Present tense or past tense for presenting someone else's paper? I am supposed to present the famous Gregor Mendel's 1865 genetics paper. 
So what tense I am supposed to present it in? Whether I must use present tense or past tense? A general advise regarding presentation viewpoint would be helpful.
It depends on your sentence construction. Use the past tense when talking about what Mendel did, since he did it 150 years ago; use the present tense when talking about what the paper says, since the paper still says that now.  For example, "Mendel did experiments on pea plants. His paper describes the results."