Presentation on theme: "Lab 1: Artificial Selection"— Presentation transcript:
1Lab 1: Artificial Selection With help from some Wisconsin Fast Plants®…
2Before the SetupWe’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!
3Things to KnowFor 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 Jiffy-Mix.We’re using a liquid fertilizer solution.A scoop of Miracle-Gro in water, diluted to a 1:4 ratio.
4Preparing the PlanterCut the top part of the bottle off, below the curve:Leave the cap on and drill a small hole in it.I’ll be doing this part.GOODSHAMEFUL
5 Preparing the Planter Feed twine through the hole in the cap. The twine should reach the end of your “top half” piece. Knot it so it stays.Invert the top half and place it in the bottom half:
6Preparing the PlanterLabel the bottle with your names and fill the top part with soil. Use masking tape if necessary.Wet the soil with fertilizer solution as best you can, ideally till it drips down the wick (twine).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.Fill the lower part of the bottle nearly up to where the upper section will sit. Use fertilizer solution and label the watermark with a marker or masking tape if necessary.Place your plant under the grow lights.Complete your lab notebook entry with Day 1 observations and notes.
7“Suggested Observations” Plants are “Wisconsin Fast Plants”Officially: Brassica rapa – Purple Stem, HairySoil is Jiffy-Mix Starter.Fertilizer is a dilute solid Miracle-Gro solution.Your bottle is ____ fl. oz.Fluorescent grow lights will be on 24/7.You’re observing both bottles, so make sure you can distinguish them.At some point, the plant stems will turn purple and trichomes (hairs) will develop. Note them.
8The 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.If you can imagine the stems being purple, the trichomes look like this:
97-12 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 trichomesY-axis = number of plants(example on next slide)
11The Selection PortionThere are 56 plants in this room (if all germinated). 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) 20% of plants in the room.We’ll also decapitate the other 80% 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 20% of plants we’re saving.
12The Selection PortionAnd exactly what kind of selection is this. Remember, we’re shifting trichome number either up or down.Directional selection.
13Day 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 only for the “selected” population.Get pollen from every flower on every plant in this first generation.
14Day 28-36: Seed PodsPrevent 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.
15Day 35-43: Replant SeedsPause 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…
16Day 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.
17Day 50-58Score the second generation (F2) the same way you did the original plants.Graph the data in a histogram as before and compare.Was our attempt at artificial selection successful?