Answer:
When calcium concentration increases during depolarization, it shifts the conformation of troponin and tropomyosin, and actin is able to associate with myosin. As calcium is taken up again by the sarcoplasmic reticulum the muscle cell relaxes.
Its common. In the last 10 million years, there have been 4 or 5 reversals per million years
All living creatures are classified into systems and sub-systems based on their similar characteristics. They are divided from bigger groups into smaller groups based on the detail of their similarities i.e. how they look, move, reproduce and how they relate to each other. A practical way of understanding the classification of living organisms is that organisms are linked to other similar organisms via family trees. The classification of all living creatures includes at least four levels: order, families, genus and species.
Well matter is basically any substance that has mass and takes up space. Example, you have a ball, or a table, or anything really. That is mass. But anything that doesn't take up space or has mass isn't matter. So, anything that doesn't have a mass or take up space is not matter. Hope this helped you understand. :D
