AQA Combined Science Biology Chapter Five


Chapter 5.1

* Health is a state of physical and mental wellbeing.

* Diseases, both comunicable and non comunicable, are all major causes of ill health.

* Other factors include diet, stress, and life situations. All of these factors have a profound effect on both pysical and mental health.

* Different types of disease may, and often do interact.

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Chapter 5.2

* Comunicable diseases are caused by microorganisims called pathogens which include bacteria,viruses, fungi and protists.

* Bactiera and viruses reproduce rapidly inside your body. Bacteria can produce toxins that make you feel ill.

* Viruses live and reproduce inside your cells, causing cell damage.

* Pathogens can be spread by direct contact, by air, or by water.

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Chapter 5.3

* The spread of diseases can be prevented by:

- Simple hygine (Eg, Hand washing)

- Destroying vectors

- Isolating infected individuals

- Vaccination

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Chapter 4.4

* Measles virus is spread by droplet infection. It causes fever and a rash and can be fatal. There's no cure. Isolation of paitents and vaccination prevents spread.

* HIV initally causes flu like illness. Unless it is sucsessfully controlled with the correct drugs  the virus attacks the body's immune cells. Late stage HIV or AIDS occurs when the body immune system becomes so badly damadges it can't deal with other infections.

* HIV is spread by sexaul contact or by exchange of body fluids such as blood, which occurs when drug users share needles.

* Tobacco mosaic virus is spread by contact and vectors. It damages leaves and reduces photosynthesis. There is no treatment. Spread is prevented by field hygine and pest control.

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Chapter 5.5

* Salmonella is spread through undercooked food and poor hygine. Symtoms include a fever, abdominal cramps, diarrhoea, and vomiting caused by the toxins produced by the bacteria. In the uk, poltry are vaccinated against salmonella  to control the spread.

* Gonorrhea is a STD. Symtomps include discharge from the penis or vagina and pain on urination. It's treated using antibiotics, although many strains are now resistant. Using condoms and limiting sexaul partners prevents is spread.

* There are relatively few bacterial diseases of plants but Agrobacterium tumefaciens causes galls.

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Chapter 5.6

* Rose black spot is a fungal disease spread in the enviroment by wind and water. It damages leaves so they drop off, affecting growth as photosynethesis is reduced. Spread is controlled by removing affected leaves and by using chemical sprays, but this isnt effective.

* Malaria is caused by parastitc protists and is spread by the bite of female mosquitoes. It damages blood and liver cells, causes fevers and shaking, and can be fatal. Some drugs are effective if given early butthe protists arebecoming resistant. Spread is reduced by preventing the vectors from breeding and using mosquito nets to prevent people from being bitten.

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Chapter 5.7

* The body has several lines of defense against the entry of pathogens. These include the skin (barrier and antimicrobial), The nose, the trachea, the bronchi, and the stomach.

* Your white blood cells help to defend you against pathogens by ingesting them and by making antibodies and antitoxins.

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