The earth is composed of three large layers: the nucleus, the mantle, and the crust. However, there are more layers within the main layers; in the case of the the asthenosphere, this is a layer of semi-molten materials that is located under the lithosphere (50 to 150km of depth) and has a thickness of around 650km. Additionally, this is located above the mesosphere, another layer of the crust that is part of the mantle, and extends to approximately 2700km deep. Additionally, this layer serves as a transition between the lithosphere and the mesosphere which are two major layers. So, the correct answer is A. Asthenosphere.
Every part of an ecosystem is vital to its survival – from the green plants to furry animals and microscopic bacteria. The group of organisms called decomposers forms the final link in the food chain. They break down dead animals and plants and return vital nutrients to the soil.
Because it is an ecological problem that could be studied by modeling more easily than by observation or experimentation, because it occurs over a large area and a long period of time
