1 Change Happens: Let’s Deal With It! A Teachable Unit for Natural Selection Deena Wassenberg and...
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Transcript of 1 Change Happens: Let’s Deal With It! A Teachable Unit for Natural Selection Deena Wassenberg and...
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Change Happens: Let’s Deal With It!
A Teachable Unit for Natural SelectionDeena Wassenberg and Rob Brooker, University of Minnesota
Lianna Etchberger and Greg Podgorski, Utah State University
Janet Batzli and Evelyn Howell, University of Wisconsin, Madison
Kimberly Hammond, University of California, Riverside
Mark Lyford, University of Wyoming, Laramie--Facilitator
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Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning Outcome 4Students will be able to
predict change in population gene
frequencies in response to natural selection
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
SystematicsSpeciation
(Macroevolution)Large
topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Learning Outcome 2Students will be able to
define and use vocabulary related to
natural selection
Learning Outcome 5Students will be able to design an
experiment to demonstrate the importance of reproductive
success associated with natural selection
Dinosaur cartoonminute paper
Classroom evolution based on
fitness
Mouse hemoglobin scenario
Laboratory Activities
Students will take vocabulary terms and make
a concept map
Clicker question:What type of
selection?
Concept map
Laboratory report
Experimental design paper
Draw a better dinosaur cartoon: correcting
misconceptions
Origin of Life – Chemical Evolution
Darwin’s Theory
Brainstorming evolution definition
Design an experiment to test if high altitude hemoglobin
confers fitness at high altitude
Homework questions
Pre-test and post-
test
Learning Outcome 1Students will demonstrate that they have overcome common misconceptions
about natural selection using diagrams and writing
Learning Outcome 3
Students will be able to identify
different patterns of natural selection
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Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
Large topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Dinosaur cartoonminute paper
Draw a better dinosaur cartoon: correcting
misconceptions
Brainstorming evolution definition
Pre-test and post-
test
Learning Outcome 1Students will demonstrate that they have overcome common misconceptions
about natural selection using diagrams and writing
4
Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
Large topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Learning Outcome 2Students will be able to
define and use vocabulary related to
natural selection
Students will take vocabulary terms and make
a concept map
Concept map
5
Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
Large topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Classroom evolution based on
fitness
Clicker question:What type of
selection?
Learning Outcome 3
Students will be able to identify
different patterns of natural selection
6
Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning Outcome 4Students will be able to
predict change in population gene
frequencies in response to natural selection
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
Large topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Mouse hemoglobin scenario
Laboratory Activities
Laboratory report
Homework questions
7
Evolution
Population Genetics(Microevolution)
Learning GoalStudents will understand the relationship between
natural selection and reproductive success
Learning GoalStudents will understand that evolution is a heritable change in one or more
characteristics of a population or species across many generations
Large topics in Evolution
Large learning
goals
Sub-learning
goals
Learning Outcomes
Activities
Assessments
Learning Outcome 5Students will be able to design an
experiment to demonstrate the importance of reproductive
success associated with natural selection
Experimental design paper
Design an experiment to test if high altitude hemoglobin
confers fitness at high altitude
8
Learning outcomes1: Students will demonstrate that she/he has overcome common misconceptions about natural selection using diagrams and writing. 2. Students will be able to define terms and identify factors that play a role in natural selection.3. Students will be able to identify patterns of natural selection.4. Students should be able to quantitatively predict changes in allele or genotype frequencies in a population based on natural selection.. 5. Students should be able to design an experiment to demonstrate the importance of reproductive success associated the natural selection.
PretestCINS
Form. Assessment 1
Form. Assessment 1
Post-TestCINS
Outcomes 1 & 2
Objectives and Overview Introduction to Natural Selection
Patterns of Selection Measures of Fitness …..
Unit Sequence
Learning Goal
Students will understand the relationship between reproductive success and natural selection Outcome 5Outcomes 3 & 4
Form. Asses. 3 Form. Asses. 4-6Formative assessments
1: Pretest - concept inventory for natural selection2: One-minute paper - misconceptions in evolution3: Change happens - class activity demonstrating natural selection4. Clicker question - what form of selection was demonstrated?5. Clicker questions - natural selection in deer mice6. Posttest - concept inventory for natural selection
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Concept inventory of natural selection (CINS) Pre-test/Post-testSample question (1/20)
How did the different beak types first arise in the Galapagos finches? a) The changes in the finches’ beak size and shape occurred because
of their need to be able to eat different kinds of food to survive. b) Changes in the finches’ beaks occurred by chance, and when there
was a good match between beak structure and available food, those birds had more offspring.
c) The changes in the finches’ beaks occurred because the environment induced the desired genetic changes.
d) The finches’ beaks changed a little bit in size and shape with each successive generation, some getting larger and some getting
smaller.
Anderson, D.L., Fisher, K.M., & Norman, G.J. (2002). Development and Evaluation of the Conceptual Inventory of Natural Selection. Journal of
Research in Science Teaching, 39, 952-978. http://www.biologylessons.sdsu.edu/CINS6_03.pdf
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What is biological evolution?Brainstorm
A heritable change in one or more characteristics of a population or species across many generations
Viewed on a small scale relating to changes in a single gene in a population over time (our focus)
Viewed on a larger scale relating to formation of new species or groups of species
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Evolution
Teachable unit flow chart:
The flow chart helps us to place our current topic within the larger picture of evolution. Our topic for the next couple of classes will be the relationship between natural selection and reproductive success.
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Learning goal
Student will be able to understand that evolution is a heritable change in one or more characteristics of a population or species across many generations
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Learning exercise
To appreciate the general ideas about natural selection that we might already have coming into this course, let’s begin with a short learning exercise.
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Minute Paper:1. Examine cartoon. 2. Explain the changes that occurred in the tree AND animal
using your current understanding of evolution by natural selection.
3. Individually, write your answer on small card and hand in.4. With a partner, list the assumptions being implied in the
cartoon.
AAAS 1999
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Learning outcome 1: Student will overcome common misconceptions about natural selection using diagrams and writing.
Learning outcome 2: Student will be able to define terms and identify factors that play a role in natural selection.
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Gene pool
All of the genes in a population Study genetic variation within the gene
pool and how variation changes from one generation to the next
Emphasis is often on variation in alleles between members of a population
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Natural selection in a population
We’re going to go through an active learning exercise to appreciate some of the general connections between genetic variation, reproductive success, and natural selection.
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Stand-up, sit-down natural selection 1. Each new generation we all stand up. 2. Individuals with green eyes, size 8 feet,
and short index fingers have children with the same traits.
3. The population size remains the same each generation.
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Modern description of natural selection
1) Genetic variation arises from random mutations that may alter the function of the protein.
2) Some alleles may encode proteins that enhance an individual’s survival and reproductive success compared to that of other members of the population
3) Individuals with beneficial alleles are more likely to survive and contribute their alleles to the gene pool of the next generation
4) Over the course of many generations, allele frequencies of many different genes may change through natural selection, thereby significantly altering the characteristics of a population Net result of natural selection is a population that is better adapted to
its environment and more successful at reproduction.
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Some genotypes have greater reproductive success, meaning that they contribute more offspring that are viable to the next generation compared with other genotypes.
Reproductive success depends on: 1. Ability to survive to reproductive age 2. Ability to find a mate 3. Fertility
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Natural selection patterns
Directional selection Stabilizing selection Disruptive selection Balancing selection
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Directional selection
Favors individuals at one extreme of a phenotypic distribution that have greater reproductive success in a particular environment
InitiatorsNew favored allele introducedProlonged environmental change
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Stabilizing selection
Favors the survival of individuals with intermediate phenotypes
Extreme values of a trait are selected against Clutch size
Too many eggs and offspring die due to lack of care and food
Too few eggs does not contribute enough to next generation
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Disruptive selection
Favors the survival of two or more different genotypes that produce different phenotypes
Likely to occur in populations that occupy diverse environments
Members of the populations can freely interbreed
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Balancing selection
Maintains genetic diversity Balanced polymorphism
Two or more alleles are kept in balance, and therefore are maintained in a population over the course of many generations
2 common waysFor a single gene, heterozygote favored
Heterozygote advantage – HS alleleNegative frequency-dependent selection
Rare individuals have a higher fitness
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Clicker question: Our class exercise involved eye color, foot size, and finger length. With regard to changes in index finger length in our population, is this an example of:
A. Directional selection
B. Stabilizing selection
C. Disruptive selection
D. Balancing selection
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Sexual selection
Form of natural selection Directed at certain traits of sexually
reproducing species that make it more likely for individuals to find or choose a mate and/or engage in successful mating
In many species, affects male characteristics more intensely than it does female
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Explains traits that decrease survival but increase reproductive success
Male guppy (Poecilia reticulata) is brightly colored compared to the female
Females prefer brightly colored males In places with few predators, the males tend to be
brightly colored In places where predators are abundant, brightly colored
males are less plentiful because they are subject to predation
Relative abundance of brightly and dully colored males depends on the balance between sexual selection, which favors bright coloring, and escape from predation, which favors dull coloring
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Learning outcome 4: Student should be able to quantitatively predict changes in allele or genotype frequencies in a population based on natural selection.
Learning outcome 5: Student should be able to design an experiment to demonstrate the importance of reproductive success associated the natural selection.
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Quantitative predictions of natural selection We now turn to natural selection on a
quantitative level, which requires that we consider allele frequencies and Darwinian fitness.
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Darwinian fitness
Relative likelihood that a genotype will contribute to the gene pool of the next generation as compared with other genotypes
Measure of reproductive success Hypothetical gene with alleles A and a
AA, Aa, aa
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Suppose average reproductive successes are…AA 5 offspringAa 4 offspringAa 1 offspring
Fitness is W and maximum is 1.0 for genotype with highest reproductive abilityFitness of AA: WAA = 5/5 = 1.0
Fitness of Aa: WAa = 4/5 = 0.8
Fitness of aa: Waa = 1/5 = 0.2
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Mice and hemoglobin
Certain populations of deer mice are found to be polymorphic with regard to a gene that encodes a subunit of the oxygen-carrying protein, hemoglobin
Hh- high altitude allele (high oxygen affinity)
Hl- low altitude allele (low oxygen affinity)
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Deer Mouse (Peromyscus maniculatus)• Cosmopolitan in North America• Live & breed in harsh conditions across all altitudes
(0 - 4000 m)• Gives birth to large litters (4-8 pups)• Genetic polymorphisms in -globin subunits
M.A. Chappell
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0 1000 2000 3000 4000
Altitude (m)
1
0.8
0.6
0.4
0.2
0
Hl allele frequency
(each of the 52 symbols is a different population of mice)
Data from Snyder (1981)
(“Low altitude” allele)
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On the next series of slides, you will be asked to use the information from these data to predict changes due to natural selection.
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0 1000 2000 3000 4000
Altitude (m)
1
0.8
0.6
0.4
0.2
0
Hl allele frequency
(each of the 52 symbols is a different population of mice)
Data from Snyder (1981)
(Low altitude)
Q1. What is the approximate allele frequency for the Hl allele in the mouse population at the red arrow?
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Q2. Based on the allele frequency you estimated from question 1, draw a graph that would describe what would happen if the mouse population at the arrow was transported to 4000 m and there were geographic barriers that prevented the population from moving to a lower altitude.
1
0.8
0.6
0.4
0.2
0
Hl allele frequency
Generations
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Q3. Make a curve similar to the one in question 2, but plot the frequency of the Hh allele instead.
Q4. Take home assignment. The curves you have drawn in questions 2 and 3 were under the hypothesis that mice carrying the Hh allele have a higher reproductive success at high altitude. Write a paper guided by the rubric available on our web site. Be sure to describe your methods and indicate what type of data you would expect if the hypothesis was correct. The rubric will be used in assessing your work.
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1. Individually, apply your knowledge of evolution by natural selection.
2. List the assumptions being applied in the cartoon and redraw/revise the drawing to reflect these assumptions.
AAAS 1999
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