GCSE EDEXCEL BIOLOGY TRIPLE [B3]

Pregunta	Respuesta
Topic 1 Control systems	Topic 1 Control systems
What does cell metabolism lead to?	Cell metabolism leads to the
How is urea produced?	Urea is produced from the breakdown of excess amino acids in the liver and is removed by the kidneys.
What are the possible treatments for kidney failure?	Kidney dialysis and Organ donation
Describe the structure of the urinary system?	The renal arteries take blood with waste products to the kidneys to be filtered. Renal veins then return the filtered blood to be circulated around the body. Blood vessels take the blood though the kidneys where the waste products are removed into convoluted tubules. These tubules join together to form the ureter, which transports urine to the bladder where it is stored. Urine is then passed from the bladder to the urethra to be released.
Describe the structure of a nephron?	The glomerulus filters blood and produces glomerular filtrate. This filtrate contains water, glucose, salts and urea. Large molecules such as protein are too large to fit through the blood capillary walls. The Bowman's capsule collects the filtrate and it enters the tubules. All glucose is reabsorbed immediately into the blood capillaries. As the rest of the filtrate travels through the tubules, water and salts needed by the body are reabsorbed into the blood capillaries. The loop of Henlé helps maintain the correct water balance in the body by filtering out salts. The waste, consisting of excess water, excess salts and urea, is urine. The collecting duct collects the urine, which is then transported in the ureter to the bladder. The bladder stores urine until the body is ready to expel it through the urethra.
Explain how the structure of the nephron is related to its function in filtering the blood and forming urine?	1) Ultrafiltration: 1) A high pressure is built up which squeezes water, urea, ions and glucose out of the blood and into the Bowman's capsule. 2) The glomerulus and the Bowman's capsule act like filters. so big molecules like proteins and blood cells are not squeezed out. They stay in blood. 2) Reabsorption: 1) All the glucose is selectively reabsorbed - it's moved out of the nephron back into the blood against the concentration gradient. 2) Sufficient water is reabsorbed, according to the level of the hormone ADH. The process of maintaining the right water content in the body is called osmoregulation 3) Release of wastes: Urea and excess water are not reabsorbed. They continue out of the nephron, into the ureter and down to the bladder as urine. Urine is released through the urethra.
How is the water content controlled by a negative feedback system?	1) If there is a water gain, the brain detects the water gain and the pituitary gland releases ADH. A lack of ADH means kidney reabsorbs less water. 2) If there is a water loss, the brain detects the water loss and the pituitary gland releases more ADH. ADH makes kidney reabsorb more water.
What hormones are the menstrual cycle controlled by?	Oestrogen and Progesterone.
Describe the stages of the menstrual cycle?	Stage 1 - Day 1 when the bleeding starts. The uterus lining breaks down and is released (manstruation). Stage 2 - The lining of the uterus builds up again, from day 4 to day 14, into a thick spongy layer of blood vessels ready to receive a fertilised egg. Stage 3 - An egg is released from the ovary (ovulation) at about day 14. Stage 4 - The lining is then maintained for about 14 days, until day 28. If no fertilised egg has landed on the uterus wall by day 28, then the spongy lining starts to break down again and the whole cycle starts over.
Explain why the uterus lining is maintained if fertilisation occurs	The lining of the uterus is maintained just in case the egg becomes fertilised.
How does FSH, oestrogen, LH and progesterone control the menstrual cycle?	1) FSH 1) Causes a follicle to mature in one of the ovaries. 2) Stimulates oestrogen production. 2) Oestrogen 1) Causes the lining of the uterus to thicken and grow. 2) A high level stimulates an LH surge. 3) LH 1) The LH surge stimulates ovulation at day 14 - the follicle ruptures and the egg is released. 2) Stimulates the remains of the follicle to develop into a structure called a corpus luteum - which secretes progesterone. 4) Progesterone 1) Maintains the lining of the uterus. 2) Inhibits the production of FSH and LH. 3) When the level of progesterone falls, and there's a low oestrogen level, the uterus lining breaks down. 4) A low progesterone level allows FSH to increase and then the whole cycle starts again.
How is the menstrual cycle controlled by a negative feedback system mechanism?	1) FSH stimulates the ovary to release oestrogen. 2) Oestrogen inhibits further release of FSH from the pituitary gland. After FSH has caused a follicle to mature, negative feedback keeps FSH level low. This makes sure that no more follicles mature.
Explain how the structure of an egg is adapted to its function?	1) The egg contains nutrients in the cytoplasm to feed the embryo. 2) Straight after fertilisation, the egg's membrane changes its structure to stop any more sperm getting in. 3) The egg contains a haploid nucleus. This is so when the egg is fertilised, the cell will have the right number of chromosomes.
Explain how the structure of a sperm cell is adapted to its function?	1) Sperm are small and have long tails so they can swim to the egg. 2) Sperm have lots of mitochondria in their middle section to provide energy from respiration needed to swim this distance. 3) Sperm also have an acrosome at the front of the head, where they store the enzymes they need to digest their way through the membrane of the egg cell. 4) Sperm contain a haploid nucleus - this means that they only have one copy of each chromosome.
What is the advantages and disadvantages of donation of eggs?	Advantages 1) It allows a women who can't produce eggs to have a baby. 2) Using donated eggs can prevent the risk of passing on a genetic disorder from the mother. Disadvantages 1) It can be emotionally difficult for the family knowing that the child has a different genetic mother.
What are the advantages and disadvantages of in vitro fetilisation (IVF treatment)?	Advantages 1) Fertility treatment can give an infertile couple a child. Disadvantages 1) Some women who have a strong reaction to the hormone, e.g. abdominal pain, vomiting, dehydration. 2) There have been some reports of an increased risk of cancer due to the hormonal treatment. 3) Multiple births can happen if more than one embryo grows into a baby
What are the advantages and disadvantages of the use of surrogate mothers?	Advantages 1) It allows a couple to have children if medical problems mean the mother can't become pregnant or it's risky for her to give birth. Disadvantages 1) The surrogate mother is legally the mother of the child until it is adopted by the intended couple. She has the right to keep the child, so she might decide that she doesn't want to give it away.
What are the advantages and disadvantages of the use of hormones?	Advantages 1) It helps a lot of women to get pregnant when previously they couldn't Disadvantages 1) It doesn't always work 2) Too many eggs could be stimulated, resulting in unexpected multiple pregnancies(twins, triplets, etc.).
What is the sex of a person controlled by?	One pair of chromosomes, XX in a female and XY in a male.
Describe Edward Jenner’s contribution to the development of vaccines?	1) Smallpox killed lots of people in the 1700, and left horrible scars on people that survived it. 2) Edward Jenner knew that people who had cowpox didn't catch smallpox. 3) In 1796 he took bits of scab from a girl with cowpox and put them into a cut on the arm of a boy. The boy was a bit unwel, but then recovered. Then Jenner exposed the boy to smallpox. The boy didn't catch smallpox. 4) The cowpox antigens triggered the boy's B-lymphocytes to produce antibodies. Smallpox has some of the same antigens as cowpox, when the boy was infected with smallpox his immune system quickly produced antibodies to stop him from getting the disease.
Explain the process of immunisation?	1) Immunisation involves injecting dead or inactive microorganisms into the body. These are antigenic, so even though they're harmless, your body makes antibodies to attack them. 2) The antigens also trigger memory lymphocytes to be made. 3) If live micro-organisms of the same type appear after that, they'd be killed immediately by the antibodies which you've already developed against them.
What are the advantages of Immunisation?	1) Big outbreaks of diseases, called epidemics, can be prevented if a large percentage of the population are immunised. Even the people who aren't immunised are unlikely to catch the disease because there are a few people able to pass it on. 2) Some diseases, e.g. smallpox, have been virtually wiped out by immunisation programme.
What are the disadvantages of immunisation?	1) Immunisation doesn't always work - sometimes it doesn't give you immunity. 2) You can sometimes have a bad reaction to a vaccine. But bad reactions are very rare.
Describe the role of memory lymphocytes?	1) Memory lymphocytes give immunity to later infection. 2) The secondary response often gets rid of the pathogen before you begin to show any symptoms.
Describe the production of monoclonal antibodies?	1) The use of B lymphocytes, produce desired antibodies but do not divide. 2) The production of hybridoma cells. 3) Hybridoma cells produce antibodies and they divide.
What are the use of monoclonal antibodies?	1) In pregnancy testing. 2) Locating the position of blood clots and cancer cells and in treatment of diseases including cancer. 3) Can target specific cells compared to drug and radiotherapy treatments.
Describe how the exponential growth of a population of bacteria can lead to rapid development of an infection?	j
What was Louis Pasteur’s contribution to the development of aseptic techniques?	He invented the process of pasteurisation- this involves heating something up to about 70 degrees, and then cooling it. This kills of most harmful germs.
Investigate the conditions affecting growth of micro-organisms (using resazurin dye)	g
How do plants defend themselves against attack from pests and pathogens?	By producing chemicals, which can be used to treat human diseases, disorders or relieve symptoms.
Demonstrate an understanding of the impact that attack by pests and pathogens on plants has on human food supply	g
Explain the importance of photoperiodicity in plants?	1) Seeds of some arctic only germinate if the days are very long. This makes sure they only germinate in the middle of summer, when temperatures are warm. 2) Some plant buds use the increasing day length to tell them that its far enough away from winter to start to grow. This makes sure they don't sprout only to be killed by frost. 3) Some plants only flower when the day is at least a certain length. Other plants only flower when the days are less than a certain length. This way they only flower when the right insects are about to pollinate the flowers.
What is circadian rhythms?	Biological processes that follow a 24 hour cycle.
Topic 2 Behaviour	Topic 2 Behaviour
What does sexual reproduction require?	It requires the finding and selection of a suitable mate, and can involve courtship behaviours to advertise themselves.
Describe how animals have different mating strategies?	1) Mate for life. 2) Several mates over a lifetime. 3) A mate for a breeding season. 4) Several mates over one breeding season.
What have birds and mammals, developed?	Special behaviours for rearing their young.
Why can parental care be a successful evolutionary strategy?	1) Increased chance of survival of offspring. 2) Increased chance of parental genes being passed on by the offspring.
Explain how, within the animal kingdom, parental care may involve risks to the parents?	1) Parental care greatly increases the proportion of the young that survive. 2) Looking after young is less risky for the mother than being pregnant, which puts strain on her body and makes it more difficult to escape predators. 3) The survival of an animal's genes into the next generation is important, rather than the survival of the animal itself.
Describe the different behaviours exhibited by animals?	1) innate behaviour. 2) Imprinting. 3) Habituation. 4) Classical conditioning. 5) Operant conditioning.
Explain how humans can make use of conditioning when training captive animals for specific purposes?	1) Training guide dogs to stop at a roadside and wait for a command. 2) Training police sniffer dogs to retrieve drugs. 3) Training police horses to only respond to commands from their riders.
Investigate animal behaviour using choice chambers	h
What do some animal behaviour require?	Communication.
Explain how animals use sound signals to communicate?	1) Whales and dolphins can communicate over long distances using low-frequency sound. 2) Birds' calls are used to declare their territory, attract a mate or warn others about predators.
Explain how animals use chemical signals to communicate?	1) Many animals use chemical scents to mark the boundaries of their territory. 2) Other chemicals can act as sexual attractants.
Explain how animals use visual signals to communicate?	1) Honey bees move in a certain way, called a waggle dance, when they return to the hive to tell others where they've found food. 2) Most mammals can communicate certain intentions, through their body posture and gestures. 3) Facial expressions is another signal.
Describe how plants can communicate using chemicals?	1) With animals (particularly insects). 2) With other plants.
What is the work of ethologists?	1) Tinbergen, innate behaviour in gulls. 2) Lorenz, imprinting in geese. 3) Fossey, social behaviour in gorillas. 4) Goodall, social behaviour in chimpanzees.
How have plants and animals co-evolved?	1) The flower structure and insect behaviour in pollination. 2) The plant defence and animal metabolism.
Describe the evidence for human evolution, based on fossils?	1) Ardi from 4.4 million years ago. 2) Lucy from 3.2 million years ago. 3) Leakey’s discovery of fossils from 1.6 million years ago.
Describe the evidence for human evolution, based on stone tools?	1) The development of stone tools over time. 2) How these can be dated from their environment.
Describe why mitochondrial DNA provides evidence for the African Eve theory for non-Africans?	1) Its inheritance down the female line. 2) Its high mutation rate.
Why is mitochondrial DNA more useful than nuclear DNA for tracking human migration and evolution?	1) Mitochondrial DNA is less likely to have degraded over time. 2) Mitochondrial DNA is more abundant.
What are the impacts of climate change on human behaviour?	1) The effect of the Ice Age. 2) Human migration.
Topic 3 Biotechnology	Topic 3 Biotechnology
What is biotechnology?	The alteration of natural biomolecules using science and engineering to provide goods and services.
What is a fermenter?	A vessel used to cultivate microorganisms for the production of biomolecules on a large scale.
Explain the need to supply suitable conditions in fermenters, and the effect they have on growth rates? aseptic precautions b nutrients c optimum temperature d pH e oxygenation f agitation	h
Investigate the effect of factors on the growth of yeast, including pH?	1) Boil water in a test tube to get rid of any dissolved oxygen. 2) When it's cooled, dissolve a small amount of sugar and yeast in the water. 3) Add a layer of paraffin to keep out oxygen. 4) Attach a bung with a tube leading to a second test tube of lime water. 5) The lime water in the second test tube lets you check that it's CO2 being given off. 6) Then you can count the bubbles produced in a certain time to measure the rate of CO2 production.
Explain the advantages of using micro organisms for food production?	1) Bacteria and fungi can grow very quickly. 2) They're easy to look after. 3) Food can be produced whether the climate is hot or cold. 4) Microorganisms can use waste products from agriculture and industry as food for their life processes
Describe how mycoprotein is manufactured?	By the role ofthe fungus Fusarium.
Explain the advantages of using mycoprotein as a food source?	1) Used to make meat substitutes for vegetarian meals. 2) Mycoprotein contains more protein and fibre, and much less fat.
how are bacteria used in the production of yogurt from milk?	By the conversion of lactose to lactic acid.
Investigate the effect of different factors on yogurt making?	1) Add 25 Cm3 of milk to 5 sterile boiling tubes. Pasteurise and then cool the milk. 2) Add 1 Cm3 of yogurt starter culture to each boiling tube and stir gently. 3) Incubate the tubes for 5 hours at 5 different temperatures- 20, 30, 40, 50 and 60 degrees. 4) Measure the pH of the tubes after 5 hours.
Describe the use of enzyme technology?	1) Chymosin, produced by genetically modified micro-organisms, used in the manufacture of vegetarian cheese. 2) Invertase (sucrase) produced by Saccharomyces cerevisiae (yeast), used in the manufacture of sweets. 3) Enzymes used in washing powders.
Investigate the use of immobilised lactase to produce lactose free milk?	Immobilising the lactase: 1) Mix sodium alignants and lactase together in a syringe. 2) Add the mixture one drop at a time to a beaker of calcium chloride. 3) You should find that beads from. Leave them to harden for a few minutes, then use a tea strainer to separate them from the calcium chloride solution. Setting up a column of immobilised lactase: 1) Put some nylon gauze in a syringeg and attach a tap to the end. 2) Add the beads that you've made to the syringe. Making the lactose-free milk: 1) Use a glucoise test strip to see if there's any glucose present in a beaker of milk. 2) Slowly add the milk to the syringe. Collect the treated milk in a small beaker. 3) Test the glucose content of the treated milk and compare it to the untreated milk.
Investigate the use of enzymes in food production?	g
Explain recombinant DNA technology using insulin?	1) A plasmid is removed from a bacterium. 2) The insulin gene is cut out of a human chromosome using a restriction enzyme. Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points. The cut leaves one of the DNA strands with unpaired bases, this is called a sticky end. 3) The plasmid is cut open using the same restriction enzyme, leaving the same sticky ends. 4) Th plasmid and the human insulin gene are mixed together. 5) Ligase is added. This joins the sticky ends together to produce recombinant DNA. 6) The recombinant DNA is inserted into a bacterium. 7) The modified bacterium is grown in a fermenter.
What is the impact of human population growth on global food security?	As the world's population continues to grow we need to grow more food, so that each person still has the same amount of food to eat.
Explain how Agrobacterium tumefaciens is used as a vector in creating transgenic plants?	1) You get a plant that already has resistance to the herbicide, and you work out which gene is responsible. 2) You cut this gene for herbicide resistance from one of the plant's cells. 3) The bacteria contains a circular loop of DNA, you remove this from a bacterium, cut it open, and insert the herbicide resistance gene. 4) The next step is to allow the genetically modified bacteria to infect cells of target plant. 5) The bacteria will insert their genes into the plant's DNA. 6) These cells are then grown on a medium containing the herbicide. Those that grow must contain the herbicide resistant gene.
The advantages and disadvantages of introducing genes for insect resistance from Bacillus thuringiensis into crop plants?	h
What are the costs and benefits of genetic modification of crop plants in the developing countries?	1) Crops can be genetically engineered to be resistant to pests, improving crop yield. 2) They can be genetically engineered to grow better in drought conditions. 3) Can be engineered to combat certain deficient diseases.
What are the costs and benefits of genetic modification of crop plants in developed countries?	1) Snapdragon flowers contain a type of flavonoid. Flavonoids are molecules found in many plants that have antioxidants affects, which are thought to protect against cancers and heart disease. 2) Scientist have genetically engineered purple tomatoes so that they contain the flavonoid gene from the snapdragon. 3) Purple tomatoes have been developed as an easy way to get antioxidants to people in developed countries, who tend not to eat enough fruit and vegetables.
Explain the increased food production for humans?	1) Selective breeding is when humans select the best plants according to what we want from them. 2) Genetically modifying plants- Increasing food production is to use GM plants. 3) Reducing pest numbers.
What are the advantages of replacing fossil fuels with biofuels?	1) They're sustainable. (They're a renewable energy source). 2) The plants grown to make biofuels photosynthesise, removing CO2 from the atmosphere. 3) Biofuels are clean fuels. (Burning biofuels produces less particulates). 4) It doesn't produce significant amounts of sulfur dioxide.
What are the disadvantages of replacing fossil fuels with biofuels?	1) Growing the crops takes up large amounts of land. (Less land available for food). 2) Power-stations and vehicles need to be adapted to run on biofuels. ( This takes time and costs money).

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