Biology: Classification

Explain the meaning of the term species

- members of a population that can interbreed

- to produce fertile offspring

- they occupy a particular niche

Methods of determining the species which can be used to interbreed

- Morphological - structural features (easiest and quickest to compare but can not cataegorise based on this alone)

- Physiological - they way the body works

- Biochemical - includes the sequence of bases in DNA and the sequence of amino acids in proteins

- Behavioural

Classification: the process of sorting living things into groups

Taxonomy: the study of the principles of classification

Phylogeny: the study of the evolutionary relationships between organisms

Why do we classify things?

• To put things in order to sort them out
• there are nearly 2 million different species of living organisms
• Each species must be placed in a group of similar organisms
• It is for our convenience
• to make the study of living organisms more manageable
• to make it easier to identify organisms
• to help us see the relationship between the species

Classification

Domain        Eukaryotae       Few feautures in common

Kingdom      Animalia            members show more diversity

Phylum        Chordata

Class            Mammalia

Order           Primate

Family          Hominidae

Genus          Homo

Species        Sapiens              more features in common - member shows similarities 

Taxonomy

• A 'taxon' is a unit of classification
• A 'species' is the smallest taxon = basic unit of classification
• Groups of similar species form the next taxon 'genus'
• Groups of similar genera form a 'family'
• Etc. up to the largest taxon, domain.

Difference between phyla are major - easy to decide which one organisms belong to

Chordata - central bundle f nerves running along back

Arthropods - have hard exoskeleton

                 - are subdivided into classes e.g. class insects

The species are classified based on the evolutionary relationships, they are grouped together based on shared, homologous features

These features are similar enough that they have to come forma  similar design e.g. vertebrates have similar limb bones, 1 bone in upper limb, 2 bones in lower limb

AS Biology F212: Smoking and Heart Disease

Cigarette smoke contains over 4000 different chemicals, many of them are toxic. Three main components posing a danger to human health: Tar, Carbon Monoxide and Nicotine.

Tar

• Tar coats the airways and alveoli
• it can cause allergic reactions which narrows the airways
• it also destroys the cilia on the surface
• mucus cannot be moved
• tar stimulates production of extra mucus
• bacteria get stuck in the mucus and multiply in the airways
• the smoke has an increased risk of infection

• chronic bronchitis
• this is the disease caused by the inflammation of the airways
• accompanied by mucus collecting in the lungs
• symptoms
• irritation
• continual coughing
• coughing up mucus
• risk of lung infection
• long term effects
• frequent infections damages the lining of lungs
• white blood cells are attracted
• have to make their way from blood to airways
• use enzymes to dissolve their way through
• elastase enzyme dissolved the elastic tissue
• airways no longer recoil properly
• bronchioles collapse trapping air
• alveoli burst due to pressure of trapped air 

• Emphysema
• disease caused by alveoli bursting
• lungs have less surface area
• so can do less gas exchange
• healthy lungs contains large quantities of elastic tissue, mostly made up of the protein elastin.
• this tissue stretches when we breathe and in and springs back when we breathe out.
• in emphysematous lungs, the elastin has become permanently stretched and the lungs no longer able to force out all the air from the alveoli
• the surface area of the alveoli is reduced and they sometimes burst
• as a result, little if any exchange of gases can take place across the stretched and damaged air sacs.
• symptoms
• shortness of breath - results from difficulty in exhaling air due to the loss of elasticity in the lungs
• if the lungs cannot be empties much of their air, then it is difficult to inhale fresh air containing oxygen so patient feels breathless
• the smaller the alveolar surface area leads to reduce levels of oxygen in the blood and so patient tries to increase oxygen supply by breathing more rapidly
• chronic coughs - consequence of lung damage and the body's effort to remove the damaged tissue and mucus that cannot be removed naturally because the cilia on the bronchi and  bronchioles has been destroyed
• bluish skin colouration is due to low levels of O2 in the blood as a result of poor gas diffusion in the lungs

• Asthma
• common allergen which can trigger an asthma attack: pollen, dust mites, mould, pet dander
• asthma is an example of localised allergic reaction
• it can also be triggered or made worse by a range of factors, including air pollutants e.g. sulphur dioxide) exercise, cold air, infection, anxiety and stress.
• one or more of these allergens causes white blood cells on the lining of the bronchi and bronchioles to release a chemical called histamine
• effects of histamine - the lining of these airways become inflamed
• the cells of the epithelial lining secret larger quantities of mucus and enter the airways
• the muscle surrounding the bronchioles contracts and so constrict the airways.
• symptoms:
• difficulty in breathing - due to constriction of bronchi and bronchioles, their inflamed linings and the additional mucus and fluid within them
• a wheezing sound when breathing is caused by air passing through the very constricted bronchi and bronchioles
• a tight feeling in chest - consequence of not being able to ventilate the lungs adequately because of constricted bronchi and bronchioles
• coughing - reflex response to obstructed bronchi and bronchiole in effort to clear them

Chronic obstructive pulmonary disease

• combination of diseases including emphysema, chronic bronchitis and asthma

Lung Cancer

• cancers are caused carcinogens
• cigarette smoke contains many carcinogens
• carcinogens are present in tar
• they enter the cells of the lungg tissue
• they mutate the DNA in their nuclei
• if the gene for the cell division is mutate then uncontrolled cell division takes place - this is cancer
• lung cancer can take up 20-30 years to develop to a size to cause problems
• symptoms
• coughing up blood
• persistent cough
• weight loss
• shortness of breath
• chest pains
• Nicotine and Carbon monoxide
• these two chemicals can be absorbed in the lungs and enter the blood
• here they cause cardiovascular disease
• Nicotine
• causes addiction
• causes release of adrenaline
• thus increased heart and breathing rate
• increased force of contraction of the heart
• constriction of arterioles
• hypertension
• increases stickiness of platelets
• chance of thrombus (clotting)
• increased blood cholesterol and LDLs
• Carbon monoxide
• combine with haemoglobin
• forms carboxyhaemoglobin
• haemoglobin has higher affinity for CO than O2
• this is irreversible
• reduces O2 carrying ability of haemoglobin
• decrease in oxygen transported
• tissues starved of oxygen
• also damages lining areteries

Cardiovascular Disease

• atherosclerosis
• nicotine and CO damages artery walls
• hypertension contributes to the damage
• this attracts phagocytes to repair the damage
• these encourage the growth of smooth muscles and deposition of fatty substances
• fatty deposits are laid down when repaired including cholesterol
• these atheromas form plaques
• these narrow artery
• also make it rougher
• this reduced blood flow
• thrombosis
• blood flows slower past plaques
• combined with stickier platelets from nicotine - blood clots can form
• these block narrow arteries
• this may result in formation of blood cot, or thrombus, in a condition aka thrombosis
• this thrombus may block the blood vessel, reducing or preventing the supply of blood to tissues beyond it
• the region of tissue deprived of blood often dies as a result of the lack of oxygen glucos and other nutrients blood normally provides
• embolism is when the thrombus is carried from its place of origin and blocks another artery
• coronary heart disease
• when the atherosclerosis occurs in the coronary arteries and reduces/stop oxygen supply to the cardiac muscle for respiration
• Angina: severe chest pain due to lack of oxygen
• Heart attack: death of part of the heart muscle due to a blockage of artery
• Heart failure: heart stops pumping due to lack of oxygen by a blockage of major coronary artery
• Risk factors
• age - older 
• sex - male
• diet high in saturated fats causes more LDLs
• plaque formation
• blood cholesterol 
• high salt intake
• hypertension
• low fibre
• obesity
• heavy alcohol consumption
• and more
• stroke
• death of part of the brain
• due to blood clot forming in artery supplying brain
• artery supplying brain bursts (aneurysm)
• aneurysm
• atheromas that lead to the formation of a thrombus also weaken artery walls
• these weakened points swell to form a balloon-like blood filled structure -  aneurysm
• frequently burst leasing to haemorrhage and therefore loss of blood to the region of the body served by that artery
• a brain aneurysm is know as a stroke

Cardiovascular diseases

• great cause of premature death
• CHD and stroke often result from atherosclerosis
• this can start in adolsescence

Treatment

• is expensive
• long term drug treatment to reduce blood pressure and cholesterol
• surgery
• therefore reduction in atherosclerosis through the reduction of risk factors is important

immunity

Person gets a splinter
- triggers a non specific inflammatory response in the region on puncture
- histamine chemical is released
- dilate the capillary in diameter and it becomes leaky
- tissue around the splinter becomes red and swollen as plasma leak in tissues

Damaged or infected tissue release proteins and other chemicals
- attracts phagocytes to the area
- advantage of leaky capillaries - white blood cells (phagocytes/neutrophils) leave capillaries easily
- phagocytes engulf the dead cell and bacteria

Cells of the immune system

• All orignate from the bone marrow
• All are leukocytes = white blood cells
• 2 main groups:
• phagocytes - neutrophils an macrophages
• lymphocytes - B and T lymphocytes
• Phagocytes - engulfs dead cells and invading micro-organism
• Neutrophils
• short live
• smaller than macrophages
• travel around the body in the blood
• squeeze through walls of capillaries
• have a lobed nucleus
• Monocytes/macrophages
• large and long lived
• circulate in blood as monocytes which then settles in organs such as lungs lymph nodes
• develop into macrophages that remain in the organ
• remove foreign matter from organs
• initiate specific immune response

Immune system

2 Parts:

• Non specific immunity
• 2nd line of defence
• immediate attack against a variety of 'attackers'
• present from birth
• does not distinguish between different pathogens
• same response each time
• e.g. phagocytosis (engulfing) and inflammation
• specific immunity
• 3rd line of defence
• body's response is tailored for a specific 'attacker'
• involves lymphocytes and antibodies
• response is slow when it meets the pathogen for the first time
• involves white blood cells particularly B lymphocytes which produce chemicals called antibodies which target specific pathogens

Antigens

• all cells have surface markers called antigens
• antigens are molecules that stimulate an immune response causing the production of antibodies 
• antibodies are specific to antigen
• the body can recognise antigen as self or non-self (foreign)
• our own antigen do not stimulate a immune response

Antibodies

• Y shaped molecules
• made of 4 polypeptide chains held together by disulphide bridges
• 2 identical short or light chains
• 2 identical long or heavy chains
• consists of two regions
• constant region - same in all antibodies
  enables antibodies to attach to phagocytes and helps in the process of phagocytosis
• variable region, differs from one type to another - result of amino acid sequence which is complementary to shape of antigen
• hinge region allows the molecule to bend so the branches of the Y shaped molecule can move further in order to allow attachment to more than one antigen

Lymphocytes

• involved in specific immune response
• have a large nucleus which fills most of the cell
• 2 types:
• B lymphocytes
• matures in the bone marrow
• T lymphocytes
• mature in the Thymus gland
• both must be mature before they can take part in the immune response.
• during maturation both B and T lymphocytes  develop receptors on their cells surface membrane.
• these specific receptors are able to combine with specific antigen in much the same way that an enzyme combines with a specific substrate
• Humans can produce several million different types of B and T cells (initially only a few of each types)
• B and T cells circulate between the blood and lymph so are distributed around the body where they may come in contact with antigens

Maturation of B and T cells

• In the bone marrow immature B and T cells divide by mitosis
• B cells matures in the bone marrow
• mature B cells each with a different antibody receptor on cell membrane
• T cells mature in the thymus
• mature T cells each with a different T cell receptor on the membrane

B lymphocytes

• many different types of each capable producing an antibody (=protein) that acts against a particular antigen
• when a pathogen enter the body, B cells with the appropriate receptors bind to the antigens = clonal selection.
• causing them to divide rapidly by mitosis to form a large clone of identical cells = clonal expansion.
• The selected B cells differentiate into 2 types of cells
• plasma cells
• produce antibodies, several thousand/second
• antibodies are secreted into the blood
• plasma cells are short lived (several weeks)
• memory cells
• long live (several years)
• remain dormant in the blood
• ready to respond immediately to further attacks by antigen
• providing an immunological memory.

The cells of the immune system originates from bone marrows where stem cells divide by mitosis to produce cells that differentiate into lymphocytes and phagocytes. Immature T lymphocytes migrate to the thymus gland where they mature. Mature B lymphocytes and mature T lymphocytes circulate and enter lymph nodes. During an immune response some B lymphocytes differentiate into plasma cells and secrete antibodies.

AS Biology F212: Vaccines

A vaccine is a preparation containing antigenic material (e.g. antigens)

Vaccination confers artificial active immunity. (Entry of antigenic material into the body stimulates an immune response, memory cells are produce)

Types of vaccination

1. Live vaccine e.g. Smallpox
   The live vaccine - less harmful pathogen but with similar antigens and can still be induce active immunity
2. Harmless vaccine e.g. measles, TB
   Harmless or attenuated version of the pathogen
3. Dead vaccine e.g. Cholera vaccine
   the pathogen has been killed either by exposure to or chemicals
4. Antigens e.g. hepatitis B
   Preparation of antigens from a pathogen
5. Toxoid vaccine e.g. tetanus
   vaccine consists of harmless form of toxin produced by the pathogen

Herd vaccination

• providing immunity to almost all of the population at risk
• with enough people immune the disease cant spread
• level of immunity needed varies depending on the disease (80-85% for small pox, 95% for measles)

Ring vaccination

• used when a  new case s reported
• vaccinate everyone in the immediate vicinity (house, village, or town)

AS Biology F212: Immunity

Primary defences

• These prevent the pathogen from entering the body
• These mechanisms have evolved through selection and are considered as adaptations

Barriers to entry

• The skin
• the skin covers the body surface providing a physical barrier that most pathogens find hard to penetrate
• Keratinocytes
• cells produced by mitosis at the base of the epidermis
• they migrate to the skins surface
• they dry out and the cytoplasm is replaced by keratin = keratinisastion
• this prcess take about 30 days
• by the time they reach the surface they are dead and everntally slough off
• Mucous membrane
• produced by the epithelial layer traps pathogens
• epithelial layer contains goblet cells
• these produce mucus that lines the airways trapping pathogens
• ciliated cells move the mucus up the oesophagus so it can be swallowed
• pathogens are killed by the acidity of the stomach (pH 1-2) which denatures their enzyme
• Mucus membranes are also found in the gut, ears and nose
• Hydrochloric acid in the stomach provides a low pH that the enzymes of most pathogens are denatured and therefore the organisms are killed

Secondary Defence

• Phagocytes (non-specific)
• Neutrophils - most common
• have multi-lobed nucleus and are produce in the bone marrow
• they are found in the blood and tissue fluid and may also be found on epithelial surfaces such as the lungs
• short lied but are released in large numbers
• Macrophage - larger than neutrophils
• manufactures in the bone marrow
• travels in the blood as monocytes
• they tend to settle in the body organs particularly the lymph nodes
• here they develop into macrophages
• they plan an important part in specific response to pathogens
• The role of macrophages
• infected cells release histamine
• this attract neutrophils
• it also causes capillaries to become more leaky
• as a result more fluid leaves the capillaries in the area of infection
• so more fluid passes the lymphatic system
• this leads the pathogen towards the macrophages in the lymph nodes
• How phagocytes work
• they engulf and destroy pathogenic cells
• these have chemical markers on their outer membranes = antigens
• these are recognised as non-self or foreign
• these are specific to pathogen
• Phagocytosis
• once bound the phagocytes envelopes the pathogen by folding its membrane inwards
• the pathogen is trapped within a phagosome
• lysosome fuse with phagosome and release enzymes lysins
• these digest the pathogen producing harmless products that can be absorbed

Specific immune response

T and B lymphocytes

• these have receptors that are complementary to the foreign antigen
• this antigen may be attached to the pathogen or on the surface of the host cell
• when antigen is detected, the lymphocyte is activated

"Describe the changes that occur to T lymphocytes during an immune response. Explain the roles of T lymphocytes in fighting infection by a pathogen, such as a virus"

• reference to antigen presentation - described
• receptors on T cell surface or complementary to the antigen
• reference to specificity in context of T cells
• clonal selection - described
• clonal expansion/T cells divide by mitosis
• T helper cells release cytokines
• stimulates B cells to divide/clone/differentiate
• stimulate macrophage to carry out phagocytosis
• T/Killer cells search and kill infected host cells
• secrete enzymes
• named enzyme
• active immunity
• memory T cells/immunological memory
• secondary response - more rapid

Antigen

• Usually large proteins or glycoproteins
• specific shape
• the antigen is specific to the pathogen
• a foreign antigen stimulates the production of antibodies = an immune response
• there is one type of antibody for one type of antigen

Antibodies

• produced by lymphocytes (WBC)
• are large proteins also known as immunlglobulins
• they have specific shape tat is complementary to particular antigen
• these antibodies are specific to the antigen
• therefore the antibody is specific to the pathogen
• antibodies attach to antigens and render them harmless

Antibody structure

• the constant region is the same on all antibodies
• this allows the attachment of phagocytic cells during phagocytosis 
• the variable region has a specific shape and differs from one type of antibody to another
• this is due to its amino acid sequence
• this makes it complementary to a particular antigen
• this allows it to bind to the antigen
• the hinge region allow flexibility 

Antigens, antibodies and phagocytosis

• the presence of a foreign antigen can trigger the production of antibodies
• antibodies (proteins) in our blood attach to foreign antigens (antigen-antibody complex)
• phagocytes have membrane bound receptor proteins
• these can bind to the antibody antigen complex
• allows the recognition of the pathogen

How antibodies work - neutralisation

• the antigen in the pathogens cell surface membrane may be used as a binding site
• this would allow it to bind to host cells
• if the antibody blocks this binding site then the pathogen cannot bind to the host cell
• this is called neutralisation 

Agglutination

• some antibodies are larger than those previously described
• they resemble several Y shaped molecules attached together with many specific variable region
• each one can bind to an antigen on a pathogen
• the attachment to many pathogens at the same time is called agglutination
• the pathogens cannot enter host cells

Producing antibodies

• Infection = antibody production
• It takes a few days before antibody levels are high enough to successfully combat the infection
• This is the primary immune response
• antibodies do not stay in the blood
• if the body is infected a second time by the same pathogen, the antibodies must be made again
• however, the production is faster and the concentration is higher
• this is the secondary immune response

Communication between cells

Cell signalling

• Communication is achieve through sell surface molecules and through the release of hormone like chemicals called cytokines
• the target cell must have a cell surface receptor

What information is communicated

• Identification - the pathogen carries antigen that identify it as foreign 
• Distress signals - these are produce when a cell becomes infected by a pathogen
• lysosomes breaks down the infecting pathogen
• parts of the pathogen end up attached to the host cells plasma membrane (antigen presentation)
• these can act as a distress signal that can be detected by other cells
• or they can act as markers so the infect host cell can be destroyed by T killer cells
• Antigen presentation
• macrophages engulf pathogens by phagocytosis
• they do not fully digest them
• they incorporate the antigen into their cell surface membrane 
• they become known as antigen-presenting cells
• its function is to find the lymphocyes that can neutralise that particular antigen
• Instructions
• chemicals called cytokines act as instructions to target cells
• they bind to specific receptors
• this causes the release of second messengers inside the cells
• e.g. macrophages release monokines to attract neutrophils
• macrophages release monokines to stimulate B lymphocytes to release antibodies
• T and B lymphocytes release interleukins which stimulate the proliferation and differentiation of T and B lymphocyte
• Many cells release interferon which can inhibit virus replication and stimulate killer T cells

AS Biology F212: Malaria

Malaria is caused by the protoctist Plasmodium. The vector for malaria is female Anopheles mosquitoes

Transmission

• Mosquitoes takes a blood meal from an infect person who has the parasites in their blood
• Then they feed on an uninfected person
• The parasites are present in the saliva of the mosquito
• Causes of illness
• red blood cells break open and release parasites into the bloodstream
• the person then has symptoms such as chills, fever and headache.
• then the person starts sweating and their body temperature falls
• cycle of symptoms repeats every 48 to 72 hours, following the life cycle of the parasites
• each cycle worsens the person's anaemia or lack of red blood cells
• less and less oxygen reaches the brain and other organs
• so the symptoms are:
• fever, anaemia, headaches, shivering, sweating, nausea

Distribution

• Fighting malaria
• best method of prevention is to get rid of the mosquitoes
• either use insecticides or get rid of breeding grounds
• some success with this method - malaria eliminated from some parts of the world
• Difficulties
• Mosquito - can become resistant to insecticides and chemicals used to contorl
• they breed very quickly
• breeds in the smallest bodies of water
• especially in rainy seasons of tropics
• difficult to drain water to prevent egg laying
• increasing areas with global climate change
• Plasmodium
• drugs are used to fight it but they can also ecome resistance to drugs
• people do not take the drugs for a long period of time so it comes back
• different strains (4 specials)
• different stages to life cycle
• complex organism so difficult to target drugs
• inside the RBC and liver cells - hard to get them as they are inside delicate cells
• No vaccine

AS Biology F212: Disease

Health is a state of mental, physical and social wellbeing - NOT just absence of diesease.
If one is in good health they are:

• able to carry out normal mental and physical tasks
• well fed with a balanced diet
• usually happy with a positive outlook
• suitably housed with proper sanitation
• well integrated into society
• free from diseases

What is disease?

• Disease is a departure from good health caused by malfunction of the mind or body
• symptoms can be physical, mental or social
• those caused by living organisms are called infectious diseases - usually physical 

Parasites and Pathogens

• Parasites
• Live on (external) or in (internal) another living thing (host)
• they cause harm to the host by taking nutrients
• they may live all or part of their life on the host
• they can overburden the host and make it more susceptible to secondary infections
• Pathogens
• this is an organism that causes disease
• they live by taking nutrition from their host and cause damage in the process
• includes a wife range of bacteria, fungi, protoctist and viruses

• Bacteria - cholera
• caused by bacterium Vibrio cholerae
• it is a water-borne disease and spreads through contaminated water, food or shell fish
• they act on the walls of the small intestine causing diarrhoea, dehydration and weakness.
• Tuberculosis
• aka TB is an infectious disease that can affect any part of the body although it is usually found n the lungs as these are the first site of infection
• it kills approx 2 million people each year - more than any other infectious disease
• tuberculosis is caued by one of two species of rod shaped bacteria
• Mycobacterium tuberculosis
• Mycobacterium bovis
• Fungi - Athletes foot and ringworm
• Caused by Tinea fungus
• many different species that causes these diseases
• they live in the skin
• cause redness and severe irritation
• Viruses - TMV and HIV
• TMV - tobacco mosaic virus - affects plants
• HIV - human immunodeficiency virus - affects humans 
• also more common diseases such as colds and flu.
• take over the cells genetic machinery and organelles to allow it to reproduce
• Protosctist
• Amoeboid dysentery 
• Malaria
• enter cells and feed on the contents as they grow

TRANSMISSION OF DISEASE

For a micro-organism to be considered a pathogen they must

• travel from one host to another
• gain entry to the host's tissues
• reproduce
• resist the defences of the host
• cause damage to the host's tissues

Forms of transmission

• by the means of a vector (carrier)
• by physical contact
• by droplet infection

• Malaria
• caused by eukaryotic Plasmodium
• Plasmodium falciparum is the most common
• spreads by the female Anopheles mosquito
• these feed on blood
• the parasite lives in the red blood cells and feed on the haemoglobin
• HIV/AIDs
• The HIV virus enters the body and may remain inactive
• This is known as being HIV positive
• once active, the virus attacks and destroys T helper cells in the immune system
• these cells help to prevent infection
• their destruction reduces the person's ability to resist infection
• EFFECT
• you are unable to defend yourself against any pathogen that enters your body
• these are known as opportunistic infections
• it is the effect of these that eventually kills as person with HIV
• AIDS stands for acquired immune deficiency syndrome
• Transmission
• Exchange of bodily fluids such as blood-to-blood contact
• unprotected sex
• unscreened blood transfusions
• use of unsterislised surical equipment
• sharing hypodermic needles
• accidents such as 'needle-stick'
• across the placenta or during childbirth
• from mother to baby during breast feeding
• Tuberculosis (TB)
• TB is an infectious disease that can affect any part of the body although it is usually found in the lungs as these are the first site of infection
• Pulmonary tuberculosis is spread through the air by droplets containing the bacteria, released into the air when infected individuals cough, sneeze or even talk.
• normally takes close contact with an infected person over a period of time rather than a causal meeting in the street to transmit the bacteria
• Symptoms (droplet infection)
• the symptoms of pulmonary tuberculosis initially include a persistent cough, tiredness, and loss of appetite that leads to weight loss.
• As the disease develops, fever and coughing up of blood may occur
• Risks
• some groups are at greater risks of contracting TB than others.
• people who are in close contact with infected individuals over long period e.g. living and sleeping in overcrowded conditions
• work or reside in long term care facilities where relatively large numbers of people live close together e.g. old people's home, care homes, hospital or prisons
• people from countries where TB is common
• have reduced immunity such as
• the very young or very old
• those with AIDS
• people with other medical conditions that make the body less able to resist disease e.g. diabetes, or lung disease such as silicosis
• those undergoing treatment wit immunosuppressant drugs eg. following a transplant surgery
• the malnourished
• alcoholics or injecting drug-users
• the homeless

The World Health Organisation (WHO)

• WHO states that good health is a human riht
• poor health causes a lot of suffering
• Ill health has an economic cost as a result of medical provision and loss of productivity
• worldwide, many peopl have no access to the basic requirements for good health
• contributing factors
• poverty
• lack of proper shelter
• lack of purified water
• poor nutrition
• poor hygiene
• lack of government investment
• poor/inadequate education on disease, it causes and transmission
• civil unrest or warfare

• Malaria
• kills around 3 million people peryear
• about 300 million are affected worldwide
• it is limited to were the vector (Anopheles mosquito) can survive
• 90% of sufferers live in sub-Saharan Africa
• It is difficult to control
• mosquito
• resistant to insecticides/pesticides/chemicals used for control
• build up in food chains/kill predators
• breeds quickly/very common/lays many eggs
• breeds in small bodies of water/inaccessible places
• especially in rainy seasons
• difficult drain/spray/cover
• difficult to encourage everyone to use netswide range of increasing because of climate change
• rests and hides in houses
• Plasmodium
• side effects of (e.g. anti-malarial) drugs/people don't take drugs long enough (think they are well but not)
• many strains and species
• resistant to drugs
• inside red blood cells or liver cells
• antigen concealment
• dormant/in body for a long time/symptomless carriers/long incubation
• different stages in life cycle in the body
• no vaccine/difficult to develop vaccine
• people lose immunity if malaria is eradicated
• HIV/AIDS
• Spreading in pandemic proportions (is an epidemic of infectious disease that is spreading through human populations across a large region)
• 45 million people living with HIV/AIDS at the end of 2005 (>half in sub-Saharan Africa)
• 5 million newly infected each year
• at the end of 2006 30 million died as result of HIV/AIDS related disease
• Epidemiology
• = patterns in the occurrence of the disease in the human population 
• it identifies the cause of a disease
• the risk factors associated with the disease
• determines the incidence of a disease
• determines the prevalence of the disease as well as the mortality and morbidity
• study how quickly it's spreading
• identify countries/part of population at risk
• identify a disease as endemic, epidemic or pandemic
• ENDEMIC: always present in a population
• EPIDEMIC: spreading rapidly to a lot of people over a large area
• PANDEMIC: a worldwide epidemic
• they target education programmes at people at most risks
• target advertisements to raise the awareness
• target screening programmes to identify individuals at risk
• provide specialist healthcare in certain areas
• provide vaccination programme for the major disease
• targeting research to find cures for the major disease