My Mishti

  Human life on earth The existence of  diverse  definitions of life, as detailed in the previous section, surely means that life is complex and difficult to briefly define. A scientific understanding of living systems has existed since the second half of the 19th century. But the  diversity  of definitions and  lack  of  consensus  among professionals suggest something else as well. As detailed in this section, all organisms on Earth are extremely closely related, despite superficial differences. The fundamental pattern, both in form and in matter, of all life on Earth is essentially identical. Also, as noted in this section, this identity implies that all organisms on Earth are evolved from a single instance of the origin of life. To generalize from a single example is difficult, especially when the example itself is changing, growing, and evolving. In this respect the biologist is fundamentally handicapped, as compared with, say, the chemi...

  Earth history Billions of years ago, Earth, along with the rest of our solar system, was entirely unrecognizable, existing only as an enormous cloud of dust and gas. Eventually, a mysterious occurrence—one that even the world’s foremost scientists have yet been unable to determine—created a disturbance in that dust cloud, setting forth a string of events that would lead to the formation of life as we know it. One common belief among scientists is that a distant star collapsed, creating a  supernova  explosion, which disrupted the dust cloud and caused it to pull together. This formed a spinning disc of gas and dust, known as a solar  nebula . The faster the cloud spun, the more the dust and gas became concentrated at the center, further fueling the speed of the  nebula . Over time, the  gravity  at the center of the cloud became so intense that  hydrogen  atoms began to move more rapidly and violently. The  hydrogen  protons began...

  Earth  Earth  is the third  Planet  from the   SUN    and the only astronomical   object   known to  harbor  life. This is enabled by Earth being a  water world , the only one in the  Solar System  sustaining liquid  surface water . Almost all of Earth's water is contained in its global ocean, covering  70.8%  of  Earth's crust . The remaining 29.2% of Earth's crust is land, most of which is located in the form of  continental   landmasses  within one  hemisphere , Earth's  land hemisphere . Most of Earth's land is somewhat  humid  and covered by vegetation, while large  sheets of ice  at  Earth's polar   deserts  retain more water than Earth's  groundwater , lakes, rivers and  atmospheric water  combined. Earth's crust consists of slowly moving  tectonic plates , which interact to produce mountain ranges, ...