Sometimes it might not be convenient to use additional lights, such as in a classroom, so it is absolutely fine to go ahead and animate without. Creativity is the thing that matters!
If you are able to block out daylight and use at least one lamp, it will increase the quality of your final animation. Daylight varies in brightness throughout the day and can create flicker in your animation.
If you want to reduce this, the best thing you can do is to block out natural light – draw the curtains and close the blinds, and use task lamps.