write a note on connecting link give in a small small points
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Connecting link is an organism having characteristics of two different group of organisms e.g, duck-billed platypus ( scientific name Ornithorhynchus anatinus) is a connecting link between reptiles and mammals i.e, it has mammary glands to feed its young ones like other mammals e.g human being, cow, buffalo etc., and ...
(I)Some plants and animals show some morphological characters by which they can be related to two different groups; hence, they are called connecting links.
(ii) E.g. In Peripatus, characters like segmented body, thin cuticle and parapodia are present like annelida and worms. Similarly, these animals show tracheal respiration and open circulatory system similar to arthropods. This indicates that Peripatus is the connecting link between annelida and arthropoda.
(iii) Similarly, Duck Billed Platypus lays eggs like reptiles but shows relationship with mammals too due to presence of mammary glands and hair.
(iv) Lung fish performs respiration with lungs irrespective of being a fish.
(v) These examples indicate that mammals have evolved from reptiles and amphibians from fishes.