Biology 1 causes of disease

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1 Causes Of Disease

1.1 - Pathogens

1.2 - Data And Disease

1.3 - Lifestyle And Health

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1.1 Pathogens

Micro organism is a single celled organism (bacteria, Virus)

Pathogens are disease causing micro organisms (bacteria, Virus, fungi)

Disease is a descriptor for symptoms either physical, mental or both

To be considered a pathogen must:    -gain entry to the host

                                                            -colonise the tissue

                                                            -Resist defences

                                                            -cause damage to host tissue

If pathogen is in host and colonises tissue = Infection, If symptoms are visible = Disease

Pathogen transferred from one person to another= transmission

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1.1 Pathogens Cont.

Get into body by body’s interfaces with environment:-breaks in skin

                                                                                    -gas exchange system

                                                                                    -digestive system

There are a number of defences:        -mucous layer in gas exchange surfaces

                                                            -production of enzymes to break down


                                                            -production of stomach acid which kills 


Pathogens affect the body by: -damaging host tissues by inhibiting D/RNA synthesis

                                              breaking down cell membrane    

                                            -produce toxins

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1.2 Data and Disease

Correlation = change in one of two variables is reflected in the other variable

Causal relationship = the change in one factor is certainly due to the change in another Factor

 Is it a coincidence or is there a link

 Looking critically

  •  Has the right factor been measured and have the correct questions been asked
  • How was the data gathered, were the methods reliable, was the right apparatus used?
  • Do those collecting the data have a vested interest in the outcome of the research
  • Has the study been repeated with the same results and conclusions by other people?
  • Are there still unanswered questions?


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1.3 Lifestyle and Health

Risk = “A measure of probability that damage will occur to health as a result of a given hazard”

Aspects of risk are: The probability that a hazardous event will occur

                                The consequences of that hazardous event

Risk measured as percentage (0-100)

Risk needs a timescale

There can be multiple factors that influence risk level







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1.3 Lifestyle and Health Cont.

 Cancer risk factors:

  • Smoking
  • Diet
  • Obesity
  • Physical activity
  • UV exposure

 CHD risk factors:

  • Smoking
  • High blood pressure
  • Blood cholesterol levels
  • BMI
  • Diet
  • Physical activity
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