Question

Which of the following is the connecting link?
A) Peripatus
B) Echidna
C) Proterospongia
D) All of the above

Answer 1

Hint:The connecting link between the organism is when an organism posse’s traits of an organism belonging to a particular family and also possess’ traits of an organism belonging to another family. This connecting link helps in the establishment of the evolutionary link between the two families.

Complete answer:
Peripatus is the connecting link between the Annelida and the arthropods. Peripatus is a primitive arthropod. It also has jointed legs and appendages and has compound eyes present. It also has the presence of tracheas. These traits show its link to the arthropods. It also has traits like the segmented body and also has segmented nephridia. The organism has a non-chitinous cuticle layer present on it. These traits of the peripatus show its link to the Annelida. So, we can say that it forms a connecting link.

Echidna is the connecting link between the reptiles and the mammals. They have a unique trait of laying eggs which is also a trait present in the mammals. Their eyes and the vision both are a hybrid variety of mammals and reptiles. They have the presence of a layer of cartilage beneath the scleral layer of the eyeball. This trait there is similar to the reptiles. So, establishing a connecting link between the reptiles and mammals.

Proterospongia is the connecting link between protozoa and Porifera. It forms a colony that is similar to that of a colony made by the sponges. It is a single-celled organism that lives in the water bodies and is found only in water in the form of a colony.

Hence, the correct answer is option ‘D’ i.e, ‘all of the above’.

Note:The connecting link is established when an organism has traits of two completely different organisms. This happens due to some evolution which leads to their formation and the other advanced species from them.