The observed frequency of heterozygotes for a particular gene is considerably greater than the frequency expected on the basis of the Hardy-Weinberg equilibrium. A population is in Hardy-Weinberg equilibrium for a gene having alleles A and a .
Older rocks contain fossils of simpler organisms.
Fossils in younger rocks are more similar to living organisms than are fossils in older rocks. Species known only from fossils are defined on the basis of the biological species concept. All of the above are true. Only a and b above are true. Mutations are usually beneficial to the organism that possess them.