bilateraalsust

Bilaterality, also known as bilateral symmetry, is a fundamental concept in biology describing a type of body plan where an organism can be divided into two roughly mirror-image halves by a single plane of symmetry. This plane, often referred to as the sagittal plane, passes through the midline of the organism and separates the left and right sides. Organisms exhibiting bilateral symmetry are called bilaterians or bilaterally symmetrical. This body plan is incredibly widespread and is found in the vast majority of animal phyla, including insects, fish, amphibians, reptiles, birds, mammals, and many invertebrates like worms and mollusks.

The evolution of bilateral symmetry is considered a significant event in the history of life, appearing early in the Cambrian period. This body plan facilitated the development of directed movement and cephalization, the concentration of sensory organs and nervous tissue at the anterior (head) end. This allows for more efficient exploration of the environment and predator avoidance. Bilaterally symmetrical organisms typically possess distinct anterior and posterior ends, a dorsal (top) and ventral (bottom) side, and a left and right side. This organized structure allows for specialized organ systems to develop in specific locations within the body.