Disease

Question 1

What are the different types of pathogen and what diseases can they cause?

Answer 1

Bacteria - can cause tuberculosis, ring rot, and bacterial meningitis
Virus - can cause HIV/ AIDS, influenza, tobacco mosaic virus
Protoctista - can cause malaria and tomato/potato late blight
Fungi - can cause black sigatoka, athletes foot, ring worm

Question 2

Explain how communicable diseases can be spread?

Answer 2

Directly - from one organism to another e.g. through droplet infection, sexual intercourse or touching
Indirectly - via an intermediate e.g. air, water, food, vectors

Question 3

Explain factors affecting the transmission of communicable diseases.

Answer 3

Social factors e.g. overcrowded conditions increase chances of TB being spread. Poor health and nutrition/ health education can lead to HIV.
Climate e.g. potato/ tomato blight is most common during wet summers as spores need water to spread. Malaria is most common in tropical countries with the ideal conditions for mosquitos to breed

Question 4

Physical plant defences.

Answer 4

Thick waxy cuticle - physical barrier and no water collection on wax so pathogens cant survive.
Cell wall - barrier and contains chemicals
Callose - polysaccharide deposited between cell walls and membranes when a plant is infected. Prevents pathogens entering cells. Can also block phloem sieve plates preventing spread of pathogen

Question 5

Chemical plant defences.

Answer 5

Plants produce antimicrobial chemicals which kill or inhibit the growth of pathogens e.g saponins destroy the membranes of fungi
Plants also produce chemicals which are toxic to insect pests that may transmit disease.

Question 6

What is the purpose of primary defences in animals?

Answer 6

They have evolved to prevent entry of pathogens into an organism

Question 7

What does non specific mean?

Answer 7

They will act on any type of pathogen