Bilateral symmetry is the same arrangement of body parts of an organism in the left and right halves on both sides of the central axis or plane. Figuratively speaking, if you draw a line from the head to the tail of an organism - both sides are mirror images of each other. In this case, the organism exhibits bilateral symmetry, which is also known as planar symmetry, since one plane divides the organism into mirror-image halves. We will learn all about bilateral symmetry and look at some examples. We will also discuss the main benefits.
Symmetry Definition
Symmetry is related to the orientation of an organism based on a plane or around an axis. Given the different shapes and orientations of different organisms, scientists have come up with three main types of symmetry:
- The first type is radial symmetry. With this type, the body plan is based on the axis. In other words, the body is oriented so that it reflects from behind an imaginary line through the center of the body. These organisms have a top and a bottom, but they do not have left and right sides, front and back. A couple of examples of radial symmetry are starfish, jellyfish and sea anemones.
- There are some organisms that don't show symmetry at all. They are classified as asymmetrical. The only animals that truly belong to this classification are sponges.
- The last type of symmetry is bilateral symmetry. This is when the body plan can be divided along a plane that divides the animal's body into right and left sides, which are mirror images of each other. Let's look at this type of symmetry in a little more detail.
Examples of bilateral symmetry
So now you can think of different animals that exhibit bilateral symmetry. Man is the first example we will discuss. Yes, we humans are an example of bilateral symmetry. This can be seen quite simply. Go and look in the mirror and see for yourself. We could draw a line right down the middle of your body, right through your nose, and divide you into right and left mirror images. Even your brain can be divided into equal right and left sides.
Let's look at another example. Do you have a dog or a cat? They also have bilateral symmetry. Other examples that youperhaps they did not think - these are sharks, butterflies and ants.
Bilateral Symmetry Benefits
So there are actually some real benefits to bilateral symmetry. The fact that we have two eyes and ears means we can see and hear more than most radially symmetrical animals. Bilateral symmetry also led to the formation of the head and tail region. This means that everything can go in one end and out the other, unlike those organisms that have to use the same opening. Without going into too much detail, let's just say that we are all very excited about this.
Another benefit is that bilateral symmetry allows the development of a more thorough nervous system that can control the body. Many animals have bilateral body symmetry, which means they can be split into matching halves by drawing a line down the center. In this respect, arthropods are built like humans: the right half of arthropods is a mirror image of the left half. This is bilateral symmetry.
Bilateral and radial symmetry
Most animals on the planet exhibit bilateral symmetry. This is what people have. It is different from radial. Radially symmetrical organisms are similar to the shape of a pie, where each part is almost identical, although they do not have a left or right side. Instead, they have top and bottom surfaces. organisms thatshow radial symmetry, such as corals, jellyfish and sea anemones, sea urchins and starfish.
Features of Bilaterally Symmetric Organisms
Organisms that are bilaterally symmetrical show front and back, top and bottom, and left and right sides. They tend to move faster than animals that do not exhibit bilateral body symmetry. It is also enhanced vision and hearing compared to those with radial symmetry.
Basically all marine organisms, including all vertebrates and some invertebrates, are bilaterally symmetrical. This includes marine mammals such as dolphins and whales, fish, lobsters and sea turtles. Interestingly, some animals have one type of body symmetry when they are first life forms, but they develop differently as they grow.
There is one marine animal that doesn't show symmetry at all: sponges. These organisms are multicellular, but remain the only asymmetric animals. This means there is no place in their bodies where you can split them in half and see mirror images.
