When using Gmail,
I would like to know if when we mark email as Spam, is it also reported to SpamCop.net or any other related site?
In Gmail, marking email as spam only marks it as spam for you, not for others.
If Google determines a message is spam, it is based on algorithms that match certain tendencies and phrasing that suggest the message is spam. Google doesn't share this information under almost all circumstances.
So, no, the message is not reported to outside companies.
I'm fairly sure all Google's anti-spam stuff is done in house, with their own algorithms and software. They wouldn't report it to third-parties, both for competitive and security reasons.