Micro-organisms Notes

Micro-organisms

• Micro-organisms are living things too small to see with the naked eye, visible only with microscopes.
• "Micro" means small, and "organism" refers to living things.
• Include viruses, bacteria, protozoans, yeasts, and some algae.
• Some are harmful, but many are useful and essential for life.

Viruses

• Very tiny agents with a size of 0.02-0.3µm (0.02 - 0.3 \mu m).
• Not classified as living organisms.
• Reproduce only inside a host.
• Not classified in any of the five kingdoms.
• Example: HIV under an electron microscope.

Bacteria

• Tiny organisms with an average size of 1µm (1 \mu m).
• Feed on dead material (decomposers) and substances in living organisms.
• Belong to the Kingdom Monera.
• Example: Bacteria under a microscope.

Protozoans

• Single-celled, animal-like organisms with a size of 10-50µm (10 - 50 \mu m).
• Feed on bacteria and other protozoans.
• Belong to the Kingdom Protista.
• Example: Red blood cells infected with the malaria parasite Plasmodium.

Yeast

• Single-celled organisms with a size of 5-10µm (5 - 10 \mu m).
• Cannot make their own food; feed on sugars.
• Produce alcohol and carbon dioxide from sugars.
• Belong to the Kingdom Fungi.
• Example: Yeast cells.

Some Algae

• Simple plant-like organisms with sizes ranging from 1 to 100s of micrometers (1 - 100s \mu m).
• Produce their own food by photosynthesis.
• Belong to the Kingdom Protista.
• Example: Green Algae