Biology Assessment Essay

Submitted By zahradelrey
Words: 1738
Pages: 7

Using a light microscope and prepared slides to gather information and estimate the size of red and white blood cells of a human and a bird and drawing scaled diagrams of each
Aim: To perform an investigation to estimate the size of red and white blood cells using a light microscope and prepared slides of human and bird blood.
Hypothesis: If the sizes of red and white blood cells are estimated then human red blood cells will be about 6-8 micrometres and human white blood cells will be about 9-12 micrometres because white blood cells approximately 1.5 times bigger than red blood cells. Whereas bird red blood cells will be about 10-12 micrometres and the bird white blood cells will be 15-18 because the bird blood cells are larger than the human blood cells.
Materials:
- light microscope
- prepared slides of human blood
- prepared slides of bird blood
- mini-grid slide
- pencil
- paper
Method:
1. Place the mini-grid slide on the microscope on low power x4 (4x10 = 40) magnification
2. Calculate the diameter of the field of view by estimating the number of squares within the mid-point diameter of the grid slide and converting it to micrometres (1mm = 1000um)
3. Place the light microscope on high power x40 (40x10=400) magnification
4. Calculate the HP (high power) field of view by multiplying the LP field of view by 40/400 (1/10)
5. Place a prepared slide of human blood under the microscope on high power
6. Identify the red and white blood cells
7. Count the number of red blood cells across the field of view and estimate the size using the equation: cell length = field of view/number of cells across field of view
8. Repeat step 6 for the number of white blood cells
9. Draw a scaled diagram of the red and white blood cells
10. Place a prepared slide of bird blood under the microscope on high power
11. Repeat steps 5-9 for the bird blood cell
12. Record all results in a table

Results: Cell membrane Cell membrane Cytoplasm Cytoplasm Nucleus 8um 12um
Human red blood cell Human white blood cell

Cytoplasm

5um 7.5um
Bird red blood cell Bird white blood cell

Name of blood cell
Diameter of field of view (high power) in um
Estimated number of cells that could fit across diameter
Estimated size of one cell (um)

Human red blood cell
400um
50
8um
Human white blood cell
400um
Not identified
12um
Bird red blood cell
400um
80
5um
Bird white blood cell
400um
Not identified
7.5um

Working out:
Low Power = 4 x 10 = 40 High Power = 40 x 10 = 400
- Estimated LP diameter = 4mm x 1000 = 4000um
- HP field of view = 40 / 400 = 1/10 x 4000 = 400um
- Cell length = field of view/ number of cells

human red blood cell: 400 divided by 50 = 8um human white blood cell: 8um x 1.5 = 12um bird red blood cell: 400 divided by 80 = 5um bird white blood cell: 5um x 1.5 = 7.5um
Therefore the results show that red blood cells are in fact smaller than white blood cells regardless of whether it is blood of a human or another species. The shape of the red blood cells also differs from that of the white blood cell as the red blood cells appear biconcave from the side while the white blood cells usually appear in a disk shape and are spherical. They also differ in colour as the red blood cell is red in colour while the white blood cell is a purple shade due to the darkly staining nucleus it contains.
Conclusion: The red blood cells for both the human and bird blood cells were identified and the size was estimated through the estimated number of cells that could fit across the diameter. However the white blood cells were not observed as they could not be identified under the light microscope. This is due to the fact that white blood cells make up less than 0.1% whilst red blood cells make up 45% of the substance (NSW Biology 2007). Therefore the number of white blood cells was estimated by using the equation…