Critical Thinking Activities - Chapter 9

Question 1. Human red blood cells develop in the bone marrow from stem cells, and lose their nucleus before maturing and being released into the bloodstream. While this gives a cell that can be densely packed with hemoglobin molecules, what are the consequences as far as the longevity of the cell and its ability to replicate?

Question 2. In some birds and true bugs, the number of chromosomes is hard to determine since chromosomes get smaller and smaller until they are too small to see. Yet, in animals it is rare to find chromosomes numbering over a hundred pairs. What is the probable reason for keeping chromosome numbers low?

Answers are available to instructors in the Instructor's Manual.
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