section 1: disease & the immune system - topic 1: pathogens & communicable diseases

Question 1

what is disease?

Answer 1

a condition that impairs the normal functioning of an organism.

Question 2

what is a pathogen?

Answer 2

an organism that causes disease.

Question 3

what are the types of pathogen?

Answer 3

bacteria.
viruses.
fungi.
protoctists.

Question 4

what is a communicable disease?

Answer 4

a disease that can spread between organisms.

Question 5

what are the diseases caused by a bacterium?

Answer 5

tuberculosis - animals, typically humans & cattle.
bacterial meningitis - humans.
ring rot - potatoes & tomatoes.

Question 6

what are the diseases caused by a virus?

Answer 6

HIV/AIDS - humans.
influenza - animals, including humans.
tobacco mosaic virus - plants.

Question 7

what are the diseases caused by a fungus?

Answer 7

black sigatoka - banana plants.
ringworm - cattle.
athletes foot - humans.

Question 8

what are the diseases caused by a protoctist?

Answer 8

potato/tomato late blight - potatoes/tomatoes.
malaria - animals, including humans.

Question 9

what is direct transmission?

Answer 9

when a disease is transmitted directly from one organism to another.

Question 10

what are the ways direct transmission can occur?

Answer 10

droplet infection (coughing or sneezing tiny droplets of mucus or saliva directly onto someone).
sexual intercourse.
touching an infected organism.

Question 11

examples of direct transmission.

Answer 11

HIV can be transmitted directly between humans via sexual intercourse.
the virus can also be transmitted directly from a mother to her unborn child through the placenta.

athletes foot can be spread via touch.

Question 12

what is indirect transmission?

Answer 12

when a disease is transmitted from one organism to another via an intermediate.

Question 13

what act as intermediates?

Answer 13

air.
water.
food.
another organism (vector).

Question 14

examples of indirect transmission.

Answer 14

potato/tomato late blight is spread when spores are carried between plants - first in the air, then water.

malaria is spread between humans (and other animals) via mosquitoes.
^ the mosquitoes act as vectors - they don’t cause malaria themselves, they just spread the protoctists that cause it.

Question 15

what are the factors that affect transmission?

Answer 15

living conditions.
social factors.
climate.

Question 16

examples of how social factors can affect transmission?

Answer 16

social factors i.e. income, occupation, area where a person lives.

the risk of HIV infection is high in places where there’s limited access to:
- good healthcare - people are less likely to be diagnosed and treated for HIV, and the most effective anti-HIV drugs are less likely to be available, so the virus is more likely to be passed onto others.
- good health education - to inform people about how HIV is transmitted and how it can be avoided i.e. through safe-sex practices using condoms.

Question 17

example of how living conditions can affect transmission.

Answer 17

overcrowded living conditions increase the transmission of many communicable diseases.

TB is spread directly through droplet infection.
it’s also spread indirectly because the bacteria can remain in the air for long periods of time and infect new people.
the risk of TB infection is increased when lots of people live crowded together in a small space.

Question 18

examples of how climate can affect transmission.

Answer 18

potato/tomato late blight is especially common during wet summers because the spores need water to spread.

malaria is most common in tropical countries - humid and hot.
^ because these are the ideal conditions for mosquitoes to breed.