Most EEB graduate students hold an assistantship to earn money while enrolled in the program.
Teaching Assistantships (or TAs) are offered in conjunction with teaching a course. The courses most often taught by EEB grads are 100s-level Biology courses, where the TA teaches several sections of the lab component. Upper-level TAs are also available for advanced grads.
Research Assistantships (or RAs) are rather rare and arise when faculty or students obtain grant money to support the RA.