Question

what is connecting link?

Answer 1

a connecting link is anything that connects or joins one thing to another
or it is also reffered to a chain link having a movable section

Answer 2

Organisms referred to as "connecting links' are those which are structurally intermediate between two different groups.

Connecting links can be found among organisms that are still living.

Examples:- 1. 'Peripatus' has segmental nephridia, thin cuticle and parapodia - like appendages as in Annelida. At the same time, it has trachea and open circulation as in Arthropoda.

                   2. The duck-billed platypus lays eggs like reptile and has hair and mammary glands like mammals.

                   3. Lung fish though a fish breathes air through it's lungs.