Evolution — BIOLOGY STD 12 Science — Question

In the classification, organisms with similar characteristics are placed in the same group. There are some animals which share the characteristics of two different groups. These animals are called connective links.
Examples of connective links are as follows :
1. Fossils of Aracheopteryx have been found in the Bavaria region of Germany. Some characteristics of this animal, such as—the shape of beak, wings and legs, are from the class Aves, while some characteristics like the presence of teeth, tail and scales on the body are from the classreptilia hence it is called the connecting link between birds and reptiles. This proves that birds have evolved from reptiles.
2. Similarly, the egg-laying mammals platypus and echidna are the connecting link between reptiles and mammals.
3. Peripatus is called the connecting link between phylum Annelida and phylum Arthropoda. Importance of Connecting Link in biological Evolution : Connective links are an important basis for proving biological evolution. Through them, knowledge of definite genealogy and ancestors of different castes and classes is available and the course and direction of biological evolution is also determined in them.