The main function of white blood cells is to help protect the human body from infection as well as other foreign materials. White blood cells are also known as leukocytes, and they develop in bone marrow from stem cells. There are five different types of white blood cells<span>, including neutrophils, lymphocytes, monocytes, eosinophils and basophils.</span>
2 because the 1st energy level can only hold 2 electrons and the 2nd holds 4
I'm not sure how exactly you wanted this question to be answered. You're either talking about the symmetry where animals would have two legs or two arms for example and thus producing a pair of each muscle on both sides of the body, or you're refering to the development of agonistic and antaonistic muscles where each of them served a different purpose; either extending or contracting.
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Answer:
Pituitary gland is known as the master gland
