Question

Addie Logan from Sydney, Australia has been observing a population of rhinoceros beetles in her backyard for over a decade. She has noticed that males use their oddly shaped exoskeleton "horns" on their head to joust with other males to gain access to breeding sites where the single females hang out. Addie noticed that the males horns came in 3 lengths, long (LL), medium (LS) and short (SS). She also noticed that over time, the average length of all the horns has increased over time as the frequency of Long-horned individuals has increased.

What PATTERN of selection are these rhinoceros beetles exhibiting?

Question 6 options:

	Stabilizing selection
	Diversifying selection
	Directional selection
	Sexual selection

If Addie counts the distribution of horn-lengths each year and notices that the population is experiencing diversifying selection. What does this mean Addie is seeing?

Question 7 options:

	There are more beetles of each phenotype
	Horns keep getting longer
	The small horns increase
	The number of long and short horns increases, but medium horns decrease

Question 8 (1 point)

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What is a possible explanation for this pattern?

Question 8 options:

	Short horns are becoming sexy to a subset of female beetles that seek them out, but long horns still win in a fight
	Medium length horns are becoming stronger and are able to be used to displace long-horned beetles
	Long and Medium horned beetles are more susceptible to a fungal infection of their horns that causes death quickly
	Addie has removed the largest and smallest horned beetles, creating this distribution through artificial selection

Answer 1

Answer 6: Sexual selection

Sexual selection is a natural selection procedure where members of one gender choose mates of the other gender to mate with. Sexual selection can be both intrasexual and intersexual. During intrasexual selection, members of the same sex try to oust their competitors. Intrasexual selection is typically responsible for the evolution of male traits like deer antlers, beetle horns, pronounced coloration, increased size, etc., that provide the males greater success in obtaining mates. Intrasexual selection between males may occur as a combat between the males. Intersexual selection occurs when females choose mates from multiple males.

Answer 7: The number of long and short horns increases, but medium horns decreases.

When natural selection does not favour the extreme characters, rather favours the extreme characters, then it is called as disruptive or diversifying selection.

Answer 8: Short horns are becoming sexy to a subset of females beetles that seek them out, but long horns still win in a fight.

Disruptive selection occurs where individuals in high density populations face a lot of competition in competing with each other for food as well as partners to mate. Over time, the useful traits will become more frequent in the population.