Biology Unit 1 - Topic 1 - Causes of disease

BIOLOGY UNIT 1

1.Causes of Disease

1.1_Pathogens

• Pathogens are microorganisms.

WHAT IS DISEASE?

• Disease is a description of certain symptoms, not a single ‘thing’.
• Could be physical, mental, or both.
• Disease suggests malfunction in the body or mind resulting in adverse effect on health.

MICROORGANISMS AS PATHOGENS

 To be a pathogen, a microoganism must:

• Gain entry to host
• Colonise tissues of host
• Resist defences of host
• Cause damage to host tissues

• Pathogens include bacteria, viruses and fungi.
• If a pathogen colonises a hosts tissues, infection is the result.
• Disease occurs when infection leads to recognisable symptoms in host.
• When a pathogen is transferred from one individual to another, this is called transmission.

HOW DO MICROORGANISMS GET INTO THE BODY?

·        Pathogens get into the body by penetrating one of the organisms interfaces with environment.

·        One interface is the skin when it is broken. (When unbroken the skin is a thick, continuous layer so is an effective barrier to infection.)

·        Some interfaces have evolved to allow exchange of material so linings here are thin, moist, have a large surface area and are well supplied with blood vessels. This makes for easy entry for molecules, including pathogens.

·        Examples include the gas exchange system – Many pathogens enter here, including ones that cause influenza, TB and bronchitis.

Digestive system – Food and water can carry pathogens into stomach and intestines via mouth, pathogens such as cholera, typhoid and dysentery enter here.

·        To try and prevent entry, body has natural defences:

-Mucus layer covers exchange surfaces and forms thick sticky barrier that’s difficult to penetrate.

-Enzymes break down pathogens.

-Stomach acid kills microorganisms.

HOW DO PATHOGENS CAUSE DISEASE?

Two main ways:

·        Damaging host tissues – sometimes just the number of them by preventing tissues functioning properly. Viruses inhibit synthesis of DNA, RNA and proteins. Many pathogens break down membranes of host cells.

·        Producing toxins – Most bacterial pathogens. Cholera bacterium produces toxin that leads to excessive water loss from lining of intestines.

·        Some diseases like malaria have just one cause, while others like heart disease have a number of causes.

·        How quickly a pathogen causes damage is related to how quickly it divides.

·        Pathogens like those causing gastroenteritis, deivide every 30mins so symptoms become apparent within 24 hours. Gastroenteritis pathogen only causes damage in large numbers.

·        Pathogens such as typhoid bacterium cause harm in small numbers.

1.2_Data and Disease

ANALYSING AND INTERPRETING DATA ON DISEASE

• Epidemiology is the study of the incidence and pattern of disease with a view to finding means of preventing and controlling it.
• Epidemiologists collect data and look for a pattern or relationship between the diseases and various factors in lives of people who have them.

CORRELATIONS AND CAUSAL RELATIONSHIPS

CORRELATIONS DO NOT MEAN CAUSATIONS!!!!!

• A correlation occurs when a change in one variable is reflected by a change in the other.
• This does not however mean that we can say that one change CAUSES the other.

1.3_Lifestyle and health

WHAT IS RISK?

A MEASURE OF THE PROBABILITY THAT DAMAGE TO HEALTH WILL OCCUR AS A RESULT OF A GIVEN HAZARD.

Concept of risk has 2 elements:

-Probability that hazardous event will occur.

-Consequences of that hazardous event.

• These factors affect how we perceive risk, e.g. risk of catching a cold is high, but consequences are minor so we don’t tend to worry much.
• Consequences of being struck by lightening are severe, but unlikely to happen so again, we don’t worry too much.
• When both factors are high = worry.

Risk is measured in %.

Health risks need timescale – telling someone risk of dying is 100% is meaningless, saying their risk of dying in the next month is 100%, has a totally different meaning.

Risk is often relative – Risk is measured by comparing likelihood of harm occurring in those exposed to a hazard with those not exposed to it. i.e. Smokers are 15x more likely to develop lung cancer.

Misleading statistics – reports in media may be misleading as they focus on a single figure, suggesting this figure applies to everyone.

LIFESTYLE CHOICES AND CANCER

Can’t do anything about our genes, or age, but lifestyle can expose us to environmental and carcinogenic factors.

*Smoking – nicotine is a carcinogen, and can affect passive smokers too.

*Diet – What we eat & drink affects risk of contracting cancer.

*Obesity – Being overweight increases risk.

*Physical activity – People who take regular excersise have lower risk from some cancers than those who do not exercise.

*Sunlight – Great exposure to UV rays increase risk of developing skin cancer.

RISK FACTORS AND CORONARY HEART DISEASE

·        CHD is largest cause of death in UK.

·        When combined, 4/5 of the risk factors produce a disproportionately greater risk.

LIFESTYLE CHOICES AND CHD

Can’t control genes age or sex.

But can control:

·        Smoking – Smokers between 2 and 6 times more likely to suffer from CHD.

·        High Blood Pressure – Excessive prolonged stress, certain diets and lack of exercise increase blood pressure and hence risk of CHD.

·        Blood cholesterol levels – Can be kept lower by includning fewer saturated fats and fatty acids in diet.

·        Obesity - BMI of over 25 = increased risk.

·        Diet – High levels of salt raise blood pressure while high levels of saturated fatty acids increase blood cholesterol concentration.

·        Physical exercise – Aerobic exercise can lower blood pressure and blood cholesterol as well as helping to avoid obesity.

Infection- invasion and multiplication of microorganisms in body tissues

Disease-  A disorder of structure or function in a human, animal, or plant, that produces specific signs or symptoms

Transmission- The transfer of a pathogen from one individual to another.

Interface- A point where two systems, subjects, organizations, etc., meet and interact.

RNA- ribonucleic acid; any of a group of nucleic acids, present in all living cells, that play an essential role in the synthesis of proteins.

Geography GLOBAL CHALLENGES - GOING GLOBAL - Globalisation

GLOBAL CHALLENGES

GOING GLOBAL

Globalisation

What is globalisation?

• The word ‘globalisation’ only came into common use in the 1990s – before this, geographers talked about ‘global economy’
• There was growing recognition that economic changes were accompanied by cultural, demographic, political & environmental changes on a worldwide scale.
• Globalisation now used to describe the many ways in which people are becoming more closely linked. Shrinking world.
• Wealth spreading to more people.
• Cultures mixing & becoming more diverse.
• In UK, people consume food, films & music from all over the world.

DOWNSIDES

• Not everyone is happy with free movement across borders, such as that in the EU.
• Issues about how it is possible for goods and resources to move around so easily and yet people still go hungry.
• Everyone looks set to bear heavy costs of environmental impacts.

NOTHING NEW – always been connected?

• Trade – Especially after 1492 - Columbus reached Americas & traditional world economy began to take shape.
• Colonialism – By end of 19^th century, British empire controlled ¼ of the world.
• Cooperation – Since WWI ended in 1918, international organisations similar to UN have existed.

THE DIFFERENCE with modern globalisation

• Lengthening of connections between people and places & products sourced from further afield, e.g. Bottled water from Fiji to UK.
• Deepening of connections to other people and places in more areas of our lives through the products we consume.

Globalisation, population change and migration.

• Demographic changes are an important aspect of globalisation.
• Economic growth tends to trigger increased numbers of people in a region  due to changes in birth rate and death rate and natural increase.
• Changes also result from internal migration of economic migrants.
• Greater levels of international migration are another aspect of the strong influence that globalisation has on population dynamics.
• Push and pull factors.
• Globalisation can concentrate wealth in some places, such as businesses setting up factories in the worlds major cities, this makes them more attractive to economic migrants.
• Rural areas usually modernise in ways that reduce job opportunities such as the mechanisation of farming.
• Mass population movements are generated, some crossing territorial borders.
• In the past, Intervening obstacles such as political barriers often meant migration could not occur, globalisation reduces this however, e.g. the EU member countries can move freely between each other.
• Sometimes, intervening opportunities can interrupt a migration flow e.g. Polish en route to Ireland, may find better work in London.

POPULATION GROWTH OVER TIME

·        Since Europe’s industrial revolution in 18^th century, societies worldwide have seen falling death rates followed by falling birth rates.

·        Modern healthcare

·        Sanitation

·        Nutrition

·        Education

·        Resulting changes in natural increase and population sizes are described by demographic transition model.

·        In most cases, economic growth has been accompanied by a period of pronounced population growth.

·        UK was first country to industrialise – population increased from 5m in 1750 to 40 million by 1900.

·        In China and India, changes are still taking place.

·        High rates of population growth occur when a society’s death rate falls but birth rate does not – benefits of modern health, medicine and food reduce mortality but there is a time lag before preferences for fewer children come into effect. This is the situation in much of Africa.

·        European nations now have near zero population growth.

The evolution of globalisation

·        Many factors are responsible for lengthening and deepening of connections interconnections between places.

·        Some factors are continuations of older processes, such as growth of international air travel, others are entirely new, like the internet.

·        The period we are concerned with begins in 1945, after the second world war, worldwide economic reconstruction began and the international monetary fund (IMF) was set up.

TRANSNATIONAL CORPERATIONS

·        TNCs are firms with bases in two or more countries.

·        They are both makers and sellers of goods and services.

·        ‘Global brands’ such as Coca-Cola, McDonalds and the BBC (which is funded by UK government) have brought both cultural and economic changes to places that their products are made and consumed.

                 TRANSPORT

·        The intercontinental Boeing 747 introduction in 1960s made international travel more common.

·        Expansion of cheap flights sector (easyjet, Ryanair) has brought air travel to the masses in richer nations.

·        Growth in container shipping since 1940s is another factor – around 200 million container movements occur annually.

                 COMPUTER & INTERNET TECHNOLOGY

·        Computers have affected how businesses operate and where they can locate. Computer-aided design and Computer-aided manufacturing (CAD and CAM) have revolutionised manufacturing processes. They help make manufacturing more flexible & less reliant on human labour.

·        ICT allows managers of offices and plants which are geographically distant to maintain communication through e-mail and video conferencing.

·        TNCs able to expand into new territories.

                INTERNATIONAL ORGANISATIONS

·        Grew in power and influence throughout 20^th century.

·        Most important of these ‘brokers’ is the IMF which is based in Washington and channels loans from the worlds richest nations to countries applying for help.

·        Governments that receive loans must agree to run free-market economies open to investment to the outside. This means TNCs can enter more easily.

·        IMF rules&regulations may be controversial , especially structural adjustment programmes (SAPs). E.g. In Tanzania, water services to shanty towns in capital Dar es Salaam were cut off when country had to privatise water services as a condition of receiving $143 million debt relief.

·        Other organisations include the World Trade Organisation (WTO) and the world bank.

·        Non-governmental organisations (NGOs) such as Oxfam and Christian Aid, also have major transglobal influences working to connect people through aid or debt relief.

                 MARKETS

·        On the rise globally.

·        More people living in major world cities have enough wealth to be significant consumers of goods and services.

·        In 2007, China had an estimated 30 million affluent consumers, predicted to become worlds largest market for consumer goods by 2015.

·        Growth of major stock markets has also been an important influence. Since 1945, several new stock exchanges have opened, notably Shanghai.

Globalisation and population movements

• Globalisation may make the world seem borderless.
• People are increasingly thinking of themselves as ‘global citizens’, visiting and relocating to distant places – especially true of the international elite.
•  The elite find few obstacles to prevent them moving between countries for work or residency. There are around 200,000 Americans living in the UK, even though the USA is not part of the EU.
• Internal movements between regions of a country have increased. Large-scale rural-urban migration taking place in many of the worlds poorest and emerging economies on an unprecedented scale. 
• 2 important reasons for this shift^
• TV and radio, books and newspapers can be received in remote and impoverished rural regions in poor countries. Knowledge of other places can trigger migration in the young.
• The Foreign direct investment (FDI) that TNCs make in urban areas of poorer countries boosts employment opportunities on offer, attracting rural migrants.
• While globalisation means easier movement of goods and money, this is not always the case for population migration.
• Since 11 September 2001 (9/11), rich countries have introduced new immigration rules and restrictions.
• It has become harder to gain a visa into the USA.
• Heightened fears of terrorism & national security have accompanied the most recent phase of globalisation.
• The worlds poor continue to gain knowledge of the affluent conditions in rich countries, while their own suffer drought and flood resulting from climate change.
• European policy-makers are toughening their stance towards migration as increasing numbers of refugees from African nations such as Somalia try to cross the Mediterranean into Europe in leaky boats.

Shrinking world - Thanks to technology, distant places start to feel closer and  take less time to reach. Sometimes called ‘time-space compression’.

Birth rate - Number of births per 1,000 people per year in a region.

Death rate - Number of deaths per 1,000 people per year in a region.

Natural increase - Difference between birth and death rate, usually a %. Negative figure suggests deaths exceed births (natural decrease).

Economic migrant - A migrant whose primary motivation is to seek employment. Migrants with jobs may seek better pay or change of career.

Internal migration - The movement of people between regions of the same nation. Hundred have migrated from countryside to cities in recent years.

 

Intervening obstacle -  Barrier to migrant such as political border or physical feature (e.g. Mediterranean sea for North Africans heading to Europe). May include family and travel costs.

Intervening opportunities - An alternative migration destination that exists between migrants origin and intended destination.

IMF - The International Monetary Fund.

Structural adjustment programmes -

Strict conditions imposed on countries receiving loans from IMF and World Bank. Receiving governments may be required to cut back on healthcare, education, sanitation and housing programmes.

World Trade Organisation - The WTO is an organisation that intends to supervise and liberalise international trade.

World Bank - A United Nations agency created to assist developing nations by loans guaranteed by member governments.

Elite -A group of people who are economically and socially powerful. Money may be inherited or entrepreneurial in origin.

Foreign Direct Investment - A financial injection made by a TNC into a nations economy, either to build new facilities or to acquire or merge with an existing firm there.

Rural-Urban migration - A movement of population from rural to urban areas. Typically a young (15-30) migration and often male-dominated, but balanced in Asian nations.

JUST IGNORE THE RANDOM TABLE BELOW - I CAN'T GET RID OF IT. :)

Shrinking world
Birth rate
Death rate
Natural increase
Economic migrant
Internal migration
Intervening obstacles
Intervening opportunities
IMF
structural adjustment programmes
World Trade Organisation
world bank
elite
The Foreign direct investment
Rural-Urban migration