Microscopic Life in Water


Introduction

There are many microscopic plants and animals that can be found in most lakes, ponds, swamps, rivers, streams, and even puddles. These tiny life forms are called plankton. Plant plankton is called phytoplankton, and animal plankton is called zooplankton. In this activity you will be examining common types of zooplankton.

A small sample of water, such as the few drops you can collect in an eyedropper, usually will not contain many zooplankton. But ten gallons of water will. Since collecting and examining ten gallons of water could take a very long time, scientists use something called a plankton net. Plankton nets collect all the zoo-plankton from a large amount of water and concentrates them into a smaller amount of water. From this smaller amount of water you can collect a lot of zooplankton using an eyedropper.

Challenge

Make a plankton net and use it to collect animals swimming in the water. Observe these animals at varying powers of magnification.


Instructions

Bend a coat hanger to make a circle with a handle. Cut off a leg from a pair of old nylon panty hose. Sew the thigh-end of the nylon onto the coat hanger by folding about an inch over the coat hanger and sewing. Now cut off the foot. Using a rubber band, attach a small plastic bottle (such as an empty vitamin bottle) onto the foot-end of the nylon by wrapping the rubber band around the top of the bottle.

Slowly drag the net through the water. The water will enter the net and leave the net through the nylon sides. The animals will enter the net and collect in the plastic bottle. Carefully remove the rubber band from the bottle to free it from the net. Now use the eyedropper to transfer some of the animals onto the well slide. Begin by observing these animals with your hand lens. If you can see any animals at 5x, draw them. Then examine the water sample at 10x and draw what you see. Now you can use a microscope. Begin at 75x and draw what you see. Increase the magnification to 150x and make a new drawing. Finally, increase magnification to 300x and create a final drawing. Don't forget to write the magnification on each of your drawings.

Further Exploration

Collect some filamentous, or "hairy" algae, from a pond. This is a good place to find zooplankton because many of the animals live on the algae, either eating the algae itself or other animals that live in the algae. Place it in a jar with pond water. Don't let the algae dry out because it will kill the animals. Cut off a small amount of algae with a pair of scissors and place it in the well slide with a drop of water. Look at your sample, first with the hand lens, then with a microscope. Draw what you see.



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