Answer:
when an object smashed into early Earth. .Explanation: no explanation just the answer
Answer:
They became closer to each other.
Explanation:
When skeletal muscles contracts the Z lines that are at the end of every sarcomere became closer to each other due to the fact that the I bands that are attached to the Z lines and contains the myosin filaments move closer to each other interacting with the actin filaments and shorten the the H zone that is in the middle of the sarcomere. In other words, It all becomes compact during a contraction.
The only independent variable in this experiment is the amount of nitrogen Sarah uses. All of the other variables are dependent on other factor and processes, but Sarah controls the amount of nitrogen that she uses for each plant.