After wind erosion, the igneous rock turns to sediment. It may be dropped into a river where the sediments go through cementation and compaction. Then it become a sedimentary rock. This cycle goes on forever. It is called the rock cycle.
Answer:
Our atmosphere (air) is comprised of 78% of nitrogen. However, this nitrogen is in its elementary state (N₂) and therefore is quite inactive, so the plants can not use it directly. Changing the elementary nitrogen into more reactive forms (NH₃, NO₂, HNO₃) is occurring through the process called nitrogen fixation. It is happening via two processes.
First one is physical nitrogen fixation. When some type of atmospheric physical energy (lightning bolt, for example) reacts with N₂, it splits it in two very reactive N atoms, enabling them to react with oxygen in order to form NO₂.
Second process is biological nitrogen fixation. It's done by bacteria, special bacteria living in the soil, able to use elementary nitrogen for its metabolical pathways resulting in production of ammonia, which can be used by plants. It's noteworthy that bacteria are responsible for about 90% of all nitrogen fixation.
Muscle is composed of small units known as myofibril which itself composed of cylindrical bundles of thread like filaments; thick filament and thin filament known as myosin and actin respectively.
These filaments make up a myofibril which is organized into a chain of contractile units called sarcomeres. . There are two more proteins known as titin and nebulin which also contribute to the structure of sarcomere.
The function of the muscle is to contract and these filaments play a major role in it
