. Recombination introduces variation into a population because: a) crossing over produces new mutations b) crossing over eliminates mutations c) crossing over places new mutant alleles next to old combinations of alleles d) crossing over changes genotypic frequencies e) crossing over changes allele frequencies

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.