Epiglottis
The epiglottis is a flap of cartilage the covers the entrance to the throat protecting the lungs from obstruction. It moves when we swallow to allow food in.
1. a sugar, a phosphate, and a base (such as Adenine.)
2. Deoxyribose
3. TCGAGTC, A pairs with T and G pairs with C
4. 55 adenines, 100-45=55
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
Some organisms observed by Charlis Darwin are as follow:
1. Beetles
2. Giant tortoise
3. Mockingbird
4. Rhea
5. Pigeon
6. Sand lady slipper
