Microorganism

Very small plants and animals called microorganisms are found on land and in the water. Like microbes, seeds, and spores, microorganisms can be important in an investigation. Try the following activity to investigate microorganisms that are found in water.

Materials

- large glass jar with lid
- water from a pond or lake
- magnifying lens
- microscope (optional)

Procedure

NOTE: This is an outdoor activity

1. Use the jar to collect some water from a pond or lake, then put the lid on the jar.
2. At home, use the magnifying lens or microscope to examine the water for microorganisms. How many different microorganisms can you find?
NOTE: Many of the microorganisms are clear or light-colored and are very small, so you will have to look carefully. They may appear to be small that move!

Explanation

Small plants and animals live in the water are the foundation of all life. These microorganisms are eaten by larger organisms, which in turn are eaten by still larger organisms. This food chain allows many different organisms to live on earth.

Microorganisms found in the water can give valuable information to a detective. Microorganisms called diatoms (microscopic algae that contain a sandlike substance called silica in their cell walls) are very important. The presence or absence of diatoms in a dead body found in water can tell forensic scientists whether the victim drowned or died before entering the water. When death is caused by drowning in natural water, such as lakes and rivers, the water in the body, aspecially that in the lungs but even water in the bloodstream, will contain diatoms. If the victim was already dead when the body entered the water, no diatoms will be found.

In investigations in which a body is found in a different location from where it drowned, forensic scientists study diatoms to determine with considerable accuracy the area of origin. This is because there are over 15,000 species of diatoms, and any combination of them found in a sample is like to be unique.