORRECT ANSWER Sum of values divided by number of values" "Median - CORRECT ANSWER The middle value of the range" "Mode - CORRECT ANSWER The most frequently occuring value" "How does a line transect work? - CORRECT ANSWER 1. Stretch a tape between 2 points. 2. Sample organisms at regular intervals along the line using a quadrat" "Why are all materials in the living world recycled? - CORRECT ANSWER To provide the building blocks for future organisms" "The carbon cycle - CORRECT ANSWER Returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis" "The water cycle - CORRECT ANSWER Provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporating and precipitating." "Describe the carbon cycle - CORRECT ANSWER " "Why is the carbon cycle important? - CORRECT ANSWER Carbon is an important element which makes up many different molecules in our environment and bodies (carbohydrates, fats and proteins). The amount of carbon on the Earth is fixed so it must be recycled." "Describe the water cycle - CORRECT ANSWER 1. Evaporation: water evaporates from the surface of land and bodies of water 2. Transpiration: loss of water vapour from plants directly into the atmosphere 3. Respiration: loss of water vapour from animals directly into the atmosphere 4. Condensation: it rises into the air and condenses to form clouds 5. Precipitation: water droplets in clouds get heavier and fall as rain, snow or hail" "Why is the water cycle important? - CORRECT ANSWER Water is vital for life. The water cycle provides fresh water for plants and animals to survive." "The role of microorganisms in cycling - CORRECT ANSWER Decay by microorganisms returns carbon dioxide to the atmosphere by respiration and mineral ions to the soil." "Detritivores - CORRECT ANSWER Detritivores/detritus feeders e.g. maggots and flies feed on dead, rotting material. They break up the dead organism into smaller pieces, increasing the surface area for digestion by microorganisms." "Describe the nutrient cycle (decay) (6) - CORRECT ANSWER 1. Decay starts after death of organism 2. Detritus feeders eat the deceased body and produce waste 3. Decomposers digest everything 4. Decomposers multiply rapidly 5. Waste from decomposers inluding water, CO2 and mineral ions are used by plants to grow 6. Plants take up mineral ions via roots to make proteins and chemicals in their cells" "How does temperature affect the rate of decay? - CORRECT ANSWER 1. High temperatures denature enzymes and other proteins, killing the organisms responsible for decay 2. Low temperatures slow decay as the rate of reaction in the organisms decreases" "How does water affect the rate of decay? - CORRECT ANSWER Lack of water slows or prevents decay - water needed for decay organisms to digest their food and to support reactions inside organisms" "How does availability of oxygen affect rate of decay? - CORRECT ANSWER Lack of oxygen slows or prevents most types of decay - needed for anaerobic respiration, but some anaerobic bacteria can survive without e.g. in biogas generators" "How is rate calculated? - CORRECT ANSWER 1/time or 1000/time" "What to farmers and gardeners do to achieve rapid decay of waste biological material? - CORRECT ANSWER Provide optimum conditions" "What is the compost produced from this decay used for? - CORRECT ANSWER A natural fertiliser for growing plants or crops" "What does anaerobic decay produce? - CORRECT ANSWER Methane gas" "How do biogas generators work? - CORRECT ANSWER Anaerobic decay of biomass produces methane gas as a fuel" "Describe an experiment to investigate the effect of temperature on the rate of decay of fresh milk using pH. - CORRECT ANSWER 1. Full fat milk, phenolphthalein indicator, and alkaline solution (eg sodium carbonate) in several tubes - this will be pink 2. Test tubes of lipase 3. Put test tubes in water baths of different temperatures - do NOT mix yet 4. When lipase and milk solution are same temperature, combine 5. Measure the time it takes for milk solution to turn colourless; the acid formed from digestion of fats has turned the solution acidic 6. Repeat 3 times for each temperature and calculate mean" "Environmental changes affect... - CORRECT ANSWER ...the distribution of species in an ecosystem" "What do environmental changes include? (3) - CORRECT ANSWER 1. Temperature 2. Availability of water 3. Composition of atmospheric gases" "These environmental changes may be... - CORRECT ANSWER ...seasonal, geographic or cuased by human interaction" "Geographical changes - CORRECT ANSWER Includes many different factors including difference in soil structure or pH, altitude, saltiness of water 2. Many species have adaptations which enable them to survive in specific geographical conditions" "Seasonal changes - CORRECT ANSWER 1. In temperate areas, the temperature rainfall, daylight and other factors change dramatically between seasons, as does the distribution of plants and animals 2. In tropical areas the dry and rainy seasons have a similar effect on species distribution" "Changes as a result of human interaction - CORRECT ANSWER 1. Global warming and climate change - nwo working to maintain rainforest 2. Acid rain - now reducing water pollution and monitoring pH 3. Pollution from farms and factories - now conservation measures such as replanting hedgerows and woodlands, resitrcung access to sites of special scientific interest" "Biodiversity - CORRECT ANSWER The variety of all the different species of organisms on earth, or within an ecosystem" "What does a greater biodiversity ensure? - CORRECT ANSWER Ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment" "What does the future of the human species on Earth rely on and why? - CORRECT ANSWER 1. Relies on us maintaining good levels of biodiversity 2. Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction" "How do humans reduce biodiversity? (4) - CORRECT ANSWER 1. Waste management 2. Land use 3. Deforestation 4. Global warming" "More pollution will be caused, unless... - CORRECT ANSWER ...waste and chemical materials and properly handled" "Why is more waste being produced? - CORRECT ANSWER 1. Rapid growth in human population 2. Increase in the standard of living 3. Increasingly more resources are used and therefore more waste is produced" "Where can pollution occur and from what? - CORRECT ANSWER 1. Water - sewage, fertiliser, toxic chemicals 2. Air - smoke, acidic gases 3. Land - landfill and toxic chemicals" "What effect does pollution have on biodiversity? - CORRECT ANSWER Pollution kills plants and animals which can reduce biodiversity" "How do humans affect biodiversity through land use? (2) - CORRECT ANSWER 1. Humans reduce the amount of land available for other animals and plants 2. By building, quarrying, farming and dumping waste 3. Destruction of peat bogs" "Why is the destruction of peat bogs a problem? - CORRECT ANSWER 1. Peat bogs and other areas of peat are destroyed to produce garden compost 2. This reduces the area of this land and thus the biodiversity (variety of different plant, animal and microorganism species that live there) 3. The decay or burning of peat releases carbon dioxide and contributes to global warming" "Why has large-scale deforestation occurred in tropical areas? (2) - CORRECT ANSWER 1. To provide land for cattle and rice fields and palm oil. 2. To grow crops for biofuels" "What factors are conflicting in the destruction of beat bogs? - CORRECT ANSWER 1. The need for cheap available compost to increase food production 2. The need to conserve peat bogs and peatlands as habitats for biodiversity and to reduce CO2 emissionsà" "Describe global warming - CORRECT ANSWER 1. CO2 and methane contribute to the greenhouse effect - they absorb some of the Sun's energy which is reflected off the earth 2. However now levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to 'global warming'" "Describe some of the biological consequences of global warming (4) - CORRECT ANSWER 1. Loss of habitats - due to rising sea levels 2. Changes in distribution - as temperatures and rain patterns change 3. Changes in migration patterns - as climates become hotter or colder 4. Reduced biodiversity - some animals will be able to survive as the climate changes eg polar bears" "What is the scientific consensus about global warming and climate change based on? - CORRECT ANSWER Systematic reviews of thousands of peer reviewed publications" "Describe programmes put in place to reduce the negative effects of humans on ecosystems and biodiversity - CORRECT ANSWER 1. Breeding programmes for endangered species 2. Protection and regeneration of rare habitats 3. Reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop 4. Reduction of deforestation and CO2 emissions by some governments 5. Recycling resources rather than dumping waste in landfill" "Describe the 4 trophic levels - CORRECT ANSWER Level 1. Producers - plants and algae make their own food Level 2. Primary consumers - herbivores eat plants/algae Level 3. Secondary consumers - carnivores eat herbivores Level 4. Secondary consumers - carnivores eat other carnivores" "Apex predators - CORRECT ANSWER Carnivores with no predators" "What is the role of decomposers? - CORRECT ANSWER Break down dead plant and animal matter by secreting enzymes into the environment. Small soluble food molecules then diffuse into the microorganisms." "Pyramids of biomass - CORRECT ANSWER Trophic level 1 is always at the bottom of pyramids of biomass. The pattern moving up through the trophic levels will always be the same. Remember to label each bar." "Why is the biomass in each trophic level less than the previous level - CORRECT ANSWER 1. Not all parts of the organism are eaten e.g. bones left behind 2. Not all ingested material is absorbed, some is egested as faeces 3. Some absorbed material is lost as waste such as carbon dioxide and water in respiration and water and urea in urine 3. Large amounts of glucose are used in respiration to transfer energy for movement, growth etc" "Producers are... - CORRECT ANSWER ...mostly plants and algae which transfer about 1% of the incident energy from light for photosynthesis" "Only around ... of the biomass from each trophic level is transferred to the level above it - CORRECT ANSWER 10%" "How do you calculate efficiency of biomass transfer between trophic levels? - CORRECT ANSWER efficiency = biomass transferred to next level/biomass available at previous level x 100" "How do the levels of biomass affect the number of organisms at each trophic level? - CORRECT ANSWER Normally as you move up trophic levels and the biomass decreases, the number of organisms also decreases" "Food security - CORRECT ANSWER Having enough food to feed a population" "Biological factors which are threatening food security - CORRECT ANSWER 1. Increasing birth rate - in some countries 2. Changing diets in developed countries - scarce food resources transported around the world 3. New pests and pathogens that affect arming 4. Environmental changes that affect food production - e.g. widespread famine in some countries if rains fail 5. Cost of agricultural inputs 6. Conflicts -have arisen in some parts of the world which affect the availability of water or food" "Example of a pathogen affecting food security - CORRECT ANSWER 'Blue tongue' disease carried by midges spreading to sheep and cattle in the UK from Europe" "... methods must be found to feed all people on Earth - CORRECT ANSWER Sustainable" "How can type II diabetes be treated? - CORRECT ANSWER It can be controlled by eating a carbohydrate controlled diet and getting regular exercise." "What is the role of the kidneys. - CORRECT ANSWER Kidneys make urine by taking unwanted waste products out of your blood. They are involved in selective reabsorption." "Name three things that are re-absorbed by the kidneys into the blood. - CORRECT ANSWER Glucose, water and ions." "Name three things that are removed from the body in the urine. - CORRECT ANSWER Urea, water and ions." "What is deamination? - CORRECT ANSWER Proteins (excess amino acids) cannot be stored by the body. Excess amino acids are converted to fats and carbohydrates. This occurs in the liver." "What is produced as a waste product of deamination? - CORRECT ANSWER Ammonia is produced as a waste product. Ammonia is toxic so it is converted into urea in the liver." "What hormone controls the amount of water absorbed by the kidneys? - CORRECT ANSWER ADH" "What happens when the concentration of water in the blood is too low. I.e. the Blood is MORE concentrated. - CORRECT ANSWER Receptors in the hypothalamus detects the water content is too low. The coordinator in the brain receives the information and coordinates a response. The pituitary gland produces MORE (Anti-diuretic hormone) ADH, which makes the kidney tubule MORE permeable. This means that MORE water is reabsorbed into the bloodstream. The kidneys produce a small volume of concentrated urine." "What happens when the concentration of water in the blood is too high. I.e. the Blood is dilute/LESS concentrated. - CORRECT ANSWER Receptors in the hypothalamus detects the water content is too high. The coordinator in the brain receives the information and coordinates a response. The pituitary gland produced LESS ADH, which makes the kidney tubule LESS permeable. This means that LESS water is reabsorbed into the bloodstream. The kidneys produce a large volume of dilute urine." "How does a dialysis machine work? - CORRECT ANSWER In a dialysis machine the patients blood flows between a partially permeable membrane surrounded by dialysis fluid. The dialysis fluid contains the same concentration of dissolved ions and glucose as healthy blood. This means they won't be lost from the blood during dialysis. Only wastes such as urea and excess ions and waters diffuse across the barrier." "What is the purpose of the partially permeable membrane in the dialysis machine. - CORRECT ANSWER To only allow small soluble molecules (e.g. urea, water and ions) to move into the dialysis fluid, not large molecules like proteins." "What are the advantages and disadvantages of a kidney transplant over dialysis? - CORRECT ANSWER Kidney transplants are a cure, but they can be rejected. Patients are treated with immunosuppressants. People are not always on the donor list, relatives have to agree to the donation. Transplants are cheaper than dialysis to the NHS. Long waiting lists for transplants. Patients have to spend 3-4 hours a day, 3 x a week which can have a negative impact on their quality of life." "What are the four stages of the menstrual cycle? - CORRECT ANSWER 1) Menstruation-the uterus lining breaks down 2) The uterus lining builds up again 3) Ovulation-Around day 14 a egg is released from an ovary. 4) The wall is maintained for about 14 days until day 28. If the egg has not been fertilised and implanted into the uterus lining it breaks down." "What is the role of FSH (Follicle stimulating hormone) in the menstrual cycle? - CORRECT ANSWER Made in the pituitary gland. Causes a egg to mature in one of the ovaries in a structure called a follicle. Stimulates the ovaries to produce oestrogen." "What is the role of oestrogen in the menstrual cycle? - CORRECT ANSWER Produced by the ovaries. Causes the lining of the uterus to grow. Stimulates the release of LH (which causes ovulation) and inhibits the release of FSH." "What is the role of LH (Luteinising hormone) in the menstrual cycle? - CORRECT ANSWER Produced in the pituitary gland. Stimulates the release of an egg (ovulation) at day 14." "What is the role of progesterone in the menstrual cycle? - CORRECT ANSWER Produced by the ovary by the remains of the follicle. Maintains the lining of the uterus. When the level of progesterone falls the lining of the uterus breaks down. Inhibits the release of LH and FSH." "Where is testosterone produced? - CORRECT ANSWER In the testes." "How does the contraception pill work? - CORRECT ANSWER Contains oestrogen and progesterone. Taking oestrogen every day prevents the release of an egg by inhibiting FSH. Progesterone reduces fertility by stimulating the production of thick sticky mucus at the cervix preventing the sperm getting to the egg." "What are the side effects of the pill? - CORRECT ANSWER Headaches and nausea. Still contract STIs." "What is the contraceptive patch? - CORRECT ANSWER Contains same hormones as the pill. Patch is stuck under the skin (5cm x 5cm). Each patch lasts a week." "What is the contraceptive implant/injection? - CORRECT ANSWER Implant is inserted under the skin. Releases progesterone. Can last for 3 years. Injection lasts less time 2-3 months." "What is an intrauterine device? - CORRECT ANSWER Is a T shaped device that is inserted into the uterus to kill sperm and prevent implantation of the fertilised egg." "Name three barrier methods, non hormonal methods of contraception. - CORRECT ANSWER Male and female condom, diaphragm, spermicide" "What is the diaphragm? - CORRECT ANSWER A plastic cup that fits over the cervix (opening to the womb) to form a barrier." "How does spermicide work? - CORRECT ANSWER It kills or disables the sperm." "Name a permanent ways to avoid pregnancy. - CORRECT ANSWER Abstinence (not having sex), sterilisation which is having Fallopian tubes or sperm duct cut." "How does IVF work to help infertile couples? - CORRECT ANSWER FSH and LH are given to a woman to help eggs mature and release. Eggs are then collected from a woman's ovaries. The eggs are fertilised in a lab with the man's sperm. The fertilised eggs are grown into embryos in an incubator. The 1-2 embryos are then transferred to the woman's uterus to increase chance of pregancy." "What are the pros and cons of IVF? - CORRECT ANSWER PRO: Gives an infertile couple a child. CON: Multiple births, these are risky, more chance of still birth and miscarriage. CON: Success rate is low CON: Emotionally and physically stressful CON: Side effects of hormones e.g. abdominal pain" "What are the ethical concerns linked to IVF? - CORRECT ANSWER IVF leads to unused embryos which are destroyed or used for medical research. (Potential life). Genetic testing could be carried out on the embryo which could lead to designed babies." "What is the sclera? - CORRECT ANSWER The tough supporting wall of the eye" "What is the cornea? - CORRECT ANSWER Outer transparent layer, bends/refracts light into the eye" "What is the pupil? - CORRECT ANSWER The hole in the centre where light enters" "What is the iris? - CORRECT ANSWER A muscle that controls the diameter of the pupil and how much light enters. The coloured part of the eye." "What is the retina? - CORRECT ANSWER Contains receptor cells called rods and cones. These are sensitive to colour and light intensity." "What is the lens? - CORRECT ANSWER Focuses the light into the retina" "What is the ciliary muscles and suspensory ligaments? - CORRECT ANSWER Control the shape of the lens" "What is the optic nerve? - CORRECT ANSWER Carries impulses from the receptors on the retina to the brain" "Why is the iris reflex needed? - CORRECT ANSWER To prevent light from damaging the retina." "Explain the iris reflex in very bright light. - CORRECT ANSWER In very bright light a reflex is triggered to make the pupil smaller. The CIRCULAR muscles CONTRACT and the RADIAL muscles RELAX." "Explain the iris reflex in dim light. - CORRECT ANSWER In dim light a reflex is triggered to make the pupil dilate. The CIRCULAR muscles RELAX and the RADIAL muscles CONTRACT." "Define accommodation. - CORRECT ANSWER Where the eye focuses light on the retina by changing the shape of the lens." "Explain how the eye focuses on something that is near to it. - CORRECT ANSWER The ciliary muscles contract which slacken the suspensory muscles. This causes the lens to become fat (more curved) so increases how much light is bent." "Explain how the eye focuses on something that is far away. - CORRECT ANSWER The ciliary muscles relax which causes the suspensory muscles to pull tight. This causes the lens to become thinner so refracts light by a smaller amount." "What is long sightedness (hypermyopia)? How is it treated? - CORRECT ANSWER People are unable to focus on near objects. This occurs when the lens doesn't refract the light enough or the eyeball is too short. The image is brought into focus BEHIND the retina. You can use glasses with a convex lens to treat it." "What is short sightedness (myopia)? How do you treat it? - CORRECT ANSWER People are unable to focus on FAR objects. This occurs when the lens is the wrong SHAPE and refracts the light too much. The image is brought into focus IN FRONT of the retina. You can use glasses with a concave lens to treat it." "How can the efficiency of food production be improved? - CORRECT ANSWER By restricting energy transfer from food animals to the environment" "How can energy transfer from food animals to the environment be restricted? (2) - CORRECT ANSWER 1. Limiting their movement 2. Controlling the temperature of their surroundings" "How is the growth of some animals increases? - CORRECT ANSWER They are fed high protein foods" "Ethical objections to modern intensive farming methods - CORRECT ANSWER 1. Intensively farmed animals suffer in uncomfortable conditions 2. They are not kept in their natural habitat 3. Furthermore intensive farming is not necessarily successful as studies show contented animals gain biomass faster" "What is happening to fish stocks in the ocean? - CORRECT ANSWER They are declining" "Why is it important to maintain fish stocks at a level where breeding continues? - CORRECT ANSWER Otherwise certain species may disappear altogether ins ome areas" "Methods for conserving fish stocks at a sustainable level - CORRECT ANSWER 1. Control of net size - larger nets mean small, young fish can escape and continue to breed 2. Fishing quotas - to ensure areas are not completely overfished" "Modern biotechnology techniques enable... - CORRECT ANSWER ...large quantities of microorganisms to be cultured for food" "A protein-rich food suitable for vegetarians - CORRECT ANSWER Mycoproten" "How is mycoprotein produced? - CORRECT ANSWER 1. The fungus Fusarium is grown on glucose syrup in aerobic conditions 2. The biomass is harvested and purified" "How can we use a genetically modified bacterium to treat people with diabetes? - CORRECT ANSWER A genetically modified bacterium produces human insulin which can be harvested, purified and used to treat people" "How GM crops could be used? - CORRECT ANSWER To provide more food or food with improved nutritional value such as golden rice" "What is reaction time? - CORRECT ANSWER The time it takes to respond to a stimulus" "What is reaction time affected by? - CORRECT ANSWER Age, drugs e.g. caffeine or gender" "Why are computers a better way of measuring reaction time than the ruler test? - CORRECT ANSWER Computers can give a more precise reaction time because they remove human error. Computers can record the reaction time to a millisecond so more accurate. Computers remove the possibility that a person can predict when to respond by using a persons body language." "What is auxin? - CORRECT ANSWER A growth hormone found in the roots and shoots of plants. It controls the growth of plants in response t light, gravity and water." "What does phototropism mean? - CORRECT ANSWER The movement of a plant towards light." "If light is coming from one side of a plant what will happen. - CORRECT ANSWER Auxin diffuses to the dark/shaded side of plant. This causes the cells to grow faster on that side (elongate) which causes the shoot to bend twards the light." "What till happen if the tip of a shoot is removed from a plant? - CORRECT ANSWER There will be no auxin as auxin is found in the shoot. The plant will not grow." "What effect does auxin have on shoots and roots? - CORRECT ANSWER Auxin promotes growth in shoots and inhibits growth in roots." "What will happen to a shoot if it is growing sideways? - CORRECT ANSWER Auxin moves to the lower side of the shoot and the root. This is caused by gravity. It cause the lower side of the shoot to grow faster so the shoot bends upwards towards the light. In the root the lower side grows slower meaning the root bends downwards." "How can auxins be used to kill weeds? - CORRECT ANSWER Most weeds growing in a field of crops or on a lawn are broad leaved, in contrast to grasses and cereals which are narrow leaves. Selective weedkillers have been developed using auxin to kill only broad leaf plants by disrupting their growth patterns." "What does ethene do? - CORRECT ANSWER Stimulates the ripening of fruit." "What does gibberellin do? - CORRECT ANSWER Stimulates seed germination, stem growth and flowering." "Give three ways auxin is used commercially? - CORRECT ANSWER Killing weeds, growth from cuttings using rooting powder, growing cells in tissue culture." "What are chromosomes? - CORRECT ANSWER Long molecules of DNA inside a nucleus. 23 pairs inside the nucleus of body cells." "What is DNA? - CORRECT ANSWER DeoxyriboNucleic Acid. It is a chemical that all genetic material in a cell is made from. It is a polymer. It is made up of two strands coiled together as a double helix." "What is the structure of DNA? - CORRECT ANSWER DNA strands are polymers made up of repeating nucleotides. Each nucleotide is made up of one sugar (deoxyribose) and a phosphate. The sugar phosphate molecules form the backbone to the DNA stands. One of the four bases ACTG joins to the sugar molecule." "How do the bases pair in DNA? - CORRECT ANSWER A-T and G-C" "How many bases code for an amino acid? - CORRECT ANSWER Three/triplets" "What is a gene? - CORRECT ANSWER Small section of DNA found on a chromosome Genes tell cells in what order/sequence to put amino acids in to make specific protein." "How are proteins synthesised? - CORRECT ANSWER DNA unwinds exposing one strand. An mRNA copy is made using the DNA as a template. U replaces T. The first stage happens in the nucleus. (Transcription). mRNA is single stranded and can leave through the DNA pore. Proteins are made in the cytoplasm. The ribosome reads the mRNA . Every three bases codes for an amino acid. The correct amino acids are brought to the ribosome by carrier molecules. tRNA. This stage is called translation." "What do genes code for? - CORRECT ANSWER A particular sequence of AMINO ACIDS put together to make SPECIFIC PROTEINS" "What is a genome ? - CORRECT ANSWER The entire set of genetic material in an organism" "Why is it important to understand the human genome? (3) - CORRECT ANSWER 1)Allows scientists to IDENTIFY GENES that link to different types of disease i.e Down Syndrome 2)Development of effective treatments 3)Can be used to trace migration of certain populations by tiny differences in GENOMES." "How many chromosomes are in a normal body cell? - CORRECT ANSWER 46 or 23 pairs" "How many chromosomes in a gamete (sex cell)? - CORRECT ANSWER 23" "Give 3 details of sexual reproduction in plants/animals - CORRECT ANSWER -Animal gametes -egg & sperm - Plant gametes-ovule & pollen -Each gamete contains 23 chromosomes -nucleus of both gametes fuses=mixture of genetic info=variation in offspring" "Give 3 details of Asexual reproduction - CORRECT ANSWER -One parent -Genetically identical offspring-clone -Happens by mitosis" "Give 2 examples of organisms that reproduce asexually - CORRECT ANSWER Bacteria Some animals&plants" "What type of cell division are gametes (sex cells) produced by? - CORRECT ANSWER Meiosis" "What are the 5 stages of Meiosis - CORRECT ANSWER 1-Duplicate genetic info-forming 'X' chromosomes that arrange themselves into pairs 2-Chromosomes line up in centre of cell in homologous pairs 3-Pairs pulled apart so each new cell only has one copy of each chromosome-some of the father's chromosomes and some of the mother's go into each cell randomly, but each cell has an equal amount of chromosomes in total 4-2nd division-chromosomes line up in centre & separated again 5=4 gametes-each with single set of chromosomes" "Give 2 details about the 4 gametes produced in meiosis - CORRECT ANSWER 1-Each contain 1 set of chromosomes 2-Each gamete genetically different" "Why are gametes produced in meiosis genetically different? - CORRECT ANSWER Because chromosomes are shuffled up during meiosis and each gamete only gets half of them at random" "Explain how/why the cell produced by gamete fusion replicates itself (3) - CORRECT ANSWER 1) After 2 gametes fused during fertilisation-resulting new cell divides by mitosis to make copy of itself 2)Mitosis repeats many times to make lots of new cells in an EMBRYO 3)As embryo develops-cells differentiate into diff types of specialised cell that MAKE UP WHOLE ORGANISM" "How many pairs of chromosomes are in a human body cell? - CORRECT ANSWER 23 Pairs" "What do each of the chromosomes control? - CORRECT ANSWER 22 pairs of chromosomes are matched/homologous pairs-control CHARACTERISTICS 23rd pair-XY or XX -Sex defining chromosomes" "What are the male and female chromosomes? - CORRECT ANSWER Males: XY-The Y chromosome causes male characteristics Females:XX-combination allows female characteristics to develop" "Explain the chances of a child being male/female using a punnet diagram. - CORRECT ANSWER 50% chance of male and 50% chance of female." "How do you use genetic diagrams to find the probability of getting a boy or a girl? (3) - CORRECT ANSWER 1-Put possible gametes from one parent down side, and from other parent along the top 2-In middle boxes, fill in letters from top & side (like multiplication) 3-There are 2 XX result & 2 XY results -50% chance of boy/girl" "What do the pairs of letters in the middle of a Punnett square show? - CORRECT ANSWER The possible gamete combinations" "What do inherited genes control? - CORRECT ANSWER The characteristics you develop. Genes code for proteins. Some characteristics controlled by single gene Most characteristics controlled by several INTERACTING GENES" "What are alleles? - CORRECT ANSWER VERSIONS of genes. You have 2 versions (alleles) of every gene in your body-one on each chromosome in a pair" "What does it mean if an organism is Homozygous? - CORRECT ANSWER If its 2 alleles for a particular gene are the same. E.g BB is Heterozygous , Bb is heterozygous" "What does it mean if an organism is Heterozygous? - CORRECT ANSWER If its 2 alleles for a particular gene are the different. e.g Bb is heterozygous , BB is homozygous dominant, bb homozygous recessive" "If two alleles are different (heterozygous), which characteristics will be expressed? - CORRECT ANSWER In heterozygous individuals the dominant characteristic will always be expressed/show up in the phenotype/characteristic." "What is a genotype? - CORRECT ANSWER The combination of alleles you have e.g- BB Bb etc" "What is a phenotype? - CORRECT ANSWER Visible characteristics of an organism, due to its genotypes' interaction with the environment eg- eye colour/hair length/features" "A person who is heterozygous for brown eyes (Bb) has children with a person who has blue eyes (bb). What percentage of their children will have blue eyes? - CORRECT ANSWER 50%" "How do you interpret a family tree diagram/pedigree diagram? - CORRECT ANSWER square-male circle-female coloured square/circle-affected blank square/circle-unaffected half coloured square/circle-carriers" "What is cystic fibrosis? - CORRECT ANSWER It is a genetic disorder of the cell membranes. Causes thick, sticky mucus to build up in air passages and pancreas." "Cause of cystic fibrosis? - CORRECT ANSWER Caused by a Recessive Allele -'f' Alleles-'Ff'-unaffected but is a carrier Alleles- 'ff'- has cystic fibrosis" "What is Polydactyly + cause - CORRECT ANSWER A genetic disorder where a baby is born with extra fingers or toes. Cause:Dominant Allele- 'D' 'Dd' has Polydactyly 'dd' unaffected" "Why can't you have carriers of Polydactyly? - CORRECT ANSWER It is caused by a dominant allele. If you get one copy of the allele the phenotype will be expressed." "What is the chance of someone not being born with Polydactyly if both parent are heterozygous (Dd) for the disease. - CORRECT ANSWER 25%" "How can genetic disorders be detected? - CORRECT ANSWER EMBRYONIC SCREENING IVF -before implantation-cell can be removed from embryo to analyse genes. Embryos with defective alleles/genes destroyed. Also possible to collect and examine DNA from embryo in womb, to test for genetic disorders-abortion is an option following a positive result." "Embryonic screening 3 pros/3 cons - CORRECT ANSWER Pros 1-helps to stop suffering 2-There are laws to stop it going too far-parents can't select sex of baby. 3-Treatment for genetic disorders costs NHS/tax payers money Cons 1-implies people with genetic disorders are undesirable, leads to prejudice. 2-Screening is Expensive. 3-Could lead to designer babies e.g. parents want a blonde eyed, blonde haired boy." "What is Variation ? - CORRECT ANSWER inherited differences in Organisms caused by genetics or environmental factors" "How can genes and environmental factors affect variation ? - CORRECT ANSWER Genes-differences in the genotype E-growth controlled by food/light/water etc" "What are mutations ? - CORRECT ANSWER Changes to the sequence of bases in DNA. Mutations include substitutions, deletions and additions." "How do mutations occur? - CORRECT ANSWER Randomly. Increased by exposure to certain substances e.g. carcinogens and radiation." "Explain why the function of a protein might be affected by a mutation. - CORRECT ANSWER Mutations in the base sequence could affect the amino acid sequence. This will change the shape of the protein. E.g. with enzymes the active site might change shape so that the substrate cannot bind." "Give an example of where genetic variants(mutations) determine phenotype - CORRECT ANSWER Cystic fibrosis caused by a mutation that affects phenotype GENE codes for a protein that controls movement of salt and water out of cells The protein produced by the mutated gene doesn't work properly = excess mucus production in LUNGS & DIGESTIVE SYSTEM-hard to breath & digest" "What is the theory of Evolution? - CORRECT ANSWER All of today's species have evolved from simple life forms that first started to develop over 3 billion years ago" "What theory did Charles Darwin come up with? - CORRECT ANSWER Evolution by Natural selection Variation in species phenotype caused by mutations. Organisms with the most suitable characteristics/better adapted for the environment would be more successful competitors and be more likely to survive. They are more likely to reproduce,passing on the genes for their beneficial characteristics to offspring. Overtime the beneficial gene increases in the population." "Explain why Darwin's theory was considered controversial when it was first proposed. - CORRECT ANSWER -Against religious beliefs about how life on Earth developed -Darwin couldn't explain how these characteristics appeared or how they were passed on." "What 3 things developed/supported Darwin's Theory of Evolution? - CORRECT ANSWER -Discovery of genetics (Mendel/Watson and Crick) -Looking at fossils-changes in organism over time -Antibiotic resistant bacteria-supports evolution by natural selection" "How did the discovery of genetics support Darwin's theory? - CORRECT ANSWER It explained WHY NEW characteristics appeared or how organisms passed on their beneficial adaptations." "Name another scientist who had a theory about evolution. - CORRECT ANSWER Jean Baptiste Lamarck" "Describe Jean Baptiste Lamarck's theory. - CORRECT ANSWER Theory of Acquired characteristics. E.g. if a giraffe stretched it's neck to reach tall branches over time the neck would get longer." "Describe speciation. - CORRECT ANSWER Speciation-over time, a phenotype of organisms will change so much due to NATURAL SELECTION that a new species is formed." "When does speciation happen? - CORRECT ANSWER When POPULATIONS of the SAME SPECIES change enough to become re productively isolated. This means that they can't inbreed to produce fertile offspring." "What is extinction +4 reasons - CORRECT ANSWER No individuals of a species remain -Change in environment -New predator kills them -Disease -can't compete with new species for food" What is homeostasis? - CORRECT ANSWER The maintenance of a constant internal environment." "What is a stimulus? - CORRECT ANSWER A change in your environment than requires a response. e.g Light, sound, touch, pressure, pain, chemical or temperature." "What do the receptors do? - CORRECT ANSWER Detect the stimulus or change in environment." "What happens after the receptors? - CORRECT ANSWER Receptors send messages to the CNS via the sensory neurone." "What makes up the central nervous system? - CORRECT ANSWER The brain or spinal cord" "What is an effector? - CORRECT ANSWER Muscles or glands that bring about a response." "What do the muscles and glands do in response to stimuli? - CORRECT ANSWER Muscles contract and glands secrete chemical substances(hormones)." "What is a sensory neurone? - CORRECT ANSWER A neurone that carry information from the receptors to the CNS." "What is a relay neurone? - CORRECT ANSWER Neurones that carry impulses from the sensory neurone to the motor neurone." "What is a motor neurone? - CORRECT ANSWER Neurones that carry information from the CNS to the effectors." "What is the nervous system? - CORRECT ANSWER It is a system that allows you to react to your surroundings." "How do signals travel across a synapse? - CORRECT ANSWER The chemical or neurotransmitter diffuses across the synapse and binds to a complementary receptor on the neurone (postsynaptic). This causes an electrical impulse to travel down the next neurone." "What is a synapse? - CORRECT ANSWER A gap between two neurones." "What is the thermoregulatory centre of the brain? - CORRECT ANSWER Near the hypothalamus, monitors the temperature of blood." "Describe the stages in a reflex arc. - CORRECT ANSWER Stimulus-Receptor-sensory neurone-CNS (relay neurone) - motor neurone - effector - response" "Name responses that reduce body temperature. - CORRECT ANSWER Hairs lie flat, sweat and blood vessels get wider(vasodilation)" "What happens during vasodilation? - CORRECT ANSWER The blood vessels supplying the skin dilate (widen). This helps to transfer energy to the environment." "Name responses that increase body temperature. - CORRECT ANSWER Hairs stand up, no sweat, shivering and blood vessels constrict(vasoconstriction)" "What happens during vasoconstriction? - CORRECT ANSWER The blood vessels supplying the skin constrict to close off the skins blood supply." "What is the body's core temp? - CORRECT ANSWER 37 degrees Celsius" "What are hormones? - CORRECT ANSWER Chemical messengers that travel in the blood to target organs." "Compare and Contrast the endocrine (hormone) system and the nervous system. - CORRECT ANSWER Nervous is faster acting than the endocrine system. Hormones have longer lasting effects compared to electrical impulses. Nerves act on a very specific area whereas hormones act more general." "What does the thyroid gland do? - CORRECT ANSWER Produces thyroxine which is involved in regulating metabolism." "What do the adrenal glands do? - CORRECT ANSWER Produce adrenaline which is used to prepare the body for fight or flight." "What is the role of the pancreas? - CORRECT ANSWER Produces glucagon and insulin which are involved in regulating glucose levels in the blood." "Name the hormone that is released if blood sugar is too high. - CORRECT ANSWER Insulin" "What does insulin do? - CORRECT ANSWER It makes the liver convert glucose into glycogen. This causes blood glucose levels to decrease." "Name the hormone that is released if blood sugar is too low. - CORRECT ANSWER Glucagon" "What does glucagon do? HINT GLU-COSE-GONE - CORRECT ANSWER It makes the liver convert glycogen to glucose. This causes the blood glucose level to increase." "What is type I diabetes? - CORRECT ANSWER When the pancreas produces little or no insulin." "What is type II diabetes? - CORRECT ANSWER When a person becomes resistant to their own insulin. Being overweight can increase your chances of type II diabetes." "How can type I diabetes be treated? - CORRECT ANSWER Insulin injections, limiting intake of foods rich is simple carbohydrates e.g. sugars and regular exercise." "Name some of the treatments for vision defects. - CORRECT ANSWER Contact lenses, laser eye surgery and replacement lens surgery." "What is the brain made from? - CORRECT ANSWER Millions of interconnected neurones" "What is the brain in charge of? - CORRECT ANSWER It is in charge of our complex behaviours, controls and coordinates everything we do breathing, sleeping, memory etc." "What is the cerebral cortex? - CORRECT ANSWER The outer wrinkly layer of the brain, controls consciousness, memory and language" "What is the medulla? - CORRECT ANSWER The base, controls unconscious activities like breathing, movement in the intestines and heartbeat" "What is the cerebellum? - CORRECT ANSWER At the back, responsible for muscle contraction & balance" "What is the hypothalamus? - CORRECT ANSWER controls homeostasis and pituitary gland" "What is the pituitary gland ? - CORRECT ANSWER It is the master gland. It produces many hormones that regulate homeostasis e.g ADH, FSH" "Name some methods by which scientists study the brain. - CORRECT ANSWER MRI, Electrical stimulation, Studying patients with damage to their brain." "Evaluate the benefits and risks of procedures carried out on the brain and the nervous system. - CORRECT ANSWER +ve- Can lead to the treatment for disorders of the nervous system -ve- The brain is complex and delicate. The treatment of brain damage is difficult. It also carries risks such as physical damage or increased problems with brain damage e.g. speech. NB: ADD A CONCLUSION." "What is selective breeding? + process - CORRECT ANSWER Humans artificially select which organisms to breed so that the GENES for particular characteristics remain in the population 1)select stock with DESIRED CHARACTERISTICS 2)breed them 3)breed best of offspring 4)continue cycle so DESIRABLE TRAIT gets stronger and stronger, until eventually, all offspring will have this characteristic" "Give some examples of selective breeding - CORRECT ANSWER Agricultural animals to produce more meat/milk Crops-disease resistance Good, friendly dogs Decorative plants with big, unusual flowers" "What is the main issue of selective breeding? - CORRECT ANSWER Reduction in the gene pool-the number of different alleles in a population" "What is inbreeding? + cons - CORRECT ANSWER Where the farmer only breeds from the 'best' of animals/plants - more chance of the organisms inheriting harmful GENETIC DISORDERS when the gene pool is limited -lack of variation in population=if one dies of a disease, the rest are likely to die too" "What is genetic engineering ? - CORRECT ANSWER The transfer of a gene for a desirable characteristic from one organism's genome into the other's, so that it also has that desired characteristic." "Process of genetic engineering - CORRECT ANSWER 1) useful gene cut from one organism's genome using ENZYMES and inserted into a VECTOR. 2)Vector(virus/bacterial plasmid) inserts useful gene into CELL of organism" "Give 3 examples of where genetic engineering has been used - CORRECT ANSWER 1)GM crops have modified genes to improve SIZE/QUALITY of fruit , and make them RESISTANT to herbicides, pesticides or disease 2)Sheep-PRODUCE DRUGS IN MILK to treat human disease 3) Bacteria have been genetically modified to produce HUMAN INSULIN which can be used to treat DIABETES." "2 pros & 2 cons of GM crops - CORRECT ANSWER +increased yield=more food +already being grown, not problematic -worries on human health/safety/allergies -long term effects-unplanned problems that could could pass on to future generations" "How might GM crops help people in the developing world? - CORRECT ANSWER People in the developing world often lack nutrients in their diet. GM crops could be engineered to contain the missing nutrient e.g. Golden rice is a GM crop that contains Beta Carotene-lack of this substance causes blindness." "Describe how animals can be cloned by adult cell cloning. [6] - CORRECT ANSWER The nucleus is removed from an unfertilised egg.[1] A complete set of adult chromosomes from an adult body cell is inserted into the egg. [1] The egg cell is then stimulated to divide to form an embryo by being given an electric shock.[1] The embryo is then implanted into an adult female [1] where it develops into a clone of the original adult body cell." "Explain the ethical implications around cloning animals. - CORRECT ANSWER -Reduced gene pool + Cloning could produce lots of 'ideal' offspring with desirable traits. - Worries that it could lead to human cloning -Cloned animals may not be as healthy e.g. Dolly the sheep had arthrisis +Study of animal embryos could lead to the understanding of the development of the embryo and age-related disorders. -Preserve endangered species. - Not natural/Against God/religions" "Describe how you could clone a plant. (Tissue Culture) - CORRECT ANSWER Tissue culture- A few plant cells are put in a growth medium with hormones and they grow into new plants. Plants can be made quickly and cheaply in very little space." "Describe how you could clone a plant. (Cuttings) - CORRECT ANSWER Take a cutting from good parent plants. Dip into rooting powder and plant. Can produce plants quickly and cheaply." "What are fossils and give 3 ways they form in rock - CORRECT ANSWER THE REMAINS OF PLANTS AND ANIMALS FORMED IN ROCK 1-gradual replacement by minerals-forming rock-like substance 2-casts/impressions soft material around it hardens, leaving cast/impression-from fossil/footprint 3-preservation in places where no decay happens glaciers/amber-no oxygen or moisture or peat bogs which are too acidic for decay" "Explain Antibiotic Resistance - CORRECT ANSWER Bacteria DNA RANDOMLY MUTATES. Taking antibiotics creates a selective pressure as the environment changes. Selects the resistant strain as better adapted. This can lead to antibiotic resistant strains. More likely to survive and reproduce. Gene for antibiotic resistance increases in the population." "Give 3 reasons for antibiotic resistance - CORRECT ANSWER 1-not taking the full course of the treatment-leaving some bacteria unkilled-ready to mutate 2-overuse & inappropriate use e.g. for viral infections. 3- Increase use in animal agriculture/farming to prevent animals become ill. Can spread to humans." "What is classification? - CORRECT ANSWER Organising living organisms into groups/kingdoms which are then divided into smaller groups of different structures/characteristics Classification systems change over time" "Explain the Carl Woese three-domain system - CORRECT ANSWER 1. Archaea-PRIMITIVE BACTIERIA often found in EXTREME PLACES such as hot springs/salt lakes 2.Bacteria-true bacteria(eg E coli)-very biochemically different to Archaea 3.Eukaryota-broad range of organisms including fungi,plants,animals,protists. These are then subdivided into smaller groups:-Kingdom, Phylum, Class, Order, Family, Genus, Species" "What is the binomial system? - CORRECT ANSWER Organisms are named according to this system. 2 part Latin name part one:GENUS the organism belongs to part two:the species" "What do Evolutionary trees show? - CORRECT ANSWER EVOLUTIONARY RELATIONSHIPS eg ancestry To investigate this they use current classification data for living organisms and fossil records for extinct species." "Competition - CORRECT ANSWER The process by which living organisms compete with each other for limited resources" "What do organisms require to survive and reproduce? - CORRECT ANSWER A supply of materials from their surroundings and other living organisms" "What do plants compete with each other for? (4) - CORRECT ANSWER Light, space, water, and mineral ions" "What do animals compete with each other for? (3) - CORRECT ANSWER Food, mates and territory" "Stable community - CORRECT ANSWER Where all the species and environmental factors are in balance so that population sizes remain fairly constant" "What happens if one species is removed from a community? - CORRECT ANSWER It can affect the whole community" "Abiotic factors - CORRECT ANSWER Non-living factors" "Biotic - CORRECT ANSWER Living factors" "Name 7 abiotic factors and how they might affect a community - CORRECT ANSWER 1. Light intensity - photosynthesis, breeding cycles linked to day length 2. Temperature - photosynthesis/plant growth, therefore animals which can survive 3. Moisture levels - both plants and animals need water to survuve 4. Soil pH and mineral content - distribution of plants, most struggle to grow where there is few mineral ions; low pH inhibits decay and therefore release of mineral ions 5. Wind intensity and direction - shape of trees and landscape, increases plant transpiration 6. Availability of oxygen - aquatic animals e.g. fish require high levels of dissolved oxygen 7. Availability of carbon dioxide - photosynthesis" "Name 4 biotic factors and how they might affect a community - CORRECT ANSWER 1. Availability of food - food allows animals to survive and breed successfully 2. New predators arriving - organisms with no defences against these predators may die out 3. New pathogens - organisms have no resistance so populations can be wiped out 4. One species outcompeting another so the numbers are no longer sufficient to breed - e.g. grey squirrels in Britain" "Adaptations - CORRECT ANSWER Features which enable an organism to survive in the conditions in which they normally live" "Adaptations may be... - CORRECT ANSWER ...structural, functional or behavioural" "Examples of structural adaptations - CORRECT ANSWER Features of body structure, shape or colour - e.g. animals living in cold environments have small ears (low SA:vol ratio), Arctic foxes have white fur, whales have blubber, herbivores have teeth for grinding up plant cells" "Examples of behavioural adaptations - CORRECT ANSWER Basking, migration, tool use - e.g. birds migrate, nocturnal to avoid heat of day" "Examples of functional adaptations - CORRECT ANSWER Processes inside body - e.g. reduced sweating, animals in extreme winter temperatures produce a chemical in cells which cacts as an antifreeze" "Extremophiles - CORRECT ANSWER Organisms that live in very extreme environments, such as high temperature, pressure or salt concentration" "Eaxmple of extremophiles - CORRECT ANSWER bacteria living in deep sea vents (at very high pressure, no light, acid pH)" "Photosynthetic organisms are... - CORRECT ANSWER .the producers of biomass for life on earth" "How can feeding relationships within a community be represented? - CORRECT ANSWER With food chains" "Describe the structure of food chains, giving examples. (3) - CORRECT ANSWER 1. All food chains begin with a producer which synthesises molecules e.g. green plants, algae, which make glucose by photosynthesis 2. Primary consumers eat producers 3. In turn these may be eaten by secondary and then tertiary consumers" "Predators - CORRECT ANSWER Consumers that eat and kill other animals" "Prey - CORRECT ANSWER Animals eaten by predators" "In a stable community, the numbers of predators and prey... - CORRECT ANSWER ...rise and fall in cycles" "What are 2 methods used by ecologists to determine the distribution and abundance of species in a ecosystem? - CORRECT ANSWER Transects and quadrats" "Quadrat - CORRECT ANSWER A square made of wire used to estimate population size of plants or slow moving animals. It may have smaller squares of wire within it." "How do you use a quadrat? - CORRECT ANSWER 1. Choose a sample area at random. Use random number tables and coordinates 2. Count the number of organisms in the quadrat 3. Repeat this several times 3. Find mean number of organisms per metre squared" "How can we ensure this quadrat investigation is a fair test? - CORRECT ANSWER 1. Sample as many areas as possible to increase sample size and make the results more valid 2. Use the same quadrat each time 3. Randomly sample areas - could improve this by using a random number generator" "What is an issue with quadrat investigations? - CORRECT ANSWER Time consuming and difficult if animals are present" "