CAUSES AND SPREAD OF

DISEASES

Module 4 – Lesson 1

Learning Objectives Success Criteria

Learn the different types of pathogen that cause communicable diseases.

Understand the means of transmission of animal and plant communicable pathogens.

Give examples of importance diseases caused by bacteria, fungi, viruses and protoctista.

Explain the factors that promote the spread of diseases and how to prevent them.

Starter How many diseases can you think of?

Write their names on a piece of paper.

Are there any similarities between them? Related symptoms? Are they caused by another organism? If so, are they caused by different type of

organisms?

Can you organise the diseases into groups?

What is Disease? Disease is a malfunction of the body or mind.

Diseases caused by living organisms are called infectious diseases.

Diseases cause symptoms, which may be physical,

mental or social.

These are usually outward signs which can be used to

diagnose the disease.

Pathogens What is a pathogen?

Pathogens are classified in 4 main groups:

Pathogen:Organism that can cause communicable diseases in plants and animals.

Bacteria

Fungi

Viruses

Protoctista

Task Complete the worksheet (Pathogen Questions).

Answers:1. Bacteria: TB, Bacterial meningitis.

Virus: HIV/AIDS, InfluenzaFungus: Ringworm, Athlete’s footProtoctista: Malaria

2. Bacteria: Ring rotVirus: Tobacco mosaic virusFungus: Black sigatoka

3. Neisseria meningitidis, Streptococcus pneumonia4. Trichophyton5. Bananas. Causes leaf spots on banana plants, reducing yield.6. Malaria – Protoctista - Plasmodium

Pathogens

Bacteria are tiny, rapidly-reproducing cells. Pathogenic bacteria cause disease by damaging cells or by

releasing harmful toxins.

Bacteria belong to the kingdom Prokaryotae.

Bacteria

Important Bacterial Diseases:

1. Tuberculosis (TB)2. Bacterial meningitis3. Ring rot (tomatoes &

potatoes)

Fungi affect animals and plants.

Fungi

• Fungi can live under the skin of animals, where their hyphae form a mycelium.

• The fungus produces reproductive spores, which causes irritation.

Black sigatokaA commercially important leaf-spot disease that has reduced yields of banana plantations worldwide.

Optional: Read the factsheet on black sigatoka.Link on vbiology and weebly site.

Viruses take over the genetic machinery in cells and use it to copy themselves.

Host cells burst and release copies of the virus.

Viruses

Important diseases caused by viruses:

HIV/AIDS Influenza Tobacco mosaic virus

The Ebola Virus

These pathogens are larger and more ‘animal-like’ than bacteria.

Common diseases caused by protoctista are dysentery and malaria.

Protoctista harm cells by entering and then feeding on their contents as they grow.

Protoctista

Exam Question

a. Explain the shape of the curve for Salmonella food poisoning.b. Explain the shape of the curve for influenza.c. Individuals with food poisoning often suffer from diarrohea. Explain

how the effects of diarrohea on the body can be treated.

Exam Question Answer the exam question on Flu &

Salmonella.

Answers:

Transmission of Pathogens

Direct or Indirect? Transmission of pathogens between animals can happen either

directly or indirectly.

How might pathogens be transmitted DIRECTLY?

Physical contact – touching/kissing/intercourse. Food contamination – faecal-oral, raw meat. Droplet infection – sneezing, coughing. Fungal spores – carried in air, on surfaces.

Discuss what could be done to minimise transmission of pathogens by the ways listed above.

Jot them down in your notes.

Social Factors What social factors affect disease transmission?

Overcrowding; Poor ventilation; Poor health, Poor diet, Homelessness, Migration.

Indirect Transmission Think about (or discuss) ways in which pathogens can be spread

indirectly.

Homework:Worksheet on Indirect Transmission.

Plenary In recent years the number of cases of TB have

increased in major European cities. The number is predicted to rise sharply again within the next few years.

Why? (Think, pair, share).

Learning Objectives Success Criteria

Learn the different types of pathogen that cause communicable diseases.

Understand the means of transmission of animal and plant communicable pathogens.

Give examples of importance diseases caused by bacteria, fungi, viruses and protoctista.

Explain the factors that promote the spread of diseases and how to prevent them.