The Body At War

Disease

Infectious• Spread from one

organism to another

• Common cold, influenza, chickenpox

• Pathogens requiring a host organism

Non-Infectious• Developed within

organism• Arthritis, diabetes

Microbes

Microscopic organisms• Viruses• Bacteria• Protozoans• Parasites • Fungi

• PATHOGENS are harmful microbes.

Viruses

• Seen with an electron microscope

H3N2 Bird Flu

Electron Microscope Cross Sections

CGI Molecular Model

Viruses

• Need a host to live

Myxomatosis

• Affects rabbits, but not humans

Warts

Rubella

Mumps

Polio

AIDS

Bacteria

• Seen under light microscope• Single cell organism

Useful Bacteria

• Organic matter decomposers

• Cheese and wine

Binary Fission

Bacteria Causes Disease

• They may produce a substance toxic to the host cells

• They may stop the host from doing normal activities

Food Poisoning

Strep Throats

Pneumonia

Pimples

Anthrax

Leaf Blight

Questions

1 Diseases can be divided into two groups. What are the groups called?

2 What is a pathogen?3 Not all bacteria are pathogens.

Describe two ways in which bacteria can be useful.

4 What are the two ways that bacteria can cause disease?

Questions

5 What is the difference between the way that viruses and bacteria reproduce?

6 Why is the cell invaded by a virus called a host cell?

7 Over two million bacteria are found per square centimetre of skin under the armpits. Why don’t they cause disease more often?

Homework

1 How does dental cavities or tooth decay form? Why is this related to a study of diseases?

2 Often, after taking medicine or being ill, people are advised to eat yoghurt. Find out what the benefits of this food might be. How is yoghurt made?

Parasites

• Internal or external

• Protozoans – single celled animalse.g. malaria, dysentery

• Tapeworm + Roundworm• Liver flukes• Fleas• Lice

Common Parasites

Parasite Condition Caused

Source of Infection

Amoeba dysentery Food and drink

Malarial parasite malaria mosquito

Tapeworm tapeworm Raw meat

Blood fluke schistosomiasis water

Ticks Skin infection Scrub, bush

Lice pediculosis Beds, clothes

Fleas Skin irritation animals

Questions

1 What is a parasite?2 What is a protozoan? List some

diseases caused by protozoans.3 What are some common tapeworms

and roundworms that infect humans? How do we get infected.

4 What is the difference between ticks, lice and fleas?

Review

1 What is the difference between a bacteria, animal and plant cell?

2 How are some bacteria good? Describe them.

LinksFollow the links to help answer your questions.

• Cells Alive .com

• The difference between bacteria, animals and plants

• Good bacteria

• Parasite Images

• Worm Learn .com

• Lots of images!!!