As you are lifting a box, someone places extra weight on top of it. for your muscle to continue contracting and lifting the box, the muscle must

The muscle must change its contraction, wave summation and twitch mode.

Explanation:

Muscle tissue is important for the contraction and movement of an organism. Muscles contain important protein like actin, myosin and troppomyosin that helps in the movement of a particular part of a body.

While lifting a box, if someone put extra weight the muscle will shift from isometric to isotonic contraction. The muscle decreases the wave summation and turns to fast twitch mode for the continuous contraction and lifting the box.

the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.