Answer:
A rotting log is nonliving. However, it can have mold, lichen, or fungus growing on it, which is not the log itself. Those three things are living. And though the log was once a living tree, at it's current state, it is nonliving.
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Scientists interpret the fossil of Ichthyostega through Comparative Embryology which states that:it has been observed that a very young human embryo look very similar with young embryos of other vertebrates in their structure and appearance.
Example: the young human ambryo look very similar with young embryos of birds, frogs,fish and reptiles.This show that,at certain stage of their development all these embryos had fish like features with gill slits and a vascular system,also they posses a simple heart with a single blood circulation.
Solution:
Nitrogen is important because, it helps us grow crops, and it produces grass for animal. It comes from lightning and is named nitrogen fixation
By which free nitrogen (N2) is extracted from the atmosphere and converted (fixed) into nitrogen compounds which are plant nutrients (fertilizer). In nature, this process is carried out by certain bacteria (present in the root nodules of legumes such as beans and peas), blue-green algae, and the lightning flash.
Thus the Nitrogen form the atmosphere the biotic part to the ecosystem converted into the biotic part.