Module 4: Disease and immunity - Pathogens & plant defences

Question 1

Define the term pathogen

Answer 1

A microorganism that causes a disease.

Question 2

Tuberculosis affected organism & pathogen type

Answer 2

Animals.

Bacterium.

Question 3

Bacterial meningitis affected organism & type of pathogen

Answer 3

Humans

Bacterium

Question 4

Ring rot organism affected & type of pathogen

Answer 4

Potatoes & tomatoes

Bacterium

Question 5

HIV/AIDs organism affected & pathogen type

Answer 5

Humans

Virus

Question 6

Influenza organism affected & pathogen type

Answer 6

Animals

Virus

Question 7

Black sigatoka organism affected & type of pathogen

Answer 7

Banana plants

Fungus

Question 8

Ringworm affected organism & pathogen type

Answer 8

Cattle

Fungus

Question 9

Athlete’s foot affected organism & pathogen type

Answer 9

Humans

Fungus

Question 10

Potato/tomato late blight organism affected & pathogen type

Answer 10

Potatoes & tomatoes

Protoctists

Question 11

Malaria organism affected & type of pathogen

Answer 11

Animals

Protoctists

Question 12

Define the term direct transmission and state two examples

Answer 12

When a pathogen is transmitted directly from one organism to another.
Droplet infection - coughing or sneezing.
Sexual contact.

Question 13

Define the term indirect transmission and state four examples.

Answer 13

When a pathogen is transmitted from one organism to another via an intermediate.
Air
Water
Food
Vector (another organism)

Question 14

State three factors linked to living conditions which can increase the rate of transmission of pathogens. For each one give an example.

Answer 14

Overcrowded conditions - any pathogen spread by droplet infection.
Climate - The mosquitos that carry the malarial parasite breed more quickly in hot and humid conditions.
Social factors - The HIV pathogen is spread more quickly in countries with limited access to barrier contraception.

Question 15

Describe three physical defences plants have to prevent pathogens entering.

Answer 15

Waxy cuticle - physical barrier against pathogens entering.
Cellulose cell wall - prevent the pathogen moving from cell to cell.
Callose - a polysaccharide deposited between plant cell walls during stress.

Question 16

Describe three chemical responses plants have to either prevent pathogens entering, or to destroy them if they have entered the pant.

Answer 16

Saponins - destroy the cell membrane of fungal pathogens.
Phytoalexins - inhibit the growth of fungal pathogens.
Toxins - prevent insects feeding and therefore reduces the risk of infection by pathogens carried by the insects.