Misc: what is the term for an organism that lives on or in another?

Questions

Which city in Sudan, the scene of a battle in 1898 was the residence of the mahdi?

In which geographical feature is a caldera found?

Who was a co founder of the German Gree party in 1979 and became one of the best known green mps in the world?

Whose law states that equal volumes of gas contain equal numbers of molecules when at the same temperature and pressure?

What is the name of the legendary norweigan sea monster which awoke in the title of the 1953 science fiction novel by John Wyndham?