Why Marquis think abortion is immoral

Why does Marquis think abortion is immoral? What is his argument? Thomson argues that abortion is permissible, at least in a wide range of cases. What are those cases and what is/are her arguments? Do Marquis's arguments challenge those of Thomson, or can one endorse both positions without contradiction? Justify your answer in either case. Cite all the texts you employ. In offering your own judgment and defence, use course concepts.