Microevolution The rate of change of a given allele frequency is a good measure of how fast the species is evolving Most changes in allele frequency are small and occur over long periods of time

Atolls

Birgus latro

Birgus latro Phenotypes

Carapace Variations RR & Rr Genotypes code for Red Carapace rr genotype codes for Black Carapace

Appendage Variations AA codes for 8 legs Aa codes for 6 legs aa codes for 4 legs

1 st Breeding Season: 1.Obtain a genotype and home atoll card 2.During the first breeding season you may either stay on your home atoll and breed or migrate (if outbreeding rules allow) 3.Using a blank form located on the atoll, perform a dihybrid cross and classify each of the 16 offspring into one of the six phenotypic classes 4.Eliminate any offspring that do not meet the selective pressures of the atoll 5.Tally the number of surviving offspring in each category and the number of R, r, A and a alleles (separately). 6.When finished place the form in the “Gene Pool” Folder

2 nd -4th Breeding Seasons: 7. Retain your original genotype card 8.During the 2 nd, 3 rd and/or 4th breeding season you may either stay on your current atoll and breed or migrate (if outbreeding rules allow) 9. Be aware that during the 3 rd and 4 th breeding seasons, random selective pressures may be applied to certain atolls 10.Repeat dihybrid cross and tallying procedures, applying the selective pressure rules for each atoll as they apply. Remember to keep offspring in the gene pool for that atoll.

Going Home… 11. At the end of the 4 th breeding season, go home to your original atoll and take out the offspring records from the gene pool. 12.Sort and total all of the offspring based on the six phenotypic categories and determine the total # of surviving offspring 13. Sort and total all of the R, r, A and a alleles and total the number of alleles (from surviving offspring) for carapace color and the number of alleles for # of legs/appendages

Calculating Phenotypic and Allelic Frequencies 14.Use the formulae provided in the lab packet to calculate the following frequencies for your atoll’s population A.Frequency of Red Carapaces B. Frequency of Black Carapaces C.Frequency of R allele D.Frequency of r allele E.Frequency of A allele F.Frequency of a allele 15. Share your data for these six frequencies by posting on the front board. Use this data to help answer analysis questions #1-10