Which term means blue discoloration of the skin caused by a lack of adequate oxygen?

Which element is used in photosynthesis found in atmosphere and fixed by bacteria?

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

Q: a: in sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins