Idon't understand this!
nucleotide substitutions occur by mistake in a segment of ribosomal rna at a constant rate of one substitution every 10,000 years. a biologist has compared the ribosomal rna of two modern0day species and found that they have six differences in their sequences. how many years ago did these species diverge from a common ancestor? (2 points)
select one:
a. 3,000 years ago
b. 60,000 years ago
c. 30,000 years ago
d. 6,000 years ago

Apea plant that is heterozygous for the tall phenotype can produce short offspring when self pollinating. which of the following explains why this occurs? a. segregation of allels b. condominance of traits c. polygenic expression of traits d. independent assortment of alleles

On a recent expedition to a remote region of northern canada, scientists uncovered skeletal remains from about 100,000 years ago. surprisingly, all the skeletal remains, which included many species from differing biological families and spanned about two thousand years, showed evidence of experiencing temperatures in excess of 1000 degrees fahrenheit (or 538 degrees celsius). which of the following, if true, best explains the apparent paradox between the cold environment and the evidence of the bones experiencing hot temperatures? (a) chemical changes that naturally occur during the process of decay in only one north canadian species produce the same evidence of the species' skeletons being exposed to hot temperatures as the expedition scientists found. (b) a little over 103,000 years ago, a large fire is known to have occurred in northern canada. (c) strong evidence exists that as early as 70,000 years ago, homo sapiens around the world relied heavily on fire to cook animals. (d) in the same expedition and in roughly the same layer of excavation, scientists found rudimentary wood cutting and hunting tools used by early humans.

Which phase of the cell cycle ensures that identical copies of the dna are made for daughter cells?