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BiologyTopic 1 Control SystemsBiological Rhythms (Humans)A circadian rhythm is a biological rhythm that happens over a 24 hour period. The human brain contains a tiny mechanism called a biological clock, which regulates things such as hormones in a day. Humans secrete increasing amounts of melatonin around 10pm which makes them feel sleepy.Melatonin levels drop in the morning, so we wake up. Our Biological clock needs exposure to day & night to keep in sync with our 24 hour cycle.

Biological Rhythms (Plants)Flowers often open in the day & close at night. This makes sure they are ready to be pollinated by insects, as they are protected from plants at night. They also only produce nectar in the day time when the flowers are most likely to be pollinated. They also have a yearly rhythm called photoperiodism. PhotoperiodismPlants respond to changing day length & use it to help them grow/flower at the right time. Many plants die in winter, with their seeds surviving. The seeds sense longer days in spring & start to germinate. Some plants grow throughout winter but respond to longer days, growing faster.In autumn, when days shorten, the plants stop growing survive the winter conditions. Flowering is also controlled by the length of light or dark periods during a 24 hour cycle.Plant DefencesMany plants such as the Lupin make their leaves poisonous to insect pests or larger herbivores that might want to eat it. Many also use chemicals to defend themselves against pathogens. People depend of plants for food; if pathogens destroy or damage crops, then our food supply is at risk.Making use of Plant PoisonsAlthough some chemicals in plants are poisonous to people, in small effects they may be useful. Quinine, produced by cinchona trees, can be used to treat malaria. Aspirin, produced by willow trees, can be used to symptoms of pain & fever. Potato plants poisonous alkaloids in their leaves or tubers that have been exposed to light. Research suggests that the alkaloids could be developed as a valuable cancer treatment.

Louis PastureShowed that microorganisms were responsible for some disease & some food going off. He proposed the idea of keeping microorganisms away from people & food in order to preserve food & stop disease. This was called aseptic techniques. This includes the process of pasteurisation, in which food such as milk are heated briefly before being stored, in oder to kill bacteria in them.VaccinesA weakened pathogen is injected into the body. A lymphocyte (white blood cells) with an antibody which fits the antigen (a chemical in the outer shell of viruses) is activated. This lymphocyte divides over & over again to produce identical clones. Some of the lymphocytes secrete antibodies, which stick to the antigens and destroy the pathogen. Other lymphocytes stay in the blood as memory lymphocytes to respond if the antigen turns up again.

Risks of ImmunisationIt is common for a person to get swelling or redness around the site of vaccination. Some children may get a mild form of the disease they are being weakened against. Very rarely, a child suffers an allergic reaction.Advantages of Immunisation A child can become immune to a disease without suffering it. Chances of long-lasting harm are much less than if a person actually has a disease. If enough children are vaccinated against a disease, then it becomes so rare, that even unvaccinated individuals are unlikely to get it.AntibodiesThe entry of pathogens into the body is known as on infection. The 1st time the pathogen infects someone, only 1 or 2 lymphocytes recognise the antigens on it. It takes a while form them to multiply & secrete enough antibodies to destroy the pathogens. (Primary response).After the infection memory lymphocytes remain & their knowledge to react & produce antibodies more quickly. (Secondary response).Monoclonal AntibodiesScientists can use antibodies to identify specific substances. Scientists need large quantities of identical antibodies to do this. (Monoclonal antibodies). Lymphocytes can clone themselves, however once it starts to make antibodies it becomes a B lymphocyte and can no longer divide.Using Monoclonal Antibodies Used in pregnancy tests to detect HGH hormone found in urine of pregnant women . The urine binds to the antibodies on the stick & causes a colour change. They can be made slightly radioactive so they can detect & bind to the platelets of cancerous cells. These cancer cells can then be detected & targeted specifically. Drugs can also be attached to monoclonal antibodies to deliver the drug to specific cells that need destroying.Getting Rid of Waste (Kidneys)The chemical reactions happening in the body produce waste products, many of which are released into the blood.The renal arteries carry blood to the kidneys. The Kidneys remove substances from the blood and make urine. The ureters carry urine from the kidneys to the bladder where it is stored. A muscle keeps the exit from the closed, until we decide to urinate. Urine flows through the urethra to the outside of the body.Treating Kidney FailureKidney failure is when both kidneys stop working properly, which leads to a build up of toxic urea in the blood. In kidney dialysis, blood is passed through a machine to remove waste urea before it is returned to the body. Another treatment is organ donation. This is where a healthy kidney is taken from someone else & connected to the blood system so waste substances can be removed.How a Nephron WorksBlood flows along the renal artery & into a network of capillaries(glomerulus) which runs inside the Bowmans capsule. The capsule has tiny holes to let small molecules(water & urea) through. The protein molecules & blood cells stay in the blood (filtration). As the fluid flows along the nephron, useful substances such as glucose are absorbed back through active transport. (selective reabsorption). At the end of the nephron, the fluid flows into the ureter. It is now called urine.Controlling Water ContentThe brain senses if there id too much/little water in the blood.If there is not enough water, the pituitary gland secretes more ADH. The ADH causes the kidneys to reabsorb more water, and only a small amount of urine is produced. If there is too much water, the pituitary gland produces less ADH. This makes the kidney absorb less water, and a large volume of dilute urine is produced.Menstrual Cycle (Days 1-14)Days 1-5: The lining of the uterus breaks down (menstruation). The pituitary gland releases FSH (follicle-stimulating hormones). Days 5-14: The FSH causes an egg follicle to grow in the ovary & oestrogen is released. The oestrogen stop releasing FSH & start releasing LH (Luteinising Hormone). Day 14: LH levels peak which causes and egg to be released. LH stops & the ovary releases oestrogen.Menstrual Cycle (Days 14-28)Days 14-21: Progesterone is released by the empty egg cell follicle. This will maintain the lining of the uterus. Days 21-28: The egg is waiting. If the egg is not fertilised, then the progesterone levels fall. The uterus lining starts to break down.Gametes (Sex Cells)Egg CellHas a haploid nucleus containing one set of genetic material.Has cytoplasm containing lipid droplets as nutrientsSperm CellTail for swimming. Its middle section contains mitochondria to release energy during respiration. Has a haploid nucleus containing one set of genetic material. At the front of the sperms head, there is an acrosome containing enzymes to digest a way into the egg.Infertility Treatments 1IVFEggs are taken from ovaries & mixed with sperm cells in a dish.One or two healthy embryos are placed into the womans uterus to develop. Positive: Useful if a man produces only few healthy spermNegative: IVF babies can be born early, which can cause problems.Egg DonationEggs from another woman are fertilized using the mans sperm via IVF. One or two healthy embryos are placed into the womans uterus to develop. Positive: mother can experience bond through birth. Negative: The egg donor may want access to the child. Infertility Treatments 2Surrogate MotherEgg & sperm from the couple are mixed in a Petri dish.The embryo is then inserted into the uterus of a surrogate mother. Positive: Baby is born normally. Negative: Surrogate mother may find it hard to had over the baby.HormonesThe woman is given extra hormones to help her ovaries release eggs. Positive: Baby is genetically theirs. Negative: Greater risk of more children being born earlier, which may cause problems at birth or in later life. Sex-linked InheritanceHaemophilia is a sex linked,genetic disease.There is no haemophilia gene on the Y chromosome.Therefore boys can only be a carrier of the disease.

Topic 2 - BehaviorCourtshipA mate that is healthy & well adapted to its environment is likely to have healthy offspring than a mate that is struggling to survive. Elaborate courtship helps to choose a mate. This often involves the male displaying to females, advertising that he is a high-quality choice. Some animals mate for life with the same partner, others will only pair up for breeding season. In some animal species, groups of females bread with one dominant male. These groups often remain together with the dominant males being replaced every few years.Caring for youngMany animals look after their young until they have developed enough to look after themselves. E.g. Female mammals feed their young on milk and teach them how to find food & avoid predators. This increases the offspring's survival & the continuation of the parents genes. Parental care can also be a successful evolutionary strategy.Innate behaviourAn innate behaviour is an automatic response to a stimulus that is hardwired into our brain.This can be shown in small animals using choice chambers. 5 woodlice are put into each chamber & left for an hour. The woodlice move towards the darker damper conditions they prefer. This is an innate response.

Imprinting & EthologyEthology is the study of animal behaviour. Niko Tinbergen studied the innate behaviour of gull chicks.He found that they peck at their parents beaks when they want food. Imprinting is the process in which young animals become attached to animals or objects they see immediately after birth. E.g. A young goose learns to recognise its mother and will stay close to it.Imprinting only happens at a particular time, but can last throughout life without changing.

HabituationHabituation is learning to switch off from repeated stimuli. For example, the sea slug has a gill sticking out of its back, which if touched, will be withdraw. If you continue to touch the gill without hurting it, the slug will eventually stop withdrawing it.Classical ConditioningIvan Pavlov found dogs salivated at the smell of food.He investigated whether they could respond to stimuli in a different way. He rang the bell before he gave them food, & the dogs learnt to associate food with the bell, so they now salivated at the sound of the bell. This is known as classical conditioning: it starts with an innate reflex, but then the animal learns to respond in a different way.Operant ConditioningOccurs when an animal discovers that a particular kind of behaviour can make something good happen. After a few times the animal then learns to associate this behaviour with an award, and will eventually carry out the action on purpose.Animal communication SignalsSound: Birds sing to establish & maintain territory, cats hiss to frighten other cats & stags roar to challenge other stags & attract females. Chemical: animals release hormone like chemicals called pheromones. Female moths do this to attract a mate. Visual: using gestures such as nodding or hand waving, body language to express feeling & emotion and facial expression such as showing teeth.

Social BehaviourSocial behaviour can increase the chance of a groups survival. By for example defending a large territory, working in a group to fight of predators & finding food. Dian Fossey was an ethologist who studied social behaviours in gorillas. She learn the meaning of many of their calls, had complex social relationships & werent violent.Plant Communication (Chemical)Flowering plants produce scents to attract insects so the animal can drink the nectar & the plant can be pollinated(Mutalistic relationship). Some plants produce chemicals in their roots that damages the roots of other plants so they have less competition for resource. Some (such as the acacia tree) release chemicals in the air when attacked by herbivores, to warn surrounding plants, which then produce poisons. This helps them to conserve energy as poisons take lots of energy to make.

Co-evolutionPlants have co-evolved the shape of their flowers so that only one or two animals species can feed at the flower. This benefit the plant as it means the plants pollen is more likely to be taken to a flower of the same species. This means that the animals is also less likely to compete with other animals for the flowers nectar. Evidence for Human EvolutionFossil evidence: The general trend of skull & limb structures through fossil discoveries down the years show the development from ape like beings, to homo sapiens. Stone tools: The earliest stone tools found 2.4 million years ago were very basic such as simple, blunt hand axes. Whereas 1.5 million years later tools were made fine flakes split from larger stones. E.g. Arrowheads & spears.Human Migration (Climate Change) In the Ice Ages more water was frozen so water levels were lower, which allowed humans to walk across places, now separated by water.Low sea levels 25,000 years ago meant humans could walk from Siberia to Asia and then North America.At the end of the ice age humans migrated north as the land became more hospitable.Mitochondrial DNAMitochondria have their own DNA.All mitochondria comes from cytoplasm in the eggs cell (all from the mother). mtDNA mutates over 100 times faster than nuclear DNA. As a cell contains more mtDNA, it is easier to extract from fossils due to a high abundance of it, and is more likely to be in a good enough condition to identify genetic sequences.Studies into mtDNA suggests that we all evolved from a woman in Africa 130-200 thousand years ago.This is evidence for how humans spread out from Africa & into the rest of the world.Topic 3 - BiotechnologyConditions Inside Fermenters Nutrients such as sugar & ammonium Ions that microorganisms need for growth. An optimum temperature ensured by circulating water in the water jacket removing excess heat & an optimum pH, ensured the best conditions for enzymes to work in. Oxygen produced by bubbling sterile air into the fermenter, so microorganisms can respire aerobically. Agitation, produced by a stirrer, to mix the oxygen & nutrients into all of the liquid.Microorganisms in FoodUsing microorganisms in food has advantages because: They grow more quickly than plants or animals. They are easy to handle & manipulate.Fermenters need a small area & can be built virtually anywhere, whereas plants & animals need particular environmental conditions. Using microorganisms can be cheaper & can reduce waste projects.

MycroproteinMade of a fungus called fusarium, which is made up of tiny fibres called hyphae.It is produced in a fermenter: Ammonia & air are added (for a source of nitrogen & oxygen). Rising bubbles cause the broth to circulate & excess gases are removed. The dense broth falls to the base of the fermenter, where glucose is added to add energy for growth.A cooling system then removes excess heat .It is then heated, to kill cells, and dried & pressed to remove water.

Benefits of MycoproteinIt has no saturated fat (risk factor in heart disease) however read meat does. The high fibre content of mycroprotein stop glucose being absorbed. This reduces glucose absorption and therefore glucose & insulin surges (factors of type II diabetes. Fibres also move through the intestines faster, allowing carcinogens to be removed more quickly, reducing the risk of bowel cancer.

Chymosin & InvertaseChymosin is an enzyme that affects proteins in milk, separating it into solid curds (used to make cheese) & liquid whey.It is extracted calves stomachs. It can also be made using genetically modified bacteria & is used to make vegetarian cheese.Invertase (sucrase) is an enzyme that converts sugar into glucose & fructose. Is commercially produced by yeast. It is used to make sweets, sweeter & for making soft centres in some sweets.Protease & Lipases in Washing PowdersProtease enzymes digest proteins found in food stains.Lipases digest fats & oils found in food stains. Washing powders that contain proteases & lipases work more quickly at a lower temperature than other washing powders, saving energy in heating water.Making Human Insulin 1It can be made from large quantities of bacteria that have been genetically modified to contain the human insulin gene. DNA from a human cell is cut into pieces using restriction enzymes, which make staggered cuts across the DNAs double strand, leaving a few unpaired bases at each end. (Sticky ends).This process is then repeated with bacterial plasmid DNA (which is taken out of the bactetium) leaving it with sticky ends with matching pairs of unpaired bases.Making Human Insulin 2The DNA containing the insulin gene is then mixed with the plasmid. The sticky end bases pair up. DNA ligase enzyme is then added, linking the DNA back into a contiguous loop. The recombinant plasmids are inserted into bacteria. The bacteria then grow in huge fermenters, where they make human insulin.Immobilising EnzymesLactase is an enzyme that breaks down lactose sugar. It can be immobilised in alginate beads to produce lactose free milk.Immobilising enzymes means they can be easily separated from the product so it can be used again.To immobilise: The enzyme (in sodium alginate solution) it is added one drop at a time to calcium chloride solution. The solutions react to produce calcium alginate beads containing the enzyme. The enzyme is now immobilised in the bead.Increasing Food ProductionGlobal food security is the ability to provide enough food for all the people on Earth. To combat a rising human population more food has to be produced. To do this, plants with good features (e.g. good yield, drought tolerance or needing less fertilizer) are crossed. Plants grow from seeds of these crosses are selected & their good feature are crossed.This selection & crossing is repeated many times, until a high-yielding variety is produced.Integrated Pest Management (Raspberries)Due to huge amounts of crops being lost to pests such as insects & fungal diseases, resistant plants are now being developed through a system called integrated pest management. In raspberries to combat viruses from aphids, raspberries have been conventionally bread so that they develop a resistance to aphids so they are less likely to get the virus. To combat beetles laying eggs in raspberries & their larvae eating the fruit from the inside, the plant is grown in environments made attractive to predators of beetles & chemicals produced by the raspberries are put into traps to lure beetles which are then killed by drowning in soap solution.BiofuelsMade from plants such as maize or oil palms. They are used as a replacement for fossil fuels which are running out.They are renewable & it doesnt take long for them to be produced. They are also carbon neutral as the CO2 released into the air when they are burnt are removed by the growing plants during photosynthesis. However, the plants do take up a lot of land that could be used for food.G-M Foods Genetically modified maize, soya & cotton are used widely grown in developing countries. Many of these crops have a herbicide resistant gene which means crops are not damaged by the chemical but the weeds are still killed. In 2008, a new purple GM tomato was developed that contained extra pigments called flavonoidas. Tests have shown that it helps mice with cancer to live longer.Making GM PlantsA transgenic organism genes transferred from another organism. Transgenic plants are often produced using a bacterium called Agrobacterium tumefaciens.The required gene is cut from DNA & inserted into the plasmid which has been removed from the bacterium. The plasmid with the required gene is then put back into the bacterium.The bacteria with the gene is then allowed to infect plants. This introduces the required gene to the plant cells.Advantages & Disadvantages of Bt cropsPlants that grow from Agrobacterium tumefaciens produces Bt toxin, a chemical that naturally kills insect pests. Advantages: Crop damage is reduced, so crop yield should increase & less chemical insecticide is used, so harmless insects are less likely to be killed. Disadvantages: Insects may become resistant to Bt toxin & transgenic plant seed is more expensive than non-transgenic varieties.