Investigating Cell Types Carolina Biological Supply 25-1001 $99.95 Included in the kit: An order form for: Paramecium culture Euglena culture Elodea sample 8 bottles Protoslo quieting solution 96 concavity slides 100 coverslips Yeast packet Congo red stain 8 typical plant cell slide + study cards 8 human cheek cell slides + study cards Toothpicks 18 pipets 16 ¼ oz jars 8 forcepts Teacher’s manual and reproducible student guide Needed, but not supplied: 16 microscopes (4x, 10x, 40x) Light source for Euglena Liquid soap or detergent 5% salt solution (8 small containers, optional) Small container for yeast 8 small containers of distilled water Other supplies as deemed necessary by students Learning Goals Students will develop the skills necessary to design and perform scientific investigations. produce testable hypotheses. differentiate between cell types. identify function of visible cell organelles as they relate to structure. observe interactions between cells. examine structural differences between plant and animal cells. investigate the effects of environmental conditions on different cell types. Overview The focus is to distinguish between the structures of plant and animal cells and to build an understanding of why an organism is classified as an animal, a plant or something else. PARAMECIUM Paramecium is a group of single-celled eukaryotes, which are commonly studied as a representative of the ciliate group, as they are covered with cilia (small hairs) which allow the cells to move with a synchronous motion (like a caterpillar) at speeds of approximately 12 body lengths per second. There is also a deep oral groove that is used to draw food inside. They generally feed on bacteria and other small cells. Water regulation is carried out by a pair of contractile vacuoles, which actively expel water from the cell absorbed by osmosis from their surroundings. Generally considered a freshwater organism, new species have recently been discovered in the oceans. EUGLENA Euglena is a single-celled photosynthetic protist that can live heterotrophically too. When acting as a heterotroph, the Euglena surrounds a particle of food and consumes it through phagocytosis. When acting as an autotroph, the Euglena utilizes chloroplasts, to produce sugars by photosynthesis. They move through the movement of a flagella (a long whip-like tail). ELODEA Elodea is a genus of aquatic plants often called the waterweeds. Elodea is native to North America and is also widely used as aquarium vegetation. The introduction of some species of Elodea into waterways in parts of Europe, Australia, Africa, Asia, and New Zealand has created a significant problem and it is now considered a noxious weed in these areas. An older name for this genus is Anacharis, which serves as a common name in North America. Activity 1 Students view prepared slides of typical plant and animal cells. They also gain experience with viewing cells under a microscope. Procedure: 1. Students are to look at the study cards and compare them to the prepared slides. They will be asked to draw what they see, looking for structures that are characteristic of each cell type. Activity 2 Students view living organisms and observe many common cell organelles. Procedure: Paramecium/ Euglena 1. place a drop of either Paramecium culture or Euglena culture on a clean slide without a coverslip. Look at them under low power and observe unimpeded movement. 2. add one drop of Protoslo to the slide. Mix thoroughly with a clean toothpick and add a coverslip. 3. Observe under low power and then under high looking for cell organelles. Determine function based on their form or shape. 4. Repeat with the other one-celled organism. Activity 2: cont. Procedure: Elodea 5. Remove several leaves (of varying shades of green) from the growing tip of the Elodea. Place one on a slide with a drop of water and a coverslip. Examine under low and then high power noting any organelles seen and try to determine their function based on shape and actions. 6. Repeat with other leaves. Activity 3 Students observe the organisms under a variety of environmental conditions. Procedure: salt 1. Students create a data table similar to the one in the student guide. 2. Place an Elodea leaf in a salt solution for use later. 3. Add one drop of salt solution to a slide containing Paramecium and Protoslo. Add a coverslip. Prepare a similar salt slide with Euglena and Protoslo. 4. Look at both slides and describe any changes in the cells. 5. Clean slides with water only and dispose of Paramecium and Euglena down the drain. Activity 3 : Continued Procedure: soap/detergent Follow the same procedure for all three organisms as the salt slides but use one small drop of soap instead. Note any changes in the cells. Again clean the slides with water. Procedure: colored yeast Use a toothpick to place a few colored granules of yeast by lightly tapping the toothpick on the slide containing the organisms and Protoslo and the Elodea and water. Cover. Observe which organisms, if any, feed on the yeast. Watch the path that takes it through the organism’s body. Clean slides with water. Activity 4 Students design and conduct an inquiry-based experiment of their own in order to view additional differences between plant and animal cells. Procedure: 1. Design an experiment to test the similarities and differences between different types of cells using supplied equipment or requesting additional items. 2. These tests will need to be repeated several times to be sure that the results are consistent. Suggestions for experiments (if students need help) Reactions to light and/or dark Reactions to ethanol or isopropyl alcohol Reactions to vinegar Reactions to heat and/or cold, or changes in temperature Reactions to caffeine Reactions to sugar solutions Students should be encouraged to come up with their own ideas and support even those ideas that stray from the norm. A grading rubric is included in the booklet. Helpful hints Discuss cleaning and disposal. Elodea leaves go in the garbage, Paramecium and Euglena can go down the drain. Wash slides with only water. Use Protoslo sparingly- too much can make cells lyse. If students are having problems, have them add the culture to a drop of Protoslo and mix well to thicken. Students will probably not be able to see all the structures on the Bioreview sheets included in the student guide. The ones that may be visible are boldfaced. If students are still having difficulty seeing the structures because of the movement of the organisms, one or two cotton fibers can be added to the slide to restrict the amount of space available. When students feed the organisms, stress the importance of adding the smallest amount of yeast possible. One tap of the toothpick on the slide is enough. If too much yeast is added, it will be difficult to view the organisms.