Life Cycle - Organisms (6A)
Lab 

   
OBJECTIVES:
  • Comparing bacteria, fungi, algae, and protozoa.
  • Exploring the lower kingdoms.
VOCABULARY:
  • bacteria
  • fungi
  • microbe
  • protozoa
MATERIALS:
  • pond water or aquarium water
  • microscope
  • microbes (enclosed sheets)
  • mushroom (fresh)
  • petri dishes (recommended)
  • worksheets

Students look at pond water using the microscope.

BACKGROUND:

This lab will help students develop a better understanding of characteristics of organisms belonging to Monera, Protista, Plantae, and Fungi. Many of the smaller representatives of these groups are called "microbes."

The Monera are single-celled organisms that do not possess a true nucleus, they are presently divided into two large Kingdoms, the Eubacteria and Archeobacteria. They are divided into these groups dependant on their nuclear structure. Their nucleus has no outer membrane and the cell is called prokaryotic. All other living organisms are eukaryotic, which have a membrane surrounding the nucleus.

Monera (sometimes referred to as bacteria or blue green algae) are microscopic. They are either autotrophic or heterotrophic. An autotroph is an organism that can build its own food from "chemicals" like carbon dioxide and water. Monera that do not make their own food are heterotrophic and must seek a supply of food. Heterotrophs depend on tissues, remains, and wastes of other living organisms for food. Bacteria come in 3 different shapes. Bacillus are rod shaped, coccus are spherical, and spirillum are spiral. Bacteria reproduce by asexual means, usually by dividing. Bacteria can be found just about everywhere, they are in air, water, inside you, outside you, in the frozen Arctic and even in hot springs.

Some bacteria are responsible for food spoilage, and others are useful in changing food to a different desirable flavor or consistency such as in making cheeses. High temperatures kill most bacteria and this knowledge led to the discovery of pasteurization or the heating of milk to kill any bacteria that would lead to spoilage. Canning food or heating food and sealing it in air tight container also prevents spoilage. Cooling bacteria slows down their decomposing action and this led to the use of refrigeration and freezing to retard spoilage.

Blue-green algae or cyanobacteria, unlike some bacteria, undergo photosynthesis. They carry on cell division and respiration. Some are harmful in that they may add to the pollution of lakes and rivers by their rapid growth, but most are benign. Cyanobacteria are one of the most primitive organisms found in the fossil record, making massive mounds 600 million years ago (stromatolites).

The Kingdom Protista are single-celled organisms that have a true nucleus (eukaryotic). Protista may be either autotrophic or heterotrophic. Movement by protists is dependent upon certain physical characteristics. Some protozoa have pseudopodia which can extend the cell membrane and push forward or surround a food particle, such as an amoeba does. A protist that possesses a single tail-like structure is called a flagellate. The flagellum will beat back and forth and propel the organism through the water, examples are trypanosome and trichosomes. Some Protozoa are covered with tiny hair-like structures called cilia which move back and forth quickly propelling the organisms through the water. A paramecium is an example of a ciliate. Some Protozoa have axopodia, or pencil-like structures, that help them to be planktonic or floaters in the water. Radiolaria are marine examples of protozoa containing this feature.

There are many debates about whether protozoa are all one-celled organisms or whether they are all one-celled organisms that are heterotrophs. Scientists who study these groups, debate on how to classify some of these organisms, like euglena and dinoflagellate. With more study these groups will be better understood.

Most protozoa are helpful in that they are important in lower levels of the food chain. They provide food for living things such as snails, clams, and sponges. Some protozoa are capable of causing diseases in humans and other animals. Some diseases caused by protozoa in humans are malaria, black fever, sleeping sickness, and some types of diarrhea.

Organisms found in the Fungi Kingdom are heterotrophic. Fungi obtain food by decomposing anything that is organic in nature. Fungi live everywhere. They grow best in warm, moist places. They are not green and do not possess chlorophyll. Fungi can grow on vegetables, bread, meat, fur, wood, leather, or anything that is in a warm and moist area.

Fungi that obtains nutrients from non-living organic matter are called saprobes. Other fungi obtain nutrients directly from a living host, these are parasites. In either case, the fungi secretes enzymes that allow digestion to take place outside of the fungal body. Nutrients are then absorbed across the cell membranes. Together with bacteria, fungi are the decomposers of the earth. Fungi include yeast, bread mold, and mushrooms.

Fungus itself is made up of a fungal body or what is called mycelium. The mycelium is a mesh of filaments that branch out in any direction living over or within the organic matter. Each filament is a hypha. Hypha are transparent thin walled tubes.

Fungi reproduce asexually through the formation of spores, through fragmentation of the mycelium or by budding. Some reproduce sexually through the formation of male and female gametes.

The organisms from the Plantae Kingdom are different from the other groups because they photosynthesize or create their own food from light. The algae are a group of water plants. They range in size from large (kelp) to microscopic (algae). The microscopic group that you will encounter in pond water will belong to some type of algae.

PROCEDURE:
  1. During lab students will look at examples from the different groups. Have pictures available of different microbes so they can compare and contrast.
      
  2. If you are looking at pond water, use the enclosed pictures of the possible different groups that students may see. The Swift GH with a 2.5X objective will only see the largest of these. If you have a 4X or 10X objective you will be able to see more. Use the list that can be found after the pictures of where these organisms belong.
      
  3. Marine water also is home for many protozoa and microscopic algae. If you live near a marine environment you may want to sample and compare.
      
  4. Prepare the following materials for students to observe and record on their lab sheet.

PROTOZOA
If you have an aquarium or have pond water, the students can look at live specimens which are much more exciting. You can use the Swift GH on the aquarium by taking the base from the microscope, putting on the 10X objective and putting the microscope right on the glass of the aquarium. Focus on the slimy surface of the glass and you will be able to see protozoa eating, playing and reproducing!

FUNGI
Cut a fresh mushroom in thin slices. Students should be able to look at the entire cross section with the microscope.

MONERA
The only "bacteria" that the students may see in pond water are the cyanobacteria which include Oscillatoria. Other bacteria require at least 100X or higher magnification.

ALGAE
The Plantae Kingdom also has representatives in the micro world. Plants are different from the other groups because they can create their own food through photosynthesis. Small algae are found in fresh and salt water. The most common in both environments are diatoms. The Swift GH with a 2.5x objective cannot distinguish individual diatoms. However, diatoms like to "clump" together. The clue is that they would have a greenish-brown tint.

  1. The most important part of this lab is for students to realize that there are many types of microorganisms. These microorganisms live in many different environments. Some of these organisms may be microscopic; others can be seen with the naked eye.

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