Mention the evolutionary significance of the following organisms :
(i)Shrews (ii)Lobefins (iii)Homo habilis (iv)Homo erectus

Explanation

(a) Shrews: About 210 mya, tree shrews-like first mammals were evolved in the early Jurassic period and were named as "Jurassic mother". These are supposed to be the earliest known ancestor of placental mammals.
(b) Lobe finned fish of group Sarcopterygii constitute a clad of bony fish. Tetrapods are thought to have evolved from primitive lobe finned fish.
(c) Homo habilis (Handy man) evolved from Australopithecus africanus about 2.4-1.4 mya and was first hominid to use stone tools. He is supposed to be the first ancestor of H. sapiens.
(d) Homo erectus (Erect man) evolved from Homo habilis around 1.5 mya. He was first human type to be found outside of Africa and displayed many anatomical characters (especially brain size and aspects of post-cranial skeleton) reflecting evolution towards the modern man.