Tools for the Pools

It’s a Matter of Size

Animals and plants come in all sizes and shapes. When you are searching for one, knowing its size can be as important as knowing what it looks like. How can you find something if you don’t even know how big it is?

Suppose you are searching for an elephant, a cat and an ant. You would not bother to look under the bed for an elephant, but you might check there for a cat or an ant. You could spot the cat right away, but you would have to look more closely to see the ant. Knowing what you are looking for and how big it is makes it much easier to find.

You need clues to find organisms (plants and animals) that you have never seen before. Scientists provide clues about size by adding a scale to drawings or photographs of an organism. The scale tells you how much the picture has been enlarged (made bigger) or reduced (made smaller) compared with the actual size of the organism.

Most of the animals in vernal pools are much smaller than an ant. Scientists use special tools called magnifiers to magnify an object, making it appear bigger than it really is. A hand lens, dissecting scope, and microscope are all magnifiers. The question is: Which tool should you use? It’s all a matter of size, so listen for a clue in the words “microscopic” or “macroscopic.”

If an organism is called microscopic, it means you will need a microscope to see it. Microscopic organisms are less than 0.25 millimeters (mm) wide, smaller than you can see with your naked eye. Algae, bacteria, detritus, protozoa, and rotifers are all microscopic. A cup of water full of microscopic organisms looks like a cup of plain water.

waterflea.jpgIf an organism is called macroscopic, it is big enough to see with your naked eye but you need a hand lens or dissecting scope to observe important details. A macroscopic organism is between 0.25 mm and 50 mm wide. Fairy Shrimp and tadpoles are macroscopic. A cup of water full of macroscopic organisms is buzzing with critters.

Larger organisms are big enough to see without any magnification. Scientists do not have a special name for this group, but it includes most of the animals that are familiar to you: birds, mammals, amphibians, and reptiles. Although these animals are more obvious to us, most of the world’s species are actually microscopic or macroscopic. You will discover them when you look more closely at life in our watershed, using the right tools.