Question

Which of the following animals is sessile?
(A) Balanoglossus
(B) Herdmania
(C) Amphioxus
(D) None of the above

Answer 1

Animals that are fixed in one place and do not show movement from one location and place to another are termed as sessile animals. Animals that are members of the phylum Porifera are all sessile. These animals remain attached and fixed to a substratum in all of their lives.

Complete answer:
There are two kinds of organisms namely sessile and free-floating. Sessile animals are those organisms that remain attached to the rock or substratum. These organisms cannot move to take their food and to catch their prey. Free-floating animals are those who can swim and move across to grab their food and to capture their prey.
Now let us find solution from the given options:
Balanoglossus belongs to the family of Hemichordates. They are also termed as the acorn worms. They show movement with the help of cilia and peristalsis of the proboscis. They are also termed as burrowing Hemichordate.
Herdmania are the members of Urochordates. They are also termed as are sea squirts. The adult form of this organism is sessile, that is they remain attached to the substratum in nature.
Amphioxus is also termed as lancelet. These are meant as marine chordates. They possess an elongated body that shows tapering at both ends. They show movement with the help of the ciliary action.
Thus, the correct answer is option B that is Herdmania

Note: Poriferans were earlier observed to be as the members of plants. They are considered plants because they were attached to the substratum and they could not move, and it was believed that animals could move and plants remained attached to the surface. However, later Elis found the water circulation in the Poriferans is known to occur and classified them as animals.