12.2 - Animal & Plant Diseases

Question 1

What is the knock on effect of plants being affected by plant disease?

Answer 1

• When plants are affected by disease there is a domino effect, when crop plant falls people starve and suffer. Economies will struggle and people will lose jobs
  
  • They threaten ecosystems as herbivores in food chains are affected

Question 2

Give an example of a plant disease:

Bacterial

Answer 2

Ring rot - in potatoes & tomatoes

• Caused by gram +ve bacteria Clavibacter michiganesis
• Direct contact between infected and uninfected plants
• No cure

Question 3

Give an example of a plant disease

Viral

Answer 3

TMV

• Direct contact between infected & uninfected species
• Also caused by indirect contant through aphids acting as vectors
• Damages leaves flowers and fruit - stunts growth & reduces yield
• Resistant crop strains availble but no cure

Question 4

Give an example of a plant disease

Protoctists

Answer 4

Protoctists (fungus like) Potato Blight

• Hyphae (branching filaments of fungus) penetrate host cells, destroying leaves, tubers & fruit
• No cure, but resistant strains exist
• Direct transmission through contact between infected and uninfected plants
• Indirect transmission from spores

Question 5

Give an example of a plant disease

Fungal

Answer 5

Black Sigatoka

• Banana disease caused by Mycosphaerella fijiensis - attacks and destroys leaves
• Fungicide & good husbandry (cultivation of plants) can control the disease spread, no cure.
• Indirect transmission through spores in wind

Question 6

Give 2 examples of bacterial animal diseases

Answer 6

TB (Tuberculosis)

• TB damages and destroys lung tissue, suppressing the immune system (body unable to fight other diseases)
• Curable by antibiotics and preventable through improved living standards and vaccination.
• Indirect transmission through water droplets in air

Bacterial Meningitis

• Infection of meninges (protective membrane on brain surface) - spread to rest of body.
• Leads to septicaemia (blood poisoning) and rapid death – affects children and teenagers
• Symptoms: blotchy red/purple rash that doesn’t disappear when glass is pressed against it (shows septicaemia). Immediate medical treatment needed
• Antibiotics can cure if delivered early, vaccines prevent some bacterial meningitis.

Question 7

What are the characteristics of HIV/AIDS?

Answer 7

• AIDS caused by HIV (human immunodeficiency virus)
• HIV targets T helper cells of the immune system, -affected people susceptible to other diseasesNo vaccine, no cure – anti-retroviral drugs slow the disease’s progress.
• Direct transmission from an infected person by blood to blood contact
  
  • Sharing infected needles
  • Infected unsterilised surgical equipment
  • Through semen/vaginal fluid in unprotected sex

Question 8

What are the characteristics of influenza?

Answer 8

• Indirect transmission by droplet infection
• Kills ciliated epithelium of gas exchange system, leaving airways open for secondary infection.
• Fatalities are due to severe secondary bacterial infection (pneumonia) on top of viral infection

Question 9

Give an example of an animal disease caused by protists and how it works

Answer 9

MALARIA

• Caused by protoctista Plasmodium and spread by the bites of infected Anopheles mosquitos (vector)
• There is no vaccine and limited cures, preventative measures such as: removing standing water where they breed; insecticide; insect repellent; mosquito nets

Question 10

Give 2 examples of fungal infection.

Answer 10

Ring worm

• Affects mammals (cattle, cats, humans, dogs). Different fungi infect different species. Causes grey/white crusty circular areas of skin. Antifungal cream is a cure
• Direct contact with spores on the skin surface

Athlete’s foot

• Human fungal disease (cause: Tinia pedia), a human form of ring worm, grows and digests in warm, moist areas of human feet. Causes cracking scaling. Use antifungal cream.
• Direct contact with spores on the skin