Question

Connecting link between chordates and non-chordates is
(A) Peripatus
(B) Balanoglossus
(C) Sphenodon
(D) Tachyglossus

Answer 1

Connecting link is represented by an organism which has characteristics of two groups. It will act as an intermediate organism between two groups. It is used for studying the characteristics of both groups via a single organism.

Complete answer: Peripatus is the connecting link between annelida and arthropoda. That’s why it is not considered as the connecting link between chordates and non-chordates. That’s why ‘option A’ is incorrect.
Sphenodon is the connecting link between amphibians and reptiles. That’s why it is not considered as the connecting link between chordates and non-chordates. That’s why ‘option C’ is incorrect.
Tachyglossus is the connecting link between reptiles and mammals. That’s why it is not considered as the connecting link between chordates and non-chordates. That’s why ‘option D’ is incorrect.
Balanoglossus is the connecting link between chordates and non-chordates. Because notochord and pharyngeal characteristics are found in Balanoglossus. These characteristics are common to chordates. Dorsal heart is found in non-chordates. Balanoglossus also bears a dorsal heart. That’s why Balanoglossus have some characteristics of chordates as well as non-chordates. Hence it is the connecting link between chordates and non-chordates.

So, the correct option is ‘option B’ .

Organism	Connecting link between two groups
Peripatus	Annelida and Arthropda
Sphenodon	Amphibian and reptiles
Tachyglossus	Reptiles and mammals
Balanoglossus	Chordates and non-chordates

Note: Blanoglossus is the connecting link between chordates and non-chordates because this organism has common characteristics of chordates as well as non-chordates. Because Balanoglossus shows presence of notochord and pharyngeal characteristics which are found in chordates. Heart is dorsal in position in Balanoglossus which resembles non-chordates features.