Season 9 Roundup

Wow - within the past two weeks we have covered so much about evolution. We started off February 13th reviewing the Voyage of the Beagle, where we took a virtual tour of the places Darwin visited, including the Cape Verde Islands, Rio de Janiero, and most famously, the Gálapagos Islands. We observed the annual rainfall and temperature changes and how that impacts the native species. The following day, we presented our virus infographics. We learned all about the history, means of replication, and the impact of Rabies virus, influenza, HIV, and more!

Anni and Michelle presenting about the Marburg Virus

Then, we learned all about the Hardy-Weinberg equilibrium. The equation, p2+2pq+q2=1, is used to calculate the proportion of genotypes and allele frequencies in a population. p2 represents the proportion of individuals who are homozygous dominant, and p represents the proportion of dominant alleles. q2 represents the recessive genotype in a population, and q represents the proportion of recessive alleles. 2pq stands for the proportion of heterozygous individuals.

After discussing the five conditions required to maintain Hardy-Weinberg equilibrium (1. Large population; 2. Random mating; 3. No mutations; 4. No gene flow; 5. No natural selection), we did our Hardy-Weinberg lab about population genetics and evolution. For the lab, we tested the impact of the population genotypes if one of these conditions were not met. This lab/game was really fun and really helped us grasp the H-W equilibrium!

Gina and Anni flipping allele cards

Lindsay and Veronica recording their new generation genotype

Then, we had a 5-day break from school; however, biology never takes a break and we needed to learn all about evolution! We watched What Darwin Never Knew on Edpuzzle, a website allowing for us to answer questions while watching the documentary to create a stronger understanding of the subject material. This video focused on descent with modification and how us, humans, evolved from fish!

Once we got back from our break, we discussed stickleback fish and Chi-squared testing. The stickleback fish is a model organism for studying evolution and natural selection. The fish show two phenotypes, either having a complete pelvic spine or a reduced/absent pelvic spine. In our virtual lab, we took a random sample of stickleback fish from Bear Paw Lake, Frog Lake, and Morvoro Lake. We then took the data we collected and calculated the Chi-squared value. Here is what our data looked like!

We formed our expected value based on our null hypothesis: that we expect there to be no statistically significant difference between the two phenotypes. Therefore in a random sample of 20 fish, based on the null hypothesis, we would expect there to be 10 fish with complete pelvic spines and 10 fish with reduced/absent pelvic spines. After looking at our Chi-squared chart to determine each p-value, we would either reject or fail to reject (accept) the null hypothesis. For Bear Paw Lake and Frog Lake, we rejected the null hypothesis; for Morvoro lake, we failed to reject the null hypothesis.

As someone who loves both biology and math, I really enjoyed these two weeks of AP Bio and am excited to learn more next season!