Bilateral symmetry divides an organism into two halves separated by an axis.
Bilateral symmetry is a concept that involves the division of an organism into a right half and a left half , separated by an axis . To accurately understand the meaning of this idea, it is important to consider several questions.
Symmetry is a notion that comes from the Latin symmetrĭa , although this word has its origins in the Greek language. The term is used with reference to the correspondence that is recorded in the position , size and shape of the parts that make up a whole. Bilateral , on the other hand, is that which is linked to both parts or both sides of something.
What is bilateral symmetry
In the context of biology , symmetry refers to the ideal arrangement of the body and its parts with respect to a plane, a center or an axis. Bilateral symmetry contemplates a single plane (the sagittal plane ), which causes the body to be divided into two halves that, in theory, are identical.
If a frontal (perpendicular) plane were taken instead of the sagittal plane, the body would be divided into a ventral half and a dorsal half .
Importantly, bilateral symmetry contributes to cephalization and the development of a central nervous system . In this way, this symmetry is linked to the formation of a head that becomes the center of the aforementioned nervous system.
It should be noted that many plant species also have bilateral symmetry, as is the case of the orchid .
The Vitruvian Man reflects the bilateral symmetry of the human body.
Species with this characteristic
Species that have bilateral symmetry are classified as bilateral . In these animals , the organism is symmetrical with respect to the sagittal plane. In these cases, the sides of the body are identical, although the lower half and the upper half have marked differences.
In relation to this symmetry in what the human body is, we have to say that the so-called Vitruvian Man takes special prominence. It is a drawing made in 1490 by the genius Leonardo da Vinci , which clearly shows it and also the set of proportions of the man's body.
Other interesting data about bilateral symmetry
No less interesting is knowing another series of data referring to living beings that have bilateral symmetry, among which are these:
- It is considered that a clear difference that identifies these animals is that they have organs and organ systems.
- It is established that these living beings are framed within what would be a higher level. And they have managed to have a more notable development of organs and tissues than those who do not have it.
- Animals that have this type of symmetry are classified into three large groups: pseudocoelomates, coelomates and acoelomates.
- It is interesting to know that certain animals have the peculiarity that, although at first they do have the symmetry that concerns us, later, as they develop, it disappears in its place. This would be the case, for example, of the starfish or the hedgehogs that start out having it but, as they grow and develop, it transforms into a secondary pentarradial symmetry.