Name ______Date ______Period ___
Observing plant and animal cell tissues lab investigation
Procedure for plant tissues
1. Obtain a section of the bulb of the onion and separate the layers. Hold one of the layers so that it curves toward you. Bend the layer of the onion sharply so that the shiny back surface snaps, exposing a thin membrane on the inner surface.
2. Using forceps, peel off a small piece of the thin membrane,called epidermis, from the inner surface of the onion layer. Place the epidermis tissue on a microscope slide, flattening it completely with forceps.
3. Prepare a wet mount of this epidermis tissue and examine it under low power magnification.
4. Sketch these cells in the circle. Be sure to give the totallow power magnification beside it.
______X (low power magnification)
a. What part(s) of a plant cell can be seen? ______
b. An onion grows underground. What organelle is missing from these cells? ______
5. Add a drop of Lugol’s iodine from the dropper bottle to one side of the coverslip. By placing a small piece of paper towel near the opposite side of the coverslip, you can “draw” the iodine stain under the cover slip and the onion epidermal tissue will now be stained.
6. Observe the stained epidermal tissue under low power and high power. Sketch several cells as they now appear stained with Lugol’s iodine. Lugol’s iodine is used to detect starch, so you may see some starch compounds stained dark blue or black.
______X (low power) ______X (high power)
7. Obtain one leaf (they are very small) of the aquatic plant Elodea. Make a wet mount of the entire leaf using water.
8. There are several layers of tissues present in this leaf. Observe the cells of this leaf under low power. When observing this leaf under low power, focus up and down through these layers. Focus on the tissue layer that contains green chloroplasts. Each rectangular cell will contain many chloroplasts. Sketch a few cells of this layer of tissue with chloroplasts. Observe under high power and sketch.
______X ______X
a. What is the function of the chloroplasts in these cells? ______
______
9. Obtain a small piece of the reddish leaf (Wandering Jew plant) and make a wet mount. Be sure that the reddish side is facing up. This is the under side of the leaf and it should contain guard cells embedded in the lower epidermal tissue cells.
Using low power, find a pair of guard cells and sketch them. Sketch a few surrounding epidermal cells also. Label the cell parts that you can see.
______X
a. What is the function of these guard cells? ______
______
Procedure for animal tissues
All of the observations of animal tissues will be made from slides that have already been prepared. The tissues were stained for better viewing of parts, and a coverslip was glued on top. This is known as a “preserved” slide of the tissue. They are expensive, so please be careful with them.
1. Obtain a preserved slide of scalp skin. These cells are still attached together as they are on the scalp to form the tissue. It has been stained for optimum viewing.
Sketch the tissue as you see it, either under low or high power.
______X
a. Comparing animal cells to plant cells, why do you think it is so difficult to distinguish one scalp cell from the other cell like we could when we looked at the onion epidermis tissue?
______
2. Obtain a preserved slide of human blood. It contains mostly red blood cells that are very small, some larger white blood cells and a few platelets. The cells have been stained for better viewing of the white blood cells and platelets. This is a smear; the cells of the tissue are not attached to each other. You will need to adjust the light. Scan the slide thoroughly to find the few white blood cells scattered among all the red blood cells. Sketch a few red blood cells and white blood cells. If you find any platelets, sketch them also. Label the different cells that you find.
______X
a. Contrast theappearance of human red blood cells and white blood cells. ______
______
b. What are the roles of the red blood cells, white blood cells, and platelets? ______
______
Discussion Questions:
1)Multicellular organisms are only made up of eukaryotic cells. Describe at least 5 differences between a generalized eukaryotic cell and prokaryotic cell.
Eukaryotic cellProkaryotic cell
2)As humans, we have many, many different types of cells in our body. Recreate the flow chart of smallest living unit in a human to the actual human, using a muscle cell as the first unit.
muscle cell human
(tissue)(organ)(organ system)
3)We don’t think of plants as having organs and organ systems, but they have many tissues working together, like us.
- The veins of the leaf and the veins in our bodies have similar functions. What is the function of our veins and what organ system are they a part of?
- Plants have stomata (formed by guard cells) as openings to allow gases in and out. What is the organ system in our bodies that has a similar function?