Final answer:
The midsagittal plane is the plane that divides an animal into equal right and left halves, and is essential for understanding anatomical divisions in biology.
Step-by-step explanation:
The plane that divides an animal into equal right and left portions is known as the midsagittal plane. This anatomical term refers to a vertical plane that runs through an organism's body, splitting it into symmetrical right and left halves. It is an important concept in understanding anatomical structures and orientations within biology.