The penultimate day of the summer term! Compared to some of our other days, this one was pretty low key, but we did have a little unexpected adventure.
I’d intended to lecture on ecosystem services in the morning, and then watch one of my favorite “teaching” films, “Hurricane on the Bayou.” And this is mostly what happened, except for a little detour part way through. When I arrived on campus, I noticed some flyers posted in the science building – one of the biology grad students, Vanessa Dodge, was giving her thesis defense. Not only was I really interested in her research, as I’d been up to the field site in Point Reyes a couple of times, but I also thought this would be a good way for my students to learn a bit more about the process of science. So, I gave them the choice – do you want to listen to me lecture all morning? Or do you want to go hear someone else talk for a while? They voted in favor of variety, so about an hour into the day we headed upstairs to the thesis defense.
Taking them was, I think, a good experience for them. The talk was good – she did her research on the effects of tule elk on soil composition, so it was very ecology focused, and not too technical. And my students were a great audience! So, that was a little bit of serendipity for our last week.
After lunch, we started talking about human populations, including an activity on population growth. This makes an easy transition to our next topic: food security, but we didn’t get all the way through the lecture . . . I decided to save one of the most interesting topics for the next day: GMOs. Oh yeah. That’s always an entertaining lecture. 🙂
We covered a lot of ground today. We started out with a lab activity, since we hadn’t had time to explore biomes fully the previous day. I started them out with a super cool Google Earth file that I found here. One of the resources is an interactive Google Earth map with layers that show various aspects of climate – average winter temperatures, average summer temperatures, that sort of thing – along with a layer that shows the location and distribution of biomes, worldwide.
After working with this data for a bit, I handed out an outline of a continent, with the instructions that they should place the biomes wherever they wanted, as long as it was in keeping with the concepts we’d just learned – which biomes are found at which latitudes, how landforms like mountains can affect climate, that sort of thing. And yes, this was another coloring project! (Always popular). Although we hadn’t talked about climate change yet (that would happen next), I set that up by asking them to think through what sort of shifts we might see in the location of biomes, if temperatures were to rise by even a few degrees.
After lunch, we talked about the movement of energy and materials through ecosystems, including the concept of food webs. For lab, we did an activity that I adapted a couple of years ago for an upper division biology course: “Trophic Interactions in the Kelp Forest: An Ecological Detective Story.” My original inspiration for this activity, an NSF case study, can be found here. In the past, I’d provided students with a matrix of trophic (feeding) relationships, and asked them to create a food web diagram:
I’d always assigned this as homework, so I needed to make some adjustments to turn it into an in-class activity. The biggest change was the addition of some little “Food Web Cards,” each of which had a picture of an organism, along with the details of what that organism eats, and also what it gets eaten by. Each group received a complete set of cards, and instead of giving them a completed matrix, they had to come up with that on their own.
Then, instead of doing their food webs online, we made good use of the white boards, and some colorful wet erase markers. (This ended up being not ideal for me – it took me AGES to clean off all the marker, since it needed to be sprayed down. But it was worth it).
The activity went REALLY well! Everything worked out just as I had hoped, and they did a great job of coming up with their food webs. A REALLY good job . . . in the past, I’d had complaints from students that the matrix was too complicated, and it took them too long to complete. I think maybe the difference was that doing this in class gave them plenty of time and space to really get into it, whereas the attitude for doing it as homework might have been to speed through it as quickly as possible? I don’t know . . . all I know is that my non-majors totally owned this activity, so next time some upper division bio students try and tell me it’s “too hard,” I’m going to have a rebuttal for them haha. 😉
While they were drawing food web diagrams, I did a bit of kelp forest artwork of my own:
I really liked the way this went using the little cards . . . I think I’ll incorporate that into the activity for the upper division students, as well.
Not a whole lot to post about this day . . . once again (as usual on exam days), I didn’t take any photos. Our morning was taken up with the third exam, including an exam review session. No Pictionary this time, though . . . instead, I put together a game of Jeopardy, using this awesome Powerpoint template.
Here is a sample of the questions (answers at the bottom of this post):
After the exam, we finished up with diversity, and talked about the evolution of humans. I do a fairly quick run-through of the main groups of ancestors (Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis), and the patterns of dispersal from Africa. I share with the class that 2.5% of my DNA was inherited from my Neanderthal ancestors (2.7% is the average for people of European heritage), and of course we talk about the appearance of Homo sapiens. I had to change up my powerpoint presentation this term, however, in light of some REALLY COOL fossils found in Morocco, which push the timeline back a great many years. Previously, we placed the evolution of humans about 200,000 years ago; now, that date has been pushed back to at least 300,000 years ago. SO COOL!!!!
Another favorite day! And another rotation lab. Today’s lectures focused on the diversity of vertebrates. We started out with chordates, and then followed the major groups all the way through their transition to land. In the morning, we covered fish, amphibians, and (some) reptilian vertebrates. Then, we stopped for some lab activities that allowed them to explore further the transition to land.
First, an activity from the National Science Foundation’s National Center for Case Study Teaching in Science, “A Strange Fish, Indeed,” This interrupted case study describes the extraordinarily COOL discovery by Marjorie Courtenay-Latimer of a living Coelacanth – a sarcopterygian fish from an order believed extinct for 70 million years. This is one of my very, very favorite biology stories, and I did touch on it briefly in lecture, but working through this case study, which allowed the story to unfold gradually, was wonderful. On the whole, I’ve found that the case study activities put out by the NSF are excellent. I used this one as is, without any modifications.
I also showed them this adorable music video about Tiktaalik – another transitional fish.
After lunch, it was time for probably my favorite lecture of the entire semester . . . *drumroll* . . . DINOSAURS!!!!!!! I do love dinosaurs, always have, so this is a big deal for me! When the students return from lunch, I have the “Jurassic Park” theme song playing to set the mood. I have animated slides, including the most epic image ever created:
The dinosaur lecture has a bunch more cool stories – how Othniel Marsh put the wrong head on his “Brontosaurus” skeleton; why the original name for Megalosaurus was Scrotum humanum; the problem with the “Velociraptors” in the Jurassic Park films.
And of course, the question that everyone wants answered: WHEN WILL I BE ABLE TO GENETICALLY ENGINEER MY OWN BABY DINOSAUR? This leads to a discussion of cloning, which, sadly, will probably not ever allow us to make baby dinosaurs, BUT there are some other genetic techniques that will – our first attempts have led to the majestic CHICKEN-O-SAURUS!!!!!
After lecture, more fun during the vertebrate rotation lab! The trick with this lab is choosing which of the LOADS OF COOL SPECIMENS from our Vertebrate Museum to pull out and put on display.
This time around, in addition to some specimens from each of the major groups (fishes, amphibians, “reptiles,” birds, and mammals), I went with a couple of stations that would allow them to explore function: skulls, to look primarily at the teeth, and hypothesize about diet, and bird feet, to determine whether they were for perching, wading, swimming, grasping prey, etc.
Once again, they really enjoyed everything! And one of my students said something really sweet at the end of the day. He’d asked if I’d set up the entire display myself (I answered honestly that I’d had assistance in pulling out the museum specimens, but I’d set up the classroom myself. During the summer semester, I am solely responsible for most of the lab set up and tear down, since I’m not technically employed by the Biology Department, but instead by the Department of Extended Education. I have access to department materials, but not the same level of support that happens during the regular semesters).
After I explained this, he said, “Thank you so much for all the hard work you put into setting all this up for us.”
It meant a lot to me, to know that he’d been enjoying the lab activities, and appreciating the work that went into putting them together. Seriously presh. <3
I know I keep saying this, but THIS IS ANOTHER OF MY FAVORITE DAYS OF THE SEMESTER! Today was pretty much fun from start to finish. In the morning, lecture on the diversity of plants, including the various adaptations that allowed plants to make the transition from the ocean onto land. After the lecture, I’d arranged for us to have a tour of the Tropical Greenhouse on campus. The greenhouse is across campus from the science building, so along the way I gave them a little walking tour of some of my favorite plants on campus, including a few Ginkgo trees, a Cycad (my all time fave), several ferns, redwood trees, and the Butterfly Garden. Unfortunately, I didn’t get any pictures along the campus tour, but I have loads of pics from our greenhouse tour! We were welcomed to the greenhouse by Kandis, who provides instructional support for the Biology Department, and she is an exceptionally gracious hostess!
To be honest, for most of my time at SSU, I didn’t know we had a tropical greenhouse. It was only when I was teaching this class last summer that I found out about it, but now I want to bring as many students here as possible. It’s not all that big, but there are so many GORGEOUS plants!
While we were there, I asked everyone to draw at least one of the plants in their field notebooks, and that occupied much of their time, but we also had time to wander around and talk about the different types of plants we were seeing.
All four main groups of plants were represented here: Bryophytes (including mosses), seedless vascular plants (including ferns), gymnosperms (evergreens), and angiosperms (flowering plants). Mostly ferns and angiosperms. Here are some highlights:
Here are a few student drawings:
Kandis did a couple of particularly cool things while we were there . . . first, she cut off a branch of the rubber tree, so we could see the sap ooze from the plant (and yes, that’s really rubber)! I remember having a rubber tree in the backyard of the house where I grew up, but I don’t think I knew sap would come out like that. (Probably a good thing for the tree; if I’d known, I’d have been cutting off branches all the time).
Kandis also gave everyone a cutting off of a spider plant that needed to be trimmed back anyway. So, we all ended up with adorable little spider plant babies to take home with us, perfect examples of asexual reproduction! (The big plant pictured below is the parent).
Everyone had a fantastic time investigating plants on campus, and then it was time for lunch. When we got back, it was time to move on to the next topic: ANIMALS! In particular, invertebrates – animals that don’t have backbones. I’d set up the classroom as a rotation lab, with a whole bunch of stations: Sponges, Cnidarians, Molluscs and Annelids, Crustaceans, Horseshoe Crab, Arachnids and Insects (including some live specimens; we took a mini-field trip upstairs to view the tarantula and stick insects in one of the 1st floor displays), and Echinoderms. I’m honestly not sure which part of today they liked better – plants, or animals. As far as I’m concerned, they’re all super cool!
Sponges, Mulloscs, and Annelids:
Here’s a cool video I took of a snail scraping algae off the side of the tank with a specialized structure called a radula:
Arthropods, including Crustaceans, and Insects:
Echinoderms (these might be my favorite. Their tube feet are SO CUTE):
Such a fantastic day! And we’ve got more fun in store tomorrow, when we talk about VERTEBRATES!
Today, it was time to leave microevolution behind, and talk about how new species form. Now that they understand how adaptations and natural selection cause populations to change, it’s an easy step to understanding how this can lead to speciation. To drive that concept home, I put together a speciation activity based on this cool online natural selection simulation: http://sepuplhs.org/high/sgi/teachers/evolution_act11_sim.html.
The simulation tracks populations of birds on an island, to see how natural selection and mutations can cause phenotypic changes. You start with 3 populations of 300 birds each, and follow them through 1,000,000 years of evolution. Throughout this time, the simulation makes a notification any time a mutation takes place, along with the overall effect – was it positive or negative? Did it help to increase, or decrease the population?
The instructions on the website call for starting with three phenotypically different populations of birds, to see how they respond differently to the various selective forces. But since I was interested in speciation from common ancestors, I had my students do things a little bit differently. They started out with three identical populations of birds, with all birds having intermediate phenotypes for all characters (medium size, rather than small or large; medium beak length and curvature, and brown plumage). This way, they could get a feeling for how both selective and random forces can affect populations.
The simulation takes place in two rounds: the first, you follow birds in a single location for 500,000 years. Then, the populations disperse to different habitats on the island, and you can then witness another 500,000 years of evolution, under different selective forces. Since we were modeling speciation, I specified that, by the end of the simulation, any populations that differed in at least two characters would be considered separate species.
We didn’t see a whole lot of change after the first 500,000 years, which makes sense since all birds experienced the same conditions. But once they dispersed to different habitats, WHOA they started differentiating quite a bit. On the whole, I was pleased with the way the activity went, and the students seemed to really enjoy it. I would definitely use this activity again in the future.
After the activity, we watched a film: the Nova Origins, “How Life Began,” featuring Neil Degrasse Tyson. This is a great introduction to our next unit: diversity of life on Earth. In the film, he talks about how life might have emerged out of the chemical constituents and conditions that were present on early Earth. I mostly like it because there’s lot of volcano eruptions, and cool stuff like that. Also, I think Neil D.T. is fantastic.
After lunch, I dove right into diversity. I tend to spend more time on this part of the course than anyone else I’ve spoken with about this non-majors curriculum, and there are a couple of reasons for this. First, the amazing variety of life on Earth is one of the things that caught my interest in science at a very early age, so I absolutely love sharing my enthusiasm with students about all the cool organisms that surround us. One of my dreams is to be able to teach a dedicated zoology class one of these days (honestly, that is the class I was BORN to teach haha). If it was just about my enjoyment, however, I would try and rein myself in, but invariably, I have students who tell me this is their favorite part of the course. So, I spend a fairly substantial amount of time on diversity.
Today, we started out with mostly teeny tiny things: prokaroyotes (bacteria and archaea), and protists (mostly eukaryotic microbes, but also including some larger things like algae). I walked through the basics in lecture, and then the fun started: MICROSCOPY LAB!
In the past, I arranged to have prepared cultures of little critters on hand – things like Euglena, Parameciums, Volvox, blue-green algae. This time around, I’d thought we’d try something different. Instead of providing samples, I took the class out to the campus lake, so they could collect their own water samples, focusing more on discovery, rather than studying any particular organisms. (Along the way, we also visited the nifty fungus we’d found back on the first day of class).
On the way back from the ponds, we stopped for a little adventure. Transfer orientation was going on that week, and there were all sorts of booths set up for the new students. We tried to get some free t-shirts, but failed (they were for incoming students only), but they did take this fabulous picture of us, pond water samples at all:
Back in the classroom, we pulled out the compound microscopes, along with some glass slides and methylcellulose quieting solution (to slow down how fast they swim), and I showed them how to make wet mounts from their samples.
So, how did it work out?
IT WAS AWESOME! WE FOUND THE COOLEST STUFF!!!!!!! Here are some photos and videos, taken with my microscope camera (I have a microscope similar to this one, but I usually just remove the camera, and insert it into the eyepiece of one of the school’s microscopes, as they have better quality optics).
To be honest, although this was supposed to be the protist lab, most of the things we found were actual animals. We did find a few protists, though, like this algae:
Another protist: Halteria grandinella
I think these might be Tetrahymena:
We found an insect, and a few crustaceans, including what I think is an Alona sp (shown in the videos):
But I think the star of the show today was this lovely critter: a HYDRA! (No, not the multi-headed dragon kind. This one is a Cnidarian, closely related to jellyfish and corals):
We ended up spending the rest of class time looking through the microscopes, and I’m pretty sure everyone found something cool in the water sample they’d collected. There’s just something very satisfying, and a bit mind-blowing, about finding all these things living in the lake we walk by every day.
Today we covered sort of a hodge-podge of things, but there was a common thread – ways in which we can see evidence of evolution, both on long time scales, as well as short ones.
First things first, though – Exam #2. Before the exam, we played a game of Pictionary, using the following prompts:
Character vs Trait
Function of tRNAs
Phases of Mitosis
Again, no photos from that day, but I’ll recreate some of the drawings . . . answers at the bottom of the post. 🙂
After the exam, I walked them through the evidence of evolution: how the fossil record demonstrates graduate change over time, in the form of transitional fossils; how geographical patterns are explained by common ancestry, such as the radiation of marsupials in Australia; how we can track the number of mutations over time in a sequence of DNA, and use this to estimate how long ago two species diverged from a common ancestor. And my favorite: comparative anatomy. At this point in the lecture, I always tell the story of the “ah-HA” moment in my own life, when this understanding clicked for me. When I was young, I spent a lot of time at the L.A. Zoo. Eventually, in high school, I’d become a student volunteer there, but even before that, I spent a lot of weekends at the zoo, sometimes attending some really cool educational programs. There’s one class I remember really clearly . . . the woman giving the program showed us a diagram of a whale’s skeleton, including the bones in the fin. Then, she showed us a diagram of the bones in a human hand . . . same configuration, both inherited from a common ancestor way back in our evolutionary history.
After lunch, we continued with evolution, but on a slightly different tack: infectious diseases. At first, it might not seem related, but when we talk about the influenza virus, and how it evolves to overcome our immune system’s adaptations, BOOM! Evolution that we can watch happening in real time. Plus, students tend to find the topic of disease really interesting. Bubonic plague, malaria, Lyme disease . . . fascinating stuff.
Today’s lab activity explored a couple of types of disease transmission, in the context of a role-playing exercise. I had the class “attend” a convention: the International Association for the Breeding of Dragons (since they are experienced dragon breeders after last week’s inheritance lab). Unfortunately for them, however, one of the conventioneers showed up carrying a nasty case of contagious Dragon Pox, and the following morning, there was a problem with food poisoning in the hotel’s breakfast buffet.
Figuring out how to do this lab took some ingenuity on my part. I found a few examples online of disease transmission labs, with the general idea of seeing how quickly a disease can travel through a population, depending on the method of transmission. Transmission would happen by exchanging “body fluids,” represented by cups of water. One “infected” individual (who wouldn’t know they were infected) would have a cup with water and sodium hydroxide, and after a sort of “musical chairs” in which students would randomly contaminate one another’s water cups, all of the water would be tested with phenolpthalein solution . . . the water of anyone who’d been infected by the disease would turn pink. Only problem: I didn’t have any phenolpthalein on hand.
So, I improvised. Instead of using sodium hydroxide, I filled the “infected” cup with 3 parts water to 1 part vinegar. It wasn’t enough vinegar so that the smell would be obvious, but it was enough that, even after mixing with two or three other “uninfected” samples of water, there would be enough acidity to see a difference using standard pH test strips. I had the students “mingle,” and everyone exchanged body fluids two times. Then, each of them had to visit the “doctor,” to be tested for Dragon Pox. Once we knew who had been infected, they tried to figure out the identify of Patient Zero – or, the original source of the infection. In our case, four of the ten students were infected, and we were only able to narrow it down to two people, but of course, I knew all along that Greg was the bearer of the disease.
As if that wasn’t bad enough, the “next morning” at the convention, I had them eat a big breakfast from the hotel’s buffet. I had a list of food items, labeled with photographs . . . in order to take a helping, they took an eye-dropper full of water out of that item’s cup. Again, I’d laced two of the cups (the ones containing “strawberries”) with vinegar. Turns out, a lot of people like strawberries, and almost all of them ended up with a case of food poisoning. This time, they compared notes as to who ate which items, and they were able to determine that the strawberries were tainted.
It went well, and the vinegar/pH paper system worked out perfectly. I’ll definitely do that again in the future, instead of trying to source less common chemicals. I think I’ll also add another section, to simulate airborne transmission, although I haven’t yet thought through how to do it.
We ended the day by watching a film – it’s one of my favorites for this class: “Why Sex?” This one follows another couple and their path to parenthood, while exploring the ways in which humans, and other animals, benefit from the process of sexual reproduction.
As usual on test days, we didn’t cover a much material as usual today, but no worries! There will be more fun tomorrow.
Started out the day by picking up where I left off on my Darwin lecture, and then moved on to adaptations, and the principles of natural selection. I frame most of this discussion around the Oldfield Mice experiment, partly because it’s a perfect example of a scientific study that demonstrates the effects of selection on populations, but also because the mice are so cute! I end up using these mice as an example all the way through evolution and speciation, so I have a bunch of slides I’ve animated showing all sorts of things happening to the mice. (Selective forces, like being caught by a hawk when the fur doesn’t match the substrate; and, later, random forces, like severe weather).
Oh! I almost forgot to mention that this is the lecture where I reveal probably the single most important biology fact of all . . . the secret connection between Charles Darwin and Abraham Lincoln. It’s common knowledge that they were born on the exact same day (February 12, 1809), but I’ve uncovered a surprising bit of information that is much less well known . . . the image at right should make it obvious what I’m talking about (all photos were found on the internet, so obviously they must be completely legit).
We completed two big lab activities today. Before lunch, we viewed a short film from HHMI about Charles Darwin and Alfred Russel Wallace, called “Making of a Theory,” along with a rotation lab that helped them explore Charles Darwin’s life, and the inspiration behind his ideas about natural selection and evolution.
I usually modify activities to some degree, to better suit how I cover the topics, but in this case, I used materials I’d found online exactly as is.
When we came back from lunch, I lectured about natural selection, and then we did some lab activities to demonstrate selection, and competition, in ACTION!
First, the predator lab: each group is provided with a bucket filled with a substrate of a particular color (mostly pink, mostly white, or mostly blue). We then populated these habitats with pink, white, and blue pipe cleaner “worms.” They then switched off hunting for prey in their habitat. After each round of hunting, they calculated how many of each color had survived, and the survivors were allowed to “reproduce” (so more worms of those colors were added to the subtrate).
The hypothesis? That worms that matched the substrate color would survive the best (because they were the hardest for hunters to spot), so over time, this color would be favorable, and the other colors would decline.
So, catching worms is a lot of fun, but did their results match up with this hypothesis? Turns out, not really! In the past, I’ve done this activity with students, and generally the data they collect is exactly what they expected: the pink habitats have more pink worms than other colors, white habitats have more white worms, etc. But we only made that finding for one of our substrate colors (and it wasn’t a strong effect at all):
So, how do we explain this? I gave them some time to come up with an answer . . . our new hypothesis is that most of the students weren’t hunting by sight (in which case, color would be under selection), but were hunting by touch, so color didn’t impact how easy or difficult the worms were to catch. I think that’s a pretty sound hypothesis. 🙂
Our final activity for the day is also one of the most exciting of the semester . . . *drumroll please* . . . COMPETITION LAB!!!!!!! In this lab, students use chopsticks to simulate the beak of a wading bird. All birds start out with short beaks, and have to compete against their team members to catch the most food out of a limited supply. Each generation, the most successful birds are able to reproduce. It is also possible for a mutation to take place, causing an adaptation of beak length. As you might guess, birds with longer beaks are more successful at catching food swimming in deeper water. Yes, this activity allows us to demonstrate some principles of natural selection. But it’s also just hilarious to watch!
Everything usually starts out nicely enough, with each bird just trying to catch some food:
But, sooner or later, things start to get brutal. This is COMPETITION we’re talking about, after all. (It doesn’t hurt that I goad them on throughout that “IF YOU DON’T CATCH ENOUGH FOOD YOUR BABIES WILL DIEEEEEEEEE!!!!!!!!!!”).
Honestly, I don’t remember what our results were. I think Cassandra (in the greyish green jacket) was the winner, overall. But really, they were all winners that day. Well, at least those that caught enough food to feed their little offspring hahahahaha.
This is always one of the favorite topics of the semester – Mendelian genetics, and inheritance. We cover a bunch of really interesting stuff, including questions like:
“Can two brown-haired people have a blond baby?”
“Why do I have green eyes and my sister has blue eyes?”
“Do twins have the exact same DNA?”
“What are the genes that determine how you look?”
“Can you choose which traits your child will have?”
We also talk about pedigree analysis, and inherited diseases, and Punnett squares (okay, they don’t usually love Punnett squares haha). But still, loads of cool stuff! My lectures on the topic are pretty well set, but I needed to figure out some lab activities. The one activity I use with my lecture-only course is designed as a homework activity, but it was pretty simple to restructure it into a rotation lab. I also found a few additional things for them to do, and explore the subject of inheritance.
Right from the start, they figure out that this isn’t going to be just any old inheritance lecture. When explaining Mendel’s breeding experiments, I make a very minor adjustment . . . instead of all those pea plants, we pretend that he was breeding dragons. Mostly because I like dragons a lot, but it also ties in with the hands-on activity I had them do later in the day. 😀
We didn’t jump right into dragons with our lab activities, though . . . we started out breeding dogs, instead. I found this really cool online activity at PBS Kids, and created a worksheet to accompany it. We took a trip over to the library, so they could use school computers, and they all got busy trying to breed dogs with desired traits.
The rest of the day’s activities I sort of switched around on the fly, as I decided I didn’t really like my original plan. So, I’ll describe what we actually did, and I’m not going to post all of the worksheets, as I ended up doing activities in a different order.
Before lunch, we did an activity on inheritance of human traits, where they assessed their own phenotype for several different classic “monogenic” traits. (In reality, many of these are probably determined by multiple genes, but I think the activity still has value).
In addition to the ones listed above, I had a station for phenylthiocarbamide (PTC). I provided strips of paper soaked in PTC, and by touching it to their tongues, students were able to discover whether or not they have the gene that allows them to taste the compound. (Of course, the ones who could taste instantly regretted it – apparently it taste AWFUL. I wouldn’t know – I don’t have the tasting gene). Interestingly enough, I had two students who appear to be heterozygotes – they could taste the PTC, but only mildly.
I asked them to add their results to a chart that tracked the entire class, so we could play around with percentages. Of course, we’re not able to make any strong statements about our results, as a sample size of 11 is pretty small.
We did have one super interesting result though – two of the students in class shared the same phenotype for EVERY SINGLE ONE of the traits. The probability of that is less than 1% (roughly 0.78%). My hypothesis? They were unknowingly separated at birth. 😉
After lunch, we go to the really fun stuff . . . the DRAGON GENETICS ROTATION LAB! As I mentioned, I usually assign this activity as a homework assignment, but it transitioned perfectly into a rotation lab. At the earlier stations, students practiced things like Punnett Squares, and interpreting pedigree charts. Then, they were able to breed a baby dragon of their own. They’re given information for how several characters are inherited, and they flip a coin to determine which allele the baby inherited from mom, and another coin flip to determine the allele from dad.
Of course, there’s not really much point in determining the baby’s alleles if we never get to SEE the baby, so the final step is to create a phenotypically-accurate dragon. Usually, when doing this for homework, students visit one of the Doll Divine sites, and make a dragon there. In class, though, I turned it into an arts and crafts project. I gave everyone a template with a generic dragon, and all the possible traits, and a huge box of colored pencils, some scissors, and glue sticks . . . and let them go to town.
The verdict? Coloring is fun. 😀
After finishing up with the activity, we still had about an hour left of class time, so I started my Darwin lecture. It’s one of my best lectures, and usually keeps a class’s attention pretty easily . . . but about 20 minutes in, I saw that I was losing them. They were getting sleepy-eyed, and slumping to the side . . . so I found a good breaking off point, and decided to pick it back up in the morning. I suppose that breeding dragons is hard work. 😉
Today? The wonders of cell division! In lecture, I framed mitosis in the context of cancer: in order to understand unregulated cell growth, we need to understand how cells operate the rest of the time. As for meiosis, that’s the gateway to understanding reproduction. (Or maybe reproduction is the gateway to understanding meiosis? Either way, they’re intimately connected). This is a pretty important concept in biology, and while I don’t think they’ll need to be able to remember all the little details on into the future, I did want them to have a really clear understanding of what happens during cell division, so we attacked it in a variety of different ways.
First: A draw-along. I interrupted lecture, and asked them all to pull out a piece of paper. Then, using Skitch on my computer, I drew out the phases of mitosis, and had them draw along with me.
Second (Which turned out to be the highlight of the day): MICROSCOPY!!!!!!!!
Honestly, I think pulling out the microscopes is one of the easiest ways to catch everyone’s interest. THEY LOVE MICROSCOPES!!!!
We did the classic “onion root tip” experiment . . . looking at prepared slides of a part of the plant where growth – and therefore mitosis – is occurring. The idea is to count the individual cells, and which phase of mitosis they are in, and use that to get an idea of what percentage of time a cell spends in each phase. We didn’t start with microscopes, though. To give them some practice identifying the stages of mitosis, we worked through this virtual lab:
After that, we did pull out the compound microscopes, and they spent the next half hour or so counting onion cells. One thing I thought was clever: some of the groups took photos (through the microscope, like mine below), and counted the cells on the photo, instead of through the microscope. This turned out to be SO much easier to keep track of the rows.
When I complied all their data together, we found (as expected) that cells spend the most time (by far) in Interphase.
Third: to reinforce the phases of mitosis in yet another way, I had them do a hands-on activity where they physically manipulated a set of “chromosomes” through the process. The previous evening, I’d made up several sets of these “chromosomes” out of Perler beads and pipe cleaners. I’d hoped that the pipe cleaners would hold the beads in place, but also allow students to remove some of them easily, to swap strands when they simulated crossing over of meiosis I. I wasn’t sure how well they’d work, but they ended up working GREAT, and the students seemed to really enjoy the activity. I also provided them with printed “cell” templates, along with a bunch of colored markers that they could use to draw out the phases. First, they worked through mitosis, and then, after lunch (and the meiosis lecture), they did the same thing again with meiosis. I was super happy with the way this one worked out – I was a little afraid it would be boring, or that they’d get through it too quickly – but the pacing was just fine.
After finishing up with meiosis, I switched gears entirely, and gave an art lesson. Yes, you read that correctly – an art lesson: Drawing for Biology. It was grounded in the fact that the art of illustration – being able to accurately draw something you see – has always been an important part of biological research. I also fear that it’s one of several naturalists skills that aren’t as much a part of the biology curriculum anymore, as I think they should be. So, I decided to give an art lesson a try. I’m going to go into more details in a future post, but in a nutshell, after giving them some background, I asked them to do an exercise. To draw this flower. The catch? They weren’t allowed to look at their hands or the paper. The could ONLY look at the flower. Here’s one that I did . . .
Did the flowers look crappy? Well, yes – the petals aren’t in the proper relationship to one another. But if you look at the individual petals, most of them are actually pretty close to being the correct shape. The point, of course, was to help them switch from drawing what they think they’re seeing, to what they’re actually seeing. Next, I did let them draw the flower without the “no looking at the paper” restriction. (I also gave everyone a little “field notebook” – I’d purchased them in bulk from Amazon, and they worked out really well)
Finally, we went outdoors, to a little garden in the courtyard, and I asked them to choose anything and draw it. Again, I’m so impressed with this particular group of students – they all dove right in, and worked diligently on their drawings (I’d kind of expected at least some of them to rush through, since they were able to go home afterward, but they all stayed and put an appropriate amount of effort into the process).
Stay tuned for more of our drawing adventures later in the semester!