On getting signal from the brain the muscles contract as the body pulls calcium from the blood to the muscle cells. Calcium binds with troponin drawing it out of its position and tropomyosin follows troponin as these two proteins are linked together. On movement of the troponin and tropomyosin, actin and myosin activation occurs and they move towards each other thus contracting the muscle. Therefore, free calcium is required for muscle contraction.
Answer:
Large quantities of water molecules constantly move across cell membranes by simple diffusion, often facilitated by movement through membrane proteins, including aquaporins. In general, net movement of water into or out of cells is negligible. For example, it has been estimated that an amount of water equivalent to roughly 100 times the volume of the cell diffuses across the red blood cell membrane every second; the cell doesn't lose or gain water because equal amounts go in and out. There are, however, many cases in which net flow of water occurs across cell membranes and sheets of cells. An example of great importance to you is the secretion of and absorption of water in your small intestine. In such situations, water still moves across membranes by simple diffusion, but the process is important enough to warrant a distinct name - osmosis.
Most likely the first one is going to happen if there's a mutation.
Answer:
Geological, chemical, paleontological.
Explanation:
Geological evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics.
Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret.
It took some time for the current theory to be worked out.
There have been at least four major ice ages in the Earth's past.
Paleontological by their bones, remains
