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We are enthusiastic about the new inquiry-based AP Biology labs that are soon to be released.

In February, the College Board will post electronic (pdf) copies of the AP Biology Investigative Labs: An Inquiry-Based Approach: Teacher and Student Manuals online at http://advancesinap.collegeboard.org/science/biology

We hope to support some interesting discussions about these inquiry-based labs as teachers begin using them with their AP students. Two of the labs involve some interesting experiments with Fast Plants, and this will be one forum where we can discuss both the logistics of growing and the pedagogy and learning outcomes.

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School is beginning, and we're starting to hear from teachers who are conducting the new AP Biology Lab #1. As questions arrive through our website, we will post them here to share as part of this AP Biology discussion.

Just posted: A new page on our network with links to lots of good resources to help with planning and conducting Investigation #1, Artificial Selection.

Here's a question from Melbourne, Florida:

I am about to conduct the new AP Biology lab #1 using Fast Plants.  The instructions have us select out some plants and then cut the tops off of the remaining plants at about 12 days old.  My question is that it appears they still want us to harvest seed from the non-selected plants that we cut the tops off of.  Will these plants recover from getting their tops cut off and grow to produce seed?
Thank you!


Good question! Step 6 of the instructions says:

"You are now ready to make selection decisions. Directional selection tends to
move the variability of a trait in one direction or the other (increase or decrease the
trait in the next population). As a class, pick a trait you want to try to affect. Find the
top (or bottom) 10% of plants with that trait in the entire class’s population (e.g., out of
a population of 150 plants, the 15 hairiest plants), and mark any that are in your plant
bottle container. Using scissors, cut off the tops of the remaining plants in your container
(those not in the top 10%)"

Then, in Step 8 the instructions continue:

"Step 8 On about day 14–16, when several flowers are present on each of the selected
plants, cross-pollinate the selected plants with a single bee stick or pollinating device.
Fast Plants® are self-incompatible — each plant must be fertilized by pollen from
another plant. Collect and distribute pollen from every flower on every plant in the
selected population. Reserve this bee stick for only the selected population. Avoid
contaminating with the pollen from the remaining Fast Plants. Pollinate flowers in the
selected population for the next three days with the same bee stick. Be sure to record
observations about pollination in your lab notebook. Likewise, with separate bee sticks
you can pollinate the plants from the larger population, but be careful to keep them
separate from the selected population."

It is true that if you leave side branches on the plants that you want to eliminate from the "selected population" and only cut off the tops, they will form flowers on the side branches. By cutting off the tops, you will both mark the plant as not being one of the selected population, and you'll decrease the likelihood that pollen from a plant eliminated from the selection experiment will drop pollen on the upper flowers of the selected population--this will help to reduce contamination during the selection experiment. Therefore, you can, by using two bee separate bee sticks, theoretically conduct two breeding experiments at once, which clearly has some advantages for time management.

I do want to voice a couple notes of caution about this procedure, however:

First, if you have never grown Fast Plants before, what is described in these steps is pretty complicated to manage. Instead, if you grow Standard Fast Plants seed--which will have LOTS of variation--the plants will be strong and have a variety of traits that can be selected for by students who make careful observations. And you can still grow a second population of Fast Plants that will produce mono- or di-hybrids for the "Who's the Father" approach that is recommended for supporting students to construct their own conceptual models to explain Mendelian inheritance patterns (a great approach!).

Second, my undergraduate interns conducted this selection experiment, and they are very thoughtful, talented students, and they encountered a number of challenges in coordinating their efforts to effectively make consistent measurements and follow procedures the same as each other (see their descriptions in their Ning group). If they had also been coordinating two bee sticks and two simultaneous experiments, I think we'd have introduced significant additional challenges.

Third, cross pollination between the selected plants in a container and those that were topped is pretty likely to occur on the flowers that develop on the side branches of both populations and simply from pollen that is moved on a student's sleeve or is shed by flowers when the growing systems are moved during observations and pollination. The only way to be sure-fire way to know you're only inter-mating the top 10% of the original population is to cut the other 90% off at the ground level.

We are really interested to hear from others who have conducted this experiment, both as it is written and with alternative procedures. It's a great experiment, and it demonstrates non-Mendelian inheritance patterns (which are more common than the Mendelian patterns we tend to focus on when teaching genetics).

Hello Hedi-

Thank you so much for this response to the Melbourne, Florida question. I learned a lot just reading your detailed answer. Since I want to start off simple, my plan is now indeed to select for the top 10% of - say - trichome numbers and cut off at the ground level the remaining 90%. This certainly will reduce confusion and potential cross-contamination.

My question for you refers to the next step: gathering data and then quantifying variability. I read the following article (http://www.fastplants.org/pdf/activities/quantitative_var.pdf) and also looked at the data charts available (http://www.fastplants.org/resources/pauls_sandbox_category_article....). I'm somewhat confused exactly as to whether AP Biology students are expected to conduct all the calculations specified (n, x, s, and r) and if they are supposed to carry these out so as to draw a conclusion about their data. If the answers are yes, then I definitely need a bit more help ensuring I understand how to do these calculations myself. Please advice. Thank you so much.

Hello Astrid,

I'm glad you found this helpful, and do I hope others might ring in about their experiences using the 90% of the population that is not selected such that the dual experimentation as suggested in the AP Biology manual works well. I don't mean to be overly critical of that idea; I can certainly appreciate the valuable time that could be saved by having two investigations emerge from a single planting. Perhaps, once you've taught this lab once or twice and have more Fast Plant rearing and breeding experience, you may want to try that approach. I wouldn't want to suggest that you rule it out.


Regarding the data collection and analyses steps, I LOVE that you pulled together a variety of our resources that relate to this new lab. I was inspired by your high quality sleuthing through our resources (some of which were pre-2000 era) and I wrote a new resource--synthesizing information from the resources you gathered--that addresses data collection and data analysis associated with conducting an artificial selection experiment. I've attached the first draft of this resource to this comment, and I welcome your and others' feedback before we format the document and share it more broadly.

--Hedi

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Hello Hedi,

Thank you again for your response. Your prompt reply is really helpful. Classes won't start for me until Thursday, September 6th and I'd like to have an even better idea what I'm doing before that time. So to give you an idea of where I'm at, I've attached a power point that details the new AP Bio set-up, followed by slides that detail the lab including notes from your pdf file that are for my own benefit. Please note that all images within the slides are linked to their web sources. Many of these sources are of course derived from the fastplant site.

Before I ask you questions about the statistical data, let me be sure I've got a good grip on the number of quads I plan to prepare with my students starting Monday, September 10. I will have available at least 6 watering trays. Each tray - I believe - should fit 4 quads. Each student is responsible for 1 quad equaling 4 plants. Each lab station is responsible for 4 quads totaling 16 plants on top of 1 watering tray.

Since I have 6 lab stations and 6 watering trays, this would mean that we plan to grow a total of 96 plants. I can throw in one extra quad as my own, making the total exactly 100. Selecting for - say - the top 10% hairiest plants would obviously be 10 plants total, meaning roughly 1 or 2 plants per lab table to isolate seeds from for the next generation. The next generation should then hopefully yield the same number of plants - 100 total - or is this sounding too optimistic? 

I know I'll have more questions regarding the statistical data analysis, but I figure I hold off a bit until I get feedback on what I have so far. My only quick question regarding statistics for now is: In the provided data table, s and r stand for selection differential and response to selection, respectively. Correct? Or do they stand for standard deviation and range? Whatever the case may be, I'm assuming that my AP Bio students should be calculating standard deviation and range to assess the question this lab is addressing. 

Finally for now: You stated that one of the objectives for this lab is:
To investigate natural selection as a major mechanism for evolution.

I'm assuming that our students are indeed investigating this objective, but they need to be aware of the fact that they are assessing this process via their own artificial manipulation of the Wisconsin Fast Plants. I believe this needs to be emphasized, because otherwise students get confused between the terms natural and artificial selection. Based on the introductions I've read from my AP Bio students this misconception certainly seems to be the case. (I assigned my students for their summer project to write an introduction to this lab.) Do you agree?

Thanks again for your advice.

Astrid

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Hi Astrid,

You're asking great questions! Let me take a crack at your latest:

First, just an FYI for you and anyone else using Fast Plants materials and resources--we are committed to the Open Education Resource (OER) movement and have a "share and share-alike" attitude about how educators use our resources. We love seeing derivative materials made by teachers, using our resources--so copyright worries are minimal! I took a quick peak at your PowerPoint slides, though I don't have time to look too closely; thank you for the context and for being thoughtful about citing us as a source.

RE: Number of growing systems: What kind of watering tray is it that you are using with your quads? If you're using those that are sold with the quads, you ought to have room for up to 8 quads per water reservoir (see this page on the Fast Plants website as a resource for calculating # quads, and # reservoirs, and # lighting systems).

If you’d like each student to plant and tend one quad, then you’ll have 4 plants per student. With 25 students, you’d have a population of 100 plants from which to select the top 10% that are expressing the trait you’re selecting for (e.g. those plants that have the greatest number of hairs on the leaf margin of the first true leaf).

The two steps in the lab manual that refer to the selection process are here:

Step 5 In your lab notebook, compile a list of all the possible traits your class identified. Calculate appropriate descriptive statistics for the class data for the first generation: mean, median, range, standard deviation, etc. Create a histogram that shows the frequency distribution of the trait that you have selected. You can find help for this in Chapter 3.

Step 6 You are now ready to make selection decisions. Directional selection tends to move the variability of a trait in one direction or the other (increase or decrease the trait in the next population). As a class, pick a trait you want to try to affect. Find the top (or bottom) 10% of plants with that trait in the entire class’s population (e.g., out of a population of 150 plants, the 15 hairiest plants), and mark any that are in your plant bottle container. Using scissors, cut off the tops of the remaining plants in your container (those not in the top 10%).

If you grow 100 plants and pick the 10 hairiest plants, AND you have students cross-pollinate those 10 plants at least every-other day for a week and a half or two, you should be able to produce enough seed to grow 100 plants for your Generation 1 population.

Regarding the reference in Paul’s data table to “s” and “r,” I think you’re right that he was calculating standard deviation and range. Let’s do talk more about the data analyses in the future.

Your point about emphasizing the difference between artificial and natural selection is important. This lab uses artificial selection in a way similar to how it informed the notion of natural selection in Darwin's day -- it is a concrete example of how selection can influence the presence or absence of a trait in future generations.

Another other important point that is worth noting here is how environment also effects phenotype. I just wrote this bit to add to the Data Analysis background information sheet that I shared with you earlier:

One important assumption in this investigation’s experimental design is worth noting here: It is assumed that all environmental factors are kept constant throughout the investigation. This is assumed to be true for all the plants within a population and across both generations of plants. If all environmental factors could be held constant, then selecting for a phenotypic trait would be a highly reliable proxy for genetic selection. In reality, there will be some variations in the environmental conditions. For example, the exact amount of potting mix, the depth at which seeds are planted, and the temperature (due to both classroom temperature variation and proximity to the lights) are all examples of factors can vary among plants and between generations. Given that phenotype is the result of an interplay between genotype and environment, it is important to consider while conducting this investigation and when analyzing data the potential for environmental influences.

Please keep us posted as you proceed!

--Hedi

Hedi -

A real quick tremendous thank you for this amazing response! That was fantastic feedback! Indeed I'm using all supplies from Carolina Biological and the Wisconsin Fast Plant materials. I have a gigantic lighting system cart, lots of quads and watering trays and so I'm all set.

Indeed, your point on the role both genetics and the environment play in this set-up is key to underscore with students. Students indeed seem to be confused about these factors and the extend to which they influence phenotype. This confusion, in addition to the natural versus artificial selection issue, already became apparent to me when reading their paper submissions. 

Let's touch base in a week or two when our plants have been planted and data analysis is more imminent. It is possible I will have some quick questions that may come up as I'm setting things up. Is this the best way to reach you if I need help fast? Or would you prefer a different way? 

Thank you again! 

Astrid

This is a great place to share ideas, Astrid. I'll keep following this thread so that I am notified any time you or anyone else posts here.

Looking forward to learning more with you as your lab progresses!

--Hedi

Hello Hedi,

It's been a REALLY busy first full week of classes. We managed to plant our WFP last Tuesday. I have a few questions for you as we're approaching data gathering next week. I would tremendously appreciate it if you could address my questions by this Sunday evening / Monday morning before I start my class later that day. I understand however if you're very busy with your own work at hand.

Briefly, we planted 100 plants on Tuesday. Today is day 4 and the plants were thinned down to one plant per cell. Almost all cells had seedlings with tiny cute cotyledons appearing. For one lab group only (out of 6) two quads failed to grow half of their cells (?!). This lab group decided to transfer 4 seedlings to a new quad so as to maintain our 100 class count. This was of course possible because many other cells contained 2 little plants each as two seeds were planted.

This Wednesday, day 9, we have an 80 minute class. I was planning to do our data gathering then. I was planning on having them come up with measuring plant height, trichomes on first true leaf's edge, perhaps stem color as well and cotyledon's width. Based on the data analysis, we will then decide to pick one trait.

Question 1:

Does it make sense to plot each trait as a class so as to determine whether there's a nice bell curve to base our trait selection on? Or can we just kind of scan our data as a whole without plotting it and judging the spread in that manner?

Question 2:

If we choose plant height, do we measure the height again after a few days and keep track of changes, or instead keep it simple and stick with one height for day 9? Or instead remeasure height on day - say - 12 and stick with the data for that day? (Seems a lot less complicated to me height data for one day as opposed to a trend.)

Question 3:

If we choose trichomes, would it make sense to rip off the leaf a given student is counting and then placing it on something black to facilitate counting? Or perhaps even look at it under a microscope? Or is it better to keep the leaf on the plant and just hold dark paper behind it?

Question 4:

Once all data for all 100 plants for our trait of choice has been gathered, who will be responsible for inserting it into one excel file? I'm assuming the students could do this one lab group at a time? Any recommendations?

Question 5:

Next of course is data analysis. Should the students calculate the mean, range and standard deviation by hand for all 16 plants per group? Or should they do it for - say - the first 5 and then write a formula so that the excel program can do it? Just a thought.

Any other recommendations that you have? 

Thank you tremendously! I know this was a lot of questions.....

Astrid

 

Good morning Astrid, here are my thoughts about your interesting questions. Hopefully, others might ring in with their thoughts, too:

Question 1:

Does it make sense to plot each trait as a class so as to determine whether there's a nice bell curve to base our trait selection on? Or can we just kind of scan our data as a whole without plotting it and judging the spread in that manner?

(response) This sounds to me like a question of learning goals, really. I believe that your goal is for students to understand how continuous variation in a trait is distributed in a population and can change over time. Visualizing this with a graph of how the trait is distributed in your current population will make it possible to compare this to the next generation. I have NOT had time to carefully read the "quiz" associated with the graphs on the link I'm about to paste here, but it is an example of the types of comparisons I'm referring to that are po.... I think these are pretty well aligned with your learning goals.

Question 2:

If we choose plant height, do we measure the height again after a few days and keep track of changes, or instead keep it simple and stick with one height for day 9? Or instead remeasure height on day - say - 12 and stick with the data for that day? (Seems a lot less complicated to me height data for one day as opposed to a trend.)

(response) The frequency with which you measure a trait is determined by the question that you're hoping to answer with those data. If your objective is for students to understand the growth curve in Fast Plants (which shows the distinctive change from growth to development for reproduction) and use those data to decide what height data to select for, then you'll need more than one data point. You're right that it's less complicated and less time-consuming to gather data from a single day; it also tells a very different story.

Here's a link to a brief description of the kind of thinking that o.... Having height data over time made this analysis possible.

Question 3:

If we choose trichomes, would it make sense to rip off the leaf a given student is counting and then placing it on something black to facilitate counting? Or perhaps even look at it under a microscope? Or is it better to keep the leaf on the plant and just hold dark paper behind it?

(response) Good idea. You can see in the PowerPoint here some images of how Paul Williams (Father or Fast Plants) has worked with trichomes.

Question 4:

Once all data for all 100 plants for our trait of choice has been gathered, who will be responsible for inserting it into one excel file? I'm assuming the students could do this one lab group at a time? Any recommendations?


(response) You could use a Google Docs spreadsheet, then students could enter the data at the same time. I've not used Docs' spreadsheet functions much, and I do know that going from Google Docs to Excel or Word is pretty clumsy. Maybe others can recommend a way. I used an overhead projector to gather the data (students wrote it in as they finished gathering), but that left someone (a student or me) to have to enter it all into a spreadsheet.

Question 5:

Next of course is data analysis. Should the students calculate the mean, range and standard deviation by hand for all 16 plants per group? Or should they do it for - say - the first 5 and then write a formula so that the excel program can do it? Just a thought.

(response) Personally, I like the idea of doing enough by hand to understand what is being calculated and then learning how to use a spreadsheet to do the calculations efficiently . . . an important skill for data analysis, too.

Great questions--have fun!!

Thank you once again so very much for your response, Hedi. All questions were answered so well. My students decided not to track for plant height after hearing about the logistics of it - counting AT LEAST twice so as to account for bolting. Too much work they said. Since this is their project, I let them decide. Indeed, we saw bolting (based on qualitative observation) of at least one plant. The stem just shot upwards.

Instead, my students wished to count trichomes. We did our analysis yesterday - day 11. Am I correct in assuming that we can select for the top 10% based on our count on that day as trichome numbers on the edge of the first true leaf should not change significantly after that day? 


I have a couple of recommendations to make for any other teachers doing the same lab based on our analysis that worked so well for us. All my students used dissection scissors to cut of the first true leaves. All 16 leaves per lab group were collected in a pre-labeled 15 well tray. They took cell phone pictures for their lab reports of both their well trays as well as their plants. The leaves were then both counted by eye, using a magnifying glass as well as by microscope count. If the counts roughly matched, each group inserted their data into a pre-created excel spread sheet (designed by one student in the class the day before). 


Although the AP College Board Lab Manual suggests that we maintain BOTH the top 10% as well as the bottom 90% (and plant both sets of seeds and grow the next generation), our plan is to cut down the 90% population with the fewest hairs. I believe this will be fine for our analysis. Based on previous threads, is this the advice, Hedi, you would also give? Cutting down / destroying the bottom 90%?

On Monday - day 14 - is cut-down day as well as pollination day for 4-5 days in a row. In the meantime students will compute average, range and standard deviation as well as create a frequency histogram all in excel.

Thank you again. And I shall keep you posted. I have attached our class data for everyone to see. Comments are always appreciated.  

Astrid

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