Write as if you are writing to someone who knows nothing about Biology. for example your younger brother or an aunt or uncle who has been out of school for a long time. It is through the process of writing and explaining that you will learn and understand Biology.   

Each write up will contain ---  
Title.  A brief descriptive title (One that describes the experiment).  
Purpose.  A paragraph or less that explains WHY the laboratory experiment was assigned.  (i.e. What principles were demonstrated.)  
Material and Methods.  This section can refer the reader to the lab manual and only discuss where the lab we did differed from what was written in the manual.
Results.   This section explains what happened during the lab. Often data are displayed in graphs and tables.  You should not use the tables that you were provided to collect data during the lab because they often contain discussion material. Only present results. Briefly summarize the key points of the results in your text in addition to the graphs and tables.. There should be no interpretation of results in this section; save that for the discussion.

• Are tables or graphs used effectively and appropriately?
• Are all the important results summarized IN THE TEXT?
• Are axes appropriately scaled on graphs?
• Is excessive detail and reporting of non-essential data avoided?

Discussion. This is perhaps the most important part. This section explains your results. Be sure to look at the purpose and see if your discussion includes all the items you wrote in the purpose. Your explanations should demonstrate a clear understanding of the lab assignment, results and  purpose for the assignment (what concepts were demonstrated?). It should also include what went "wrong", why and how things might be improved the next time.

• Is the audience a person who needs to be told about the lab in order to understand it?
• Is there reasonable and creative speculation when needed?
• Are the arguments cogent and convincing?
• If the discussion question requires a calculation, is it clearly shown?
• Is there an in-depth, informed discussion, based upon supplemental reading?

Conclusions.  This should be a brief summary that states what occurred during the lab and what you learned from it.   You should restate the principles that were demonstrated during the lab and how the lab was successful (or not) in showing them.

Recall that you are providing me with a piece of material that demonstrates your knowledge and understanding of the lab, why it was done, and how it helped clarify principles in this course.