For each of the three groups, a clinic recorded the average number of sperm cells in 1 cm3 of semen and the percentage moving forward. The groups were diffe...
Question 1 Report
For each of the three groups, a clinic recorded the average number of sperm cells in 1 cm3 of semen and the percentage moving forward. The groups were different adult male volunteers who had provided samples after the same period without ejaculation.
| group | mean sperm concentration / million per cm3 | sperm moving forward / % |
|---|---|---|
| A | 52 | 61 |
| B | 18 | 58 |
| C | 49 | 19 |
(a) Complete the sentence: group B has the lowest sperm __________. [1]
(b) Which group has a sperm concentration closest to 50 million per cm3 and the lowest percentage moving forward? [1]
(c) Calculate the mean number of sperm cells moving forward in 1 cm3 of semen for group A. [2]
(d) Describe why both sperm concentration and movement are relevant to the chance of fertilisation. [3]
(e) State three variables the clinic should control when comparing samples from different male volunteers. [3]
Answer Details
(a) Group B has the lowest sperm concentration, or sperm count. [1]
(b) The group with a concentration closest to 50 million per cm3 and the lowest percentage of sperm moving forward is group C. Its concentration is 49 million per cm3 and 19% move forward. [1]
(c)
\[52\ \text{million cm}^{-3}\times\frac{61}{100}=31.72\ \text{million cm}^{-3}\]
The mean number moving forward is 31.72 million per cm3, or 31.7 million per cm3. [2]
(d) A greater sperm concentration increases the chance that sperm reach the ovum. However, sperm also need to move through the female reproductive tract. A motile sperm can reach and fertilise the ovum, so both number and movement are relevant. [3]
(e) Three suitable control variables are the period since last ejaculation, temperature during testing, and the time between producing and testing the sample. Sample volume and using the same counting method or microscope magnification are also acceptable. [3]
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