You have incorporated diagrams and charts from various textbooks into a class presentation. You thought source citation was not required since you used the course textbook and other reference resources on the suggested reading list. Have you violated the Code?
Why is this an issue?
The authors of the diagrams and charts and the sources where they were found must be acknowledged. Without these attributions, the student is presenting the work of others as their own. Also, a TA may not recognize every chart, diagram or table from every suggested reading, and grades for originality could be allocated for what is in fact copied work.
An interview with the disciplinary officer will be required. See the Code of Student Conduct and Disciplinary Procedures in the Handbook on Student Rights and Responsibilities for more details.
How can it be avoided?
When the instructor or TA advises students to include explanatory tables, charts and diagrams, a discussion of citation expectations would be helpful. Students could be referred to the liaison librarian for the relevant academic discipline for assistance with citation requirements.
I may have copied, but I still learned! That should count for something.
Copying the work of another student harms the learner in two ways. First, it is an academic offence that carries serious consequences. Second, it affects what and how you learn; research has found that students who copy answers that require analysis or problem solving tend to receive poorer grades as their terms progress (Palazzo et al. (2010). Patterns, correlates, and reduction of homework copying. Phys. Rev. ST-Phys. Educ. Res. 6, 010104-1-11).
"Inhibitions against copying are further reduced by the fact that, when I make a virtual copy, I do not take anything physical away fromt he person who owns the original. People who would never seal a book or a painting from someone else often without hesitation copy articles and pictures on-line, especially when they feel that they are not doing so (just) to make money."
- Hinman, L.M. (2002). The impact of the Internet on our moral lives in academia. Ethics and Information Technology, 4, 31-35. doi: 10.1023/A:1015231824812