KEY CONCEPT Germs cause many diseases in humans.

Germ theory states that microscopic particles cause certain diseases. Germ theory proposes that microorganisms cause diseases. proposed by Louis Pasteur led to rapid advances in understanding disease

Louis Pasteur proved that spontaneous generation was not true. Prior experiment by Redi did not prove. Francesco Redi - One of the first to disprove spontaneous generation. An Italian doctor who proved maggots came from flies. (Italian 1668) Spontaneous Generation The idea that organisms originate directly from nonliving matter. "life from nonlife" abiogenisis - (a-not bio-life genesis-origin)

Redi's Problem Where do maggots come from?  Hypothesis: Maggots come from flies. Redi put meat into three separate jars. Jar 1 was left open  Jar 2 was covered with netting Jar 3 was sealed from the outside

Redi's Experiment Step 1 Jar-1 Left open  Maggots developed Flies were observed laying eggs on the meat in the open jar Redi's Experiment Step 2 Jar-2 Covered with netting  Maggots appeared on the netting Flies were observed laying eggs on the netting

Redi's Experiment Step 3 Jar-3 Sealed  No maggots developed Redi's Experiment Results What did Redi's experiment show?  Was his hypothesis correct or incorrect?

Louis Pasteur was given credit for disproving spontaneous generation.

Koch’s postulates support the theory. Disease-causing agents are called pathogens.

Koch’s Postulates The microorganism or other pathogen must be present in all cases of the disease. The pathogen can be isolated from the diseased host and grown in pure culture. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal. The pathogen must be reisolated from the host and shown to be the same as the originally inoculated pathogen.

There are different types of pathogens. Bacteria are single-celled organisms. cause illness by destroying cells release toxic chemicals

Viruses are genetic material surrounded by a protein coat. force host cells to make more viruses very small

Fungi can be multicellular or single-celled. take nutrients from host cells occur in warm and damp places

Protozoa are single-celled organisms. use host cells to complete their life cycles take nutrients from host cell

Parasites are multicellular organisms. grow and feed on a host possibly kill the host

Different pathogen cause common infectious diseases.

Pathogens can enter the body in different ways. Pathogens can be transferred by direct or indirect contact. Indirect contact does not require touching an infected individual. touching an infected surface breathing in infected air

Vectors carry a pathogen and transmit it into healthy cells. Direct contact requires touching an infected individual. Includes: kissing sexual intercourse hand shaking tick