A warm air does always rise and cold air falls
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.
Answer:
by washing ourselves with soap
Answer:
The term "atom" is from the Greek word for 'indivisible',atoms are the smallest things in the matter that ould not be divided
Atoms consist of a nucleus made of protons and neutrons orbited by electrons.
Atoms are the basic units of matter and the defining structure of elements.
