4.3 Infection and response – Biology notes
4.3.1 Communicable diseases
4.3.1.1 Communicable (infectious) diseases
Health is the state of the physical and mental wellbeing of an organism
Factors like … have a big effect on our health:
o Diet
o Stress
o Life situations – gender, financial status, ethnic group, levels of free health, № of
kids, local sewage and garbage disposal
Pathogens are microorganisms that enter the body and cause infectious diseases
The cause communicable (infectious) diseases – those that can be easily spread
They depend on their host to provide the conditions and nutrients that they need to grow
and reproduce
Pathogens can be bacteria, viruses, protists and fungi
They frequently produce toxins that damage tissues and make us feel ill
Both plants and animals can be infected by pathogens
Pathogens can spread in many ways:
o Water – drinking or bathing in dirty water (e.g. cholera)
o Air – pathogens can be carried in the air by droplets (from other individual’s
cough/sneeze) and can be breathed in (e.g. influenza)
o Direct contact – pathogens can be picked up by touching contaminated surfaces like
skin or unprotected sex (e.g. HIV)
The disease can be prevented by limiting the spread of pathogens:
o Hygiene – mosquito nets, disinfectant, washing hands, protective clothing
o Vaccination
o Isolation/quarantine
o Destroying vectors – insecticides, nets
4.3.1.2 Viral diseases
Viruses are much smaller than cells
Like bacteria, they reproduce rapidly
They live inside the cells and replicate themselves using cells’ machinery to produce many
copies of themselves, the cells would usually burst afterwards, releasing all the new viruses
The cell damage is what makes you feel ill
Measles:
o A highly contagious viral disease
o Spread by droplets from an infected person’s sneeze or cough
o Symptoms: red skin rash, fever
o With complications can be very serious or even fatal
o Can be prevented by being vaccinated and quarantine
4.3.1 Communicable diseases
4.3.1.1 Communicable (infectious) diseases
Health is the state of the physical and mental wellbeing of an organism
Factors like … have a big effect on our health:
o Diet
o Stress
o Life situations – gender, financial status, ethnic group, levels of free health, № of
kids, local sewage and garbage disposal
Pathogens are microorganisms that enter the body and cause infectious diseases
The cause communicable (infectious) diseases – those that can be easily spread
They depend on their host to provide the conditions and nutrients that they need to grow
and reproduce
Pathogens can be bacteria, viruses, protists and fungi
They frequently produce toxins that damage tissues and make us feel ill
Both plants and animals can be infected by pathogens
Pathogens can spread in many ways:
o Water – drinking or bathing in dirty water (e.g. cholera)
o Air – pathogens can be carried in the air by droplets (from other individual’s
cough/sneeze) and can be breathed in (e.g. influenza)
o Direct contact – pathogens can be picked up by touching contaminated surfaces like
skin or unprotected sex (e.g. HIV)
The disease can be prevented by limiting the spread of pathogens:
o Hygiene – mosquito nets, disinfectant, washing hands, protective clothing
o Vaccination
o Isolation/quarantine
o Destroying vectors – insecticides, nets
4.3.1.2 Viral diseases
Viruses are much smaller than cells
Like bacteria, they reproduce rapidly
They live inside the cells and replicate themselves using cells’ machinery to produce many
copies of themselves, the cells would usually burst afterwards, releasing all the new viruses
The cell damage is what makes you feel ill
Measles:
o A highly contagious viral disease
o Spread by droplets from an infected person’s sneeze or cough
o Symptoms: red skin rash, fever
o With complications can be very serious or even fatal
o Can be prevented by being vaccinated and quarantine
