What could account for this distribution of height in a population?

[Source: Graph adapted from Six Minutes http://sixminutes.dlugan.com/good-public-speaker-average/]

A. Gene linkage

B. Dominant alleles

C. Independent assortment

D. Multiple genes

The graph shows the relationship between mass at birth and the percentage that die shortly after birth for Scottish Blackface lambs.

[Source: Dwyer, C.M., Conington, J., Corbiere, F., Holmoy, I.H., Muri, K., Nowak, R., Rooke, J., Vipond, J. and Gautier,
J.-M., 2016. Invited review: Improving neonatal survival in small ruminants: science into practice. Animal, 10(3),
pp. 449–459.]

What type of selection for the lambs is shown in the graph?

A. Disruptive selection, as there is a drop in mortality at intermediate birth masses

B. Stabilizing selection, as lambs with low or high birth mass are less likely to survive

C. Directional selection, as lambs with a high birth mass have high mortality

D. There is no evidence in the graph of selection, as survival frequency is not shown

Explain how speciation occurs, including the different processes of isolation and selection.

Describe the changes that occur in gene pools during speciation.

Three-spined stickleback fish (Gasterosteus aculeatus) vary in the number of armour plates. The graph shows the frequency of individuals with low, partial or complete plating in a three-spined stickleback population living in Kennedy Lake, Vancouver Island, Canada.

[Source: Reprinted from Current Biology, 24, Marchinko, K.B., Matthews, B., Arnegard, M.E., Rogers, S.M. and Schluter, D., Maintenance of a Genetic Polymorphism with Disruptive Natural Selection in Stickleback.
2014.  pp.1289–1292 with permission from Elsevier.]

Which type of natural selection could result in this pattern of variation in the population?

A. Disruptive

B. Directional

C. Stabilizing

D. Convergent