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.
Answer:
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water 
Physical property is defined as the property of a substance which becomes evident during physical changes. Water is liquid at room temperature whereas hydrogen and oxygen are gases at room temperature.
Chemical property is defined as the property of a substance which becomes evident during chemical changes. Water reacts with metals to form bases, hydrogen reacts with metals to form hydrides and oxygen reacts with metals to form oxides.
B.the mass of carbon dioxide plus water is less than that of paper plus oxygen.
Phenotypic variations in genetically identical organisms that grow in the same controlled environment may be due to mutation.
<h3>Mutation</h3>
This refers to a sudden change to the DNA sequence of living organisms.
When the DNA base sequence of organisms changes, the effect is shown in the morphology of organisms.
For organisms that are genetically identical but grow in different environments, phenotypic variations might exist as a result of environmentally acquired traits during the struggle to adapt to their environments.
In the same environment, however, genetically identical organisms are not expected to be phenotypically different, unless a mutation to the DNA of one has occurred.
More on mutation can be found here: brainly.com/question/17106056
