History - History
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Q: Explain the history of earth?
| Option | Answer | Is Correct |
|---|---|---|
| 1 | Scientists have been able to reconstruct detailed information about the planet’s past. Earth and the other planets in the Solar System formed 4.54 billion years ago out of the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun. Initially molten, the outer layer of the planet Earth cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon after wards, possibly as the result of Mars-sized object with about 10% of the Earth’s mass impacting the Earth in a glancing blow. Some of this object’s mass would have merged with the Earth and a portion would have been ejected into space, but enough material would have been sent into orbit to form the Moon. Out gassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered b3 comets, produced the oceans. The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later, the last common ancestor of all life existed. | |
| 2 | form of molecular oxygen [031) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called Eukaryota. True multi cellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized the surface of Earth. As the surface continuously reshaped itself, over hundreds of millions of years, continents formed and broke up. The continents migrated across the surface, occasionally combining to form a super continent. Roughly 750 million years ago (mya). the earliest known super continent, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600—540 mya, then finally Pangaea, which broke apart 180 mya. Since the l960s, it has been hypothesized that severe glacial action between 750 and 580 mya, during the Neoproterozoic, covered much of the planet in a sheet of ice. This hypothesis has been termed ‘Snowball Earth”, and is of particular interest because it preceded the Cambrian explosion, when multi cellular life forms began to proliferate. Following the Cambrian explosion, about 535 mya, there have been five mass extinctions. The last extinction event occurred 65 mya, when a meteorite collision probably triggered the extinction of the dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life has diversified, and several mya, an African ape-like animal gained the ability to stand upright. This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain. The development of agriculture, and then civilization, allowed humans to influence the Earth in a short time span as no other life form had, affecting both the nature and quantity of other life forms. The present pattern of ice ages began about 40 mya, then intensified |
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