POV-Ray is a free 3D rendering package, and includes the capability to produce series of frames for animation. BUT unless you have a separate mesh editor, the scenes have to be described in code (think many lines of BASIC). It’s not bad for robots, but biological subjects are
very difficult. You would also need several computers running 24/7 to render all the frames you require in a reasonable time span.
To produce the animation from the rendered frames (and add sound) you’d need an encoder such as
VideoMach. It’s shareware with a free evaluation period, after which it remains functional but watermarks the files produced. It’s so versatile it’s worth registering.