Lab 1: Artificial Selection
With help from some Wisconsin Fast
Plants®…
Before the Setup
• We’re working with Wisconsin Fast Plants®
(Brassica rapa).
• Professor Paul Williams of the University of
Wisconsin-Madison developed these plants over
30 years.
• These are plants that, through artificial selection
(more on that later), undergo their life cycles
extremely quickly.
– This lets us study the plants in a more reasonable,
school-year-friendly time frame.
– We still need to set them up now, though. We’ll take
observations frequently!
Things to Know
• For now, don’t worry about the actual content
of the lab.
– We’re doing set up now; we’ll tie in the “meat” of
the lab when we get around to the notes.
• Our “soil” is Miracle-Gro Potting Mix.
• We are not using fertilizer.
Preparing the Planter
1. Cut the top part of the bottle off, below the
curve:
GOOD
SHAMEFUL
2. Leave the cap on and drill a small hole in it.
– I’ll be doing this part.
http://3.bp.blogspot.com/_Xlc0mlCPbAQ/TNGpy-nJLrI/AAAAAAAAAE0/Rh4882XAFlw/s200/soda-bottle.png
http://mt-st.rfclipart.com/image/thumbnail/e7-ed-05/retro-scissors-silhouette-Download-Free-Vector-File-EPS-2596.jpg
Preparing the Planter
3. Feed twine through the hole in the cap. The
twine should reach the end of your “top half”
piece. Knot it so it stays.
4. Invert the top half and place it in the bottom
half:

Preparing the Planter
5. Label the bottle with your names and fill the top part with
soil. Use masking tape if necessary.
6. Wet the soil with tap water as best you can, ideally till it
drips down the wick (twine).
7. Plant 4 seeds by placing them on top of the soil – don’t bury
them! Place them evenly. Try to label the plants so you
know which are which.
8. Fill the lower part of the bottle nearly up to where the upper
section will sit. Use tap water and label the watermark with
a marker or masking tape if necessary.
9. Place your plant under the grow lights.
10. Complete your lab notebook entry with Day 1 observations
and notes.
“Suggested Observations”
• Plants are “Wisconsin Fast Plants”
– Officially: Brassica rapa – Purple Stem, Hairy
•
•
•
•
Soil is Miracle-Gro Potting Mix.
Your bottle is ____ fl. oz.
Fluorescent grow lights will be on 24/7.
You’re observing multiple bottles, so make sure
you can distinguish them.
• At some point, the plant stems will turn purple
and trichomes (hairs) will develop. Note them.
The Lab Begins…
• Your plants are a specific
lineage called “Purple Stem
Hairy.”
– The stems are, literally, purple
and hairy.
• The hairs are known as
trichomes and are easy to
quantify.
– Trichomes provide minor
defense against herbivory.
– The trichomes look like this:
7-12 Days Old: The Lab Begins…
• The reason I mention trichomes is because we’re
going to use this trait for our artificial selection.
• Now, measure each of your plants by counting
their trichomes.
• Create a histogram showing the class distribution:
– X-axis = number of trichomes
– Y-axis = number of plants
• (example on next slide)
Example Histogram
http://api.ning.com/files/05STLkayuoUnqU4uxD6ELPhAQwYR*bIPkk1jWSoD2EfO2CxCyYMuW0C*BOy35mNsSlGqENhDlDycHxgg2FqovGXs5j2iFK
Dy/ScreenShot20121010at12.15.50PM.png1
The Selection Portion
• We’re going to select for the trait of trichome
density.
– Shall we increase trichomes or decrease them?
– In that case, we’ll select the (top/bottom) 25% of
plants in the room.
• We’ll also decapitate the other 75% and keep them
separate.
• Make a new histogram while we’re at it.
– Same axes, but this time it’s only going to display
data for the 25% of plants we’re saving.
The Selection Portion
• And exactly what kind of selection is this.
Remember, we’re shifting trichome number
either up or down.
– Directional selection.
Day 14-16: Cross-Pollination
• Because Fast Plants® are self-incompatible, we
need to have them pollinate one another.
– We’ll achieve this by using a pollinating stick.
– Reuse this pollinating stick (Q-Tip and/or paint
brush) only for the “selected” population.
– Get pollen from every flower on every plant in this
first generation.
How to Pollinate
• Rub your Q-Tip
on the stamen of
the flower (the
male parts).
• Then rub it on
the pistil (female
part, attached to
the ovary) of
another plant.
Pistil 
http://www.life.illinois.edu/help/digitalflowers/picts/Brassicaceae/06-Brassica%20flowers.jpg
Class Data [updated 2015-2016]
• Seeds planted:
• Seeds germinated:
• Plants selected:
• Plants cut:
Day 28-36: Seed Pods
• Prevent the plants from
developing more than
around 9 seed pods.
• Once the pods turn yellow,
dry out your plant by
removing the water from
the reservoir.
http://farm4.static.flickr.com/3550/3369966059_ba715db18d.jpg
Day 35-43: Replant Seeds
• Pause for a second and think about what’s
happened:
– You found a trait you wanted to accentuate/minimize.
– You controlled mating and made it random but only
with certain individuals (the selected plants).
– You are now raising a second generation.
• If all goes well, your second generation should
experience a shift toward the trait for which you
are selecting (trichomes/no trichomes).
– We can figure out if we have a greater difference than
random chance using statistics! More later…
Day 35-43: Replant Seeds
• Take the seeds from the now-dried seed pod.
• Place them in a paper bag to dry even further.
• Thoroughly clean out the bottles and replace
the wicking cord/soil.
• Plant the seeds of the selected plants to make
a new generation.
– You’ll need to break the seed pods open first.
– Use a petri dish lid.
Day 50-58
• Score the second generation (F1) the same way you
did the original plants (P generation).
• Graph the data in a histogram as before and
compare.
• Was our attempt at artificial selection successful?
• Other questions for an informal lab report:
– Answer the first three questions on page S23.
– How might we increase the artificial selection pressure?