1 Change Happens: Let’s Deal With It! A Teachable Unit for Natural Selection Deena Wassenberg and Rob Brooker, University of Minnesota Lianna Etchberger

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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


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






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

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Evolution







Large learning

goals

Sub-learning

goals

Learning Outcomes

Activities

Assessments


define and use vocabulary related to

natural selection

Students will take vocabulary terms and make

a concept map

Concept map

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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

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Evolution





predict change in population gene

frequencies in response to natural selection




Large learning

goals

Sub-learning

goals

Learning Outcomes

Activities

Assessments

Mouse hemoglobin scenario

Laboratory Activities

Laboratory report

Homework questions

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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

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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

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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Population

Group of individuals of the same species that an interbreed with one another

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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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http://www.youtube.com/watch?v=nsmO2rLxIv0&mode=related&search=

LOST

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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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Learning outcome 3: Student should be able to identify different patterns of natural selection.

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What have we learned?

Has this population evolved?

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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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Figure 24.3

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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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Figure 24.4

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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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Figure 24.5

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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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Figure 24.6

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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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Figure 24.7

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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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Allele and genotype frequencies

Related but distinct calculations

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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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52Time

Elements of a correct answer.

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Images from Biology I-e, McGraw Hill 2008

Documents

1 Change Happens: Let’s Deal With It! A Teachable Unit for Natural Selection Deena Wassenberg and Rob Brooker, University of Minnesota Lianna Etchberger