23_Biol221_04_14_2-11

Basolo 1990 showed that female platysh preferred

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Industrial RevoluLon the air was very sooty so tree bark was dark because of soot. Dark moths were hard to see whereas the light moths were easy to see; birds ate the light moths. As a result the dark moths became common and the light moths became rare. In recent years, since the major efforts to improve air quality, the light moths are replacing the dark moths. 51 Requirements for Hardy Weinberg Equilibrium 6. Selec=on does not act on the alleles under considera=on. NegaLve selecLon removes certain genotypes from the populaLon thereby decreasing fitness. PosiLve selecLon: increase in frequency of genotype due to increased fitness, the ability to reproduce. 52 53 Sexual SelecLon Sexual selecLon depends on the success of certain individuals over others of the same sex, in relaLon to the propagaLon of the species; while natural selecLon depends on the success of both sexes, at all ages, in relaLon to the general condiLons of life. • Males compete for females. • Females select the males on the basis of a specific trait. 54 Sexual SelecLon Sexual selecLon depends on the success of certain individuals over others of the same sex, in relaLon to the propagaLon of the species; while natural selecLon depends on the success of both sexes, at all ages, in relaLon to the general condiLons of life. • Males compete for females. • Females select the males on the basis of a specific trait. Possible benefits to being choosy: • Lower risk of maLng with the wrong species (species recogniLon) • Mate may provide paternal care • Mate may provide territorial defense • Mate may provide food (eg nupLal package) • Mate may be more compaLble • Mate may be more fecund • Mate may be less likely to pass diseases/parasites to female • Offspring may be more fit (Good genes hypothesis) 55 Sexual SelecLon alt. Female are choosy because of sensory bias Baker and Carde (1979) showed that males aHract females using pheromones normally present in their food. Searcy (1992) found that female common grackles preferred males singing an arLficial repertoire with four song types even though males in this species sing only one song type. Basolo (1990) showed that female platyfish preferred males with swords arLficially aHached, arguing that evoluLon in the sister taxa (swordtails) was shaped by this pre ­exisLng bias for swords. 56 How SelecLon Leads to EvoluLon Consider a recessive lethal phenotype like Tay ­Sachs Disease in which individuals that are homozygous recessive do not survive to reproduce. 57 How SelecLon Leads to EvoluLon Consider a recessive lethal phenotype like Tay ­Sachs Disease in which individuals that are homozygous recessive do not survive to reproduce. Only A/A and A/a survive: A/A 0.81 A/a 0.18 a/a .00 58 How Sel...
View Full Document

This note was uploaded on 01/20/2014 for the course BIOL 221 taught by Professor Gallagher,kimberly during the Spring '13 term at UPenn.

Ask a homework question - tutors are online