Who does product and project requirements and why?

I am sorry Naomi! A Business Analyst exist in most and any meaning organization. The BA's role is doing the needs assessment of an organization and coming up with the Business Case for the project. After the Business case the BA is responsible for the Product requirements and the Project requirements is the so responsible of the Project Manager. Many folks on this platform said the same thing i am saying now. Naomi is however, adding alot of spice into the conversation. Bring it on Naomi.

Wow! Many assumptions on these two requirements. The topic doesn't seem to be an easy and straightforward question that i thought it was. However, let's continue and wait for other folks on this platform comments.

Let's be practical here. A PM is selected to manage an identified project. Failing to do at least an initial business analysis to determine if any requirement exists is not logical. That would say the PM creates his/her own requirement, forms a team, then solves their own defined requirements.

In the practical world, that is not how requirements are generated, through analysis of a need for change, followed by a decision well above any PMs level to pursue that change, and the PM inherits the initial BA for use in further fleshing out their approach to solving the requirements. That may include additional analysis by the BA assigned to the team.

The project exists because a business analyst have performed the activity to define the solution, create a business case and get the approval for the project.

Perhaps so, but I would suggest that the role of the Business Analyst is to define a REQUIREMENT, and develop an initial business case, using that BA to enable a sponsor to secure approval of the project. The BA is not a manager or PM, he/she is by their title and analyst, and not a solution creator per se. They will control the products during the project, but many if not most BAs limit their analysis to identification of the problem, why it is occurring, and that it needs fixing.

I fully agree with you John. Just one comment to clarify why I fully agree with you. To develop the business case the BA needs somebody that help her/him to define the future (if approved) project requirements because inside the business case the cost must be estimated. That person must be somebody with knowledge about project management to define all related to the project (obviously with the level of degree that it is possible with the information available at this time) and other people could to be included . Sometimes that person is not the assigned project manager to the project when it is approved.