Question

Which one of the following groups of animals is bilaterally symmetrical and triploblastic?
A. Ctenophores
B. Sponges
C. Coelenterates
D. Aschelminthes
Solution:

Answer 1

Hint: The great majority of creatures display a clearly symmetrical shape. Animals have four of these symmetry patterns: spherical, radial, biradial, and bilateral. Three germ layers—an inner layer (endoderm), an exterior layer (ectoderm), and a middle layer—are formed in animals with bilateral symmetry (mesoderm). Triploblasts are animals having three germ layers.
Complete step-by-step solution:
Animals are divided into two categories based on their body plans' symmetry and the number of germ layers they include, named triploblastic and diploblastic, respectively.
The obsolete phylum of pseudocoelomates and other similar species that are no longer thought to be closely linked and have been upgraded to phyla in their own right is known as the Aschelminthes, which is closely connected to the Platyhelminthes. Aschelminthes are triploblastic and bilaterally symmetrical.
Worldwide, sea waters are home to a phylum of marine creatures known as comb jellies, or Ctenophora. Ctenophores are diploblastic and biracially symmetric, while some species are also triploblastic.
As the sister animal group of the Diploblasts, sponges, which belong to the phylum Porifera, are a primitive animal clade. Sponges are diploblastic and asymmetric.
Coelenterates are mostly marine and aquatic species. The body is tissue-level organised and radially symmetrical. Coelenterates are diploblastic and radially symmetric.
Hence, option D is correct.
Aschelminthes is bilaterally symmetrical and triploblastic.
Note: Ecto-, meso-, and endo-derms make up the three germ layers in an animal's early embryo; this is true for triploblastic mammals. Porifera, Cnidaria, and Ctenophora are diploblastic animal phyla that solely produce ectoderm and endoderm.