The kingdoms in a water drop: an introduction to microscopy and the kingdoms of life
Close your eyes and picture a kingdom. What do you see? Do you picture a castle with walls? Are there farms in the distance? A king on his throne and knights in shining armor? What would you say if someone told you an entire kingdom can fit in a drop of water? Or that sometimes there can be as many as five kingdoms in a water droplet? Would you believe that?
The kind of kingdom that exists in a drop of water, is one that consists of living organisms that feed, breathe, move and reproduce. Biological classification is a system that scientists use to organize life into categories based on similarities and differences. Scientists group organisms into five or six different kingdoms of life. The kingdoms of life are Plant, Animal, Protist, Fungi, Eubacteria and Archaebacteria. The last two kingdoms are sometimes grouped into one kingdom called Monera.
Plants get their energy from the sun. For this reason plants tend to be the color of the light they reflect, such as green, red or orange, while the light they absorb is used to make energy. Animals get their energy by eating other living organisms. When they become hungry they eat plants, other animals, protists, fungi or even bacteria. Protists are an interesting group. They can have things in common with both plants and animals. Fungi include yeast, mold and mushrooms. Bacteria are everywhere, including on your hands and in your mouth, but you won't see them with the naked eye, as they are microscopic in size!
Salt, sugar and water are components of the food you eat every day. Their molecules are made up of basic units called atoms. Like molecules of salt, sugar and water, all living organisms are made up of basic units called cells. Cells allow the organism to breathe, eat, move and reproduce. Since the smallest cells are smaller than a pencil tip, we need to use a microscope in order to see very small organisms, which are made up of one or a few cells. Microscopes enlarge organisms that we can't see with our eyes.
In this science project you are going to identify several kingdoms of life in a water sample. First, you will collect water from a pond or lake, then bring it to your microscope for observation. In order to observe these small creatures, you will make a wet mount. Wet mounts are slides containing your sample in a solution; they are used to observe living organisms.
When observing a freshwater sample in the microscope you will encounter a few of the kingdoms. The largest organisms you may see in the microscope are in the animal kingdom. In a pond water sample, animals are larger than organisms in other kingdoms because they are multicellular. They may also have elaborate appendages, and complicated feeding behavior and movement. Most bacteria need to be stained to view in a microscope; however, in water samples long green chains of bacteria are common. These bacteria are called cyanobacteria or filamentous algae, but the latter term is also used to refer to protists or plants. Protists often have flagella (whip-like tails) or cilia (hair-like fringe). Some will have color from pigments, while others will be transparent. You may also find single-celled algae with flagella in the plant kingdom. It may be hard to distinguish these plants from protists, but protists are often more elaborate and fantastical in appearance. Protists can have amoeboid or angular shapes, more than one flagella, and noticeable eyespots.
Practice good hygiene after collecting and handling water samples from a pond. Some ponds may contain pollutants or fecal material (such as from waterfowl, fish or sewage).