Biology Lesson Overview: Infectious Diseases PDF

Lesson Overview Infectious Disease Lesson Overview 35.1 Infectious Diseases Lesson Overview Infectious Disease Agents of Disease Infectious diseases are caused by pathogens—organisms that invade the body a...

Lesson Overview Infectious Disease Lesson Overview 35.1 Infectious Diseases Lesson Overview Infectious Disease Agents of Disease Infectious diseases are caused by pathogens—organisms that invade the body and disrupt its normal functions. bacteri viru protozo parasite a s a s Lesson Overview Infectious Disease Lesson Overview Infectious Disease Causes of Infectious Disease During the mid-nineteenth century, Louis Pasteur and Robert Koch established a scientific explanation for infectious disease. Pasteur’s and Koch’s observations and experiments led them to conclude that infectious diseases are caused by microorganisms. Microorganisms were commonly called “germs,” so this conclusion was called the germ theory of disease. https://www.youtube.com/watch?v=KSLCkT2ttXQ Lesson Overview Infectious Disease Lesson Overview Infectious Disease Koch’s Postulates Koch’s studies with bacteria led him to develop rules for identifying the microorganism that causes a specific disease. These rules are known as Koch’s postulates. 1. The pathogen must always be found in the body of a sick organism and should not be found in a healthy one. 2. The pathogen must be isolated and grown in the laboratory in pure culture. 3. When the cultured pathogens are introduced into a healthy host, they should cause the same disease that infected the original host. 4. The injected pathogen must be isolated from the second host. It should be identical to the original pathogen. Lesson Overview Infectious Disease Symbionts vs. Pathogens LiveSymbionts / grow in Pathogens Viruses and bacteria human body directly destroy the without disturbing cells of their host. functions. Some bacteria Harmless or release poisons that beneficial kill the host’s cells or Yeast /bacteria in interfere with their the mouth or normal functions. throat. Parasitic worms may Bacteria in the block blood flow intestine help through blood vessels produce vitamins or organs, take up the host’s nutrients Lesson Overview Infectious Disease How Diseases Spread Coughing, Contaminated Spread to humans sneezing. water or food from infected Symptoms that (pathogens that animals help pathogens infect digestive (zoonoses). spread and infect tract) with feces An animal new host. If you from infected (vector) carries, or touch objects with people or other transfers, zoonotic virus droplets and animals. diseases from an then touch your Food (fruits or animal host to a mouth or nose you vegetables) human host. get infected. without being Exchange ofcontact Physical body washed fluids (STDs), shared (skin infections). thoroughly. syringe. Meats and seafood are not stored and