Download EB tenta_110228 - Umeå universitet

Umeå universitet
EMG
Barbara Giles
Code number:
Examination formalities
Course name: 5BI097 Evolutionary Biology 15 hp VT11
Date: 2011-02-28
Time: 09.00-15.00
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:
Code number:
EXAMINATION, Evolutionary Biology 2011-02-28
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
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
2
Code number:
EXAMINATION Evolutionary Biology 2011-02-28
(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.
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
3
Code number:
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)
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
4
Code number:
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)
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
5
Code number:
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).
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
6
Code number:
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)
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
7
Code number:
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
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
8
Code number:
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
1.50
1.20
1.00
0.80
0.60
0.40
0.20
0.00
0.00
2.00
4.00
6.00
8.00
10.00
12.00
time since most recent common ancestor
14.00
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)
Umeå universitet 901 87 Umeå. Telefon: 090-786 55 21. Telefax: 090-786 67 05.
9