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Date November 2017 Marks available 1 Reference code 17N.3.HL.TZ0.02
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Identify Question number 02 Adapted from N/A

Question

The light micrograph shows a cross section of seminiferous tubules.

[Source: Micrograph of a seminiferous tubule with sperm by Nephron (https://commons.wikimedia.org/wiki/File:Seminiferous_tubule_and_sperm_low_mag.jpg)]

Concerns have been raised about the effect of rising pollution levels on sperm production in men. To investigate the possible effects of pollution on spermatogenesis, sperm samples from men of similar ages were collected in Kolkata in the 1980s and 2000s. The box plot represents the mean and range of sperm counts in the 1980s and 2000s.

[Source: Republished with permission of Elsevier Science and Technology Journals, from ‘Semen quality and age-specific changes: A study between two decades on 3729 male partners of couples with normal sperm count and attending an andrology laboratory for infertility-related problems in an Indian city’, Dyutiman Mukhopadhyay, Alex C. Varghese, Manisha Pal, Sudip K. Banerjee, Asok K. Bhattacharyya, Rakesh K. Sharma, and Ashok Agarwal, Fertility and Sterility, 93 (7), 2009; permission conveyed through Copyright Clearance Center, Inc]

 

A hypothesis has been suggested that pollution may have a negative effect on spermatogenesis. Evaluate whether the data support this hypothesis.

 

[3]
a.

Calculate the actual size of the seminiferous tubule in the area indicated by the line across it, giving the units.

[1]
b.i.

Identify the type of cell labelled Z.

[1]
b.ii.

Markscheme

a. hypothesis not supported as there is a «slight» increase/not much difference in sperm count between the 1980s and the 2000s

    OR

    hypothesis not supported as similar means/values for both groups

b. no information on sample size

c. no information/data provided on pollution levels/types of pollution

d. other factors affecting sperm count not considered

    OR

    other elements than sperm count could be affected

e. data limited to Kolkata/one country/one city

    OR

    pollution may affect spermatogenesis elsewhere

[Max 3 Marks]

a.

62 mm Υ400 = 0.155 mm/155 μm/micrometers/10-6 m

OR

61 mm Υ400 = 0.153 mm/153 μm/micrometers/10–6 m

Calculation and units required. Accept correct answers expressed in cm

b.i.

spermatogonium

OR

primary spermatocyte

b.ii.

Examiners report

[N/A]
a.
[N/A]
b.i.
[N/A]
b.ii.

Syllabus sections

Core » Topic 1: Cell biology » 1.1 Introduction to cells
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