Answer:
pericardium
Explanation:
A double-walled membrane, the pericardium, separates the right and left chambers, preventing oxygen-rich blood from mixing up with the one without oxygen. So, the heart functions go smoothly. Deoxygenated blood enters the right atrium.
Producers, because they're the start of the food chain and without them there will be no food chain.
1) MRNA
2) Triplet code
3) Amino acid
4) protein
