IGCSE Revision- Biology
Chapter 10- Diseases and immunity
10.1 Transmission of pathogens
- Pathogen: A microorganism that causes disease
- Many diseases are caused by pathogens that get into our bodies and breed there
- Viruses: influenza, common cold, poliomyelitis, measles, AIDS
- Bacteria: cholera, syphilis, whooping cough, tuberculosis, tetanus
- Protoctists: malaria, amoebic dysentery
- Fungi: athlete’s foot, ringworm
- Host: an organism in which a pathogen lives and reproduces
- Transmissible diseases: a disease that can be passed from one host to another
- Toxin: a poisonous substance; a chemical that damages cells
- Some pathogens cause harm to a cell by producing toxins which spread around
the body
HOW PATHOGENS ENTER THE BODY
- The movement of a pathogen from one host to another is called transmission
- The entry of the pathogen into the body is known as infection
DIRECT CONTACT
- Some diseases are passed on when an infected person is in direct contact with
an uninfected person
- Diseases like this are known as transmissible diseases
INDIRECT TRANSMISSION
- Breathing in droplets containing pathogens
- Touching a surface that someone with the pathogen has touched
- Eating food or drinking water that contains pathogens
- Contact with animal that is carrying pathogens
BODY DEFENCES
- The human body has natural defences against pathogens
- Some of them prevent pathogens from getting to body parts where they can
breed
- Pathogens can get through all of these defences are usually destroyed by white
blood cells
- Skin prevents pathogens from entering the body. If the skin is broken, a blood
clot forms to seal the wound and stops pathogens from getting in
- The stomach contains hydrochloric acids, which kills a lot of the bacteria in our
food
- Hairs in the nose help to filter out particles from the air, which could contain
pathogens
Chapter 10- Diseases and immunity
10.1 Transmission of pathogens
- Pathogen: A microorganism that causes disease
- Many diseases are caused by pathogens that get into our bodies and breed there
- Viruses: influenza, common cold, poliomyelitis, measles, AIDS
- Bacteria: cholera, syphilis, whooping cough, tuberculosis, tetanus
- Protoctists: malaria, amoebic dysentery
- Fungi: athlete’s foot, ringworm
- Host: an organism in which a pathogen lives and reproduces
- Transmissible diseases: a disease that can be passed from one host to another
- Toxin: a poisonous substance; a chemical that damages cells
- Some pathogens cause harm to a cell by producing toxins which spread around
the body
HOW PATHOGENS ENTER THE BODY
- The movement of a pathogen from one host to another is called transmission
- The entry of the pathogen into the body is known as infection
DIRECT CONTACT
- Some diseases are passed on when an infected person is in direct contact with
an uninfected person
- Diseases like this are known as transmissible diseases
INDIRECT TRANSMISSION
- Breathing in droplets containing pathogens
- Touching a surface that someone with the pathogen has touched
- Eating food or drinking water that contains pathogens
- Contact with animal that is carrying pathogens
BODY DEFENCES
- The human body has natural defences against pathogens
- Some of them prevent pathogens from getting to body parts where they can
breed
- Pathogens can get through all of these defences are usually destroyed by white
blood cells
- Skin prevents pathogens from entering the body. If the skin is broken, a blood
clot forms to seal the wound and stops pathogens from getting in
- The stomach contains hydrochloric acids, which kills a lot of the bacteria in our
food
- Hairs in the nose help to filter out particles from the air, which could contain
pathogens
