Question

Which phylum shows bilateral symmetry and no body cavity?
A. Coelenterate
B. Platyhelminthes
C. Aschelminthes
D. Annelida

Answer 1

Symmetry body means that when any plane passing through the body it can divide the body into two equal halves. Coelom (body cavity) is a body cavity present between the body wall and gut wall.

Complete answer:
The broad classification of Animalia based on common fundamental features such as body symmetry, an arrangement of cells, nature of coelom, patterns of the digestive, circulatory and reproductive system. Apart from the fundamental features, there are several other features which are specific for each phylum or class.
Let us look at some common features of the given phylum:

Features Phylum	Level of organisation	Symmetry	Diploblastic or triploblastic organisation	Coelom
Coelenterate	Tissue level organisation	Radially symmetrical	Diploblastic	central gastro-vascular body cavity
Platyhelminthes	Organ level organisation	Bilaterally symmetrical	Triploblastic	Acoelomate animals
Aschelminthes	Organ system level of body organisation	Bilaterally symmetrical	Triploblastic	Pseudocoelomate animals
Annelida	Organ system level of body organisation	Bilaterally symmetrical	Triploblastic	Coelomate animals

Therefore, from the above-given comparison Platyhelminthes phylum has bilateral symmetry and no body cavity.
Hence, the correct answer is option (B).

Note: Symmetry- Body symmetry can be-
-Radially symmetrical –the body divided into two identical halves when the plane passes through the central body axis.
-Bilaterally symmetrical- In this body can be divided into identical left and right halves in only one plane.
-Asymmetrical – The body does not divide into two equal halves when the plane is passing through the body axis.
Coelom: The body cavity can be of different types depending upon the presence, absence or partially presence of body cavity
-Coelomate- Full presence of body cavity.
-Pseudocoelomate – Partially presence of body cavity.
-Acoelomate- An absence of body cavity or no body cavity,