Life first originated on earth around 4.1 billion years ago according to some geological evidence. Within the first billion years of Earth’s history, life appeared in the oceans and began to affect Earth’s atmosphere and surface, leading to the rapid increase of anaerobic (don’t need oxygen to survive) and, later, aerobic (need oxygen to survive) organisms. Over 99% of all species that ever lived on Earth are extinct.
Life as we know it is possible on Earth due to many favourable conditions which can’t be found on any other planet of our solar system such as strong magnetic field to deflect the harmful cosmic rays, ozone layer to protect the life form from UV rays, falling in habitable zone of sun, atmosphere composition, enough water for life to take a breath and many more.
The shape of Earth is nearly spherical. There is a small flattening at the poles and bulging around the equator due to Earth’s rotation. To second order, Earth is approximately an oblate spheroid, whose equatorial diameter is 43 kilometres (27 mi) larger than the pole-to-pole diameter.