Single Celled Organisms Plants & Animals are multi-celled organisms. –Most cells depend on the other cells in the body to survive (eg: muscle cells require blood cells to bring O 2 and remove CO 2 ) –Specialized cells carry out their tasks in the organism efficiently, but cannot carry out all the tasks necessary to survive independently. Most organisms are single celled organisms – –Make up most of the biomass on earth. – –By far earth’s dominant life form!

The Protists single celled organisms with a nucleus and some other organelles. – –Most have mitochondria (cellular respiration) – –some may have chloroplasts (photosynthesis) – –eg: amoebas, algae – –May be beneficial (algae produces much of the O 2 in our atmosphere) – –Some can cause disease (amoebic dysentery, malaria) amoeba

Bacteria single celled organisms without nuclei or other organelles. – –First life form to evolve on earth. – –Found everywhere and often very abundant. – –Many are mobile Beneficial uses: – –breakdown dead plants and animals – –make yogurt – –some can photosynthesize Some can cause disease – –infections, strep throat, etc. – –Bacterial disease can be treated by antibiotics (eg: penicillin (mold))

Viruses Bundles of DNA in a protein covering. – –No nucleus, no organelles Very small: micrometers – –Can only be seen by an electron microscope Are not alive. – –Do not grow, do not use energy. – –Reproduce by attaching to living cell, injecting it’s DNA into cell. – –Cell is forced to produce more viruses. the flu, colds, warts are all caused by different viruses – –(see page 350 for more examples)

Bacterial & Viral Diseases Disease is fought by body’s immune system. – –White blood cells and “antibodies” attack and eat harmful viruses and bacteria by detecting their “antigens”. Vaccine = mild form of disease causing bacteria or virus. – –Body can successfully fight off vaccine, allows body to form “antibodies” to fight off more deadly diseases that look similar. Homework: Page 350 “Review 15.5” Questions 1-6