what internal features allow you to identify the dorsal and ventral sides of the earthworm
Bilateral Symmetry Definition
Bilateral symmetry refers to organisms with torso shapes that are mirror images along a midline chosen the sagittal plane. The internal organs, however, are not necessarily distributed symmetrically.
The vast majority of animals display bilateral symmetry; also known as aeroplane symmetry, this is a trait that applies to 99% of all animals, in the majority of phyla: Chordata, Annelida, Arthropoda, Platyzoa, Nematoda, and nearly Mollusca.
On the other paw, the Cnidaria brandish radial symmetry and the Porifera showroom no symmetry.
The Echinodermata are unique, in that they display bilateral symmetry in their larval stage, and a special form of fivefold radial symmetry, pentamerism in their developed life stage.
Bilaterally symmetrical animals have a dorsal side (superlative), a ventral side (bottom) and singled-out left and correct sides. They also accept an anterior side (head), and a posterior side (tail), and exhibit cephalization. Cephalization is the clustering of sensory organs at the inductive; a torso plan that arose considering animals use forward motion, and so this finish is the first to come across the environmental stimuli to which an organism must react. The bilateral body plan may also be advantageous because it permits organisms to exist more than streamline. This would have been particularly important for bequeathed organisms, which moved through the oceans.
To determine whether an animal has bilateral symmetry, information technology is possible to describe an imaginary (or real!) line down the center from its tip to the finish; a bilaterally symmetrical animal volition have two sides which are near identical, albeit a mirror image.
Examples of Bilateral Symmetry
Butterflies
Butterflies are an excellent example of near perfect bilateral symmetry. Not only practice they take a body shape that can be divided into symmetrical halves, just also the patterns on each wing of a butterfly are well-nigh identical to each other.
Humans
The bilateral symmetry in humans has been widely studied, and many advantages of the body type accept been determined. It may help united states of america to help the brain recognize when different office of the trunk are in different positions, making visual perception easier and meliorate coordination of motion. Symmetry is also beneficial in terms of balance, and is important for forward-propelling movement in a specific direction as well every bit making the process of motion easier; for example, if a human had 1 leg longer than the other, they would exist unable to walk or run effectively in the face up of danger, so this is a trait which has stuck equally being advantageous through evolution.
Lack of symmetry may be useful for identifying certain health atmospheric condition. Additionally, humans have been shown to discover faces, which are bilaterally symmetrical, more than bonny, as this is an indicator of wellness and genetic fettle. Yet, faces are never truly symmetrical, and when examined in fine particular, display much dissimilarity betwixt left and correct.
Bivalve Mollusks
Bivalve mollusks are a class of marine or freshwater organisms that have shells consisting of two hinged, bilaterally symmetrical halves; however, some species have secondarily lost their bilateral symmetry, for example oysters and gastropods such every bit snails. In this group of organisms, the sagittal plane lies along the hinge, which allows the organism to firmly close its crush and protect the soft inner trunk.
The image shows the shell and internal torso of a bivalve mussel. The symmetry of the two halves of the shell tin can be seen in the lesser prototype.
- Radial Symmetry – Refers to an organism, which has several planes that it could be cut through, to produce roughly identical pieces.
- Spherical Symmetry – Refers to organisms, which could be cut directly through the center in any direction without distinguishable departure between segments.
- Torso Plan – The group of morphological characteristics, which tin identify an organism as belonging to a particular taxonomic group, such as a phylum.
Quiz
1. Which area of the trunk does cephalization occur?
A. The Ventral Side (the bottom)
B. The Dorsal Side (the top)
C. The Anterior Side (the head)
D. The Posterior Side (the tail cease)
2. Which of the following is ¬non an reward of bilateral symmetry?
A. Better control of movement direction
B. Indication of poor health
C. Improve Visual perception
D. Allows sensory organs to be distributed throughout the body
three. Which of the following organisms is bilaterally symmetrical?
A. Lobster
B. Starfish
C. Coral Polyp
D. None of the above
Source: https://biologydictionary.net/bilateral-symmetry/
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