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Flashcards in Biology 3 Deck (217):
1

What is a biological rhythm?

-The variations of the timing and duration of biological activity in living organisms occur for many essential biological processes. These occur in animals (eating, sleeping, mating, hibernating, migration, cellular regeneration, etc.), in plants (leaf movements, photosynthetic reactions, etc.), and in microbial organisms such as fungi and protozoa. They have also been found in bacteria, especially among the cyanobacteria (aka blue-green algae).

2

What is a circadian rhythm?

-Many biological rhythms happen over one day and these are known as circadian rhythms.
-Circadian rhythms are physical, mental and behavioural changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment.

3

How can a circadian rhythm be broken down further?

-Diurnal, which describes organisms active during daytime
-Nocturnal, which describes organisms active in the night
-Crepuscular, which describes animals primarily active during the dawn and dusk hours (e.g. white-tailed deer, some bats)

4

Where are circadian rhythms found?

-Circadian rhythms are found in most living things, including animals, plants and many tiny microbes.

5

What is the study of circadian rhythms called?

-The study of circadian rhythms is called chronobiology.

6

What are biological clocks?

-The biological clocks that control circadian rhythms are groupings of interacting molecules in cells throughout the body. The human brain contains the biological clock which is a timing mechanism, which regulates many things that happen in our bodies over a 24-hour period.
-Circadian rhythms are not the same thing as biological clocks but they are related. Our biological clocks drive our circadian rhythms.

7

What is the master clock?

-A master clock in the brain coordinates all the body clocks so that they are in sync.
-The master clock that controls circadian rhythms consists of a group of nerve cells in the brain called the sprachiasmatic nucleus, or SCN. The SCN contains about 20,000 nerve cells and is located in the hypothalamus, an area of the brain just above where the optic nerves from the eyes cross.

8

Do circadian rhythms have a genetic compound?

-Researchers have already identified genes that direct circadian rhythms in people, fruit flies, mice, fungi and several other model organisms used for studying genetics.

9

Does the body make and keep its own circadian rhythms?

-Circadian rhythms are produced by natural factors within the body, but they are also affected by signals from the environment.
-Light is the main cue influencing circadian rhythms, turning on or turning off genes that control an organism's internal clocks.

10

How do circadian rhythms affect body function and health?

-Circadian rhythms can influence sleep-wake cycles, hormone release, body temperature and other important bodily functions.
-They have been linked to various sleep disorders, such as insomnia. Abnormal circadian rhythms have also been associated with obesity, diabetes, depression, bipolar disorder and seasonal affective disorder.

11

What are hormones?

-Hormones are 'chemical messengers' that are made in the body. They are carried in the blood and affect different parts of the body.

12

How are circadian rhythms linked to sleep?

-Circadian rhythms are important in determining human sleep patterns. The body's master clock, or SCN, controls the production of melatonin, a hormone that makes you sleepy. Since it is located just above the optic nerves, which relay information from the eyes to the brain, the SCN receives information about income light. When there is less light - like at night, the SCN tells the brain to make more melatonin so you drowsy. Levels of melatonin drop in the morning, so we wake up. That's why most people feel sleepy at night and more alert during the daytime.

13

How are circadian rhythms related to jet lag?

-Jet lag occurs when travellers suffer from disrupted circadian rhythms. Although our biological clock has its own built-in rhythm, it need regular exposure to day and night to keep it in sync with a 24-hour cycle. If we travel east or west round the globe, then the day-night cycle comes earlier or later than the one the body is using. This can make a person feel less alert and less able to think clearly.Your body's clock will eventually reset itself, but this often taken a few days.

14

Do plants have circadian rhythms?

-Plants have circadian rhythms too. Flowers often open during the daytime and close at night. This makes sure they are ready for insects to visit them for pollination during the daytime, and the pollen is protected from wind, cold and damp at night. The flowers only produce nectar during the daytime, when insects are likely to visit the flowers.

15

What is photoperiodism?

-As well as their circadian rhythms, many plants have yearly rhythms. They use change in day length to help them grow or flower at the right time. Responses to changing day length are called photoperiodism.

16

What happens to many species of plants in winter?

-Many species of plants die in the tough conditions of winter, but their seeds survive. In spring, as the days get longer, the seeds sense this and germinate.

17

What happens to the plants that do grow through winter?

-Some plant species may grow all through the winter, but respond to the lengthening of days by growing faster. In the autumn, as days get shorter, other plant species stop growing and get ready to survive the hard times ahead.

18

How is flowering of plants controlled?

-In many plant species, flowing is also controlled by the length of dark or light during a 24-hour period.

19

How many hours of sunlight a day does there have to be for Iris. Poinsettia and Spinach to flower?

-Iris, flowers when there are more than 12 hours of light in a day
-Poinsettia, flowers when there are more that 14 hours of light in a day
-Spinach, flowers when there are more that 14 hours of light in a day

20

What are plant defences?

-Some plants produce poisonous chemicals to protect themselves against insect pests, larger herbivores and pathogens. The production of these chemicals follows a circadian rhythm.

21

How do young lupin leaves defend themselves?

-Young lupin leaves produce poisonous chemicals called alkaloids. The production of these chemicals follows a circadian rhythm - production starts in the early morning and stops at night.
-The chemicals makes the leaves poisonous to insect pests or larger herbivores that might want to eat them. Even though the plant may have to use a lot of energy and materials to make the chemicals, it is worth it.

22

Why do plants need to protect themselves from pathogens?

-Many plants also use chemicals to defend themselves against pathogens - organisms that cause disease.

23

What is an example of a plant that defends itself from pathogens?

-Potato plants are often attacked by a fungus-like organism called potato blight that destroys their leaves, killing the plant. A few varieties of potatoes respond to attack from potato blight by producing chemicals that kill it. Scientists are attempting to produce high-yielding varieties of potatoes that readily produce these chemicals and so are resistant to potato blight.

24

How does potato blight kill potato plants?

-Parts of the potato blight pathogen grow out through the stomata (breathing pore) of a potato leaf to shed spores. The swellings of the potato blight pathogen contain spores that will burst out and spread to other plants.

25

Why is it important for plants not to get killed by pathogens?

-People depend on plants for much of their food. If pathogens destroy or damage a crop then our food supply is at risk.
-For example, the famine caused by potato blight in Ireland in 1845 and 1846 is estimated to have killed over 1 million people.
-Some crops people rely on for food are; rice, wheat, maize, potatoes, barley and soybeans.

26

How can we make use of plant poisons?

-Although some chemicals in plants are poisonous to people, in small amount they may have useful effects. For example, we use many different plant poisons as medicinal drugs.

27

How is digoxin used?

-Digoxin is a chemical found in foxgloves. At high doses it can kill because it affects how the heart beats. However, at low doses, it was found to improve the heartbeat. So now it is commonly used to treat heart disorders.

28

How is quinine used?

-Quinine, produced by cinchona trees, has been used to treat the disease malaria.
-Aspirin, produced by willow trees, has been used to treat symptoms of disease, such as pain and fever.

29

What new possibilities of uses of plant poisons are being researched?

-New possibilities of uses are being researched all the time. For example, potato plants produce poisonous alkaloids in their leaves or in tubers that have been exposed to light. In one incident in 1978, 78 English schoolchildren because ill after eating school lunch containing potatoes that had been left in the light and had gone green. However, research suggests that these alkaloids could be developed as valuable treatments for cancer.

30

Who is Louis Pasteur and what did he contribute to preventing diseases?

-As well as treating diseases, we also try to prevent them. Louis Pasteur showed that microorganisms were responsible for some diseases and for foods going off. He proposed the idea of keeping microorganisms away from people and foods in order to stop some diseases and to preserve foods.
-Today, we refer to the methods used to keep things fee from living microorganisms as aseptic techniques. This includes the process of pasteurisation, in which foods (such as milk) are heated briefly before being stored in order to kill the bacteria in them.

31

What affects the rate that microorganisms grow?

-If bacteria have everything they need (such as food, oxygen and warmth) they can grow very quickly. When a bacterial cell is large enough, it reproduces by dividing in two. If all the bacteria cells in a culture keep dividing in two. If all the bacterial cells in a culture keep dividing in two, the number of cells increases exponentially. We say the population shows exponential growth.
-In the right conditions some kinds of bacteria can divide every 20 minutes.

32

What happens if milk with bacteria in it is drunk?

-If milk with high levels of bacteria is drunk it could cause infections in the gut, such as food poisoning, or other illnesses.

33

How can we measure how much bacteria there is in a sample?

-One way of measuring how many bacteria there are in a sample is to use resazurin dye. This shows how quickly the oxygen is used up. The more bacteria there are, the more quickly the oxygen levels fall.
-Resazurin dye is blue when there is plenty of oxygen. It turns pink and eventually colourless when oxygen levels fall.

34

What is Smallpox?

-Smallpox was a common and very serious disease in the 1700s, and even it did not kill a person it often left them severely disfigured.

35

Who is Edward Jenner and what did he discover?

-Edward Jenner noticed that milkmaids didn't seem to get smallpox. He thought that perhaps getting cowpox (a mild disease that people caught from cows) might stop you getting cowpox.
-In 1796, Jenner took pus from a cowpox blister and rubbed it into the skin of an 8-year-old boy called James Phipps. James got a mild fever but that was all. Some time later, Jenner did the same with pus from a smallpox blister. James did not get smallpox. The cowpox vaccine had made him immune to smallpox.

36

How do we use antibodies?

-All viruses and cells have chemicals on their outer surfaces, called antigens. Our bodies recognise 'foreign' antigens and so destroy foreign viruses and cells, often by using antibodies that stick to the pathogen antigens.

37

What is a vaccine?

-A vaccine contains harmless versions of a pathogen, or parts of it. White blood cells, called lymphocytes, respond to the vaccine. Some of these become memory lymphocytes. The way the body responds to infection is called the immune response. Making someone immune to a disease is called immunisation.

38

How does a vaccine make you immune?

1. A weakened pathogen is injected into the body. It has antigens on its surface.
2. A lymphocyte with an antibody that perfectly fits the antigen is activated.
3. This lymphocyte divides over and over again to produce clone of identical lymphocytes.
4. Some of the lymphocytes secrete large amounts of antibodies. The antibodies stick to the antigens and destroy the pathogen. Other lymphocytes remain in the blood as memory lymphocytes, ready to respond immediately if the same antigen ever turns up again.

39

How did children suffer before immunisation?

-All young children in the UK are offered immunisation against dangerous childhood diseases, such as measles and whooping cough. Before immunisation was introduced many children died or were harmed by these diseases. For example, about 1 in every 2000 children infected with measles suffered permanent brain damage or died.

40

What do people think of immunisation in children now?

-Today, very few children are affected by these diseases. However, some react to the vaccines. About 20% of children may get a mild fever rash from the measles vaccine, and about 1 in a million has a dangerous reaction. Because people have forgotten what the diseases are like, they are more concerned about the risk of immunisation. Media scares about the risks of immunisation can persuade parent to not have their children immunised.

41

What is the MMR vaccine?

-The MMR vaccine protects children against measles, mumps and rubella.

42

What are the advantages of immunisation?

-A child can become immune to a disease without having to suffer from it.
-The chances of any long-lasting harm are much, much less than if a person actually has a disease such as measles, mumps, rubella or diphtheria.
-If enough children are vaccinated against a disease, then it becomes so rare that even unvaccinated individuals are unlikely to get it.

43

What are the disadvantages of immunisation?

-It's quite common for a person to get swelling or redness around the site of the vaccination.
-Some children may get a mild form of the disease they are being vaccinated against.
-Very, very rarely a child suffers an allergic reaction - as some people do to bee stings.

44

What is an infection?

-The entry of a pathogen into the body is known as infection.

45

What is a primary response?

-The first time a pathogen infects a person, only one or two lymphocytes recognise the antigens on it. It takes a while for them to multiply and secrete enough antibodies to destroy the pathogens. This is the primary response.

46

What is the secondary response?

-After an infection or immunisation, memory lymphocytes remain in the blood, sometimes for the rest of a person's life. They can immediately make the right antibodies if the same pathogen re-enters the body. This is the secondary response. It's more than likely that the lymphocytes will be able to destroy the pathogens before they have a chance to increase in numbers enough to make the person ill.

47

What are monoclonal antibodies?

-Since antibodies are very specific, scientists can use them to identify particular substances. To do this, scientists need large quantities of identical antibodies. These are monoclonal antibodies.

48

What is a B lymphocyte?

-A lymphocyte can divide over and over again to make identical copies (clones) of itself. However, once it has started to make antibodies it becomes a B lymphocyte, and can't divide anymore.

49

How do people in laboratories get around the problem of B lymphocytes not being able to divide anymore?

-A B lymphocyte is fused with a cancer cell that can divide hundreds of times. The resulting cell is called a hybridoma.

50

How are monoclonal antibodies?

1. A particular antigen (e.g. HGH) is injected into a mouse. The mouse produces lymphocytes that makes antibodies against the antigen. Myeloma (cancer) cells grow in culture medium.
2. A B lymphocyte is taken from the mouse and a cancer cell is taken from the culture medium. They are fused together to form a hybridoma cell.
3. The hybridoma cell can both divide and make antibodies against the antigen. These are monoclonal antibodies.

51

What are the uses of monoclonal antibodies?

-Pregnancy testing
-Diagnosis (bloods clots and cancer cells)
-Treatment of cancer

52

How are monoclonal antibodies used for pregnancy testing?

-Pregnancy testing kits use monoclonal antibodies to detect a hormone called hCG, found in the urine of pregnant women. A dipstick is dipped into some urine and, if there is any hCG in it, it binds to the monoclonal antibodies on the stick and causes a colour change.

53

How are monoclonal antibodies used for diagnosis (blood clots and cancer cells)?

-Monoclonal antibodies can be made slightly radioactive. Some monoclonal antibodies bind to substances found in the membranes of platelets or cancer cells. (Platelets are fragments of cells that help to form blood clots - in the wrong places, such as the brain or heart, these can kill.) The antibodies are injected into the patient's body, where they stick to the platelets or cancer cells. Radiologists can then detect where the antibodies are (which then tells them where any blood clots or cancer cells are) so they can be treated.

54

How are monoclonal antibodies used for treatment of cancer?

-Many people with cancer are given drugs (chemotherapy) or ionising radiation (radiotherapy) to kill cancer cells. With both of those types of treatment, it's difficult to make sure that only the cancerous cells are targeted.
-However, drugs can be attached to monoclonal antibodies, to deliver the drug only to the cells that need to be destroyed. This means less of the drug is needed, as none of it is wasted in parts of the body that are healthy. There is also much less risk of harming healthy cells.

55

What do metabolic reactions produce?

-The chemical reactions happening inside the body (metabolic reactions) produce waste products.
-For example, respiring cells produce carbon dioxide and liver cells produce urea from excess amino acids. Both of these waste products are put into the blood. Carbon dioxide is removed in the lungs and the kidneys filter out the urea.

56

How is urea removed from the body?

-Blood is brought to the kidneys in the renal arteries. Urea and other substances are filtered out of the blood and form urine. The cleaned blood flows out of the kidneys in the renal veins and the urine is excreted.

57

What makes up the urinary system?

-Kidneys, ureters, bladder and urethra.

58

What happens in the urinary system?

-The renal arteries carry blood from the body to the kidneys.
-The kidneys remove substances from the blood and make urine.
-The ureters carry urine from the kidneys to the bladder and the renal veins carry cleaned blood back to the body.
-The bladder stores urine.
-A muscle keeps the exit from the bladder closed until we decide to urinate.
-Urine flows through the urethra to the outside of the body.

59

What is kidney failure?

-Sometimes (e.g. due to an infection) both of a person's kidneys stop working properly. The person's life will be in danger, because poisonous urea starts to build up in the blood.

60

What are the two ways to treat kidney failure?

-Kidney transplants
-Kidney dialysis

61

What is a kidney transplant?

-If the kidneys have failed and cannot be repaired, the best treatment is a kidney transplant. This is where a kidney is removed from a donor and transplanted into someone else.

62

What are the problems with kidney transplants?

-You can't put just any kidney into a person's body. Kidney cells, like all cells, have antigens on them, and the cells in the immune system quickly recognise any strange antigens. They attack the foreign cells and kill them - we say the organ has been rejected.
-The antigens on the donated organ must therefore be very similar to those on the patient's cells. This means it can take a long time to find a suitable kidney for a patient. Sometimes, a family member may be able to donate a kidney (you can manage perfectly well with just one kidney). Close relatives are more likely to have similar antigens then strangers.
-Even with a good match, the patient will need life-long medication to prevent the kidney being rejected. This medication affects the body's response to infection, so the patient may catch diseases like colds more easily.

63

What is kidney dialysis?

-While a person is waiting for a kidney transplant, they will be treated with a kidney dialysis machine that remove waste products from their blood. Dialysis machines are expensive, and the patient will have to be connected to one for several hours, several times a week.

64

What does each kidney contain?

-Each kidney contains thousands of tiny, microscopic tubes called nephrons.

65

How does a nephron work?

-Blood flows along the renal artery and into a network of capillaries called a glomerulus, which runs inside the Bowman's capsule of the nephron.
-The capsule has tiny holes that that let really small molecules, such as water, urea and glucose, through into the nephron. Big molecules like proteins, and blood cells stay in the blood. This process is called filtration.
-The fluid flows along inside the nephron. Some substances are absorbed back through the walls of the nephron into the blood. Only useful substances that the body needs return to the blood, such as glucose, so this is called selective reabsorption. Water is also reabsorbed depending on how much the body need. This is called osmoregulation.
-At the end of the nephron the remaining fluid flows into the ureter. The fluid contains excess water that the body doesn't need, plus urea and other substances It is now called urine.

66

Other than remove urea, what else do the kidneys do?

-As well as getting rid of urea, the kidneys help to control the water content of the blood.

67

How do the kidneys control water content of the blood?

-The kidneys are controlled by the pituitary gland, which secretes several hormones. One of these, ADH (antidiuretic hormone), helps to control the water content of the blood.

68

How do the kidneys control water content if there is not enough water in the blood?

-The brain senses there is not enough water in the blood.
-The pituitary gland secretes more ADH.
-The ADH causes the kidneys to reabsorb more water.
-A small volume of concentrated urine is produced.

69

How do the kidneys control water content if there is too much water in the blood?

-The brain senses there is too much water in the blood.
-The pituitary gland secretes less ADH.
-The ADH causes the kidneys to reabsorb less water.
-A large volume of dilute urine is produced.

70

What is the kidneys' control of water content an example of?

-The control of water content is a good example of a mechanism called negative feedback. This is where a change in a factor leads to the opposite change happening to keeps things fairly constant, even if their tendency is to keep changing.

71

How does negative feedback work?

-Factor increases --> sensor detects the increase --> sensor causes an effector to do something to reduce the factor.
-Factor decreases --> sensor detects the decrease --> sensor causes an effector to do something to increase the factor.

72

What is the menstrual cycle?

-Between the ages of about 12 and 50 (the ages vary in different women) most women have a menstrual cycle that last for roughly 4 weeks.

73

What happens during the menstrual cycle?

-During the cycle, an egg cell is released from an ovary. This is called ovulation. The lining of the uterus thickens to receive the egg cell. After a few weeks the uterus lining breaks down and is lost with the egg in menstruation.

74

What happens in week one of the menstrual cycle?

-Menstruation takes place for between 4 and 7 days in the first week of the cycle.

75

What happens in week two of the menstrual cycle?

-During the second week, the lining of the uterus is gradually built up.
-Ovulation usually takes place around day 14.

76

What happens in week three and four of the menstrual cycle?

-Days 14-16 are the days when fertilisation is most likely to take place.
-The lining of the uterus continues to build up throughout week three and four.

77

What are oestrogen and progesterone?

-Oestrogen and progesterone are hormones that are secreted by the ovaries and control the menstrual cycle.

78

When does the menstrual cycle stop?

-The menstrual cycle stops if an egg cell is fertilised. When that happens, the thickened lining of the uterus stays in place, so the embryo can embed into it and begin to develop. Missing a normal menstrual period is usually the first clue that a women may be pregnant.

79

Other than oestrogen and progesterone, what other hormones control the menstrual cycle?

-Oestrogen and progesterone are not the only hormones that control the menstrual cycle.
-FSH (follicle-stimulating hormone) and LH (luteinising hormone) are hormones secreted by the pituitary gland that also play a part.

80

What are the levels of FSH and LH controlled by?

-The release of FSH and LH is controlled by the levels of oestrogen (which increases as the egg follicle matures) and progesterone (which is secreted by the follicle after it releases the egg and becomes the corpus luteum).

81

What happens to the corpus luteum if fertilisation occurs?

-If fertilisation occurs, the corpus luteum continues to secrete progesterone so that levels of the hormone remain high.

82

how do the hormones interact throughout the menstrual cycle?

-FSH starts the cycle off. It tells the ovary to make an egg.
-The follicle and egg starts to develop. This gives a signal to the ovary telling it to make oestrogen.
-Oestrogen causes the lining of the uterus to thicken and prevents more eggs from developing.
-Oestrogen passes to the pituitary in the blood and it stops the pituitary from making any more FSH. Instead it gives the signal for another pituitary hormone to be produced, LH.
-LH makes the ovary release an egg (ovulation). It also turns the empty follicle into a yellow body.
-The yellow body starts to make progesterone Progesterone makes the uterus lining thicken even more.
-Both oestrogen and progesterone make sure the lining of the uterus is ready for implantation of the fertilised egg.
-If pregnancy occurs these two hormones continue to be produced. They make sure that the lining of the uterus stays thick and they stop the women's menstrual cycle.

83

What are gametes?

-Egg cells and sperm cells are gametes (sex cells). They are highly specialised for their very important functions.

84

What are the features of an egg cell?

-Haploid nucleus contains one set of genetic material (23 chromosomes).
-Cytoplasm containing nutrients, including lipid droplets.

85

What are the features of a sperm cell?

-Haploid nucleus contains one set of genetic material (23 chromosomes).
-Acrosome containing enzymes to digest a way into the egg.
-Middle section containing mitochondria ton release energy by respiration.
-Tail for swimming.

86

What happens during fertilisation?

-During fertilisation, a sperm cell burrows into an egg cell. The sperm cell nucleus enters the egg cell and at this point the membrane around the egg quickly changes so that no more sperm cell nucleus can enter. The two nuclei fuse together and the resulting cell is called a zygote.
-The zygote is diploid (has two sets of chromosomes) and divides repeatedly to form an embryo, which embeds into the uterus lining to grow and develop.

87

What does it mean that a couple is infertile?

-Many couples who would love to have children are not able to. There are many reasons why a couple may be infertile, and it is important to find out what the problem is before a solution can be tried.

88

What are the different infertility treatments?

-IVF
-Egg donation
-Surrogate mothers
-Hormones

89

What is IVF as an infertility treatment?

-IVF stands for in vitro fertilisation. Some of the woman's egg cells are taken from her ovaries and fertilised in a dish with her partner's sperm cells. One or two embryos are then put into her uterus to develop.

90

What is a problem with IVF?

-IVF babies are born early more often than naturally conceived babies, which may cause problems at birth or in development later.

91

What is egg donation as an infertility treatment?

-If the woman's ovaries aren't producing eggs, then eggs can be taken from another woman who agrees to donate some. She will be given hormones to make her ovaries to release the eggs. Then IVF is carried out using sperm from the first woman's partner.

92

What is a problem with egg donation?

-A few women who donate eggs react badly to the high levels of hormones used to collect them.

93

What is a surrogate mother as an infertility treatment?

-If the woman isn't able to grow an embryo in her uterus, then her partner's sperm may be used to fertilise one of her eggs, or another woman's eggs. A fertilised egg is then placed in another woman's uterus to develop. She is the surrogate mother, and she gives birth to the baby.

94

What is a problem with surrogate mothers?

-Handing the baby over to the couple may cause problems if the surrogate mother has developed a strong bond with the baby and does not want to give it up.

95

What is hormones as an infertility treatment?

-Giving a woman extra hormones may help her ovaries to produce more eggs, but this increases the risk of her having more than one baby at the same time.

96

What is a problem with extra hormones as an infertility treatment?

-The babies tend to be born earlier than usual, increasing the risk of problems at birth or later. Some women react badly to this hormone treatment.

97

What are sex chromosomes?

-Humans have 46 chromosomes in each of their body cells. Two of these determine what gender a person is, so they are called sex chromosomes?

98

What sex chromosomes do women have?

-Women have two X chromosomes, XX.

99

What sex chromosomes do men have?

-Men have one X and one Y chromosome, XY.

100

What is a phenotype?

-What an individual looks like.

101

What is a genotype?

-The genetic material of the individual.

102

Why is there an equal chance that a baby will be a boy or a girl?

-Possible female gametes = X X
-Possible male gametes = X Y
-XX XX
-XY XY

103

What does it mean that out chromosomes come in matching pairs?

-Most of out chromosomes come in matching pairs. The two chromosomes in a pair have the same genes in the same places. So we have two copies of each gene, which may be different alleles.

104

Is the X chromosome or the Y chromosome bigger?

-The X chromosome is much bigger than the Y chromosome. There are many more genes on the X chromosome than there are on the Y chromosome. This means that males will only have one copy of most of the genes on the X chromosome.

105

What is an example of a sex-linked genetic disease?

-One gene found only on the X chromosome codes for a substance that helps blood to clot properly. The normal allele, H, allows the blood to clot. The recessive allele, h, prevents normal clotting and causes a disease called haemophilia. Haemophilia is an example of a sex-linked genetic disease.

106

What are the genotypes and phenotypes for the haemophilia gene?

-XHXH = female, normal blood clotting
-XHXh = female, normal blood clotting (carrier of the h allele)
-XhXh = foetus does not usually develop
-XHY = male, normal blood clotting
-XhY = male, haemophilia

107

How is colour blindness an example of something that is sex-inherited?

-The gene for green-red colour blindness is also on the X chromosome. The normal allele of this gene gives normal colour vision, but there is a recessive allele that means a person cannot distinguish red from green.

108

How can we define behaviour?

-We can define the term behaviour as the ways in which an animal responds to external stimuli (things that are happening outside it).

109

Why is choosing a mate an important behaviour?

-For an animal that reproduces sexually, choosing a mate is a very important behaviour. A mate that is healthy and well adapted to its environment is of good reproductive quality. It is more likely to have healthy offspring than a mate that is struggling to survive.

110

How does courtship behaviour help choosing a mate?

-Elaborate courtship behaviour helps with choosing a mate. This often involves the mate displaying to females. He is advertising that he is a high-quality choice. This is why male birds are often brightly coloured. The female is more usually well camouflaged, so that she can care for her young without being spotted by a predator.

111

What are the different mating strategies?

-Social monogamy
-Monogamy
-Promiscuity
-Several mates over a life time

112

What is social monogamy?

-One mate for life
-For security
-E.g. swans

113

What is monogamy?

-Mate for breeding season
-Because of migration
-E.g. Birds

114

What is promiscuity?

-Several mates for breeding season
-E.g. hares

115

What is having several mates over a lifetime?

-Having several mates over a lifetime
-E.g. sloths

116

How do animals look after their young?

-Many animals look after their young until they have grown and developed enough to look after themselves.
-Female mammals feed their young on milk and teach them how to find food and avoid predators.
-Many birds keep their young in a nest, sitting on them to keep them warm and bringing them food, until the young are able to fly. This increases their chances that their offspring will survive, and that the parents' genes will carry on into future generations.

117

What is an evolutionary strategy?

-An evolutionary strategy is any process that affects how a species changes over time and spreads.

118

How does parental care act as an evolutionary strategy?

-Parental care helps ensure that plenty of offspring survive. The more offspring there are, the more likely that there will be offspring adapted to changes in conditions and so the species can evolve and spread. Parental care can therefore be a successful evolutionary strategy.

119

What is innate behaviour?

-'Innate' means 'inborn'. Innate behaviour is something that we do not learn. It is 'hardwired' into our brain.

120

What is an example of simple innate behaviour?

-The human baby's startle reflex

121

What is an example of complicated innate behaviour?

-A dragonfly nymph crawling out of the water, going through a set of complicated manoeuvres to shed its skin, and then flying off as though it has been flying all its life.

122

Why is innate behaviour important?

-Innate behaviour increases the chances of an animal surviving and is controlled by genes. Animals with useful innate behaviour patterns are more likely to survive, reproduce and pass on their genes than animals without this behaviour.

123

Who was Niko Tinbergen and what did he discover about herring gulls?

-Niko Tinbergen was on of the first people to make scientific studies of innate behaviour. He founded the science of ethology - the study of animal behaviour.
-One of his investigations in the 1940s involved in innate behaviour in birds called herring gulls. He noticed that the chicks pecked at their parents' beaks, to make the parent regurgitate food from its stomach for the chick.
-An adult's beak has a red spot on it. Tinbergen made cardboard models of gulls' heads, using different colours for the spot on the beak, and presented the cardboard models to young gull chicks to see if they pecked at the stops.
-Black was pecked at the most, then red, blue, white and yellow.

124

Who was Konrad Lorenz and what did he discover?

-In the 1930s, an ethologist Konrad Lorenz was studying the behaviour of young animals. People knew that goslings and ducklings learned a new behaviour just after they hatched. In the wild, the first things they would see would be their mother, and they immediately learned to stay close to her. This is useful behaviour as it ensures that the young birds are protected and can learn from their mother how to find food.
-Lorenz found that when the birds hatched in an incubator, they became attached to whatever they first saw and interacted with. This could be a wooden cube, or even Lorenz himself. He called this behaviour imprinting.

125

What is imprinting?

-Imprinting is a kind of simple learning, We can define learning as a change in behaviour as a result of experience, Imprinting only happens during a very short 'window' of time, very early in the animal's life. But it lasts well into adulthood.

126

How can choice chambers be used to investigate animal behaviour?

-A choice chamber is a piece of equipment with different sections or chambers in it. The chambers have different conditions (such as dry or damp) and the animal can choose where it wants to be. Different types of choice chambers can be used to investigate innate behaviour in animals such as woodlice and also conscious choices in animals such as rats.

127

What is habituation?

-Although innate behaviour helps animals to respond appropriately to a particular stimulus from birth, they also need to learn to adapt their behaviour to different circumstances.
-One simple kind of learning is 'switching off' from a repeated stimulus.

128

How is the sea hare an example of habituation?

-The sea hare, a marine slug, has a gill that sticks out from its back, If a sea hare is touched suddenly it withdraws the gill. This response helps to stop predators damaging its gill. However, if you keep on touching the sea hare but don't hurt it, it eventually stops withdrawing its gill.

129

What is classical conditioning?

-Classical conditioning starts with an innate reflex action but then the animal learns to respond to a new stimulus in the same way.

130

What is an example of classical conditional with dogs, as investigated by Ivan Pavlov?

-Dogs produce saliva when they smell food. This is an innate response. Ivan Pavlov investigated whether dogs could learn to respond to other stimuli in the same way.
-Pavlov rang a bell just before giving food to a dog. The dog pricked up its ears when it heard the bell, but it didn't salivate until it was given the food. After repeating this several times, the dog produced saliva when it heard the bell. It had learned to associate the sound of the bell with the food.

131

What is operant conditioning?

-Operant conditioning is a simple kind of learning and it occurs when an animal discovers that a particular kind of behaviour can make something good happen - or something bad not happen.
-For example, a rat might happen to press a bar when it is exploring and discovers that an unpleasant bright light switches off. After this happens a few times, it associates the behaviour with the reward. Eventually it will carry out the action on purpose.

132

How is operant conditioning used to train animals?

-Operant conditioning begins with a change behaviour, which produces a reward. The reward reinforces the behaviour. We use this to train animals.

133

How are sniffer dogs trained?

-When a sniffer dog is being trained, it is given an object with a smell to sniff. Then it is presented with several objects with various smells. When it indicates the one with the original smell the dog is rewarded. After many repeats the dog learns to search for that particular smell.

134

What ways do animals communicate?

-Visual signs
-Sound
-Chemical substances

135

How do animals use visual signals to communicate?

-A female glow-worm's light tells males where to find her. Courtship behaviour also uses visual signals. Mammals often use gestures, facial expressions and body language to communicate their mood.

136

How do animals use sound to communicate?

-Many birds keep other out of their territory by singing. Male grasshoppers rub their hind legs against their wing-cases to make a high-pitched sound that attracts females

137

How do animals use chemical substances to communicate?

-Many animals produce pheromones - hormone-like substances that diffuse into the air and influence the behaviour of others.

138

What is social behaviour?

-Communication is especially important when animals live and interact in close groups, such as wasps, meerkats, chimpanzees, gorillas and humans. Behaviour between members of the same species is called social behaviour.

139

Why is social behaviour good?

-Social behaviour can improve survival chances. Different individuals in the group can take on different tasks, such as watching for predators or searching for new food sources. And groups may also have a better chance of defending a territory if they communicate and work together.

140

What did Dian Fossey find by studying social behaviour in mountain gorillas in Rwanda?

-By imitating their behaviour towards each other, she was partly accepted into the group. She discovered that the groups had complex family relationships and that, contrary to what had previously been believed, they were not violent. She was able to work out the meanings of many of their calls, and was the first person to begin to understand how gorilla society worked.

141

What did Jane Goodall find by studying social behaviour in chimpanzees in Tanzania?

-Until Goodall's research, we knew very little about how chimps lived in the wild. Jane lived closely with chimpanzees and, like Dian Fossey, recorded their behaviour and the ways in which they interacted with one another. She was the first person to learn that chimpanzees make and use tools to help them to obtain food. She also discovered that they hunt together as a group.

142

Why is Fossey's and Goodall's research about social behaviour beneficial?

-Fossey's and Goodall's work helps us to understand the complex societies and uses of communication in gorillas and chimps. Their work have given us insights into our own behaviour.

143

Why do plants need to communicate with animals?

-Many plants rely on insects to transport pollen from one flower to another.

144

How do plants communicate with animals?

-Their flowers have evolved brightly coloured chemicals in the petals that attract insects to them. They also produce chemical scents that spread out in the air. Insects find the flower by moving in the direction where the concentration of the chemical is greatest.
-Some plants produce brightly coloured fruit. Animals, such as birds, recognise that this means the fruits are ready are ready for eating. Inside the fruits, the seeds are ready for dispersal. The seeds may be carried a long way from the parent plant in the animal's gut before they are released in the animal's waste and can start growing.
-Plants often produce chemicals that harm insects, to provide protection against being eaten. The Labrador tea plant of northern Europe produces chemicals in its leaves that are poisonous to insects. These chemicals diffuse out into the air, so the insects don't even land on the plant's leaves.

145

How do plants communicate with other plants?

-Some plants send signals to other plants. The leaves of some Acacia trees in Africa produce distasteful, poisonous chemicals to deter herbivores. As this takes a lot of energy, they only do it when they are attacked.
-When an insect attack occurs, the leaves also produce a gas called ethene. This diffuses through the air to nearby Acacia trees. These trees pick up the warning and start to make the distasteful chemicals even before the herbivores start to eat them.

146

What is co-evolution?

-Evolution is the change in a species over time. Co-evolution is where two species change together over time.

147

How is flower pollination by insects an example of co-evolution?

-Insects that recognise the signals of flower scent and colour have a survival advantage, because they are more likely to be pollinated. So, as one species changes, the individuals of the other species that are best suited to those changes are more likely to survive. This happens over and over again and so the two species co-evolve.

148

How does co-evolution occur in plant chemical defence?

-Several plant species that grow in the dry grasslands of Australia make poison in their leaves. Grey kangaroos can eat leaves that contain quite high levels of poison. In places where there are few kangaroos, the plants don't waste energy making poison.

149

What evidence do we have for human evolution?

-Many different fossils that are similar to, but not exactly alike, modern humans have been discovered.

150

What are the different types of ancient human species?

-Ardipithecus Ramidus (Ardi)
-Australopithecus Afarensis (Lucy)
-Homo Habilis
-Homo Erectus
-Homo Sapiens

151

When did the human species of Ardi (Ardipithecus Ramidus) exist?

-4.4 million years ago

152

When did the human species of Lucy (Australopithecus Afarensis) exist?

-3.6 to 2.8 million years ago

153

When did the human species of Homo Habilis exist?

-2.4 to 1.4 million years ago

154

When did the human species of Homo Erectus exist?

-1.8 to 0.5 million years ago

155

How long have modern human (Homo Sapiens) existed?

-195,000 years ago to present.

156

What is Ardipithecus Ramidus (Ardi)?

-Scientists decided that the fossil bones of a 4.4 million-year-old, human-like, female animal were from an extinct species. They were given the binomial name Ardipithecus Ramidus or Ardi for short.
-Ardi was about 120cm tall, and would have weighed about 50kg. Her leg bones showed that she walked upright, more like a human than an ape. But she had very long arms, and her big toes would have been able to grasp branches. Her brain was small, about 350cm3, similar to a chimpanzee. (A human brain is about 1500cm3).

157

What is Australopithecus Afarensis (Lucy)?

-The fossilised bones of a female from another human-like species were called Australopithecus Afarensis and nicknamed Lucy. She lives about 3.2 million years ago and was only about 1.07m tall. She had long arms, and her bones suggest she didn't walk completely upright, more like a chimpanzee than a human. Her brain volume was about 400cm3).

158

What is Homo Habilis?

-In the 1960's, British scientists Mary Leakey and Louis Leakey found fossils of a more recent human-like species. They decided it was closely related to modern humans and so gave it the first word for its binomial name. It is called Homo Habilis, which translates as 'handy man'.
-Fossils of this species are between 2.4 and 1.4 million years old. They walked upright, and were quite short with long arms, Their brains were between 500 and 600cm3.

159

What is Homo Erectus?

-The fossil of another close relative of modern human, Homo Erectus, was found by Richard Leakey in 1984. This almost-complete skeleton showed it was a tall (1.79m) but strongly-built species with a brain volume of about 850cm3.

160

What are the trends of the human species?

-Less hair than before
-Arm length got shorter (no need to be in trees)
-Got taller
-More muscular (needed to hunt)
-Brain got bigger (head shape changed)

161

How can we link stone tools with humans?

-No tools were found with Ardi or Lucy, but tools have been found with Homo Habilius and Homo Erectus fossils. Stone tools cannot be dated directly, but we can date the layers of rock or sediment they are found in. So we assume that the tool is the same age as that layer of rock or sediment.

162

What are the oldest stone tools that have been found?

-The oldest stone tools so far discovered were not found with fossil bones, and are at least 2.6 million years old. They were very simple, but would have helped with skinning an animal or cutting up meat. Tools found in more recent rock are more sophisticated.

163

How have stone tools used by humans evolved?

-The oldest tools have very little structure, they were normally sharp at one end and still had the natural shape of the rock.
-As time has gone on, the tool shape has developed and got more structured, for example attaching it to a handle to make it easier to use.
-It was only 6000 years ago, that humans started using metals for tools, previously they just used stone.

164

Where is it believed that modern humans have evolved from?

-We think that modern Homo Sapiens first evolved in Africa about 200,000 years ago, but may have spread out of Africa about 60,000 years ago.

165

How did the Ice Age encourage humans to spread out of Africa?

-An Ice Age is a time of very cold periods called 'glacials' and warmer 'interglacials'. Around 60,000 years ago in a glacial period, a lot of water was locked up in ice and sea levels were much lower. It would have been easier to cross from Africa to Yemen.
-These people would move to hunt and gather food. As they spread through Asia and Europe during the interglacial, they adapted their tools, clothing, homes and equipment to suit new environments.

166

How did another cold period, about 25,000 years ago, after the Ice Age also encourage humans to spread out?

-About 25,000 years ago, another cold period produced a land bridge between Siberia and North America. We think that humans then spread from Asia into North America.

167

What happened to human settlement about 11,000 years ago, as the climate became more stable?

-About 11,000 years ago, the climate became more stable, and it is around then that we can see the first signs of people settling down in the same place and starting to grow crops.

168

What is mitochondrial DNA?

-In each cell there are many tiny organelles called mitochondria in which energy is released from food. Mitochondria have their own DNA.

169

Where does mitochondrial DNA come from?

-Each person begins life as a zygote. The nuclear DNA in the zygote comes from both the mother and father.
-However, all the mitochondria comes from the cytoplasm of the egg cell, so the mitochondrial DNA (mtDNA) only comes from the mother.

170

How fast does DNA change over time?

-All DNA changes over time due to mutations. However, mtDNA mutates around 100 to 1000 times faster than nuclear DNA. This means that over the past 50,000 years many more mutations have happened in the mtDNA.

171

Why is mtDNA often more useful than nuclear DNA for tracking evolution using fossil matter?

-After death, tissues start to decay and the chemicals in cells break down, including DNA. The longer the time since death, the greater the decay. However, scientists have been able to extract cells from fossils that are several tens of thousands of years old. As each cell contains many mitochondria but only one nucleus, there is likely to be a greater abundance of mtDNA in the sample than nuclear DNA. There is also a greater chance that it will be in a good enough condition to identify the genetic sequence. This makes mtDNA often more useful than nuclear DNA for tracking evolution using fossil matter.

172

What does mtDNA provide evidence for?

-Studies of mutations in mtDNA in people all over the world suggest that all of us have mtDNA that has evolved from the mtDNA of a woman in Africa, between 130,000 and 200,000 years ago. She has been called 'mitochondrial Eve' or 'African Eve'. This doesn't mean she was the only woman living then, but she is the only one where there is an unbroken female-female line all the way down from her generation to ours.
-The evidence also shows which people are most closely related to others. This suggests how humans spread out of Africa and populated the rest of the world.

173

When humans made migrations, what did they discover, regarding food?

-When humans were making their long migrations, hundreds of thousands of years ago, they would have wanted to carry long-lasting food with them. Probably even the earliest humans would have hung up strips of meat to dry. Later, they discovered the milk could be kept for much longer by allowing it to turn into yoghurt and cheese.

174

What are most changes in food caused by?

-Today, we know that most of the changes in food are caused by microorganisms - bacteria and microscopic fungi. The microorganisms produce enzymes that change molecules in the original substance into different molecules. We call processes like this 'biotechnology'.
-E.g. bacteria act on protein called casein in milk when it turns to cheese.

175

What is biotechnology?

-We can describe biotechnology as the alteration of natural biomolecules using science and engineering to provide goods and services.
-We don't just use biotechnology to make food, but to make all sorts of different substances that we use in many different ways, such as making medicines.

176

What is a biomolecule?

-A biomolecule is a substance made by living organisms.

177

How are fermenters used in biotechnology?

-Modern biotechnology often involves big steel vessels, called fermenters, in which microorganisms are grown. Inside the fermenter, the microorganisms are provided with exactly the right conditions to encourage them to grow and produce the substances we require. For example, the fungus penicillium is used to produce the antibiotic penicillin.

178

What are aseptic precautions?

-Before the microorganism is put into the fermenter it's essential to kill any other microorganisms already in there, as they might grow instead. The fermenter is sterilised using high-pressure steam. Everything that is added to the fermenter is first sterilised to prevent microorganisms getting into the culture. These are called aseptic precautions.
-Also, wearing overalls, gloves and a face mask help prevent microorganisms getting into the fermenter.

179

Why are optimal conditions supplied for the microorganisms in fermenters for biotechnology?

-Inside the fermenter, optimal conditions for the microorganism are supplied, so that it produces as much product as possible in the shortest time.

180

What are the optimal conditions supplied in fermenters for biotechnology?

-Nutrients: including sources of carbohydrates and nitrogen, such as sugar and ammonium ions.
-An optimum temperature: so the enzymes in the microorganism can work at a fast rate but don't get denatured.
-The optimum pH: to allow the enzymes to work efficiently.
-Oxygen: provided by bubbling sterile air into the fermenter, so the microorganism can respire aerobically.
-Agitation: produced by a stirrer, to mix the oxygen and nutrients into all of the liquid.

181

What types of things are made using biotechnology?

-Ethanol fuel (biofuel)
-Medicines
-Bio-steel

182

What is bio-steel?

-High strength based fibre material made of the recombinant spider silk-like protein extracted from the milk of transgenic goats.

183

In the early 1960s, how did scientists try to find cheap sources of protein?

-In the early 1960s, scientists were looking for cheap sources of protein for people in parts of the world where food was in short supply. They tried cultivating various kinds of microorganisms, including single-celled plants, microscopic fungi and bacteria.
-Only one of these foods was successful, mycoprotein.

184

What is mycoprotein?

-Mycoprotein is made from a fungus called Fusarium. It is sold as Quorn.

185

What is Fusarium?

-Fusarium is a fungus which mycoprotein is made up of.
-It is made up of tiny fibres called hyphae.

186

How is mycoprotein made?

-Mycoprotein is made in a fermenter. As fusarium is made up of tiny fibres (called hyphae), there is no stirrer in the fermenter because this would tangle and break the fibres. Instead it is stirred with air.
-The hyphae are collected and heat-treated to remove a bitter-tasting substance that they contain. They are dried and pressed to form a fibrous substance, which has a similar texture to meat.

187

Why is it easier to grow protein from fusarium rather than getting it from animals?

-Fusarium can be grown in fermenters all year round, whatever the weather.
-For its energy source, wheat-starch mix is added that comes from leftover bits of making flour. This is loads cheaper than buying glucose in specially.
-Two large fermenters can produce around 100 tonnes of protein a year. That's about the same amount of protein as in the meat you get from 400 cows, in much less space and much less hassle.

188

What does mycoprotein need for growing well?

-A large and constant supply of oxygen bubbling through the liquid in the fermenter because the fusarium respires aerobically.
-Wheat/starch mix is added for its energy source from leftover bits of making flour. Other waste products that are rich in carbon are used in other countries.
-Source of nitrogen, such as ammonia, so that it can make the mycoprotein.
-Vitamins and minerals to make sure the fungus has all it needs to grow as rapidly as possible.
-After it has been in the fermenter, the fungus is heated to 65degrees celcius. This helps to break down the nucleic acid in it, which tastes bitter.

189

What are the advantages of eating mycoprotein instead of protein from meat?

-Virtually nob saturated fat in it, which helps to protect our hearts.
-Lots more fibre, which is good for the gut.
-Tastes like meat and have a fibrous texture to the protein at the end, which makes it feel a bit more like eating meat.

190

What is mycoprotein like as a food source?

-Mycoprotein is an excellent food source from a health point of view.
-Saturated fat is a risk factor in heart disease; mycoprotein contains no saturated fat but meat does.
-The high fibre content of mycoprotein slows the rate at which glucose is absorbed from food. This stops blood glucose concentration rising rapidly after a meal. This, in turn, means that insulin isn't secreted so quickly or in such large amounts. Glucose and insulin surges are thought to contribute to the risk of developing type II diabetes, so it's possible that eating mycoprotein could reduce the risk.

191

What are the advantages of making food from microorganisms rather than growing crops and keeping animals?

-Microorganisms populations can double in number in as little as 20 minutes. This is much faster than crops or animals can grow.
-Microorganisms are easy to handle and manipulate. They can be grown in fermenters, rather than taking up space in fields or buildings.
-Microorganisms can be grown in any part of the world, no matter how hot, cold, dry, or wet it is outside.
-Microorganisms an often be grown using waste materials from other processes as their food source. Fusarium is grown on waste material produced when flour is made from wheat grains.

192

How is yoghurt made?

-Yoghurt is made from milk by bacteria such as Lactobacillius bulgaricus. The bacteria live on the sugars in the milk.
-They convert lactose (milk sugar) into lactic acid as they respire anaerobically.

193

What are the different factors that affect yoghurt making?

-A variety of factors affect yoghurt making, such as the type of bacteria used, the type of milk used, the levels of nutrients in the milk, the temperature of the mixture of milk and bacteria and the pH.
-These factors can affect both the speed at which yoghurt is made from milk, and also the type of yoghurt that is produced.

194

What enzymes are used to produce sweets?

-One enzyme that is widely used in food manufacture is invertase (an alternative name is sucrase)..
-Invertase is produced by cultivating a yeast called Saccharomyces cerevisae in fermenters.

195

How is invertase used in the production of sweets?

-The sugar that we get from sugarcase and sugar-beet is mostly sucrose. Invertase converts sucrose to glucose and fructose.

196

Why is using invertase in the production of sweets good?

-The mixture of glucose and fructose is sweeter than the original sucrose, so less is needed to make sweet foods. It is also good for making soft-centred sweets.

197

How are enzymes used in washing powders?

-Washing powders contain detergents that cannot remove some kinds of stains. Therefore, many washing powders also contain enzymes, including proteases and lipases. Proteases break down proteins, such as haemoglobin in blood stains. Lipases break down fats, such as grease.

198

How are enzymes used in fruit juice making?

-Enzymes such as cellulase and pectinase are used in the manufacture of fruit juice. Pectinase separates thr plant cells from each other, and cellulase breaks down the cellulose cell walls. Ths lets us extract much more juice from the cells.
-Cellulase is produced by the microorganisms which are found in the digestive system of cows. It is the enzyme which makes it possible for cows to digest the cell walls of grass.

199

How are enzymes used in cheese-making?

-Cheese is made from milk. Traditionally, an enzyme from calves' stomachs, called chymosin, is added to the milk.
-It affects the protein in the milk, making the milk separate into curds (a semi-solid mix of proteins and fat) and liquid whey. The curds are pressed to produce cheese.

200

How can chymosin, used in cheese making, be made?

-In the 1980s, scientists found a way of making chymosin using bacteria. They took the calf gene for chymosin and put it into the bacteria, which then produced chymosin. This is called genetic modification. Today, most chymosin is made from genetically modified yeast. It's much easier and cheaper to produce large quantities of very pure chymosin in this way rather than to get it from calves. It also makes a lot of cheese suitable for vegetarians.

201

What is recombinant DNA technology?

-Making a genetically modified organism uses recombinant DNA technology. This means that different pieces of DNA are 'recombined' in a new way.
-One of the first examples of this technology was the production of bacteria that contained the human gene for insulin.

202

How is bacteria genetically modified to produce human insulin?

1. DNA from a human cell is cut into pieces using enzymes called restriction enzymes. These make staggered cuts across the double-stranded DNA, leaving a few unpaired bases at each end, called sticky ends.
2. Bacteria cells contain small circles of DNA called plasmids. The same restriction enzymes are used to cut plasmids open, leaving sticky ends with matching sets of unpaired bases.
3. The pieces of DNA containing the insulin genes are mixed with the plasmids. The bases in the sticky ends pair up. Am enzyme called DNA ligase is added, linking the DNA back into a continuous circle.
4. The recombinant plasmids are inserted into bacteria. The bacteria can now be grown in huge fermenters, where they make human insulin.

203

What is the global food security crisis?

-As the human population continues to grow, people in many parts of the world do not get enough food. The World Health Organization calls this the 'global food security crisis'; we won't have enough food for everyone. New varieties of crops with higher yields are being produced to provide more food.

204

What is a conventional breeding programme?

-Most new plant varieties to provide more food for the world are produced by conventional breeding programmes.
-For example, to produce a very high-yielding wheat variety, one high-yielding wheat variety is crossed with another. All the resulting seeds are sown and allowed to grow into adult plants. From these, the individuals producing the most grain are selected and bred together. This is repeated for at least 20 generations, eventually producing a high-yielding variety that is named and sold.

205

What is integrated pest management (IPM)?

-Each year, huge amounts of crops are lost to pests such as insects and fungal diseases. Resistant plants can be developed, but the best way of combating pests is often to use a system called integrated pest management (IPM). This uses different pest control strategies at the same time.

206

What is crop rotation?

-Crops like raspberries stay in the same field for many years. However, for annual crops a different crop can be planted in the same field each year in a 3- or 4-year cycle, such as potatoes, oats, beans and cabbages. This is called crop rotation and helps prevent the build up of soil pests for each crop.

207

What are biofuels?

-Our increasing population needs more energy for industry, transport and other uses. Yet almost everyone agrees we nee to reduce our use of fossil fuels. One possible replacement for them is biofuels. These are fuels that are made by, or from, living organisms, including plants such as maize or oil palms.

208

What are the advantages of biofuels?

-Biofuels are renewable; it doesn't take long to produce them and we can keep growing the plants from which they are produced, year after year.
-They are also said to be 'carbon neutral'. This means that the carbon dioxide released into the air when they are burned balances out the carbon dioxide that the growing plants removed from the air for photosynthesis.
-Help the economy because more people will need to be employed because more are needed to produce biofuels than petrol.

209

What are the disadvantages of biofuels?

-The plants take up land that could be used for growing food, cause food shortages and food prices to go up.
-Could lead to deforestation, due to forests being cut down to grow plants for biofuels, causes loss of habitats etc.

210

How is maize, soya and cotton genetically modified?

-Genetically modified maize, soya and cotton are widely grown in both developed and developing countries. Many of these have a gene that makes them resistant to a herbicide. This means crops are not damaged by the chemical but the weeds crowing with them are killed.

211

What new purple GM variety of tomato was developed?

-The new GM variety of tomato contained snapdragon genes that produce extra pigments called flavonoids. Tests have shown that it helps mice with cancer to live longer and this might be useful for humans. This tomato will probably be too expensive for people in developing countries to grow or buy.

212

What is the problem with growing GM seeds in developing countries?

-GM crop seeds produced in developed countries are more expensive than normal seeds. In India, many farmers borrowed money to buy GM seeds because they believed they would give a better crop yield than normal plants. However, many found that the GM plants produced less food because they were not adapted to the Indian soil and climate. The farmers then had even less money.

213

What is a transgenic organism?

-A transgenic organism contains genes transferred from another organisms. Transgenic plans are often produced using a bacterium called Agrobacterium Tumefaciens.

214

How is the bacterium Agrobacterium Tumefaciens used to produce transgenic organisms?

-The gene for the required characteristic is inserted into Agrobacterium Tumefaciens, which is then allowed to infect plants. This introduced the required gene into the plant cells. So the Agrobacterium Tumefaciens acts as a go-between or vector.

215

What is Bacillius Thuringiensis?

-Bacillius Thuringiensis is a bacterium that is normally found in soil. It produces Bt toxin when eaten by insects, which is poisonous.
-The gene for Bt toxin has been identified in the bacterium and transferred into crop plants using Agrobacterium.

216

What are the advantages of Bt crops?

-When insects eat the plant cells, the cells release Bt toxin, which kills the insects. This means that less insecticide has to be sprayed onto the crop, reducing damage to the environment. Higher yields should be produced, as less of the crop is lost to the pests.

217

What are the disadvantages of Bt crops?

-There are worries that the toxin could kill other, harmless, insects such as butterflies and bees. The Bt gene might also spread into closely related wild plant species if pollen from a Bt crop is transferred to a related wild plant and leads to a fertilisation of that plant.
-Another problem is that many insect populations have evolved resistance to the Bt toxin, so they can live and breed on the Bt plants.