b2

• Communicable disease

  Disease than can spread between organisms. They are caused by pathogens infecting the organism.
• Non communicable disease

  Disease cannot be passed from one organism to another e.g. cardiovascular disease. They generally last for a long time and progress slowly. They are associated with genetic mutations, lifestyle and environmental factors.
• Ash dieback disease(fungal)

  Some pathogens are carried in the air. E.g. hymenoscyphus fraxineus is a fungus which infects ash trees and causes ash dieback disease. It's transmitted from infected plants through the air, by the wind.
• Influenza (viral)

  Airborne pathogens can be carried in droplets produced when you cough or sneeze - so other people can breathe them in. E.g. influenza virus that causes flu is spread this way.
• Tobacco mosaic disease (viral)

  Some pathogens can be picked up by touching contaminated surfaces. E.g. tobacco mosaic disease affects many species of plants e.g. tomatoes. It's caused by a virus called tobacco mosaic virus (TMV) that makes the leaves of the plants mottled and discolored. The discolouration means the plant can't photosynthesise as well so the virus affects growth. It's spread when infected leaves rub against healthy leaves.
• Athlete foot (fungal)

  Athlete's foot is a fungal disease which affects human - it makes skin on the feet itch and flake off. It's most commonly spread by touching the same things as an infected person e.g. shower floors and towels.
• What is a sexually transmitted infection?

  Disease that are spread through sexual contact.
• HIV (viral)

  HIV is a virus spread by exchanging body fluids. It initially causes flu-like symptoms for a few weeks, but after that, the person doesn't usually experience any symptoms for several years. The virus enters a lymph nodes and attacks the immune cells. If the immune cells isn't working properly, it can't cope with other infections or cancer. After this stage, the virus is known as late stage HIV, or AIDS.
• Malaria ( Protist)

  Animals that spread disease are caused vectors. Malaria is caused by a protist. Part of the malarial protist's life cycle takes place inside a mosquito. Mosquitoes act as vectors - they pick up the malarial protist when they feed on infected animal. Every time the mosquito feeds on another animal, it infects by inserting the protist into the animal's blood vessels. Malaria causes repeating episodes of fever. It can be fatal.
• Crown gall disease (bacterial)

  Some pathogens live in the soil so plants in the contaminated soil may be infected. E.g the Agrobacterium tumefaciens that cause crown gall disease are able to live freely in some soils and on the roots of some plants. If the bacteria enter a plant, they can cause growths or tumours called galls on roots stems and branches. The galls can damage the plant tissue, restricting the flow of water through the plant. This causes the plant to become weaker and die.
• Salmonella (Bacteria)

  Some pathogens are picked up by eating contaminated food. E.g. Salmonella bacteria are found in some foods e.g. raw meat. If these foods are kept too long or not cooked properly, the bacteria can cause food poisoning.
• Whole respiratory tract

  • Lined with mucus and cilia (hair like structure)
  • Mucus traps particles that could contain pathogens
  • Cilia wafts the mucus back up the back of the throat where it can be swallowed
• Skin

  Acts as a barrier to pathogens
• If the skin gets cut

  Pathogens could enter the bloodstream through the wound. This is where platelets come in ...
• Platelets

  • Clump together to 'plug' the wound
  • This is known as blood clotting
  • Blood clots stops you losing too much blood
  • Help to prevent microorganisms from entering the blood
• Chemical defences

  1. Eye produce (in tears) an enzyme called lysozyme, which breaks down bacteria on the surface of the eye.
  2. Saliva produced in the mouth contains molecules which kill pathogens that enter the mouth, so they don't reach the stomach.
  3. The stomach produces hydrochloric acids. This kills pathogens.
• Microbial defences

  1. Some pathogens manage to make it past the saliva in the mouth and the acid in the stomach and enter the gut.
  2. Here they have to compete with the bacteria which naturally live in the gut (intestines) in order to survive.
• What are platelets?

  Platelets are tiny fragments of cells. They contain lots of different substances that are needed to help form the clot. They also have lots of proteins on their surface which help them stick together and to the site of the wound.
• Explain the role of the immune system of the human body in defence against disease

  If the pathogens make it into your body, the immune system kicks in to destroy them. The most important of the immune system is the white blood cells. They travel around in your blood and crawl into every part of you patrolling for pathogens.+
• 3 main functions of the white blood cell

  1. Phagocytostis
  2. Producing antibodies
  3. Producing antitoxins
• Phagocytosis

  Some white blood cells (phagocytes) have a flexible membrane and contain lots of enzymes. This enables them to engulf foreign cells and digest them.
• How do they produce antibodies?

  1. When white blood cells come across foreign antigen on a pathogen, receptors bind to the antigen. The white blood cells then start to produce antibodies which lock onto the antigens of the invading cells. The antibodies produced are specific to the type of antigen.
  2. White blood cells detect the pathogen then divide to produce more copies of the same white blood cell so more antibodies.
  3. Antibodies are produced rapidly and are carried around the body to lock on to all similar pathogens.
  4. Antibodies may disable the pathogen so the phagocytes can engulf them.
• What do memory cells do?

  If the white blood cells are infected again with the same pathogen again, the memory cells will trigger rapid production of the antibodies needed to destroy it before the pathogen causes the disease - the person is naturally immune to the pathogen and won't get ill.
• Explain how the spread of communicable disease may be reduced or prevented in animals

  1. Being hygienic - washing hads regularly to remove pathogens
  2. Sterilising wounds in the skin - this kills microorganisms including pathogens near the wound so stops them from entering the blood.
  3. Living in sanitary conditions - having access to clean drinking water.
  4. Destroying infected animals - prevents them from passing it on.
  5. Isolating infected individuals - prevents spreading
  6. Vaccinations
  7. Contraception
• Reducing or preventing the spread of communicable disease in plants

  1. Regulating movement of plant material

  2. Destroying infected plants

  3. Using sources of healthy seeds

  4. Polyculture (growing different types of plants in a single area at the same time)

  5. Chemical control - fungicides can be used to kill fungal pathogens

  6. Biological control
• Regulating movement of plant material

  Makes sure that infected plants don't come into contact with healthy plants
• Using sources of healthy seeds

  Stops disease from being introduced into the population.
• Polyculture

  • Growing different types of plants in a single area at the same time
  • If a pathogen specific to a single plant enters one plant, it's less likely to infect the neighbouring plants because they are different species
• Chemical control

  Fungicides can be used to kill fungal pathogens
• Biological control

  This is when another organism is used to control a pest or pathogen. For example ladybirds each aphides (insect pest) so ladybirds can be released into an area to reduce aphid numbers. However in some cases, the control organism may become a pest itself and cause my problems.
• Vaccination

  Vaccination involves injecting dead, inactive or weakened pathogen into the body. These carry antigens so even though they're harmless they still trigger an immune response - your white blood cells produce antibodies to attack them. Some of these white blood cells remain in the body as memory cells so if live pathogens of the same type appear, the antibodies that helped destroy them will be produced immediately.
• Pros of vaccination

  Vaccines have helped controls lots of communicable disease that were once common. In the UK (e.g. polio, measles, whooping cough, rubella, mumps). Small pox no longer occurs at all and polio infections have fallen 90%.
• Cons of vaccination

  1. Vaccines don't always work- sometimes they dont give you immunity.
  2. You can sometimes have a bad reaction to a vaccine (e.g. swelling, or maybe a fever or seizures). But bad reactions are very rare.
  3. It can be expensive to make vaccines and carry out vaccination programs - if a disease occurs only very rarely or the vaccination isn't very effective. The cost of carrying out the programme may outweigh any benefits to society.
• Many communicable diseases such as some cancers, cardiovascular disease, some lung diseases, livers diseases are caused by several risk factors interacting with each other. For example lack of excerise and high fat diet are heavily linked to an increased chance of CVD but they can't cause it directly. It's the resulting high blood pressure and high "bad" cholesterol levels that can actually cause it.
• How can exercise affect the risk of non communicable disease?

  1. Exercise increases the amount of energy used by the body and decreases the amount of stored body fact. It also builds muscle which helps to boost your metabolic rate. A higher metabolic rate means that energy from food is used more quickly. So people who exercise regularly are less likely to suffer from health problems like obesity.
  2. A lack of exercise increases risk of CVD because it increases blood pressure.
• Eating too much

  Can lead to obesity
• Obesity

  Risk factor for some cancers. Linked to type 2 diabetes, high blood pressure and CVD
• Too much saturated fat in your diet

  Can increase your blood cholesterol ( LDL ).
• Too much LDL cholesterol in the blood


  Can cause fatty deposits to form inside the wall of arteries which lead to coronary heart diseases
• Malnutrition

  Caused by eating too little. Can lead to issues such as fatigue and poor resistance to infection. Some diseases (called deficiency diseases) can be caused by lack of certain vitamins or minerals.