Biology Quarterly Exam 3 Practice 2025 – Complete Test Preparation

An organism with bilateral symmetry is one that can be divided into two mirror-image halves along a single plane, usually running from head to tail. This type of symmetry means that the left and right sides of the organism are similar in structure and arrangement, which allows for streamlined movement and specialized functions. Many animals, including humans, exhibit bilateral symmetry, which is essential for coordinated movement and complex behaviors.

The other descriptions do not accurately capture the concept of bilateral symmetry. While the first option discusses general symmetry, it does not specify the crucial aspect of having symmetrical left and right sides. The second option mentions the absence of right and left sides, which contradicts the definition of bilateral symmetry. The fourth option addresses the presence of nerve cells, which pertains to nervous system structures rather than symmetry itself. Therefore, the correct answer emphasizes the defining feature of bilateral symmetry—having a symmetrical left and right side when divided.