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Artificial Selection Lab:An Example of Experimental

Evolution In ActionDr. Tricia Radojcic (Bella Vista Middle School, Murrieta, California)

andDr. Theodore Garland, Jr. (University of California, Riverside)

(with assistance from Dr. Heidi Schutz)

Preparation Supported by the National Science Foundation,the American Physiological Society, and the University of California, Riverside

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A process by which individuals that are better suited to their environment survive and reproduce more successfully (yielding higher Darwinian fitness) than those that have less favorable characteristics and behaviors.

Answer: Natural selection Who/what selects the ones that survive &

reproduce? Answer: Nobody/nothing.

Copy the definitions below and match with the correct term.

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Artificial selectionWho/what selects the ones that survive &

reproduce?People

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Born to Run:Born to Run:Experimental Evolution of Experimental Evolution of

Hyperactivity in MiceHyperactivity in Mice

Professor Theodore Garland, Jr.Dept. of Biology

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StarStar ting (Base) Population:ting (Base) Population:224 mice of the outbred Hsd:ICR strain Levels of genetic variation similar to populations of wild Mus and to human populations; Used for several other selection experiments

Design:Design:8 lines: 4 up, 4 control10 mating pairs in each (litter size ~10)Within-family selection (Ne ~35 for each line)

Selection Criterion:Selection Criterion:Wheel revolutions on days 5 + 6

Experimental Design

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Wheels are Attached to Standard Housing Cages: whether or not mice run is entirely voluntary

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200 total wheels,100 in each of two rooms

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Impor tant point!

● We did not select for low voluntary running because it might not be the same trait (other end of continuum) as high wheel running.

● For example, selection for low running might simply increase fear of entering the wheels.

● Active behaviors may not be opposites of sedentary behaviors (e.g., jogging is not the opposite of watching TV).

● Also, selection for low per formance might just increase frequency of any deleterious recessive alleles in the population, thus leading to sickly mice from a variety of causes.

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1000

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0 5 10 15 20 25 30 35 40 45 50

Revolutions/Day on days 5 + 6

Selected

Control

14FRUN56.DSF

0 5 10 15 20 25 30 35 40 45 50Generation

Wheel Circum-ference = 1.12 m

Females from the 4 replicate Selected lines run ~3X more than those from 4 replicate non-selected Control lines

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1000

3000

5000

7000

9000

11000

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0 5 10 15 20 25 30 35 40 45 50

Revolutions/Day on days 5 + 6

Selected

Control

0 5 10 15 20 25 30 35 40 45 50Generation

14MRUN56.DSF

Wheel Circum-ference = 1.12 m

Males always tend to run less than females, but the factorial difference between Selected and Control is the same as for females.

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Show movie that accompanies:Show movie that accompanies:

Girard, I., M. W. McAleer, J. S. Rhodes, and T. Garland, Jr. 2001. Selection for high voluntary wheel running increases intermittency in house mice (Mus domesticus).Journal of Experimental Biology 204:4311-4320.

http://www.youtube.com/watch?v=RuqhC7g_XP0

http://www.biology.ucr.edu/people/faculty/Garland/Girard01.mov

Mice from the Selected lines (on Mice from the Selected lines (on left in video) mainly run left in video) mainly run fasterfaster than than those from the non-selected those from the non-selected Control lines (on right), rather than Control lines (on right), rather than for more minutes per day.for more minutes per day.

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What would you expect to be true about the legs of a good runner?

True for other animals? Cat (http://www.youtube.com/watch?v=pWyrOuH-x7k&feature=related)

Horse (http://www.youtube.com/watch?v=OcD1_jvhc_g)

True for extinct animals? Tyrannosaurus rex (http://www.youtube.com/watch?v=T8-gcXkNTAE)

True for human beings (Homo sapiens)? Human (http://www.youtube.com/watch?v=pgkWhcapWLU)

What about the bones of good runners? Human skeleton (http://www.youtube.com/watch?v=aASjtC-l_i8)

http://www.dublinphysio.com/blog

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Would these characteristics also be true for legs of mice bred for

wheel running?

List these characteristics:

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Right and left femurs (thigh bones) of mice from Selected and Control lines have been photographed:

Identification # of this individual mouse

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Various dimensions of these femurs might be important during sustained, relatively high-speed running.

The round head of the femur fits into the hip socket.

Femur seen from front of mouse.

Femur seen from back of mouse.

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Various dimensions of these femurs might be important during sustained, relatively high-speed running.

The bottom end of the femur (two condyles) articulates with (touches) the top end of the calf (shin) bones (tibia & fibula).

Arrows point to the medial condyle.

Femur seen from front of mouse.

Femur seen from back of mouse.

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What things could you measure on the pictures of the thigh bones (femurs)?

List them on a piece of paperAs a group, decide which features you will measureWrite one or more hypotheses

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Artificial Selection Lab

Question: How would the legs of mice from lines (populations) artificially selected for wheel running differ from those of non-selected control mice?

Hypothesis: If legs from selected mice are … then the leg bones will be ... because …

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Automated Measurement using ImageJ

Select File – Open: Click on the first imageSelect Line tool on the tool barDraw a line on the ruler that is 15 mm (1.5 cm)On menu bar: Select analyze – set scaleDraw a line on the femurOn the menu bar: Select analyze - measurement

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Graph your data

Make a bar graph of the average values for the mice from selected and control lines

Use a rulerLabel axes

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Conclusion Write a paragraph that includes the following information:

• Explain your results. What effect did selecting for the trait of wheel running have on your measurements of the femurs?

• Restate the average measurements for selected and control groups.

• Was your hypothesis supported or not?• What parts of your method might have

resulted in inaccuracies?• Suggest further questions to address.

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Performing measurements manually

The following slide can be inserted in place of slide 14 above if students are using printed images instead of Image J

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Selected vs. Control mice group data

Selected leg measurement (cm)

Control leg measurement (cm)

Average measurement =

Average measurement =

Collect the data from every member of your group.Average the measurements.Round to the nearest tenth.