The two main sources of genetic variation are: a) single-gene traits and polygenic traits. b) directional selection and disruptive selection. c) genotypes and phenotypes. d) gene shuffling and mutations.

d) gene shuffling and mutations.

Explanation:

During meiosis-I, the exchange of genetic segments between the homologous chromosomes occurs. This is called crossing over. The recombinant chromatids formed during crossing over have new combinations of alleles that were otherwise not present in the parental chromatids. Similarly, the random assortment of alleles of different genes towards the opposite poles of the cell during anaphase-I also creates new gene combinations. These events of gene shuffling during meiosis recombine the genetic material and add genetic variations in the progeny.  

When genetic material undergoes any random change in its sequence, the corresponding mRNA sequence is also altered. This results in the formation of faulty, nonfunctional, less functional or no protein from the mutated mRNA. Therefore, the sudden changes in DNA called mutations also add variations.

events in order:

1.       vishnu schist

2. zoroaster granite

3. bass limestone

4. hakatar   shale

5. igneous intrusion

6. shinumo quartzite

7. dox sandstone

8. tapeats limestone

9. bright angel shale

10. muav limestone

11. temple butte limestone

12. redwall limestone  

nonconformity

answer: the unkar group shows angular unconformity because the layers are turned at angle.

unconformity

answer: specifically the angular unconformity occurs between the cambrian and precambrian rocks. the dox sandstone, shinumo quartzite, hakatar shale, and bass limestone have been filled. an angular unconformity occurs between the cambrian and precambrian rocks. the dox sandstone, shinumo quartzite, hakatar shale, and bass limestone have been filled.

disconformity

answer: the disconformities aremarked irregular lines between the sedimentaryrocks layers.