User:Crithikacella

The earlier multicellular animals were soft marine invertebrates including sponges, snakes, jellyfish, clames ,and worms. The first true vertebrate (jawless fish )-an animal with a backbone ,appeared around 530 million years ago. Jawless fishes gave way to cartilaginous fish like sharks and later on to bony fish. About 430 millions years ago, life began to move to land with the first land plants and animals appearing on earth. Early amphibians -the first land animals ,ressembled fish but had legs and could breathe in air. They were very much like the tadpoles of frogs we see today. Another hundred million years later, reptiles like crocodiles and turtles appeared on earth. Reptiles were better suited to live on land and spend the majority of their time on land. After reptiles ,came the early mammals that resembled reptiles. The first mammals evolved from therapsids -the link between reptiles and mammals. As mammals became more common, the first of birds appeared. Both mammals and birds are believed to have originated from reptile-like ancestors. It was around 1.8 million years ago when the newer groups of mammals -monkeys ,gorillas and chimpanzees came. Between 1.8 million years to present, humans appeared and soon dominated the land.