What is plate tectonics, and how does this theory explain past movement of the continents? How have past tectonic movements affected the present-day distribution of plant and animal species on Earth's surface?

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Answer 1

Plate tectonics is a "grand theory" that "helps us to understand earthquakes and volcanic activity, and is key to understanding the geographic distribution of present-day biota." The lithosphere "can be visualized as huge slabs of rock floating on an elastic layer beneath. This is much like crackers floating next to each other in a bowl of soup. These slabs of rock are called tectonic plates. Some fourteen major plates and a few minor ones make up the lithosphere. "Within Earth's semi-molten interior, hot material rises toward the surface and spreads out at some locations, while cooler material sinks toward the interior at other locations. Riding atop these convection currents, the plates move slowly, but inexorably, with respect to one another. The spreading process of the past 225 million years has brought the continents to their present positions. It also accounts for the other interactions between tectonic plates. In addition to the periodic catastrophic destruction that may be caused in localized regions by earthquakes and volcanic eruptions, tectonic movement may gradually lead to major shifts in climate in three ways. First, as continents gradually move to different positions on the globe, their climates change accordingly. Second, the movement of continents alters the direction and flow of ocean currents, which in turn have an effect on climate. Third, the uplifting of mountains alters the movement of air currents, which also affect climate." We find every region on Earth occupied by well-adapted living organisms, so it is clear that they have been able to evolve, undergo speciation, and adapt to these geological changes. We can understand the present-day distribution of plants and animals only in light of continental drift and plate tectonics.