Difference Between Radial Symmetry vs. Bilateral Symmetry

Main Difference

The main difference between the Radial Symmetry and Bilateral Symmetry is that Radial Symmetry produces mirror images around the central axis and Bilateral Symmetry produces left and right sides.

Radial Symmetry vs. Bilateral Symmetry

Radial Symmetry produces identical halves of the body along the central axis, whereas Bilateral Symmetry produces left and right side along the sagittal plane. Radial Symmetry arranges the body parts in a regular pattern along the central axis, whereas Bilateral Symmetry arranges body part equally both in left and right sides. Radial symmetry is good for sessile organism while Bilateral symmetry allows good movements. Radial symmetry does not allow quick access to food. On the other hand, Bilateral symmetry permits quick access to food. Radial symmetry does not lead to the development of the head at the front side of the body, while Bilateral symmetry leads to the development of the head at the front side of the body. Radial symmetry in flowers is termed as actinomorphy, whereas Bilateral symmetry in flowers is termed as zygomorphy. Radial symmetry does not have body characteristics of top and bottom, anterior and posterior while Bilateral symmetry have body characteristics of top and bottom, anterior and posterior

Comparison Chart

Radial SymmetryBilateral Symmetry
Radial symmetry is the arrangements of parts in the organisms in a way that when the organism is through the center of the structure from any direction, it produces two halves that are mirror images of each other.Bilateral symmetry is the arrangements of body parts into left and right halves in such a way that they are mirror images along the central axis.
Division of Body
Do not divide the body into left and right sidesDivide body into left and right by sagittal plane
Development of Head
Head development on the front side of the body is rare.Head development on the front side of the body is a significant feature.

Examples

Jellyfish
Sea Urchin
Sea Anemone
Humans
Insects
Crustaceans

What is Radial Symmetry?

Radial symmetry is defined as the arrangements of parts in the organisms in a way that when a cut is made through the center of the structure from any direction, it produces two halves that are mirror images of each other. For example, In plants stems and roots exhibit radial symmetry, and in animals, the radial symmetry is shown by the organisms of the phylum Cnidaria and Echinodermata. Radial symmetry is also exhibited by the flowers, but in flowers, Radial symmetry is termed as actinomorphy. All the radial symmetry exhibiting organisms resemble a pie and produce identical pieces when they are cut from any plane. Radially symmetric animals are mostly symmetric about their axis. Radial symmetry is good for sessile organisms, slow-moving organism and floating organisms, e.g. sea anemone, starfish and jellyfish respectively. Radial symmetry has some special forms like tetrameric, pentamers, hexamers, and octamers. Tetramerism radial symmetry is exhibited by the jellyfish as it has four canals arranged radially. Pentamerism is also called pentaradial or pentagonal symmetry. Pentamerism describes that the organism has five parts around a central axis, which are 72° apart. Examples of Pentamerism are members of echinoderms like a sea urchin. Hexameric is found in the organisms having hexameric body plan, their polyps have tentacles in a multiple of six and possess sixfold internal symmetry. Examples of hexameric exhibiting organisms are corals and sea anemones. Octamer is found in corals having polyps with eight tentacles and possessing octameric radial symmetry.

What is Bilateral Symmetry?

Bilateral symmetry is defined as the arrangements of body parts into left and right halves in such a way that they are mirror images along the central axis. Bilateral is a combination of two words i-e bi, meaning two and latus meaning side. Similarly, the word symmetry is also a combination of two words i-e syn meaning together and metron meaning meter. Bilateral symmetry is also called the left/right symmetry. The left and right halves are not the same, but the fact is many organisms exhibit the bilateral symmetry, approximately 90% including most advanced creature humans. All vertebrates and a little number of invertebrates show Bilateral symmetry. The plan that divides the organism vertically into left and right halves are called the sagittal plane. Bilateral symmetry is, therefore, reflection symmetry. Animals that possess the bilateral symmetry exhibits a type of movement that refers to one end of the body as the end, which leads. Organisms having the bilateral symmetry must have head and tail, anterior and posterior, top and bottom and left and right regions. Bilateral symmetry allows the organisms to move faster as compared to any other body symmetry. Bilateral symmetry also allows organisms to find food or avoid predator easily. Bilateral symmetry is also possessed by flowers, and in flowers, the bilateral symmetry is termed as the zygomorphy.

Key Differences

  1. Radial symmetry produces identical halves of the body along the central axis whereas Bilateral symmetry produces left and right side along the sagittal plane.
  2. Radial symmetry does not produce the right, and left halves of the body, on the other hand, Bilateral symmetry produces the right and left halves of the body.
  3. Radial symmetry produces mirror images, while Bilateral symmetry does not produce mirror images.
  4. Radial symmetry arranges the body parts in a regular pattern along the central axis whereas Bilateral symmetry arranges body part equally both in left and right sides.
  5. Radial symmetry does not lead to the development of the head at the front side of the body while Bilateral symmetry leads to the development of the head at the front side of the body.

Conclusion

The conclusion of the above discussion is that Radial and Bilateral symmetry is the arrangement of body parts of the organism and it differentiates organisms into two classes based upon the arrangement of body parts in organisms

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