Identify the correct statement about the human respiratory system: MCQ with Answer and Explanation

Explanation:
A codon is a triplet of nucleotides in mRNA that codes for a specific amino acid or signals termination of translation. There are 64 codons; 61 code for amino acids and 3 are stop codons. Anticodons are on tRNA, exons are coding regions of DNA, introns are non-coding.

Explanation:
Primary succession begins on lifeless, barren substrates like bare rock, where no soil exists initially. Secondary succession occurs in areas where an existing community has been destroyed by disturbances like forest fires, floods, or logging, but soil remains. A climax community is the final, stable, and self-perpetuating stage of ecological succession, in equilibrium with the environment. Thus, statements 1 and 2 are correct.

Explanation:
The right atrium receives deoxygenated blood from the systemic circulation via the superior and inferior vena cavae. It pumps blood to the right ventricle. The left atrium receives oxygenated blood from the lungs, the left ventricle pumps to the body, the right ventricle to the lungs.