B6

Question 1

Abundance

Answer 1

How many individual organisms in an area (population size).

Question 2

Distribution

Answer 2

Where an organism is found in a habitat.

Question 3

Pooter

Answer 3

Suck on the mouthpiece to draw small insects into the holding chamber. A fine mesh prevents the insects from being breathed in. Repeat this sampling technique for two similar-sized sample areas for the same amount of time and compare results.

Question 4

Sweep nets

Answer 4

Used to catch (flying) insects in areas of long grass by sweeping the net left to right in two different sample areas. The net is turned out into a container and the insects are counted. Compare the number of organisms found in each sample.

Question 5

Pitfall traps

Answer 5

Dig a steep-sided hole into the ground which is partly open and covered with a roof (to prevent rainfall). Leave the trap overnight in two sample areas and count how many insects fell in the trap. Compare results.

Question 6

Quadrat

Answer 6

To sample plants place a square-framed grid on the ground of an known area eg. 1m². Use a random number generator to pick coordinates of the entire area for the sample. Count all the organisms you are studying in the quadrat. Find the mean for the first area by repeating this process - the larger the sample size the more reliable the results. Repeat this process for the second sample area and scale up results by multiplying the mean by the total area of the habitat.

Question 7

Transect

Answer 7

To investigate how the distribution of an organism gradually changes across an area using a quadrat to sample along the length of the transect (belt transect). Move the quadrat along the transect at intervals of 2m or directly after the first. If it’s difficult to count the individual organisms (eg. grass) count the individual squares they are found in to calculate percentage cover. Plot the results in a kite diagram.

Question 8

Capture-Recapture

Answer 8

1) Capture a sample of organisms and mark them in a harmless way.
2) Release back into the community.
3) Recapture another sample of the organisms and count how many there are in total and how many are marked.
4) Estimate population size: Population size = number in 1st sample x number in 2nd sample / number in 2nd sample with marks.
Potential assumptions made:
- There has been no change in population size (births or deaths).
- The marking has affected the individual’s chance of survival (making them more visible to predators).

Question 9

Measuring abiotic factors

Answer 9

Abiotic factors may affect the distribution of the organism being sample.

1) Use a thermometer to measure temperature.
2) Use an electronic light sensor to measure light intensity.
3) Use a soil moisture meter to measure the moisture level in the soil.
4) Measure soil pH using an electronic pH monitor or universal indicator.

Question 10

Random sampling

Answer 10

Individuals are selected by chance. Mark out a grid of the sample area and use a random number generator to determine the coordinates of where to place the quadrat. This prevents bias eg. placing quadrat in areas where there is a greater abundance of the organism.

Question 11

Non-random sampling

Answer 11

Studying how the distribution of an organism varies over distance eg. a transect for the change in plant species from the sea to inland.

Question 12

Biodiversity

Answer 12

The variety of living organisms in an area.

Question 13

Deforestation

Answer 13

The permanent removal of large areas of forest which provides wood for building and fuel, creates space for roads and agriculture. This reduces the number of trees and the number of supported animal species as their food source or habitat is lost. This can therefore affect predator species. Overall, reduces biodiversity.

Question 14

Agriculture

Answer 14

More land is being intensively farmed to feed the increasing population which leads to a loss of biodiversity. Using pesticides kills pests that eat crops which reduces the number of pest species and the food source of other organisms. Pesticides can also accumulate in the food chain, killing animals that were not targeted. Monocultures clear large areas of land leading to the destrucution of habitats in order to grow a single type of crop.

Question 15

Hunting and fishing

Answer 15

Overfishing has led to a decrease in fish species or being lost from areas. This disrupts the food chain and can also kill other marine species. Hunting decreases the target species’ population, which removes food for other species. It can cause the uncontrollable growth of some plant species which out-compete other plants, further reducing biodiversity.

Question 16

Pollution

Answer 16

Waste produced by humans kills organisms living in the polluted environment. Toxic chemicals can run into lakes, leading to eutrophication and causing the death of many plant species below the algal bloom. Other chemicals from nuclear waste and household waste can run into water supplies and kill fish and plants. Smoke and gases released into the atmosphere can pollute the air such as sulfur dioxide which causes acid rain. This can effect the distribution of plant species such as lichen , further reducing biodiversity.

Question 17

Conservation

Answer 17

Protecting a natural environment to ensure a habitat is not lost.

Question 18

Protecting habitats

Answer 18

National parks and nature reserves restrict the development of land, protecting the organisms and the habitat. Marine ecosystems are protected by banning human activities such as fishing. This increases, or conserves, the biodiversity in a habitat.

Question 19

Captive breeding

Answer 19

Breeding animals in human-controlled environments such as zoos. This helps to create a stable and healthy population of a species in order to eventually reintroduce the species back to its natural habitat. This helps maintain biodiversity. Although sometimes genetic diversity is difficult due to limited breeding partners and organisms born in captivity may not know how to hunt for food.

Question 20

Seed banks

Answer 20

A way of conserving plants by storing the seeds so that new plants may be grown in the future. This helps provide a backup against the extinction of a plant species in order to protect biodiversity.

Question 21

Benefits of maintaining biodiversity

Answer 21

• Protecting the human food supply: reducing fishing can ensure that future generations will have fish to eat.
• Ensuring minimal damage to the food chain.
• Providing future medicines: many plants contain new medicinal chemicals.
• Providing materials and fuels: resources may become more difficult to produce with extinction of plants and animals.

Question 22

Conservation agreements

Answer 22

Local and international cooperation to preserve habitats and individual species. Many animals move naturally between countries so global action is required.

Question 23

Difficulty in gaining agreements for conservation schemes

Answer 23

International agreements require several countries to work together, however sometimes countries are not willing to sign up to an agreement. Conservation schemes can be objected by local residents as it may reduce their income eg. bans on logging.

Question 24

Difficulty in monitoring conservation schemes

Answer 24

Sometimes it is difficult to see how successful a scheme is and if countries or a community is obeying the scheme eg. fishing quotas.

Question 25

Ecotourism

Answer 25

A form of tourism that supports the conservation and sustainable development of ecosystems. This aims to ensure that tourism does not have a negative impact on the natural environment by restricting tourist access and educating visitors. Landowners gain a source of revenue and are encouraged to maintain biodiversity otherwise tourists will no longer come.

Question 26

Food Security

Answer 26

The ability to access affordable food of sufficient quality (nutrition) and quantity.

Question 27

Changing Diets (factors that affect food security)

Answer 27

As populations become wealthier, diets change to include a wider variety of foods such as more meat which is more energy extensive to produce than plant products.

Question 28

New Pests and Pathogens (factors that affect food security)

Answer 28

Can evolve and result in the loss of crops or livestock and could lead to widespread famine.

Question 29

Climate change (factors that affect food security)

Answer 29

Increased temperatures could lead to more droughts, rising sea levels and desertification, which reduces the land available for food production. They can also affect the growth pattern of crops which could result in reduced yields.

Question 30

Costs of Agricultural Inputs (factors that affect food security)

Answer 30

Inputs such as fuel/chemicals/animal feed have increased in price, which has increased the cost of storing and distributing food. This can make it expensive for countries to start or maintain food production, creating a deficit in food to feed the population. These high input costs can be passed onto the consumer as high food prices making some food unaffordable.

Question 31

Sustainability (factors that affect food security)

Answer 31

Meeting the needs of today’s population without harming the environment so that future generations can still meet their own needs. Unsustainable farming practices, such as relying on non-renewable energy, can have a negative impact of food security.

Question 32

Fertilisers (increasing agricultural yields)

Answer 32

As plants grow minerals (N,P and K) are removed from the soil. Fertilisers can increase crop yield by replenishing the missing elements and keeping the soil fertile. However this can lead to eutrophication.

Question 33

Pesticides (increasing agricultural yields)

Answer 33

Chemical pest control sprayed onto crops which destroy pests that damage the plant. Examples include insecticides, herbicides and fungicides. However pesticides can be poisonous and can accumulate in organisms consuming the crops, damaging the food chain.

Question 34

Biological control (increasing agricultural yields)

Answer 34

Crop pests have natural predators which organic farmer can exploit to kill pests instead of using pesticides. Predators are bred in large numbers and released onto crops where they eat pests. This is a safer alternative as no chemicals are used reducing pollution and risk to the food chain.

Question 35

Intensive Farming (increasing agricultural yields)

Answer 35

Techniques that aim to produce the maximum food product yield from the minimum area of land by using fertilisers/pesticides, maximising animal growth rates (high protein diet) and minimising labour inputs by using machinery.

Question 36

Organic Farming (increasing agricultural yields)

Answer 36

A natural method of producing crops and rearing livestock that avoids the use of artificial chemicals however yields are smaller and therefore products are more expensive.

Question 37

Hydroponic System (increasing agricultural yields)

Answer 37

Ensures a plant receives the minerals it requires to grow in water containing dissolved minerals (no soil). Used by commercial growers as it enables plants to grow more quickly and more plants can be grown in the same space as they are stacked above each other.

Question 38

Genetic Modification (increasing agricultural yields)

Answer 38

Transfers useful genes into plants (and animals) in order to develop useful characteristics. Crops can be insect resistant, which reduces the use of pesticides and increases crop yield, virus resistant, which means they won’t be damage by a disease and herbicide resistant which means crops can be sprayed without being damaged.

Question 39

Selective Breeding

Answer 39

The process of selecting parents with the best characteristics such as those with the highest meat/grain yield or disease resistance. These individuals are bred and the offspring with the most desirable trait are selected and bred again. This process is repeated over several generations until all the organisms develop the desired characteristic.

Question 40

Disadvantages of Selective Breeding

Answer 40

• Reduces the gene pool (number of alleles in a population) of a species, thus reducing variation. This means if a new disease arises there may not be an allele in the reduced gene pool that can resist the disease and therefore the species may become extinct.
• Limited gene pool increases the chances inheriting harmful genetic disorders due to ‘inbreeding’.
• Takes place over many generations which requires time.

Question 41

Genetic Engineering

Answer 41

Altering an organism’s genome by targeting single genes in order to produce an organism with desired characteristics. It is a very accurate process which takes places in one generation.

Question 42

Disadvantages of Genetic Engineering

Answer 42

• Eating genetically modified (GM) foods may eventually lead to health problems such as introducing new allergens that may cause people to become allergic to the organism.
• Genetically engineered crops may cross-pollinate with wild plants which could introduce the new gene to wild plants. This disrupts the balance of an ecosystem.
• There are many ethical issues as we do not understand the long-term consequences and it is unnatural to change an organism’s genome.

Question 43

Advantages of Genetic Engineering

Answer 43

• Eating genetically modified (GM) foods may eventually lead to health problems such as introducing new allergens that may cause people to become allergic to the organism.
• Genetically engineered crops may cross-pollinate with wild plants which could introduce the new gene to wild plants. This disrupts the balance of an ecosystem.
• There are many ethical issues as we do not understand the long-term consequences and it is unnatural to change an organism’s genome.

Question 44

Producing a Cell Using Genetic Engineering

Answer 44

1) The desired gene is isolated from the organism using a restriction enzyme. Restriction enzymes recognise the specific sequences of DNA and cut at these points.
2) The same restriction enzyme is the used to cut the DNA of the plasmid from the bacterial cell.
3) This creates exposed complementary sticky ends on the DNA.
4) The gene is inserted (as well as the antibiotic resistant gene) to make a recombinant plasmid. The enzyme DNA ligase repairs the sticky ends of the two pieces of DNA.
5) The plasmid becomes a vector as it carries the foreign gene. It is inserted back into the host cell (bacteria) to produce the desired characteristic.
6) The bacteria is now a transgenic bacteria. Not all of the host cells will have been modified successfully (eg. the vector may not have been transferred properly). The individuals which have received the desired gene are then selected.

Question 45

Identifying Transgenic Host Cells

Answer 45

In order to identify the host cells which contain the new DNA , antibiotic resistant markers are used:

• A marker gene, which codes for antibiotic resistance, is inserted into the vector as the gene for the desired characteristic is inserted.
• The host bacteria are grown on an agar plate containing the selected antibiotic.
• Only the bacteria that contain the marker will be able to survive and reproduce, therefore they must also contain the desired gene.

Question 46

Genetically Modifying Organisms

Answer 46

1) A gene which controls a useful characteristic such as pesticide resistance is identified in a plant with a natural resistance to the pesticide.
2) Using genetic engineering, the gene is cut and inserted into a vector such as a virus or bacteria (agrobacterium tumefaciens).
3) The vector can then invade a plant cell and insert the GM genes into the cell (insertion).
4) The new gene is inserted into the host DNA and the transgenic organism is grown.
5) The GM organism is cloned, producing large numbers of identical individuals, resistant to the pesticide.

Question 47

Disease

Answer 47

A condition which impairs the normal functioning of an organism (mentally and physically).

Question 48

Communicable Diseases

Answer 48

Diseases which can be spread between organisms and is caused by a pathogen infecting an organism.

Question 49

Non-communicable Diseases

Answer 49

Diseases which cannot be spread between organisms such CVD, respiratory diseases, cancers and diabetes. They are long-lasting and progress slowly.

Question 50

Fungi

Answer 50

Penetrates human skin and surface of plants, causing disease. Produces spores which can be spread to other organisms.
Animal - Athlete’s foot
Plant - Powdery mildew

Question 51

Bacteria

Answer 51

Very small cells which can reproduce rapidly and produce toxins which damage your cells and tissues making you feel ill.
Animal - Tuberculosis
Plant - Crown gall disease

Question 52

Viruses

Answer 52

Replicate themselves inside infected organisms cells, which bursts, releasing the new viruses.
Animal - Influenza
Plant - Tobacco mosaic virus (TMV)

Question 53

Protozoa

Answer 53

Protists that cause disease are often parasites
Animal - Malaria
Plant - Coffee phloem necrosis

Question 54

Causes of Non-communicable Diseases

Answer 54

• Poor diet: lack of fresh fruit/vegetables/vitamins/minerals leads to deficiencies.
• Obesity: being overweight can lead to arthritis, type 2 diabetes and CVD.
• Inheriting genetic disorders: passed through genetic material from parents such as cystic fibrosis.
• Body processes not functioning correctly: uncontrollable replication of cells leads to cancer.

Question 55

HPV and Cervical Cancer

Answer 55

The Human Papilloma Virus (HPV) can infect the reproductive system and can be transmitted through bodily fluids. People normally recover from HPV infection without long-term problems. In some cases, HPV can cause cell changes that result in the development of types of cervical cancer. Nearly all cervical cancer cases result from HPV infection and girls are now routinely vaccinated against the virus.

Question 56

HIV and Tuberculosis

Answer 56

The Human Immunodefiency Virus (HIV) causes Acquired Immune Deficiency Syndrome (AIDS) which prevents the immune system from operating correctly. Our immune system normally destroys pathogens before symptoms of the disease can develop. However a weakened immune system allows the bacteria which causes TB to develop very rapidly (people with HIV are more likely to show signs of TB). This also makes it more difficult to recover from TB.

Question 57

Spread of Communicable Diseases (Water)

Answer 57

Contaminated water contains pathogens which are spread through drinking and bathing in the water eg. cholera (bacteria).

Question 58

Spread of Communicable Diseases (Air)

Answer 58

Pathogens can be air-borne such as spores blown between plants in the wind eg. powdery mildew (fungi) and droplets produced by coughing and sneezing eg. influenza (virus)

Question 59

Spread of Communicable Diseases (Contact)

Answer 59

Pathogens can be spread by touching contaminated surfaces such as the TMV when infected leaves touch healthy leaves and athlete’s foot (fungi) from sharing towels.

Question 60

Spread of Communicable Diseases (Bodily fluids)

Answer 60

Pathogens can be spread through the blood and semen. For example, HIV is spread by the exchange of bodily fluids during sexual intercourse.

Question 61

Spread of Communicable Diseases (Vectors)

Answer 61

Animals that spread diseases (without causing it themselves) are called vectors. Malaria is caused by a protist and part of its life cycle takes place in a mosquito. Once the mosquito feeds on the blood of animal, it infects the organism by inserting the protist into the animal’s blood.

Question 62

Spread of Communicable Diseases (Soil)

Answer 62

Pathogens can survive is soils, so plants in that are grown in the contaminated soil may be infected. For example the bacteria that cause crown gall disease are able live freely in some soils on the roots of plants.

Question 63

Spread of Communicable Diseases (Food)

Answer 63

Pathogens are spread through eating contaminated food. If food is not cooked properly or kept for too long the bacteria can cause food poisoning eg. Salmonella.

Question 64

Incubation Period

Answer 64

Between when a pathogen enters an organism’s body and when organism to starts to experience symptoms, there is a time delay. During this time the pathogens reproduce rapidly and as they grow they cause cell damage. Some pathogens may also produces toxins which cause symptoms such as fever, rashes and sores.

Question 65

Viral Replication

Answer 65

A virus cannot replicate by themselves. When a virus attacks a cells, it inserts its genes which causes the nucleus to copy the virus’ genes. Once new viruses are made, the cell bursts, releasing the new viruses which destroys the cell.

Question 66

Reducing and Preventing the Spread of Disease

Answer 66

• Good healthcare systems and education (knowledge on how infections are spread)
• Being hygienic (washing hands/covering mouth and nose when coughing or sneezing)
• Vaccinations.
• Destroying infected plants (prevents source of infection)
• Crop rotation (changing plants that are grown prevents pathogens from establishing in an area. Also allows any pathogens in the soil to be destroyed over time)
• Chemical control such as fungicides and pesticides.

Question 67

Detection of Antigens

Answer 67

The ELISA test is used to detect antigens (proteins on the surface of the microorganism). They are detected using antibodies (proteins that bind to a specific antigen). Antigens represent the pathogen the plant is infected by. The antibodies are added to the sample being tested and washed off. If the antibodies have bind to the antigen, they will remain in the sample. The antibodies already have enzymes attached to them which can react with a substrate to cause a colour change, therefore if there’s a colour change when the substrate is added, it demonstrates that the antigen (and so the pathogen) is present.

Question 68

DNA Testing

Answer 68

To detect if a pathogen is present in a plant sample, the PCR test is performed. Parts of the DNA strand that are complementary to that of the pathogen are used as primers (template). Any DNA from the sample that matches the pathogen is copied repeatedly. If the pathogen is present, lots of DNA will be made and show up on images of the DNA.

Question 69

Athlete’s Foot

Answer 69

Caused by a group of parasitic fungi called dermatophytes. The fungi lives and multiplies in a warm, humid environment. This causes symptoms such as cracked, flaking and itchy skin and is treated using anti-fungal cream. It is very contagious and spread through direct and indirect contact.

Question 70

Food Poisoning

Answer 70

Salmonella and E.coli are types of bacteria that cause food poisoning. They are found in raw, undercooked meats and unpasteurised milk and dairy products. They can survive in freezers and refrigerators but thorough cooking kills them. Symptoms can include stomach pains diarrhoea and vomiting.

Question 71

HIV and AIDS

Answer 71

HIV is the Human Immunodeficiency Virus which invades white blood cells and reproduces inside the cells. This weakens the immune system, as the affected cells should be producing antibodies to defend against disease but cannot. Without them, the body is susceptible to infections and cell changes. AIDS is the final stage of HIV infection, when the body can no longer fight life-threatening infections. People with HIV may take years to show symptoms. Treated with anti-retroviral drugs where lifetime treatment is required.

Question 72

STIs

Answer 72

Spread through skin to skin contact or bodily fluids during sexual intercourse.

• Chlamydia: bacteria causes pain when urinating. Treated with antibiotics.
• Gonorrhea: bacteria causes burning pain when urinating. Treated with antibiotics.
• Genital herpes: virus causes painful blisters or sores. No cure.

Question 73

Tobacco Mosaic Virus

Answer 73

The virus attacks the leaves and prevents the chloroplasts from forming. This makes them mottled or discoloured and stunts the growth of plants. It does not usually kill the plant but lowers crop quality and yield. To prevent the spread of the disease, the infected plants should be removed (washing hands and equipment after). Crops that are resistant to the virus should be planted in the previously infected areas to avoid soil re-infecting.

Question 74

Crown Gall Disease

Answer 74

Agrobacterium tumefaciens is a bacterium with a tumour-inducing plasmid, that contains the genes to cause crown gall disease. The bacteria enters the plant through a wound and the plasmid intergrates into the host’s genome, which causes the production of greater amounts of growth chemicals than normal. This leads to the production of large tumour-like growths (galls). The galls encircle the plant’s stem or trunk, cutting off the flow of the sap which stunts growth and eventual death. The infected must be destroyed and removed and replanting susceptible plants should be avoided.

Question 75

Barley Powdery Mildew

Answer 75

A fungal disease caused by different species of fungi such as Erysiphe graminis. Infected plants display white powdery spots on the stems and leaves. The fungus reduces growth and makes leaves fall off early which reduces crop yield. Grows in areas of high humidity and moderate temperatures. Releases spores spread by wind to infect new crop. Can be controlled with fungicide.

Question 76

Physical Plant Defences

Answer 76

• Waxy cuticle: acts as a waterproof barrier and stops pathogens entering plant which limits chance of infection. Prevents water collecting on the cuticle so stops pathogens that are transferred from water entering the plant.
• Cell wall: forms a physical barrier against pathogens made of cellulose which provides structure. Contains a variety of chemical defences that are activated when the cell detects pathogens eg. callose which reinforces the cell wall.

Question 77

Chemical Plant Defences

Answer 77

• Insect repellents: pine resin and citronella repel insect vectors that carry disease.
• Antibacterial compounds: kill bacteria such as phenol which disrupt the bacterium’s cell wall.
• Antifungal compounds: kill fungi such as caffeine which is toxic to fungi and insects.
• Cyanide: some plants produce chemicals that break down to form cyanide compounds when the plant cell is attacked. This is toxic.

Question 78

Scab

Answer 78

This prevents pathogens entering cuts in the body and stops blood loss.

• Once the skin is cut the wound starts to bleed.
• Platelets change the blood protein fibrinogen into fibrin which forms a network of fibres in the cut.
• Red blood cells are trapped in the fibres. This forms a blood clot.
• The clot hardens to form a scab. This keeps the skin clean and gives it time to heal.

Question 79

Non-specific Body Defences

Answer 79

• Skin: acts as a physical barrier to pathogens. Sweat gland produce antimicrobial substances which kill pathogens.
• Stomach: produces hydrochloric acid which kills bacteria in contaminated food/drink.
• Respiratory tract (nasal passage, trachea and lungs) lined with mucus and cilia. Mucus traps particles that could contain pathogens and cilia move mucus up the throat to be swallowed.
• Nasal hairs: keep out dust and larger microorganisms.
• Tears: contain lysozymes, enzymes which break down bacteria on the surface of the eye.

Question 80

Phagocytes

Answer 80

A type of white blood cell that has a flexible membrane to engulf pathogens. Contain enzymes that enable them to digest the foreign cells (phagocytosis).

Question 81

Lymphocytes

Answer 81

A type of white blood cell that produces antibodies or antitoxins (counteract toxins produced by invading bacteria).

Question 82

The Immune System

Answer 82

• An unique antibody (proteins that bind to antigens on the surface of pathogens) is produced when a B-lymphocyte comes across a foreign antigen. The antibodies are specific to that type of antigen.
• Antibodies are produced rapidly to lock to all similar pathogens around the body.
• The antibodies help allow the pathogen to be ingested by a phagocyte cell and destroyed.
• Some white blood cells, called memory cells, will remain in the blood after a pathogen has been destroyed. This means if the person is infected again the white blood cells are able to produce the same antibodies more quickly. The body will now have immunity to the disease and will not get ill again.

Question 83

Vaccinations

Answer 83

• A small amount of a dead, inactive or weakened pathogen is injected into the body.
• The antigens in the vaccine stimulate the white blood cells to produce antibodies. The antibodies destroy the antigens without any risk of getting the disease.
• Some of the white blood cells will remain in the blood as memory cells so if live pathogens for the same disease enter the body, the white blood cells can rapidly make the correct antibody.

Question 84

Antiseptics

Answer 84

A method of prevention that destroys microorganisms or prevents them from growing but does not damage human tissue, whereas disinfectants are applied to non-living surfaces. Used outside the body to clean wounds. Common examples include alcohol and iodine.

Question 85

Antivirals

Answer 85

Drugs which are used to treat viral infections, usually by preventing them from replicating. Many are specific and only work on one type of virus eg. influenza. The activity of the drug might include:

Question 86

Antibiotics

Answer 86

Drugs that kill bacteria without damaging normal body cells. There are several different types used to treat different bacteria and usually produced naturally eg. penicillin. Some bacteria are naturally resistant to antibiotics however the misuse of the drugs has increased the rate of development of resistant strains.

Question 87

Zone of Inhibtion

Answer 87

To measure the effectiveness of an antibiotic, calculate the area of the zone of inhibition. The more effective the antibiotic, the larger the zone of inhibition.

Question 88

Aseptic technique

Answer 88

Prevents foreign microorganisms from being introduced into a test sample. This ensures that apparatus and the environment remain sterile.

Question 89

Alcohol

Answer 89

Washing working areas with alcohol before working ensures there are no microorganisms present in the working area.

Question 90

Gloves

Answer 90

Reduces the risk of working with harmful pathogens. Prevents microorganisms from passing into the sample from your skin and vice versa.

Question 91

Autoclave

Answer 91

A pressurised chamber used to sterilise equipment. Autoclave glassware and apparatus before and after use ensures there is no unwanted contamination of a sample.

Question 92

Bunsen Burner

Answer 92

Working close to a Bunsen burner flame prevents unwanted microorganisms from falling into an open sample.

Question 93

Inoculating loop

Answer 93

Microorganisms are transferred from one medium to another using a wire loop. This must be sterilised before by heating the loop in a Bunsen burner flame until it glows red before use.

Question 94

Identifying Bacteria

Answer 94

• Dip a sterilised inoculating loop into a sample of the bacteria.
• Make 4/5 streaks across one edge of an agar plate (provides a medium for the bacteria to grow).
• Flame and cool the loop.
• Make a second series of streaks by crossing over the firs set, spreading the cells out across a new section of the plate.
• Repeat for a third and four set of streaks.
• Fix the lid with tape but do not seal all the way due to anaerobic conditions often promote the growth of pathogenic bacteria.
• Incubate the plate upside down for several days, allowing the cells to form colonies.

Question 95

Monoclonal Antibodies

Answer 95

Produced from clones of a single white blood cell. All the antibodies are identical and only target one specific antigen. Lymphocytes do not divide easily therefore are fused with myeloma cells (cancerous tumour cells) from the bone marrow which reproduce very quickly. The combination of B-lymphocyte and myeloma cell is called a hybridoma. These cells reproduce to form clones which produce the required antibody (monoclonal antibodies). These are collected and purified to produce the protein monoclonal antibodies.

Question 96

Pregnancy Testing

Answer 96

Pregnant women produce a specific hormone (hCG). Monoclonal antibodies (which are attached to blue beads) bind to the hCG protein when the woman urinates on the stick. If the woman is pregnant the hormone binds to the antibodies, the urine moves up the stick carrying the hormone and the beads, the beads and hormone bind to antibodies on the test strip and become stuck on the strip, turning it blue.

Question 97

Detecting Disease Using Monoclonal Antibodies

Answer 97

Monoclonal antibodies can be used to diagnose cancer when labelled with a radioactive element in order to detect cancers such as prostate cancer. The antibodies are given to a patient through a drip where they enter the blood and carried around the body. They antibodies bind to the to the tumour markers (antigens on the cell membrane of cancerous cells). Using a camera the radioactivity will appear as a bright spot which marks where the cancer is located.

Question 98

Treating Cancers Using Monoclonal Antibodies

Answer 98

An anti-cancer drug is attached to a monoclonal antibody eg. a radioactive substance which stops the cancer from growing. The antibodies are given to the patient through a drip and target the specific cells as they only bind to tumour markers. The drug kills the cancer cells without affecting the normal body cells.

Question 99

Preclinical Trials

Answer 99

-Computer models are used to simulate a human’s response to the drug. The computer software however is not accurate as it is not a living organism.

Question 100

Clinical Trial

Answer 100

• The drug is tested on healthy volunteers to check for unexpected side-effects.
• The drug is then tested on a small sample of volunteers who suffer from the condition to check the effectiveness of the drug. These can last for a long time to check for long term side effects.
• The drug is then tested on a large number of people with the condition to check its effectiveness and to ensure it is safe.
• The drug is then approved if the tests are positive.

Question 101

Placebo Effect

Answer 101

In clinical trials there are two groups of patients. One group is given the drug whereas the other is given a placebo (a substance that looks like the drug but is not). This allows scientists to see if the drug has any effect or the patients simply feel better because they expect the treatment to work). However it is sometimes unethical to use a placebo if the patients in the trial are seriously ill because they do not benefit from the drug.

Question 102

Double Blind

Answer 102

The clinical trials are blind as the patient does not know whether they are receiving the drug or the placebo. In some cases the doctors do not know if the patient has received the drug so that monitoring the patients and analysing the results are not impaired by their knowledge.

Question 103

Smoking

Answer 103

Tobacco smoke contains many harmful substances:

• Tar: toxic chemicals collect in lungs which are carcinogenic. This increases the risk of many cancers due to cell changes that cause uncontrolled growth and division.
• Nicotine: an addictive drug that affects the nervous system. Makes the heart beat faster and narrows blood vessels, increasing the risk of high blood pressure.
• Carbon monoxide: a poisonous gas which attaches to haemoglobin in the red blood cells which reduces the oxygen carrying capacity of the blood. This makes the heart rate increase, which also increases the risk of CVD. If the cardiac muscle does not receive enough oxygen it can lead to a heart attack.
• Other substances: paralyse the cilliated cells in the lining of the bronchi/bronchioles, allowing mucus to flow into the lungs. This causes infections such as bronchitis and a ‘smoker’s cough’.

Question 104

Alcohol

Answer 104

Alcohol is poisonous and is broken down by the liver which produces toxic products. Drinking alcohol over a long period exposes the liver to these toxic substances which can cause death of liver cells, forming scar tissue, which makes the liver less effective. This is cirrhosis. -Ethanol: a drug which affects the nervous system. It is a depressant and slows down the body’s reactions. Long-term or heavy drinkers can experience brain damage such as memory loss and depression.
-Toxic products: the production of these substances damages the DNA which causes cells to divide faster increasing the risk of cancer.

Question 105

Lack of Excercise

Answer 105

Increases the risk of CVD due to increasing the blood pressure. There is more stored body fat and a slower metabollic rate so people are more likely to become obese. There joints are healthier decreasing the risk of athritis and due to lower body mass.

Question 106

Poor Diet

Answer 106

• High food intake: causes obesity which is linked to type 2 diabetes, high blood pressure and CVD.
• Eating food high in salt: causes more water to be absorbed back into the blood which causes high blood pressure increasing the risk of CVD.
• Eating too much saturated fat: increases the blood cholesterol level which can cause fatty deposits to form inside arteries leading to coronary heart disease. This narrows the vessels, restricting blood flow and increasing blood pressure.
• Lack of vitamins/minerals: causes deficiency diseases eg. lack of vitamin C causes scurvy.

Question 107

Cardiovascular Disease (CVD)

Answer 107

A non-communicable disease of the heart and blood vessels.

Question 108

Coronary Heart Disease

Answer 108

Caused by the build up of fatty deposits inside the coronary arteries due to high blood cholesterol levels. The fatty deposits harden forming atheromas which causes atherosclerosis (a hardening and narrowing of the arteries). This eventually restircts blood flow to the heart.

Question 109

Heart Attack/Stroke

Answer 109

CVD can also occur as a result of a blood clot ( a thrombosis) when atheromas break off the blood vessel. The blockage of an artery supplying the heart muscle can cause a heart attack, where the cardiac muscle is deprived of oxygen. If a blockage occurs in a artery supplying the brain it can cause a stroke.

Question 110

Lifestyle Changes to Treat CVD

Answer 110

-Eating less processed foods: reduces salt and saturated fat intake, thus reducing cholesterol levels and high blood pressure. Can also lower risk of type 2 diabetes by eating less sugar.

Question 111

Drug Treatments for CVD

Answer 111

• Statins: reduce blood chloresterol by causing the liver to remove more cholesterol from the blood. Slows down rate of fatty deposits forming.
• Antiplatelets/anticoagulants: reduces heart attack risk by reducing the stickiness of blood platelets making blood clots less likely to form.
• Antihypertensives: reduce blood pressure which reduces risk of atheromas blood clots forming.
• Nitrates: widen blood vessels by relaxing blood vessel walls allowing more blood to flow through at lower pressure.

Question 112

Surgical Treatments for CVD

Answer 112

• Replacing valves that have been damaged by infection/age. This means blood can flow backwards which leads to heart failure if not enough oxygenated blood reaches the heart muscles.
• Widening arteries using stents which keep the arteries open so blood can pass through to the cardiac muscle. Lowers risk of heart attacks for people with CHD. Overtime the artery may narrow again and the stent can irritate the artery and make scar tissue grow. The patient has to take drugs to prevent blood clotting on the stent.
• Coronary bypass surgery allows for part of a blocked vessel to be replaced by a healthy vessel from elsewhere in the body to bypass the blocked section.
• Heart transplant.

Question 113

Organ Transplant

Answer 113

Damaged organs can be replaced with donated organs. The donor organ must match the recipient’s tissue type/blood group otherwise the body will recognise the organ as foreign material and it will be rejected. Immunosuppressant drugs will need to be taken by the recipient for the remainder of their life to reduce the effect of the body’s immune system rejecting the organ, which can make them more susceptible to infections. There are also major risks in surgery of blood clotting, infection and bleeding.

Question 114

Stem Cells

Answer 114

Unspecialised cells that differentiate to become specialised cell types. They can be extracted from early human embryos and be used to replace faulty cells eg. nerve cells for people who are paralysed by spinal injuries.

Question 115

Benefits of Stem Cells

Answer 115

• Can be sourced directly from the patient which reduces the risk of immune rejection because they will have the same antigens.
• Can treat many different diseases when refined such as leukaemia, Parkinson’s disease and athritis.
• Treatment with stem cell’s is less invasive than organ replacements. Could eventually develop to tissues and entire organs for transplant.

Question 116

Disadvantages of Stem Cells

Answer 116

• There are no established success rate as the research is very recent and long-term risks are not yet fully understood.
• Cannot yet develop into larger more complex organs.
• Concerns of injecting rapidly dividing cells (stem cells) could increase risk of cancer.
• Ethical issues of sourcing stem cells from embryos - potentially destroying a life.

Question 117

Gene Therapy

Answer 117

The placement of a fully functioning allele into a cell containing a faulty allele for the same gene.

• The normal allele for the gene is cut out from a donor’s DNA.
• The allele is inserted into the modified virus.
• The virus is injected into the body where it can insert its DNA into the person carrying the disease.
• The introduced gene will be expressed leading to the production of a correctly functioning protein.

Question 118

Benefits of Gene Technology

Answer 118

• Allows for locating genes that may be linked to genetic disorders.
• Developing personalised drugs which make them more effective for people with common genetic variations.
• Developing drugs that target disease-causing genes.

Question 119

Disadvantages of Gene Therapy

Answer 119

• The healthy allele may not be inserted into every cell.
• Treatment may be short-lived as the treated cells are replaced by the patient’s own untreated cells.
• Patients could still pass on their faulty gene to their children as it is illegal to modify gametes.

Question 120

Disadvantages of Gene Technology

Answer 120

• Increased stress because if parents knew they carried a faulty gene which their child may inherit, or the child may grow up worrying over the effect of the disease they may never develop.
• Practical risks of the unknown side-effects and long-term problems gene technology could cause.
• Discrimination by insurers who may charge high prices for insurance for people who are more likely to develop a serious disease.