Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice - AQA - A-Level Biology - Question 3 - 2017 - Paper 1

The trained mice are able to sustain prolonged exercise due to enhanced muscle efficiency and increased oxidative capacity. Regular exercise improves the muscle's ability to utilize oxygen, which results in better aerobic energy production, allowing the trained mice to exercise for longer periods without fatigue.

Given that the diameter of the field of view is equal to the diameter of 15 muscle fibres and the area of a field of view is 1.25 mm², we can relate the area to the diameter. The mean diameter can be calculated as:

d = rac{area}{n imes rac{ ext{π}}{4}}

where n is the number of muscle fibres:

Area = 1.25 ext{ mm}^2 = 1250 ext{ µm}^2

Thus, the mean diameter is:

rac{1250 ext{ µm}^2}{15} = 83.33 ext{ µm}

So, Mean Diameter = 83.33 µm.

1. Young mice have a larger range of muscle fibre diameters compared to adult mice, indicating greater variability in muscle fibre size during development.
2. The mean diameter of muscle fibres in young mice is generally smaller than in adult mice, reflecting growth and maturation of the muscle tissue.