Which question could be answered using dna as a molecular clock? how old is a dinosaur bone? how long ago was a dinosaur track left in the mud? how long ago did two species of birds share an ancestor? how old was a bird when it died?

How long ago did two species of birds share an ancestor?

Explanation:

Molecular clocks estimates the time of divergence of two species or populations from each other. The process compares the total number of different nucleotide present in genome of two organisms. The average rate at which the specific gene evolves tells about the dates of evolutionary branch points. By comparing the total number of different nucleotides present in genome of two birds species, molecular clock can answer "How long ago did two species of birds share an ancestor?"

name and explain one of the event that occurs during meiosis that increases the variation in offspring even more than simple reproduction?

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.