Singled-Celled Organisms Protists Bacteria Viruses

Protists  Eukaryotes – have a nucleus  Most have mitochondria for cellular respiration  Most have chloroplasts to make their own food  Most live in water

There are good protists and bad protists Good  protists are able to create O 2 through photosynthesis Bad  protists cause disease in humans

Found in fresh water and ocean No harmful effects on humans or environment

Bacteria  Smallest and simplest forms of life on the earth  Prokaryotes – do not have a nucleus  Do not have most of the organelles  Have only 1 DNA molecule which controls their functions  1 spoonful of garden soil may have bacteria

There are good bacteria and bad bacteria Good  bacteria make oxygen and nutrients for other plants and animals Bad  bacteria cause disease in humans

Bacterial Disease Bacteria and Protists that cause disease are called Pathogens. Pathogens invade the body of other organism and interfere with the normal cell functions.

Neisseria gonorrhoeae

Salmonella enteriditis

Viruses  Lack most of the characteristics of living cells,therefore most scientists do not call them living cells  Do not move around by themselves  Do not use energy  Do not grow  ALL THEY DO IS REPRODUCE!  Only have 1 piece of DNA with a protective coating of protein

How viruses reproduce The virus invades another cell, that cell is called a host cell. The virus uses that host’s DNA to reproduce.

Influenza virus

Herpes Virus

Hepatitis B virus causes both acute and chronic liver infections

Rotaviruses infect the lining of the intestine and cause diarrhea, especially in children.