Ariana Rivens

  • I changed two words in my question

Question:

How does sexual selection fit into evolution?

Initial Model:

1851hmkl_Orignal-Model.jpg

Claim:

Sexual selection play a role in evolution by making the distinction of male and female animals of a species by the act of mating and who produces the offspring, which in turn are affected by natural seleciton, a main part of evoultion.

Evidence:

  • The male and female duck have distinctively different body and feather colors because of their unique purposes. For instance, the anas playtyrhynchos male (drake) has the bright green head and blue patch of feathers to attract the female for mating. The anas platyrhynchos female (hen) has the brown/white colored feathers that are passed down to the offspring from reproduction.external image Anas_platyrhynchos_4,_Tallahassee,_20020309.jpg external image 220px-Mallard_speculum.jpgexternal image Anas_platyrhynchos_(female)_1c,_Tallahassee,_20020309.jpg
  • Male and female sheep have a significant difference in horn shape and size because of the male's need to win fights (showing dominance) to gain the female's affection. The male's horns are longer and more curved, while the female's are much shorter and only round slightly.
external image 200px-Big_Horn_Seep_4304c.JPGexternal image 200px-Bighorn_sheep_%28Ovis_canadensis%29.JPG
  • Competition between members of one sex for the affection of the other, using natural selection to determine the most fit, aka the one with the most offspring.+
    • Characteristics Favored in Competing Sex : Endurance Rivalry/Contests/Mate Choice/Sperm Competition/Scrambles.
  • Male mating success is determined by how long it takes to attract a female, and the fitness of their offspring in their environment.
  • Female choice is a huge part of sexual selection.

Final Model:

1851gxkh_New-Sheet.jpg

Reasoning :

My original claim was proven correct through the evidence I found in my articles. Animals ability to produce offspring through sexual reproduction involving a male/female are affected by the mating process. This in turn means the male animals of a species have distinctively different features to be eligible for mating. In the bighorn sheep, the rams horns are specifically bigger and more curved to help protect in territorial fights. On the other hand, bighorn sheep ewes have smaller, less damaging horns because of their role to carry the offspring and be courted. The most fit males are the ones who end up with the most number of offspring, resulting in them having successful lives. The males without these traits usually die off without reproduction, confirming the use of natural selection within the sexes. Without sexual selection, much of the diversity between male/female genders would be less significant. As the offspring grow and produce their own offspring, these specific traits are either helpful or harmful towards them, allowing an evolution of the species.


Andersson, M. B. (1994) Sexual Selection. From
http://books.google.co.uk/books?hl=en&lr=&id=lNnHdvzBlTYC&oi=fnd&pg=PR15&dq=+sexual+selection&ots=duYcijIxu-&sig=231-xYjTSrU0I83TabAIcSCphDc#v=onepage&q&f=false accessed on November 30, 2011.

Birkhead, T. R. and Anders Pape Moller. Sperm Competition and Sexual Selection. (1998) From
http://books.google.com/books?hl=en&lr=&id=FhvmHW972mAC&oi=fnd&pg=PP2&dq=sexual+selection&ots=Ns2cOTMxWS&sig=kJj9En-AdBVJdngqdCUIaKgonsY#v=onepage&q&f=false accessed on December 1, 2011.

Emien, Stephen T. and Oring, Lewis W. (1977) Ecology, Sexual Selection and the Evolution of Mating Systems. From
http://www4.nau.edu/shustercourses/BIO%20698/Literature/Emlen_Oring1977.pdf accessed on December 1, 2011.

Rice, William R. (1983) Sex Chromosomes and the Evolution of Sexual Dimorphism. From
http://www.jstor.org/pss/2408385 accessed on December 2, 2011.