What is the ancestor of fish?

Pikaia

The first ancestors of fish, or animals that were probably closely related to fish, were Pikaia, Haikouichthys and Myllokunmingia. These three genera all appeared around 530 Ma. Pikaia had a primitive notochord, a structure that could have developed into a vertebral column later.

Explanation:

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answer; ///(b) it is composed of four protein chains and four heme groups;

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