Evolution of Plants and Animals

Evolution of Plants

Ø Cellular life forms occurred on earth about 2000 million years ago.

Ø Some of these cells had the ability to produce oxygen through reactions similar to photosynthesis.

Ø Slowly, single-celled organisms became multicellular.

Ø Seaweeds and some plants probably existed around 320 million years ago.

Evolution of Animals

Ø Animals evolved about 500 million years ago. The first of them to evolve were invertebrates.

Ø Jawless fishes evolved around 350 million years ago.

Ø Some of the fishes could go on land, and then come back to water. These were the first amphibians. In 1938, a fish Coelacanth, which was thought to be extinct, was caught in South Africa. This variety of fish, called lobefins, is believed to have evolved into the first amphibians.

Ø Amphibians evolved into reptiles. In the next 200 million years, reptiles of different sizes dominated the earth. However, about 65 million years ago, some of them such as dinosaurs disappeared.

Ø The first among the mammals were small shrew-like mammals.

Ø During continental drift when North America joined South America, primitive mammals suffered, but pouched mammals of Australia survived the same drift because of lack of competition from other mammals.