**************************************************************

Transcription

1 Umeå universitet EMG Barbara Giles Code number: Examination formalities Course name: 5BI097 Evolutionary Biology 15 hp VT11 Date: Time: Authorised aids: English Swedish, English German, English Spanish, English-Bengali lexicons and Pocket Calculators ************************************************************** Name: Personal number: ********************************************************************* This examination has been coded to maintain student anonymity in the marking process. Coding is done as follows: Students write their names and personal number in the space specified on this page. Students must write the code assigned to them (see top of this page) on each and every submitted answer page When students submit their answers, the invigilator will separate this page from their submission. The student may keep the strip below as a receipt for their code number ********************************************************************* Code number:

2 EXAMINATION, Evolutionary Biology EMG, Umeå universitet This exam consists of 3 sections. Each section is connected to a subject area within the course and reflects the expected learning outcomes specified in the course plan and given below. After participation in this course, students will be able to: apply scientific methods within the field of evolutionary biology explain the central processes that govern evolutionary processes in natural populations understand simple mathematical models of evolutionary processes identify and define evolutionary problems independently summarize, critically analyse and evaluate the literature within the field demonstrate knowledge in written form communicate the principles, theories, problems and research results associated with questions that lie within the framework of the course. Each section consists of a number of questions. The maximum number of points, the number of points required for a pass (= 60%) and a pass with distinction (= 80%) are given at the beginning of each section. The final grading of the entire exam is based on the following: A pass requires that you have obtained a score 60% in each and every section. A pass with distinction within each section requires that your total section score 80%. This requires that you have answered in an organised, well-formulated manner that attempts to analyse and/or explain what you are asked for. Short, point-form answers without logical connectors will not earn you a pass with distinction, nor will excessively long answers that contain everything you think you remember written in the hope that it contains something that fits the question. A pass with distinction on the entire exam requires that your total score from the 3 sections 80% and that you have passed all sections. In the event of failed sections, you must rewrite these sections but you will not be required to rewrite the sections you have passed. On this exam: Full marks = 40 points; Pass 24 points; Pass with Distinction 32 points. Write your answers on the official examination paper provided. Note: ANSWER EACH QUESTION ON A SEPARATE SHEET. Don t forget - write your personal examination code on every sheet of paper! Good Luck! Barbara, Pelle, Frank, Kenyon, Folmer and Xiao-Ru 2

3 EXAMINATION Evolutionary Biology (1) Start by reading through the entire exam. There are 14 questions, spread over 6 pages (pg 4-9). The exam is worth 40 points. You have 6 hours which is just over 6 points/hour. (2) Get a feeling for how many points each question is worth and portion out your time. (3) Start by answering the questions/sections for which you know the answers (easily earned points for you) leave the questions you find most problematic to the end (harder earned points for you). Don t panic. (4) Attempt to answer each and every question; do not be afraid to guess but tell us how you are thinking. Guesses will not be penalized, especially if they are explained well. (5) Some questions may look as though a short phrase may suffice as an answer we, however, are looking for your explanation and motiviation of your answer. This does not mean that should write down absolutely everything you know about the subject it means that should demonstrate how you have reasoned in answering the question. (6) Structure your answers and write so that we can read it. We will be coming to the examination at ca. 11:30. If you have trouble with understanding what a question is asking and we are not there to answer your question, write down your own interpretation of it and answer that question. You may answer questions in Swedish or English as you wish. 3

4 Section 1: Microevolution: Genetic mechanisms of evolution Barbara Giles, Pelle Ingvarsson. Max 17p, Pass = 10.2p, with distinction = 13.6p 1. Imagine that in a local population, such as an island population, a recessive homozygote A2A2 has a selective advantage of 0.2. Gene flow from another (continental) population in which A1 is fixed, introduces A1 at a rate m. With the aid of the following diagram, specify which selection model is operating in this system and then explain how the interaction between gene flow and selection affects the allele frequencies on the island and the degree to which the island population can adapt to local conditions. Rates of migration are lowest in (a) and highest in (c). (5p) (a) (b) (c) 2. A species of Amazonian tree frog has a selectively neutral allozyme locus, PGM, with two alleles, each having a frequency of 0.5. With recent forest fragmentation, the species now consists of 1,000 isolated subpopulations with an average of 20 individuals each. Compare and contrast the expected effects of genetic drift within subpopulations to those expected for the species as a whole over the next several dozen generations. Assume no gene flow among subpopulations and structure your answer to cover the four main aspects of genetic drift that we discussed in class. Motivate your answer (5p) 4

5 3. In a population of plants flower color is determined by a single locus, where the C allele codes for red color and c codes for white color. In the same species, petals can either be spotted or plain (nonspotted). This is also single gene trait with P coding for the spotted phenotype and p coding for the plain phenotype. The frequency of the 4 possible genotypes in the population are as follows: Spotted, red-colored flowered (PC): 0.36 Spotted, white-colored flowers (Pc): 0.15 Plain, red flowers (pc): 0.06 Plain, white flowers (pc): 0.43 a. Calculate the linkage disequilibrium (D) in the population. (1p) b. Assume that the observed linkage disequilibrum is caused by natural selection. What conclusions can you draw about the form of selection acting on flower color and pattern from the value of D? (1p) 4. Explain the two-fold cost of sex (1p) 5. The figure describes the distribution of bill shape (width [a] and length [b]) in a population of Blackbellied seedcrackers, an African finch. The dark colored graph are represents individuals that survived to adulthood where as the light colored bars represent individuals that died. a. What type of selection is the finch population experiencing (1p)? b. Given the distribution of bill shapes in the population, which trait do you think is experiencing stronger selection and why? Why do you think that selection has a much weaker effect on the other trait? Motivate you answer (3p) 5

6 Section 2: Microevolution: Adaptation Frank Johansson, Kenyon Mobley. Max 13p, Pass = 7.8p, with distinction = 10.4p 6. Adaptation can be studied at several levels, for example: experimental study, observational study and a comparative study. Give an example where you study the adaptation of a trait by using an experimental and a comparative approach. Explain the advantage and the disadvantage between both approaches in your example. (4p) 7. This figure shows (a) the age of the Hawaiian islands and (b) a phylogeny of 5 species of Drosophila that occur on the Hawaiian islands. Explain with the aid of these two figures why some of the speciation events in the Drosophila could be a result of dispersal. Explain how this dispersal can result in new species formations. That is, why did we not end up with the same species on all islands when dispersal occurs? What mechanisms occurred? (3p) 8. Darwin described two types of sexual selection, mate choice and mate competition. Define these two types of sexual selection and give one example of each (2p). 9. Hamilton s rule is one hypothesis to explain the evolution of altruistic/cooperative behavior. 1) What is the formula for Hamilton s rule? 2) Under what conditions should we expect cooperative behavior to evolve following his rule? (2p). 6

7 10. What is sensory bias? Give an example of how sensory bias may be exploited in the evolution for female preference. (1p) 11. Name and give an example of post-copulatory sexual selection. (1p) 7

8 Section 3: Macroevolution: Phylogenetics, Systematics and Diversity Folmer Bokma, Xiao-Ru Wang Max 10p, Pass = 6p, with distinction = 8p 12. One major difficulty in the study of phylogeny is the existence of convergent evolution. Explain what convergent evolution is and why it makes it difficult to study phylogeny. Explain why convergent evolution occurs in morphological data. Explain why convergent evolution also occurs in DNA sequences, state where in the DNA sequence we are most likely to see convergence. (2p) 13. What are the major transitions in the evolution of land plants, and explain what are the adaptive advantages associated with those changes? (3p) 14. see next page 8

9 14. A much debated issue in evolutionary biology is the question whether species become phenotypically different quickly when they originate (left panel) or littleby-little over time (right panel). Below you see a time-calibrated molecular phylogeny of apes (Oran utang, Human, Chimpanzee, and Gorilla) and a table listing these species logarithmic brain sizes. Using these data, we can plot the difference in logarithmic brain size [log(brain size of species A)- log(brain size of species B)] against the time since the most recent common ancestor of species A and B, for all possible species pairs AB. This plot is also shown below (Fig. III/3). Species name log(brain size) Homo sapiens 2.50 Gorilla gorilla 2.00 Pan troglodytes 2.20 Pongo pygmaeus time since most recent common ancestor Fig. III/3 a. For both gradual change over time (right panel above) and sudden change upon speciation (left panel above): draw the expected difference in brain size size as a function of time since the most recent common ancestor. (3 p) b. Explain whether the observed differences in brain size size as a function of time since the most recent common ancestor (Fig. III/3) support gradual change of phenotypes or quick change when species emerges. (2p) 9