Ch. 7 Cells
State Standard: H.1L.4 -- Explain how cellular processes and cellular differentiation are
Name:
regulated both internally and externally in response to the environments in which they exist.
10
Response
Excellent
8
Proficient
6
Adequate
4
Incorrect
1
Fails to complete
Scoring Rubric 1-4
Responses are clear, complete and demonstrate a thorough
understanding of the subject matter
Completes the assignment or experiment satisfactorily, but the
explanations have minor flaws
Begins the assignment and explanation satisfactorily; but omits
significant parts or fails to complete.
Assignment and its explanations are not accurate. Group did not
demonstrate understanding or authentic knowledge
Did not participate
Score
Are There More Dividing Cells or Resting Cells in a Root Tip?
A plant grows in length at the tip of the stem and root. In the stem and root top there is a small group of cells
that divide many times; however, not all cells in the parts may be dividing. A dividing cell may be next to several
resting cells and a resting cell can be surrounded by several dividing cells.
Cells in mitosis are different from resting cells. Some parts of a cell are seen best only when a cell is dividing.
These parts seem to disappear after a cell has divided.
Keywords
Define the following keywords:
Dividing cell
Resting cell
Root tip
Procedure
1. Obtain a picture of an onion root tip as seen under a microscope.
2. Look for a cell that resembles Step 1 of mitosis, as shown in Figure 2.
3. Count the cells in your field of view that resemble Step 1 of mitosis. Count
the cells a column one at a time going from left to right.
4. Record in Table 1 the number of cells that resemble Step 1.
5. Draw the cell in the space provided and label the parts.
6. Repeat steps 3, 4 and 5 for the remaining steps of mitosis shown in Figure 2.
Step 1 prophase
Step 2 metaphase
Step 3 anaphase
FIGURE 1. -low power
Area of
mitosis
Step 4 telophase
Interphase (rest)
FIGURE 2.
Step 1
prophase
Step 2
metaphase
Step 3
anaphase
Step 4
telophase
Interphase
(rest)
Table 1.
Number of
Steps of
Cells seen
Mitosis
1
2
3
4
Resting cells
Total
7. A biology student was looking at an onion root tip through the microscope and made a drawing of the cells she
saw as seen in Figure 3. Record on the chart how many cells you think she saw in each step of mitosis and the
number of resting cells.
Table 2
Cells Seen by a Student
1
Figure 3.
The Student's Drawing
2
3
4
Resting Cells
Total Cells Seen
Questions
1. What part is seen in the resting cells that is missing in cells that are dividing?
2. What parts are seen in dividing cells that are not visible in the resting cells?
3. Look at Figure 4 again. Why do you think new cells are sometimes called resting cells?
4. Which cells did you see more of in the onion root, dividing cells or resting cells?
5. Which step of mitosis was most common in the onion root?
6. Which step of mitosis was least common in the onion root?
7. Suppose you examined another root tip and saw that half of the cells were dividing. Would this root be
growing faster or slower than the one you examined in this exercise? Explain your answer.