Symmetry is the arrangement of body parts such that they can be divided equally along an imaginary line or axis. Considering various organisms’ different shapes and orientations, scientists have developed three basic types of symmetry – radial, bilateral, or asymmetrical.
Types of Symmetry in Biology
Radial symmetry is the arrangement of body parts around a central axis. It is similar to the sun’s rays or a sliced pie. Radially symmetrical organisms have a top and a bottom surface. However, they do not have left or right sides and separate front or rear portions.
In contrast, bilateral symmetry is a body arrangement that divides the organism into two halves through a sagittal plane. The two halves, left and right, are mirror images. Animals with bilateral symmetry have a head (anterior) and tail (posterior), front (dorsal) and back (ventral), and right and left sides.
Again, in the phylum Porifera (sponges), organisms have no body symmetry and are thus called asymmetrical . These groups of animals share a simple body plan. Sponges have no brains, nerve cells, or organs. Some fish species, like flounder, also lack symmetry as they become adults.
What is the Difference between Radial and Bilateral Symmetry
Radial vs Bilateral Symmetry
Conclusion
Bilateral symmetry is the most spread biological symmetry among organisms, particularly in higher and complex organisms. Most animals we know have bilateral symmetry. In contrast, radial symmetry is mainly found in marine organisms and some plants. Also, organisms with bilateral symmetry have some survival advantages over radially symmetrical organisms.
- References Difference between Radial and Bilateral Symmetry – Researchgate.net Symmetry in the Animal Kingdom – Study.com Features Used to Classify Animals – Courses.lumenlearning.com Animal Characterization Based on Body Symmetry – Bio.libretexts.org Bilateral Symmetry – Study.com Radial Symmetry in Biology – Study.com
Article was last reviewed on Friday, February 3, 2023
