Researchers looking for fossils of the earliest life-forms face many hurdles. for example, few sedimentary rocks date back more than 3 billion years. review what you learned about plate tectonics in section 16.7. then, explain why so few remaining samples of these early rocks remain.

No one has ever been able to show exactly when plate tectonics began. Several studies had pegged the beginning of plate tectonics at around 3 billion years ago, but the new research suggests this dynamic started 3.5 billion years ago — only about a billion years after the formation of the planet.

Explanation:

Whatever the Earth looked like before plate tectonics, these powerful forces define the world as it is today. The diving and crashing of tectonic plates not only created the continents we know and live upon today, it also recycles minerals and nutrients through  Earth's system. One 2014 study in the journal Proceedings of the National Academy of Sciences, for example, argued that the formation of continents on early Earth brought phosphorous to the surface, feeding microbes that then oxygenated the atmosphere. [What Was the First Life on Earth?]

b - the respond is innate and varies over time.

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