Biology Unit 1a

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lauramarypowell
Created by lauramarypowell almost 6 years ago
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AQA Biology Unit 1a from the CGP revision guide.

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Question Answer
How does a balanced diet work to keep you healthy? 1) For good health, your diet must provide the energy you need (but not more). 2) But that's not all. Because the different food groups have different uses in the body, you need to have the right balance of foods as well. So you need: - enough carbohydrates to release energy, - enough fats to keep warm and release energy, - enough protein for growth, cell repair and cell replacement, - enough fibre to keep everything moving smoothly through your digestive system, - and tiny amounts of various vitamins and mineral ions to keep your skin, bones, blood and everything else generally healthy.
What is metabolic rate and what is the metabolism? 1) You need energy to fuel the chemical reactions in the body that keep you alive. These reactions are called your metabolism, and the speed at which they occur is your metabolic rate.
How does people's energy needs vary? 1) There are slight variations in the resting metabolic rate of different people. For example, muscle needs more energy that fatty tissues, which means people with a higher proportion of muscle to fat in their bodies will have a higher metabolic rate. 2) However, physically bigger people are likely to have a higher metabolic rate than smaller people - the bigger you are, the more energy your body needs to be supplied with (because you have more cells). 3) Men tend to have a slightly higher rate than women - they're slightly bigger and have a larger proportion of muscle. Other genetic factors may also have some effect. 4) And regular exercise can boost your resting metabolic rate because it builds muscle.
How does the amount of exercise/activity you do affect the amount of energy you need? 1) When you exercise, you obviously need more energy - so your metabolic rate goes up during exercise and stays high for some time after you finish (particularly if the exercise is strenuous). 2) So people who have more active jobs need more energy on a daily basis - builders require more energy per day than office workers, for instance. 3) This means your activity level affects the amount of energy your diet should contain. If you do little exercise, you're going to need less energy, so less fat and carbohydrates in your diet, than if you're constantly on the go.
How many kilojoules are burned per minute when you sleep, watch TV, Cycle at 5mph, jog at 5mph, climb stairs, swim, row and walk slowly? 1) Sleeping = 4.5kJ/min. 2) Watching TV = 7kJ/min. 3) Cycling (5mph) = 21kJ/min. 4) Jogging (5mph) = 40 kJ/min. 5) Climbing stairs = 77kJ/min. 6) Swimming = 35kJ/min. 7) Rowing = 58kJ/min. 8) Slow walking = 14kJ/min.
How is malnourishment different from starvation? 1) People whose diet is badly out of balance are said to be malnourished. 2) Malnourishment is different from starvation which is not getting enough food of any sort. 3) Malnourished people can be fat or thin, or unhealthy in other ways.
How can eating too much lead to obesity? 1) Excess carbohydrate or fat in the diet can lead to obesity. 2) Obesity is a common disorder in developed countries - it's defined as being 20% or more over maximum recommended body mass. 3) Hormonal problems can lead to obesity, though the usual case is a bad diet, overeating and a lack of exercise.
How can obesity lead to other health problems? 1) Health problems that can arise as a result of obesity include: arthritis (inflammation of the joints), type 2 diabetes (inability to control blood sugar level), high blood pressure and heart disease. It's also a risk factor for some kinds of cancer.
How can over eating cause other health problems? 1) Too much saturated fat in your diet can increase your blood cholesterol level. 2) Eating too much salt can cause high blood pressure and heart problems.
How can eating too little cause problems? 1) Some people suffer from lack of food, particularly in developing countries. 2) The effects of malnutrition vary depending on what food are missing from the diet. But problems commonly include slow growth (in children), fatigue, poor resistance to infection and irregular periods in women. 3) Deficiency diseases are caused by a lack of vitamins or minerals, for example a lack of vitamin C can cause scurvy, a deficiency disease that causes problems with the skin, joints and gums.
How can your health be affected by not getting enough exercise? 1) Exercise is important as well as diet - people who regularly exercise are usually healthier than those who don't. 2) Exercise increases the amount of energy used by the body and decreases the amount stored as fat. It also builds muscle so it helps boost your metabolic rate. So people who exercise are less likely to suffer from health problems such as obesity. 3) However, sometimes people can be fit but not healthy - e.g. you can be physically fit and slim but malnourished at the same time because your diet isn't balanced.
How can inherited factors affect your health? 1) It's not just about what you eat and how much exercise you do - your health can depend on inherited factors too. 2) Some people may inherit factors that affect their metabolic rate, e.g. some inherited factors cause an underactive thyroid gland, which can lower the metabolic rate and cause obesity. 3) Other people may inherit factors that affect their blood cholesterol level. Cholesterol is a fatty substance that's essential for good health - it's found in every cell in the body. Some inherited factors increase blood cholesterol level, which increases the risk of heart disease.
There are loads of slimming products (e.g. diet pills, slimming milkshakes) and slimming programmes (e.g. the Atkins Diet) around - and they all claim they'll help you lose weight. What should you look for to decide whether or not the claims are true or false? 1) It's a good idea to look out for these things: a) Is the report a scientific study, published in a reputable journal? b) Was it written by a qualified person (not connected with the people selling it)? c) Was the sample of people asked/tested large enough to give reliable results? d) Have there been other studies which found similar results? E.g. a common way to promote a new diet is to say, "Celebrity A has lost x pounds using it". But effectiveness in one person doesn't mean much. Only a large survey can tell if a diet is more or less effective than just eating less and exercising more - and these aren't done often.
There are loads of slimming products (e.g. diet pills, slimming milkshakes) and slimming programmes (e.g. the Atkins Diet) around - and they all claim they'll help you lose weight. What really works? 1) Really, all you need to do to lose weight is to take in less energy than you use. So diets and slimming products will only work if you: - eat less fat or carbohydrates (so that you take in less energy), or do more exercise (so that you use more energy). 2) Some claims may be true but a little misleading. E.g. low-fat bars might be low in fat, but eating them without changing the rest of your diet doesn't necessarily mean you'll lose weight - you could still be taking in too much energy.
What are the two main types pathogen? Bacteria are very small living cells: 1) Bacteria are very small cells (about 1/100th the size of your body cells), which can reproduce rapidly inside your body. 2) They make you fell ill by doing two things: a) damaging your cells, b) producing toxins (poisons). Viruses are not cells - they're much smaller: 1) Viruses are not cells. They're tiny, about 1/100th the size of a bacterium. 2) They replicate themselves by invading your cells and using the cells' machinery to produce many copies of themselves. The cell will usually then burst, releasing all the new viruses. 3) This cell damage is what makes you feel ill.
What is your body's defence system? 1) Your skin, plus hairs and mucus in your respiratory tract (breathing pipework), stop a lot of nasties getting inside your body. 2) And to try and prevent microorganisms getting into the body through cuts, small fragments of cells (called platelets) gel blood clot quickly to seal wounds. If the blood contains low numbers of platelets then it will clot more slowly. 3) But if something does make it through, your immune system kicks in. The most important part is the white blood cells. They travel around in your blood and crawl into every part of you, constantly patrolling for microbes. When they come across an invading microbe they have three lines of attack.
What are the three ways that white blood cells kill invading microbes? 1) Consuming them: white blood cells can engulf foreign cells and digest them. 2) Producing antibodies: a) Every invading cell has unique molecules (called antigens) on its surface. b) When your white blood cells come across a foreign antigen (i.e. one they don't recognise), they will start to produce proteins called antibodies to look onto and kill the invading cells. The antibodies produced are specific to that the of antigen - they won't lock on to any others. c) Antibodies are then produced rapidly and carried around the body to kill all similar bacteria or viruses. d) If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won't get ill. 3) Producing antitoxins: these counteract toxins produced by the invading bacteria.
How do vaccinations work? 1) When you're infected with a new microorganism, it takes your white blood cells a few days to learn how to deal with it. But by that time, you can be pretty ill. 2) Vaccinations involve injecting small amounts of dead or inactive microorganisms. These carry antigens which cause your body to produce antibodies to attack them - even though the microorganism is harmless (since it's dead or inactive). For example, the MMR vaccine contains weakened versions of the viruses that cause measles, mumps and rubella (German measles) all in one vaccine. 3) But if live microorganisms of the same type appear after that, the white blood cells can rapidly mass-produce antibodies to kill off the pathogen. 4) Some vaccinations "wear off" over time. So booster injections may need to be given to increase levels of antibodies again.
What are the Pros of vaccinations? 1) Pros: a) Vaccines have helped control lots of infectious diseases that were once common in the UK (e.g. polio, measles, whooping cough, rubella, mumps, tetanus…), smallpox no longer occurs at all, and polio infections have fallen by 99%. b) Big outbreaks of disease - called epidemics - can be prevented if a large percentage of the population is vaccinated. That way, even the people who aren't vaccinated are unlikely to catch the disease because there are fewer people able to pass it on. But if a significant number of people aren't vaccinated, the disease can spread quickly through them and lots of people will be ill at the same time.
What are the cons of vaccinations? 1) Cons: a) Vaccines don't always work - sometimes they don't give you immunity. b) You can sometimes have a bad reaction to a vaccine (e.g. swelling, or maybe something more serious like a fever or seizures). But bad reactions are very rare.
How do some drugs just relieve symptoms? 1) Painkillers (e.g. aspirin) are drugs that relieve pain. However they don't actually tackle the cause of the disease, they just help to reduce the symptoms. 2) Other drugs do a similar kind of thing- reduce the symptoms without tackling the underlying cause. For example, lots of "cold remedies" don't actually cure colds.
How do some dugs cure the problem? 1) Antibiotics (e.g. penicillin) work differently- they actually kill (or prevent growth of) the bacteria causing the problem without killing your own body cells. Different antibiotics kill different types of bacteria, so it's important to be treated with the right one. 2) But antibiotics don't destroy viruses (e.g.flu or cold viruses). Viruses reproduce using your own body cells, which makes it very difficult to develop drugs that destroy just the virus without killing the body's cells.
How can bacteria become resistant to antibiotics? 1) Bacteria can mutate - sometimes the mutations cause them to be resistant to (not killed by) an antibiotic. 2) If you have an infection, some of the bacteria might be resistant to antibiotics. 3) This means that when you treat the infection, only the non-resistant strains of bacteria will be killed. 4) The individual resistant bacteria will survive and reproduce, and the population of the resistant strain will increase. This is an example of natural selection. 5) This resistant strain could cause a serious infection that can't be treated by antibiotics. E.g. MRSA (methicillin-resistant staphylococcus aureus) causes serious wound infections and is resistant to the powerful antibiotic methicillin. 6) To slow down the rate of development of resistant strains, it's important for doctors to avoid over-prescribing antibiotics. So you won't get them for a sore throat, only for something more serious.
How can you investigate antibiotics by growing microorganisms in the lab (part 1)? 1) Microorganisms are grown (cultured) in a "culture medium". This is usually agar jelly containing the carbohydrates, minerals, proteins and vitamins they need to grow. 2) Hot agar jelly is poured into shallow round plastic dishes called petri dishes. 3) When the jelly's cooled and set, inoculating loops (wire loops) are used to transfer microorganisms to the culture medium. The microorganisms then multiply. 4) Paper discs are soaked in different antibiotics and placed on the jelly. Antibiotic-resitant bacteria will continue to grow around them but non-resistant strains will die.
How can you investigate antibiotics by growing micro-organisms in the lab (part 2)? 5) The petri dishes, culture medium and inoculating loops must be sterilised before use, e.g. the inoculating loops are passed through a flame. If equipment isn't sterilised, unwanted microorganisms in the culture medium will grow and affect the result. 6) The petri dish must also have a lid to stop any microorganisms in the air contaminating the culture. The lid should be taped on. 7) In the lab at school, cultures of microorganisms are kept at about 25 degrees celcius because harmful pathogens aren't likely to grow at this temperature. 8) In industrial conditions, cultures are incubated at higher temperatures so that they can grow a lot faster.
How did Semmelweis cut deaths? 1) While Ignez Semmelweis was working in Vienna General Hospital in the 1840s, he saw that women were dying in huge numbers after childbirth from a disease called puerperal fever. 2) He believed that doctors were spreading the disease on their unwashed hands. By telling doctors entering his ward to wash their hands in an antiseptic solution, he cut the death rate from 12% to 2%.
How did Semmelweis' method work and why was it not accepted? How has it changed the way people control disease today? 1) The antiseptic solution killed bacteria on doctors' hands, though Semmelweis didn't know this (the existence of bacteria and their part in causing disease wasn't discovered for another 20 years). So Semmelweis couldn't prove why his idea worked, and his methods were dropped when he left the hospital (allowing the death rates to rise once again). 2) Nowadays we know that basic hygiene is essential in controlling disease (though recent reports have found that a lack of it in some modern hospitals has helped the disease MRSA spread).
Why is antibiotic resistance becoming more common? 1) For the last few decades, we've been able to deal with bacterial infections pretty easily using antibiotics. The death rate from infectious bacterial diseases (e.g. pneumonia) has fallen dramatically. 2) But bacteria evolve antibiotic resistance, e.g.MRSA bacteria are already resistant to certain antibiotics. And overuse of antibiotics has made this problem worse-by increasing the likelihood of people being infected by antibiotic-resistant strains. 3)People who become infected with these bacteria can't easily get rid of them (because antibiotics don't work) and may pass on the infection to others. 4)So antibiotic resistance is a big problem and it's encouraged drug companies to work on developing new antibiotics that are effective against these strains. 5)Meanwhile, bacteria that are resistant to most known antibiotics ('superbugs') are becoming more common.
What new and scary dangers do we face with bacteria all the time? 1) As you know, bacteria can mutate to produce new strains. 2) A new strain could be antibiotic-resitant, so current treatments would no longer clear an infection. 3)Or a new strain could be one that we've not encountered before, so no-one would be immune to it. 4)This means a new strain of bacteria could spread rapidly in a population of people and could even cause an epidemic - a big outbreak of disease.
What new and scary danger do we face all the time with viruses? 1)Viruses also tend to mutate often.This makes it hard to develop vaccines against them because the changes to their DNA can lead to them having different antigens. 2) There'd be a real problem if a virus evolved so that it was both deadly and very infectious. (Flu viruses, for example, evolve quickly so this is quite possible). 3)If this happened, precautions could be taken to stop the virus spreading in the first place (though this is hard nowadays - millions of people travel by plane everyday). And vaccines and antiviral drugs could be developed (though these take time to mass produce). 4) But in the worst-case scenario, a flu pandemic could kill billions of people all over the world.
What is a pandemic? A pandemic is when a disease spreads all over the world.
What is a stimulus? A stimulus is a change in your environment which you may need to react to (e.g. a grizzly bear looking hungrily at you). You need to be constantly monitoring what's going on so you can respond if you need to.
What are receptor? Receptors are a group of cells which are sensitive to a stimulus. They change stimulus energy into electrical impulses.
How do sense organs detect stimuli? 1) You have 5 different sense organs - eyes, ears, nose, tongue and skin. 2) They all contain different receptors and these receptors change the stimulus energy into electric impulses. 3) A stimulus can be light, sound, touch, pressure, pain, chemical or a change in position or temperature.
What receptors do eyes, ears, nose, tongue and skin contain? 1) Eyes - light receptors are sensitive to light. These cells have a nucleus, cytoplasm and cell membrane (like most animal cells). 2) Ears - sound receptors are sensitive to sound. Also,"balance" receptors which are sensitive to changes in position. 3) Nose - smell receptors are sensitive to chemical stimuli. 4) Tongue - taste receptors are sensitive to bitter, salt, sweet and sour, plus the taste of savoury things like monosodium glutamate (MSG) - chemical stimuli. 5)Skin - sensitive to touch, pressure, pain and temperature change.
What are sensory neurones? Sensory Neurones - the nerve cells that carry signal as electrical impulses from the receptors in the sense organs to the central nervous system.
What are relay neurones? Relay Neurones - the nerve cells that carry signals from sensory neurones to motor neurones.
What are motor neurones? Motor Neurones - the nerve cells that carry signals from the central nervous system to the effector muscles or glands.
What are the effectors? Effectors - muscles and glands are known as effectors - they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones.
How does the central nervous system coordinate a response? 1) The Central Nervous System (CNS) is where all the information from the sense organs is sent, and where reflexes and actions are coordinated. The Central Nervous System consists of the brain and spinal cord only. 2) Neurons (nerve cells) transmit the information (as electrical impulses) very quickly to and from the CNS. 3) "Instructions" from the CNS are sent to the effectors (muscles and glands) which respond accordingly.
What are synapses? 1) The connection between two neurones is called a synapse. 2) The nerve signal is transferred by chemicals which diffuse across the gap. 3) These chemicals then set off a new electrical signal in the next neurone.
What are reflexes and how do help prevent injury? 1) Reflexes are automatic responses to certain stimuli - they can reduce the chances of being injured. 2) For example, if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye- this stops it getting damages. 3) Or if you get a shock, your body releases the hormone adrenaline automatically- it doesn't wait for you to decide that you're shocked.
What is a reflex arc? The passage of information in a reflex (from receptor to effector) is called a reflex arc.
What happens when a stimulus is detected use a bee stinging your finger as the example? 1)The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain. 2) When a stimulus (e.g. a painful bee sting) is detected by receptors, impulses are sent along the sensory neurone to the CNS. 3) When the impulses reach a synapse between the sensory neurone and a relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone. 4)When the impulses reach a synapse between the relay neurone and motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone. 5) The impulses then travel along the motor neurone to the effector (in this example it's a muscle). 6)The muscle then contracts and moves your hand away from the bee. 7) Because you don't have to think about the response (which takes time) it's quicker than normal responses.
Make a flow chart/ block diagram to show a reflex arc. 1) Stimulus. 2) Receptor. 3) Sensory Neurone. 4) Relay Neurone. 5) Motor Neurone. 6) Effector. 7) Response.
What are hormones? Hormones are chemical messengers which travel in the blood to activate target cells.
What are hormones and what do they do? 1) Hormones are chemicals released directly into the blood. They are carried in the blood plasma to other parts of the body, but only affect particular cells (target cells) in particular places. Hormones control things in organs and cells that need constant adjustment. 2) Hormones are produced in (and secreted by) various glands. They travel through your body at "the speed of blood". 3) Hormones tend to have relatively long lasting effects.
Where in the body are hormones produced and which hormones do they produce? 1)The pituitary gland - this produces many important hormones including FSH and LH, which are involved in the menstrual cycle. 2) Ovaries (women only) - produce oestrogen, which is involved in the menstrual cycle.
How can you tell if a response is nervous or hormonal? 1)Nerves: if the response is very quick, it's probably nervous. Some information needs to be passed to effectors really quickly (e.g. pain signals, or information from your eyes telling you about the lion heading your way), so it's no good using hormones to carry the message - they're too slow. 2)Hormones: but if a response lasts for a long time, it's probably hormonal. For example, when you get a shock, a hormone called adrenaline is released into the body (causing the fight-or-flight response, where your body is hyped up ready for action). You can tell it's a hormonal response (even though it kicks in pretty quickly) because you feel a bit wobbly for a while afterwards.
How are hormones and nerves slightly different in their jobs, even though they both do the same job? 1) Nerves: a) very fast action. b) act for a very short time. c) act on a very precise area. 2) Hormones: a) slower action. b) act for a long time. c) act in a more general way.
Describe each stage of the menstrual cycle. 1) Stage 1: day 1 is when the bleeding starts. The uterus lining breaks down for about four days. 2) Stage 2: the lining for the uterus build up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg. 3) Stage 3: an egg is released from the ovary at day 14. 4) Stage 4: the wall is then maintained for about 14 days, until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts again.
How do hormones control different stages of the menstrual cycle? There are three main hormones involved: 1) FSH (Follicle-Stimulating Hormone): a) Produced by the pituitary gland. b) Causes an egg to mature in one of the ovaries. c) Stimulates the ovaries to produce oestrogen. 2) Oestrogen: a) Produced in the ovaries. b) Causes pituitary gland to produce LH. c) Inhibits the further release of FSH. 3) LH (Luteinising Hormone): a) Produced by the the pituitary gland. 2) Stimulates the release of an egg at around the middle of the menstrual cycle.
What is progesterone? Progesterone is another hormone involved in the menstrual cycle - it's produced by the ovaries.
How can hormones be used to reduce fertility? 1) Oestrogen can be used to prevent the release of an egg - so it can be used as a method of contraception. 2) This may seem kind of strange (since naturally oestrogen helps stimulate the release of eggs). But id oestrogen is taken every day to keep the level of it permanently high, it inhibits the production of FSH, and after a while egg development and production stop and stay stopped. 3) Progesterone also reduces fertility e.g. by stimulating the production of thick cervical mucus which prevents any sperm getting through and reaching an egg. 4) The pill is an oral contraceptive. The first version was made in the 1950s and contained high levels of oestrogen and progesterone (known as the combined oral contraceptive pill.)
What are the pros and cons of the oestrogen pill? There were concerns about a link between oestrogen in the pill and side effects like blood clots. The pill now contains lower doses of oestrogen so has fewer side effects. 1) Pros: a) The pill's over 99% effective at preventing pregnancy. b) It reduces the risk of getting some types of cancer. 2)Cons: a) It isn't 100% effective - there's till a very slight chance of getting pregnant. b) It can cause side effects like headaches, nausea, irregular menstrual bleeding, and fluid retention. c) It doesn't protect against STDs. There's also a progesterone-only pill - it has fewer side effects than the pill (but it's not as effective).
How can hormones be used to increase fertility? 1) Some women have levels of FSH (Follicle-Stimulating Hormone) that are too low to cause their eggs to mature. This means that no eggs are released and the women can't get pregnant.
What are the pros and cons of using hormones to increase fertility? 1) Pros: - It helps a lot of women to get pregnant when previously they couldn't. 2) Cons: - a) It doesn't always work - some women may have to do it many times, which can be expensive. b) Too many eggs could be stimulated, resulting in unexpected multiple pregnancies.
How can IVF be used to help couples have children? 1) IVF ("in vitro fertilisation") involves collecting eggs from the woman's ovaries and fertilising them in a lab using the man's sperm. These are then grown into embryos. 2) Once the embryos are tiny balls of cells, one or two of them are transferred to the woman's uterus (womb) to improve the chance of pregnancy. 3) FSH and LH are given before egg collection to stimulate egg production (so more than one egg can be collected).
What are the pros and cons of IVF? 1) Pros: - Fertility treatment can give an infertile couple a child. 2) Cons: a) Some women have a strong reaction to the hormones - e.g. abdominal pain, vomiting and dehydration. b) There have been some reports of an increased risk of cancer due to the hormonal treatment (though others have reported no such risk - the position isn't really clear at the moment). c) Multiple births can happen if more than one embryo grows into a baby - these are risky for the mother and babies (there's a high risk of miscarriage, stillbirth ……).
What is auxin? 1) Auxin is a plant hormone that controls growth near the tip of shoots and roots. 2) It controls the growth of a plant in response to light (phototropism), gravity (gravitropism or geotropism) and moisture. 3) Auxin is produced in the tips and moves backwards to stimulate the cell elongation (enlargement) process which occurs in the cells just behind the tips. 4) If the tip of a shoot is removed, no auxin is available and the shoot may stop growing. 5) Extra auxin promotes growth in the shoot but inhibits growth in the root - producing the desired result.
What causes shoots to grow towards the light? 1) When a shoot tip is exposed to light, more auxin accumulates on the side that's in the shade than the side that's in the light. 2) This makes the cells grow (elongate) faster on the shaded side so the shoot bends towards the light.
What causes shoots to grow away from gravity? 1) When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. 2) This causes the lower side to grow faster, bending the shoot upwards.
What causes roots to grow towards gravity? 1) A root growing sideways will also have more auxin on its lower side. 2) But in a root the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards.
What causes roots to grow towards moisture? 1) An uneven amount of moisture either side of a root produces more auxin on the side with more moisture. 2) This inhibits growth on that side, causing the root to bend in that direction, towards the moisture.
How have plant hormones been used in agriculture? Plant hormones can be extracted and used by people, or artificial version can be made. 1) Most weeds in crop fields are broad-leaved, unlike grasses and cereals which have very narrow leaves. Selective weedkillers are made of plant growth hormones - they only affect the broad-leaved plants. They disrupt their normal growth patterns, which soon kills them, but leave the crops untouched. 2) Plant cutting won't always grow in soil. If you ass rooting powder, which contains the plant hormone auxin, they'll produce roots rapidly and start growing as new plants. This helps growers to produce lots of clones of a really good plant very quickly.
What things in your body need to be kept constant? Bodily levels that need to be controlled include: 1) Ion content. 2) Water content. 3) Sugar content. 4) Temperature.
How is ion content regulated by the kidneys? 1) Ions (e.g. sodium, NA+) are taken into the body in food, then absorbed into the blood. 2) If the food contains too much of any kind of ion then the excess ions need to be removed. E.g. a salty meal will contain far too much Na+. 3) Some ions are lost in sweat (which tastes salty). 4) The kidneys will remove the excess from the blood - this is then got rid of in urine.
How is water lost from the body? There's also a need for the body to constantly balance the water coming in against the water and going out. Water is taken into the body as food and drink and is lost from the body in these ways: 1) Through the skin as sweat. 2) Via the lungs in breath. 3) Via the kidneys as urine.
How does the balance between sweat and urine depend on what you're doing and the weather? 1) On a cold day, or when you're not exercising, you don't sweat much, so you'll produce more urine, which will be pale (since the waste carried in the urine is more dilute). 2) On a hot day, or when you're exercising, you sweat a lot, and so you will produce less urine, but this will be more concentrated (and hence a deeper colour). You will also lose more water through your breath when you exercise because you breathe faster.
How is body temperature controlled by the brain? 1) All enzymes work best at a certain temperature. The enzymes within the human body work best at about 37 degrees celcius - and so this is the temperature your body tries to maintain. 2) A part of the brain acts as your own personal thermostat. It's sensitive to the blood temperature in the brain, and it receives messages from the skin that provide information about skin temperature.
Why do blood sugar levels need to be controlled? 1) Eating food containing carbohydrates puts glucose into the blood from the gut. 2) The normal metabolism of cells removes glucose from the blood. But if you do a lot of vigorous exercise, then much more glucose is removed. 3) A hormone called insulin helps to maintain the right level of glucose in your blood, so your cells gat a constant supply of energy.
How do drugs change your body chemistry? Some of the chemical changes caused by drugs can lead to the body becoming addicted to the drug. If the drug isn't taken, an addict can suffer physical withdrawal symptoms - and these are sometimes very unpleasant. E.g. heroin, cocaine, nicotine and caffeine are all very addictive.
What are medicinal drugs? Medicinal drugs are medically useful, like antibiotics. For some of these drugs you don't need prescription (e.g. paracetamol), but for others you do (e.g.morphine) because they can be dangerous if misused.
What are recreational drugs? Recreational drugs are used for fun. These can be legal or illegal.
What are performance-enhancing drugs? Performance-enchancing drugs can improve a person's performance in sport.
What are the health impacts of performance-enhancing drugs? 1) Some athletes take performance-enhancing drugs to make them better at sport. 2) There are several different types, including anabolic steroids (that increase muscle size) and stimulants (that increase heart rate). 3) But these drugs can have negative health effects, e.g.steroids can cause high blood pressure. 4) Some of these drugs are banned by law, some are prescription only, but all are band by sporting bodies.
What are the ethical problems with taking performance-enchancing drugs? 1) Against drugs: a) It's unfair if people gain an advantage by taking drugs, not just through training. b) Athletes may not be fully informed of the serious health risks of the drugs they take. 2) For drugs: a) Athletes have the right to make their own decision about whether taking drugs is worth the risk or not. b) Drug-free sport isn't really fair anyway- different athletes have access to different training facilities, coaches, equipment, etc.
What are the claims about drugs called statins? Claims about the effects of drugs (both prescribed and non-prescribed) need to be looked at critically. E.g. Statins: 1) Statins are prescribed drugs used to lower the risk of heart and circulatory disease. 2) There's evidence that statins lower blood cholesterol and significantly lower the risk of heart disease in diabetic patients. 3) The original research was done by government scientists with no connection to the manufacturers. And the sample was big - 6000 patients. 4) It compared two groups of patients - those who had taken statins and those who hadn't. Other studies have since backed up these findings.
What are the claims about the drug cannabis? Claims about the effect of drugs (both prescribed and non-prescribed) need to be looked at critically. But research findings are not always so clear cut. E.g. Cannabis: 1) Cannabis is an illegal drug. Scientists have investigated whether the chemicals in cannabis smoke cause mental health problems. The results vary, and are sometime open to different interpretations. 2) Basically, until more definite scientific evidence is found, no one's sure.
What is the first main stage of drug testing? 1) Drugs are tested on human cells and tissues in the lab. 2) However, you can't use human cells and tissues to test drugs that affect whole or multiple body systems, e.g. testing a drug for blood pressure must be done on a whole animal because it has an intact circulatory system.
What is the second main stage of drug testing? 1) The next step is to test the drug on live animals. This is to see whether the drug works (produces the effect you're looking for), to fins out about its toxicity (how harmful it is) and the best dosage (the dose at which it's most effective). 2) The law in Britain states that any new drug must be tested on two different live mammals. Some people think it's cruel to test on animals, but others believe this is the safest way to make sure a drug isn't dangerous before it's given to humans.
What is the third of the three main stages of drug testing? 1) If the drug passes the tests on animals then it's tested on human volunteers in a clinical trial. 2) First, the drug is tested on healthy volunteers. This is to make sure that it doesn't have any harmful side effects when the body is working normally. At the start of the trial, a very low dose of the drug is given and this is gradually increased. 3) If the results of the tests on healthy volunteers are good, the drugs can be tested on prop;e suffering from the illness. The optimum dose is found - this is the dose of drug that is the most effective and has few side effects.
How is the drug tested to make sure it works in the third main stage of drug testing? 1) To test how well the drug works, patients are put into two groups. One is given the new drug, the other is given a placebo (a substance that's like the drug tested but doesn't do anything). This is so the doctor can see the actual difference the drug makes - it allows for the placebo effect (when the patient expects the treatment to work and so fells better, even though the treatment isn't doing anything). 2) Clinical trials are blind - the patient in the study doesn't know whether they're getting the drug or the placebo. In fact, they're often double-blind - neither the patient nor the doctor knows until all the results have been gathered. This is so the doctors monitoring the patients and analysing the results aren't subconsciously influenced by their knowledge.
How have thing in drug testing gone wrong in the past? An example of what can happen when drugs are not thoroughly tested is the case of thalidomide - a drug developed in the 1950s. 1) Thalidomide was intended as a sleeping pill, and was tested for that use. But later it was also found to be effective in relieving morning sickness in pregnant women. 2) Unfortunately, thalidomide hadn't been tested as a drug for morning sickness, and so it wasn't known that it could pass through the placenta and affect the fetus, causing abnormal limb development. In some cases, babies were born with no arms or legs at all. 3) About 10,000 babies were affected by thalidomide, and only half of them survived. 4) The drug was banned, and more rigorous testing procedures were introduced. 5) More recently thalidomide has been used in the treatment of leprosy and other diseases, e.g. some cancers.
Why are some recreational drugs illegal and some legal? 1) Illegal drugs are often divided into two main classes - soft and hard. Hard drugs are usually thought of as being seriously addictive and generally more harmful. 2) But the terms "soft" and "hard" are a bit vague - they're not scientific descriptions, and you can certainly have problems with soft drug use. E.g. heroin and ecstasy (hard drugs) and cannabis (soft drug) can all cause heart and circulatory system problems.
What are the various reasons for why people use recreational drugs? So if all these recreational drugs are so dangerous, why do so many people use them: 1) When asked why they use cannabis, most users quote either simple enjoyment, relaxation or stress relief. Some say they do it to get stoned or for inspiration. 2) But very often this turns out to be not the whole story. There may be other factors in the user's background or personal life which influence them in choosing to use drugs. It's a personal thing, and often pretty complicated.
Why do some studies link cannabis and hard drug use and others don't and what are the three main opinions? Almost all users of hard drugs have tried cannabis first (though most users of cannabis do not go on to use hard drugs). The link between cannabis and hard drugs isn't clear, but three opinions are common: 1) Cannabis is a "stepping stone" : - the effects of cannabis create a desire to try harder drugs. 2) Cannabis is a "gateway drug" : - Cannabis use brings people into contact with drug dealers. 3) It's all down to genetics: - Certain people are more likely to take drugs generally, so cannabis users will also try other drugs.
How do some legal drugs have more of an impact than illegal drugs? 1) Tobacco and alcohol have a bigger impact in the UK than illegal drugs, as so many people take them. 2) The National Health Service spends loads on treating people with lung disease caused by smoking. Add to this the cost to businesses of people missing days from work, and the figures get pretty scary. 3) The same goes for alcohol. The cost to the NHS are huge, but are pretty small compared to the costs to related crime (police time, damage to people/property) and the economy (lost working day etc.). 4) And in addition to the financial costs, alcohol and tobacco cause sorrow and anguish to people affected by them, either directly or indirectly.
What are the massive impacts on people and society of smoking? 1) Smoking causes disease of the heart, blood vessels and lungs. 2) Tobacco smoke also causes cancer. 3) Nicotine is the drug found in cigarettes - it's addictive so it's hard to stop smoking.
What are the massive impacts on people and society of alcohol? 1) Alcohol affects the nervous system and slows down the body's reactions. 2) Too much alcohol leads to impaired judgement, poor coordination and unconsciousness. 3) And excessive drinking can cause liver disease and brain damage. 4) Alcohol is also addictive.
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