Download BIOLOGY 201 SECTION 007 Drs. Willett and Reice
FIRST MIDTERM SEPTEMBER 20, 2007 and more Schemes and Mind Maps Biology in PDF only on Docsity!
PRACTICE PROBLEM SET F OR E XAM 1
BIOLOGY 201 SPRING 2023
Answer all of the following problems prior to your recitation and submit the completed worksheet on Gradescope as a pdf. Show calculations as well as results if possible.
- Use the phylogenetic tree below to answer questions 1A-1D. Snakes, turtles and crocodiles form a paraphyletic group called reptiles. The tetrapod clade is marked on the tree.
1A. The root of the tree represents which of the following? Circle all correct answers:
a. A common ancestor of birds and crocodilians
b. A common ancestor to all tetrapods
c. The ancestral lineage from which all other lineages on the tree are derived.
1B. Are mammals more closely related to amphibians or to birds? Explain. Mammals would be more closely related to amphibians due to fewer branch number.
1C. Are lampreys the most recent common ancestors of cartilaginous and ray-finned fishes? Explain. They would be MRCA since they share the same root and have fewer branch numbers.
1D. Did the most recent common ancestor of Crocodiles and Birds most likely have feathers? Explain. No. no ancestor of birds had feathers that they must have gotten from.
- (HWE) Electrophoresis was used to study the gene for phosphoglucose isomerase- in the evening primrose Oenothera biennis. Two alleles ( A and a ) were observed that affected electrophoretic mobility of the enzyme, and 40 AA, 2 Aa, and 18 aa genotypes were found among 60 individuals. a. Calculate the allele frequencies p = f(A) and q = f(a).
P=6.3, q=4.
b. What numbers of the genotypes would be expected if the HW assumption were met?
P=6.3, 1=4.
c. Is this population in HWE? Test using a chi-square test with a significance cutoff of p<0.05 and with d.f.=1 this is 3.84.
Not HWE due to chi-square test.
- (Natural Selection) Draw plot of p (frequency of A) against time for the following scenarios. In every scenario assume that p is initially 0.5. Make sure you illustrate the direction of change in p AND whether the equilibrium state is at p = 0, p = 1, or intermediate between 0 and 1.
a) Selection against aa graph going up and p=1 b) Mendelian inheritance (alone) gragraph goes down and p=
p p
- You are studying a cohort of Darwin’s finches in the Galapagos. The wingspan of newly fledged, but full-grown adults is 17 cm on average. For the surviving birds that reached reproductive age, their average wingspan was 15 cm. After they breed you measure the narrow-sense heritability of wingspan and find it to be 0.20.
a. What is the selection differential on wingspan in this population?
2
b. What do you expect the wingspan of newly fledged adults in the next generation to be?
c. If the phenotypic variance in the population is 2.1cm, what is the additive genetic variance for wingspan?
50%
- In trying to figure out the relationships between a closely related set of species of finches, you have examined the sequence of a section of mitochondrial DNA from each of these bird species. You find four fixed differences between the species in the sequences. The matrix of these sequence characters is shown below. Answer the following questions:
Sequence Characters Taxon 1 2 3 4 Purple Finch ( PF ) G T G C Evening Grosbeak ( EG ) A C C T House Finch ( HF ) G C C C Goldfinch ( GF) G C G T Outgroup ( OUT ) G T G T
- Map the changes in each of the four sequence characters onto each of the two trees below by placing a dash on a branch and an indication of the character number and direction of change [e.g. --- 1 (G to A)]. Places the changes on each tree such that you minimize the number of changes that you need to make for each character. Note: character 1 has been done for you.
- Circle the most parsimonious tree of the two based above based on these sequence characters only: right one
OUT GF^ HF^ EG^ PF^ OUT^ EG^ HF^ GF^ PF
-- (1, G to A)
-- (1, G to A)
