Spec Led Biology Revision
Chapter 10 - Disease of Animals and Plants
THE HUMAN BODY AS A HOST
The Human body is rich in nutrients for a variety of organisms
Some organisms are TEMPORARY visitors:
• Mosquitoes and bed bugs
Some organisms are PERMANENT visitors:
• Bacteria and external parasites
• Some parasites breach our defences and enter the bloodstream and then spread throughout the
body.
• Some of these are extracellular parasites living on the surfaces of cells or in the spaces between
cells
• Many, including all the viruses that infect us, are intracellular parasites, since they can enter
cells, survive and produce.
• Some of these organisms are obligate parasites, because they cannot exist as free-living
organisms
PATHOGENS AND COMMUNICABLE DISEASES
Parasites:
• Live inside or on the surface of another organism known as the host
• They obtain nutrients and energy from the host, as well as protection
• Some of our parasites do not cause many problems, such as the ones which live in our gut.
Pathogen:
• A microorganism which causes disease
• All diseases caused by pathogens are COMMUNICABLE DISEASES / INFECTIOUS
DISEASES
• All diseases NOT caused by pathogens are called NON-COMMUNICABLE DISEASES, e.g.
genetic diseases, deficiencies due to diet
TRANSFER OF PATHOGENS:
• Transfer from an infected host to an unaffected host is DISEASE TRANSMISSION
• If it is known how the disease spreads then a CONTROL METHOD can be implemented to stop
it spreading
PATHOGENS EFFECTING ANIMALS
Pathogen Disease Method of Transmission
Bacterium Tuberculosis TB DIRECT - Droplets through the air
Bacterial Meningitis DIRECT - Droplets in in the air,
and through exchange of fluids
Virus HIV/AIDS DIRECT - Contact between
Influenza DIRECT - In droplets in the air
Protoctist Malaria INDIRECT - Via female
Anopheles mosquitoes
Page 1 of 5
Chapter 10 - Disease of Animals and Plants
THE HUMAN BODY AS A HOST
The Human body is rich in nutrients for a variety of organisms
Some organisms are TEMPORARY visitors:
• Mosquitoes and bed bugs
Some organisms are PERMANENT visitors:
• Bacteria and external parasites
• Some parasites breach our defences and enter the bloodstream and then spread throughout the
body.
• Some of these are extracellular parasites living on the surfaces of cells or in the spaces between
cells
• Many, including all the viruses that infect us, are intracellular parasites, since they can enter
cells, survive and produce.
• Some of these organisms are obligate parasites, because they cannot exist as free-living
organisms
PATHOGENS AND COMMUNICABLE DISEASES
Parasites:
• Live inside or on the surface of another organism known as the host
• They obtain nutrients and energy from the host, as well as protection
• Some of our parasites do not cause many problems, such as the ones which live in our gut.
Pathogen:
• A microorganism which causes disease
• All diseases caused by pathogens are COMMUNICABLE DISEASES / INFECTIOUS
DISEASES
• All diseases NOT caused by pathogens are called NON-COMMUNICABLE DISEASES, e.g.
genetic diseases, deficiencies due to diet
TRANSFER OF PATHOGENS:
• Transfer from an infected host to an unaffected host is DISEASE TRANSMISSION
• If it is known how the disease spreads then a CONTROL METHOD can be implemented to stop
it spreading
PATHOGENS EFFECTING ANIMALS
Pathogen Disease Method of Transmission
Bacterium Tuberculosis TB DIRECT - Droplets through the air
Bacterial Meningitis DIRECT - Droplets in in the air,
and through exchange of fluids
Virus HIV/AIDS DIRECT - Contact between
Influenza DIRECT - In droplets in the air
Protoctist Malaria INDIRECT - Via female
Anopheles mosquitoes
Page 1 of 5
