Biological history of earth
First Era to 600 million years ago If we trace back the history of our earth, it first began with the formation of earth and lasted for over billion years The earth comprised a single land mass or continent called Pangaea meaning ‘all earth’ The region of Pangaea located at the north of equator, was called Laurasia and the region located at the south of equator was called Gondwanaland Daurasia consisted of present Europe and Asia, except India, Pakistan and North America, Ganwanaland consisted of Australia and Antarctica, Indo-Pak sub-continent, Africa was nothing on earth but rocks, water, and air The clumate was generally cool, having little oxygen in the atmosphere About three billions years ago, during this era, we came across evidence of the first life forms Probably, bacteria and blue green algae were the first living things to appear on the earth. Later, soft body animals such as worms and jelly fish appeared 225 to 600 million years The second era began about 600 million years ago and it D lasted about 375 million years. In the beginning, most of the land was covered with ice, and the climate was generally cool and dry This era was also called the because b during this penod, animals without backbones appeared and became permanent. Common invertebrates of this era were trilobites which had a shell that was divided length wise into three lobes They ate small organusms and decaying animals and plant materials. Trilobites became
extinct in the end of this era, Frogs and toads also appeared during middle of this era Along with algae, land animals began to appear on the land These animals included cockroaches, dragon files, scorpions, snails, spiders and many kinds of insects. 3.Third Era: 65 to 225 million years ago “The third era began about 225 million years ago, and it sted about 160 million years. Dunng this era, Pangaea started breaking up into contunents which began with moving towards present world map locations New oceans appeared between continents. The climate was cool and dry in thr beginning, but later it changed into a warm and humid This era is also called the age of because during gun this era, the number of lived on land in the oceans and air. The well-known reptiles of this age are Dinosaurs Some of une dinosaurs were very large in size measuring more than 7,000 kg Birds also appeared in this era. In the end of this era, all the dinosaurs died due to changes in the and environment, and became extinct The land also had dia, flowering plants and forests (TV) Fourth Era: 65 million years ago The fourth era began about 65 mullion years ago and is continued. This era is called the age of mammals. The mammals are the group of vertebrates which produce milk to feed their young ones, Dunng this era, they dominated world. Man, a mammal, appeared on earth about a million years ago. Animals and plants slowly continued to develop into present day forms The reptiles such as crocodiles alligators, turtles, lizards, and snakes, which belong to a previous era, adjusted themselves in this cra also. The present toothless birds with beaks also made their a map During this, the joumey of continents to present day location is said to have been completed. its journey and The Indo-Pak sub-continent ended The sea started became connected with Chitral and Ladakh towards the shirking as this land mass moved more and more north and ultimately disappeared when the Indo-Pak sub- continent got joined with Iran, Alghanistan, and Tibet Due to movement of land, mass and its collision with Asia continent, uplifting of the Himalayan mountains and mountain ranges of Khirthar, Sulaiman, Ras koh and Makran (coast ranges) formed.