Disease

Question 1

What is a disease?

Answer 1

A condition that impairs the normal functioning of an organism.

Question 2

What is a pathogen?

Answer 2

A disease causing organism.

Question 3

What are the main types of pathogen?

Answer 3

Bacteria, viruses, fungi, and protoctista.

Question 4

What is a ‘communicable’ disease?

Answer 4

A disease that can spread between organisms.

Question 5

What are some examples of a bacterial disease?

Answer 5

Tuberculosis (animals), bacterial meningitis (humans), ring rot (potatoes, tomatoes).

Question 6

What are some examples of a viral disease?

Answer 6

HIV/AIDS (humans), influenza (animals inc. humans), tobacco mosaic virus (plants)

Question 7

What are some examples of a fungal disease?

Answer 7

Black sigatoka (banana plants), ringworm (cattle), athlete’s foot (humans)

Question 8

What are some examples of a protoctistal disease?

Answer 8

Potato/tomato late blight, malaria (animals inc. humans)

Question 9

Explain ‘direct transmission’.

Answer 9

A disease is transmitted directly from one organism to another.
E.G. Droplet infection, sexual intercourse, touching an infected organism

Question 10

Explain ‘indirect tranmission’.

Answer 10

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

Question 11

What are the main factors that affect disease transmission?

Answer 11

Living conditions, climate, and social factors.

Question 12

How does overcrowding affect the transmission of communicable diseases?

Answer 12

Disease can spread directly as lots of people are in direct contacts, as well as indirect as bacteria can remain in the air for long periods of time and infect new people. With lots of people living in a crowded space, a lot of people will come into contact with any lingering bacteria.

Question 13

How does climate affect the transmission of communicable diseases?

Answer 13

E.g. late blight is especially common during wet summers because the spores need water to spread.
Malaria is most common in tropical countries, which are humid and hot as these are ideal conditions for mosquitoes to breed.

Question 14

How do social factors affect the transmission of communicable diseases?

Answer 14

The risk of HIV infection is high in places when there is limited access to good healthcare and good health education as these can inform people about the virus and diagnose/treat it.

Question 15

What barriers do animals have against infection?

Answer 15

• Skin (physical barrier, chemical barrier, lower pH)
• Mucous membrane (protect body openings)
• Blood clotting (prevents pathogen entry)
• Inflammation (increases permeability of blood vessels)
• Wound repair (prevents pathogen entry)
• Expulsive reflexes (expels foreign objects.

Question 16

What defences does a plant have against pathogens?

Answer 16

• Waxy cuticle (physical barrier and stops water collecting on leaf)
• Cell walls (second physical barrier)
• Callose (between cell walls and plasma membranes during stress,makes it harder for pathogens to enter)