We had a 200 point biology lab report. My lab partner had the same content as me, and got a 200/200, while I got a 100/200. The only note I received was that my writing was almost impossible to read; there was no criticism on the actual material. This was the last big project of the year, and I have never gotten feedback regarding my handwriting on a project before. I admit that my handwriting was sloppy for the assignment, but I have all the content necessary to get a 100%. What should I do to get my grade up?
Go talk to the teacher. If you point out The answers, he may relent.
And slow down your writing from now on.
You should ask if you can redo it with the same material in better handwriting
Type or write legibly. Help your teacher grade your paper by making it an easy or even pleasant task. Imagine being a teacher and having to grade all of that stuff.
I am a doctor and have some experience with poor handwriting. We dictate thousands of pages of reports. If you talk with a transcriptionist they will tell you that they love to be assigned doctors who speak in an organized fashion, enunciate clearly without mumbling, insert punctuation or difficult spellings into the dictation etc. They hate being assigned to the person with an accent who mumbles and drones on in a stream of consciousness. We save a bunch of time if we do it well in the first place.
In the meantime apologize to the teacher for making the job difficult and ask for a verbal walkthrough of the assignment or a legible re-do.
Try to write better, and be glad your teacher didn’t give you a 0 
Was your handwriting a problem just for this assignment, or have you noticed that it is a constant problem? Kids who have been diagnosed with dysgraphia can get accommodations for school assignments, like being allowed to type them on a computer or being given extra time when the assignment involves writing.
My handwriting is nearly illegible so I understand. In fact my physics teacher wrote in my lab notebook “next time in English Please”. Best bet is to talk to the teacher and see what he or she can do
Maybe type the paper?
Remember that presentation is as important as content. If your audience can’t read or understand what you’ve written, it’s worthless.
^ was exactly my reaction. Material that isn’t legible hasn’t been presented. If you bought a book and half of its text had been blurred beyond legibility, would you feel you had read it, even if you went cover to cover?
Sorry if that sounded harsh, OP. It immediately brought up my frustration with my students, who complain about my grading in their world language for their spelling/grqammatical errors – because I couldn’t actually read their handwriting. I agree with previous posters who suggested offering to rewrite, type or explain. I would be very happy for a student to do that.