Complex organisms need cells that can perform many different functions. they need to be supported on a cellular level. Without specialized cells you they won't be able to perform different functions.
The mitotic spindle forms during pro-phase, and the centrosomes move to the opposite ends of the cell. The mitotic spindle has micro tubules that capture the chromosomes. While this process begins in prophase it continues over into metaphase.
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What is the name of this website or the book?