BIOLOGY
... Purpose(s) The aim of this experiment is - to measure the visual field using the hemocytometer, - to estimate the diameter of the scalp hair, and - to observe the differences between the plant and the animal cell using cells of Elodea leaves and the epithelial cells from the buccal smear. Materials • Light microscope • Glass slide • Coverslips • Hemocytometer • Ethanol • Distilled water • Scalp hair • Elodea leaves • a toothpick • Safranin stain • Methylene blue Procedure At first the visual field diameter was measured using the hemocytometer under both the 10x and 40x objectives of the microscope by counting the number of squares appearing on the counting chamber. The real value is to be calculated afterwards. After sterilizing a glass slide with ethanol, a scalp hair is placed, a drop of distilled water is added and a cover slip is put onto the slide. Now knowing the visual field diameter the diameter of the hair is estimated by comparing its thickness to the visual field. The second specimen to be observed was the Elodea leaf. A single young leaf was removed and put onto the slide. Distilled water was added and a coverslip was put on the leaf. The specimen was observed under the 40x objective. Afterwards a drop of safranin stain was added to the specimen in order to make the cell wall more obvious. Then the observation was repeated. Third, epithelial cells in the buccal smear were observed. Using a toothpick, buccal was collected by scraping the inside of the cheek. Methylene blue was dropped onto the slide and the buccal was stirred in the stain. The specimen was again observed under the 40x objective. At last the both types of cells – plant cell and animal cell – were compared and the differences were stated. Results * Under the 10x objective 36 squares were counted which corresponds to: 36 x 0.05 mm = 1.80 mm The diameter of the visual field of the microscope using 10x objective is 1.80 mm. Under the 40x objective 9 squares were counted which corresponds to: 9 x 0.05 mm = 0.45 mm The diameter of the visual field of the microscope using 40x objective is 0.45 mm. The scalp hair covered approximately 1/5 of the visual field while 40x objective was being used, which corresponds to: 0.45 mm / 5 = 0.09 mm The diameter of the scalp hair is approximately 0.09 mm. * (Fig. 1.3) Elodea leaf cells are rod-shaped and have thick and dark cell walls. The most abundant structure in the plant cell is the chloroplast, which is enumerate and fills up almost the whole cytoplasm. The nucleus was not visible within the plant cells. But as time passed on a faint cytoplasmic streaming was visible (chloroplasts began to move along the cell walls). After addition of safranine stain cell walls became more obvious (Fig. 1.4). • (Fig. 1.5) Epithelial cells are shapeless and lack a cell wall structure. Nuclei are easily distinguished with the aid of methylene blue and also some other small and stained particles are to be observed. No chloroplasts exist in epithelial cells. Discussion: • The number of the squares counted on the hemocytometer using first 40x and then 10x objective agreed with the expected ratio 1:4 (9:36). With the higher magnification (40x) fewer squares (9) with more detail and with the lower magnification more squares (36) with less detail were observed....