Question

QUESTION 3 [2 marks] Escherichia coli are bacteria commonly found in the large intestines of humans and other animals. They obtain nutrients by absorption, but nutrients are scarce in the large intestine. They are rod-shaped, approximately 3 µm long and 0.5 µm in diameter. Suggest why they are so small.​[2 marks] Your answer:

Answer 1

The small size of the bacterium is an adaptation to live in the small intestine where nutrients are limiting. By maintaining a small size, they maintain a very high surface area to volume ratio. As we know diffusion is directly proportional to the area, because of the high surface area they are able to absorb enough nutrients from the large intestine required for survival. If the bacterial size is increased, it will reduce the surface area to volume ration which will decrease the absorption of nutrients. So bacteria have a small size to maximize surface area to volume ratio for maxiumum absorption.