Which of the following must occur for speciation to happen?
geographic isolation
reproductive isolation
temporal isolation
behavioral isolation

Use the drop-down menus to label each of the following changes p for physical change and c for chemical change.

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.

What percentage of light hits earth's surface directly?