State what is meant by "pathogen." - answer A pathogen is a microorganism that
causes disease. There are four main types of pathogens: bacteria, viruses, fungi and
protists.
State what is meant by "infection." - answer an infection is the invasion and
multiplication of pathogenic microbes in an individual or population.
State what is meant by "disease." - answer It is a disease when the infection causes
damage to the individual's vital functions or systems.
Describe how a bacterial cell and a virus can make us feel ill. - answer Bacteria are
living cells that can multiply rapidly.
- They live inside the body, releasing poisons called toxins that make us feel ill.
- Sometimes, they directly damage cells.
Viruses are much smaller than bacteria.
- They consist of a fragment of genetic material inside a protein coat.
- They live inside body cells, where they multiply rapidly, eventually causing the cells to
burst.
- These cells are destroyed.
Suggest two reasons why a disease produces symptoms. - answer Symptoms
associated with disease are caused by the way the body responds to the cell damage
and toxins produced by the pathogens.
Outline four ways that a pathogen can be spread. - answer- Air - Droplet infection is
common.
Sneezing, talking and coughing when ill expels droplets full of pathogens from the
breathing system, which others inhale.
- Direct Contact - Kissing, sexual intercourse, touching, breast milk and the placenta.
- Vector - Animals can act as a vector of both plant and animal diseases by carrying a
pathogen between infected and uninfected individuals.
- Water - Eating raw, under-cooked or contaminated food. Drinking dirty water
containing sewage may lead to cholera.
Outline the significance of the work of Ignaz Semmelweis, Louis Pasteur and Joseph
Lister. - answerThe work of Ignaz Semmelweis, Louis Pasteur and Joseph Lister has
helped:
- develop the modern understanding of pathogens
- prevent their spread
- sometimes to cure the diseases they cause.
, Describe the work of Louis Pasteur. - answerLouis Pasteur showed that
microorganisms cause disease. He developed vaccines against diseases such as
anthrax and rabies.
Describe the work of Joseph Lister. - answerJoseph Lister started to use antiseptic
chemicals to destroy pathogens before they caused infection in operating theatres.
Outline the significance of the development of the scientific microscope. - answerAs
microscopes improved, it became possible to see pathogens more clearly, helping to
convince people that there were present.
Give four ways that hygiene can be maintained in order to reduce the spread of
communicable disease. - answer· Washing hands
· Using disinfectants on work surfaces to reduce the number of pathogens.
· Keeping raw meat away from food that is eaten undercooked to prevent the spread of
pathogens.
· Maintaining hygiene of people and agricultural machinery to help prevent the spread of
plant diseases.
Outline three other ways to prevent the spread of communicable disease. - answer-
Someone with an infectious disease must be kept in isolation, to prevent the spread of
pathogens to healthy individuals.
- If vectors are destroyed, such as mosquitoes, the spread of disease can be prevented.
- Vaccination is a successful way of protecting large numbers of humans and animals
against serious diseases.
Describe the work of Ignaz Semmelweis. - answer- Semmelweis noticed that his
medical students went from dissecting dead bodies in the mortuary to delivering babies
without washing their hands.
- Patients being cared for by female midwifery students were less likely to contract the
disease.
- Semmelweis hypothesised that the students were carrying the cause of disease from
the corpses to their patients.
- He insisted that the medical students wash their hands before delivering babies,
preventing the spread of the disease, so fewer mothers died from the child-bed fever.
Outline the importance of cultivating bacteria in a laboratory setting. - answerScientists
need to culture bacteria in order to:
- find out what nutrients they need to grow.
- to investigate which chemicals are most effective in destroying the bacteria cells.
Suggest one substance that is needed to culture microorganisms. - answer- To culture
microorganisms, they need to be given a liquid or gel containing nutrients, known as a
culture medium.
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