Hands-on biology

Hands-on science exploration clarifies difficult concepts and engages learners who have difficulty in more traditional classrooms. This article looks at an inquiry-based classroom that meets the needs of all of its students.

By Waverly Harrell

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• Learn more about asexual reproduction, biology, botany, discovery learning, diverse learners, inquiry-based classroom, learning disabilities, life science, plants, seed germination, and teaching methods.

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A prospective customer was visiting Carolina Friends School, a biology professor who had just moved to the area and was considering sending his daughter to the school. The admissions director was giving him a tour, and Blythe Dyson invited him into her classroom. Students, mostly high school juniors and seniors, were clustered around window plants that they had been dissecting. They weren’t the top students in the school; in fact, many of them had severe learning disabilities. Some had trouble with memorization, others with written language. The prospective customer asked them some questions about how the window plants worked and why they had evolved that way. "And boy, they could answer them, like that ,” Dyson says, snapping her fingers.

These kids impressed him so much with their motivation and their excitement about the material and their knowledge of the material, that he decided to send his daughter to our school based on that. That was really cool, because that was all them. They became stars in this class because of the way it was structured for them to succeed.

Because Dyson teaches biology at a private school, she has unusual latitude in designing classes. However, hands-on science activities can be included in any science classroom. “Science as inquiry” is a new strand in the North Carolina Standard Course of Study, and starting in 2007, end of grade tests are expected to include questions on the process of science. Activities such as those described here encourage students to participate in the scientific processes of observation, questioning, testing, and drawing conclusions based on available evidence.

A number of Dyson’s students came to Friends School because they did not succeed in the public schools. “We had a crop come through where there was a significant portion of kids with different learning styles, and we knew that they probably wouldn’t thrive in [science classes] that focused on memorization or precise verbal communication through writing,” she says. “We wanted to design a class that would use their skills more.”

Dyson designed a series of classes for these students that focused on hands-on work, experimentation, and making connections between scientific theories and the physical world. One of the most successful was Plant Propagation, which engaged and stimulated not only students with learning disabilities but also those with conventional academic skills. Some of the activities she designed for this class could be used with younger students or as short segments in more broad ranging biology classes.

Dissection

After teaching some plant anatomy at the chalkboard, Dyson would take the students outside with pruning knives to cut open trees. “We’d cut limbs off and look at the different layers, and we’d skin the bark off and look at the green cambium layer. So I’d explain all this, and they retained it for the whole rest of the term, that there’s only one living layer of cells in a woody plant. That the wood itself is not alive.”

Dyson was working with high school students, but a teacher with students too young to wield knives could dissect trees while the students watched. Dyson reminded the students that the knives and razor blades they used in experiments were sharp and required special care. Classroom management was no more difficult in this class than any other, she reports. In fact, she observed less problem behavior than usual, perhaps because students were highly engaged.

Dyson focused on woody plants, but she notes that you could also use any plants available on the school grounds to differentiate woody from herbaceous plants. “Even a very urban area is going to have some kind of sapling growing up through the concrete,” she says. Having the students’ hands busy helps them to focus, and uncovering the layers of the plant makes the earlier anatomy lesson salient and memorable.

When the class studied evolution, they cut open window plants (Haworthia cuspidata), and Dyson explained how these plants have adapted to the harsh, dry conditions of their native South Africa. Window plants are small succulents that live under the sand, with only part of the leaf exposed to the sun. The exposed part is clear, like a window. All the chlorophyll is on the buried exterior of the leaf, so sun shining through the window hits chlorophyll on the other side of the leaf. Window plants have evolved this way to get sun without drying out.

First the students examined the leaves of the window plants, and Dyson asked them what they noticed. “Oh, it looks juicy, it’s thick, it’s not a flat leaf, it’s got this little clear top.” Then they sliced the leaves open using razor blades. “Oh my gosh, the green’s only around the outside, it’s not in the middle.” Rather than telling the plants’ story and then showing the students the leaves, Dyson let them discover how window plants are unusual. “What do you think’s going on?” she would ask.

Asexual reproduction

The Plant Propagation class used division to propagate window plants. “We’d learn about division and how that’s an asexual form of reproduction. And then we would talk about some benefits of asexual reproduction. For example, if you live in a very harsh climate, asexual reproduction might be more advantageous because very few phenotypes could survive in that climate.” Although producing variation through sexual reproduction usually helps plants to survive, window plants probably wouldn’t benefit from variation because they have successfully adapted to a narrow and unforgiving environmental niche.

The class also looked at other plants that reproduce asexually, such as strawberries and spider plants, which reproduce by means of runners, and Rex begonias, which when sliced across a vein will sprout a new plant from the slice. “Kids think it’s like magic. They love it. So then you can get into the vascular structure of plants, because you’re slicing the veins. They have vascular structure, like we do, but it’s different than us, because they don’t have a heart. So that gives you an opportunity to talk about more botany, and they’re fascinated.” It takes at least a month for the new begonia to grow, so it may be necessary to teach students how to slice the leaves first, then discuss the concepts later when the results are apparent. A dissecting microscope, which can magnify an opaque object ten to twenty times, will help students to see the rootlets as soon as they develop.

Germination

While working with seeds, the class learned about the evolutionary advantages of sexual reproduction and discussed the characteristics for which people breed seeds: new colors, higher fungal resistance, drought tolerance, insect resistance. “We’d talk about how sexual reproduction occurs, and the formation of seeds, and we’d dissect seeds, and then I would just teach them basic seed germination skills,” Dyson says. They discussed “the biology out there in the wild and how we have to work with that biology when we try and create new plants in a controlled environment, which is what plant propagation is. It was a way to teach a lot of botany, but frankly, I think if you told kids, we’re going to learn botany, a lot of them would not be excited. But here they’re learning that it has practical value.”

Some seeds, like avocado pits, are easy to germinate. Others will only germinate after prolonged exposure to cold temperatures, or after their shells have been penetrated. To propagate plants commercially, breeders might refrigerate seeds or penetrate their shells by cracking, filing, or dipping the seeds in acid. Dyson’s students experimented with these methods to see what worked best for each type of plant. These experiments have the added benefit of illustrating how to gather evidence scientifically.

Germination also opens the door to dicussions of evolution and adaptation that are surprisingly engaging:

We’d take seeds that we had treated and seeds that hadn’t been treated and we’d look at their germination success rate. And we would talk about reasons why a plant might have evolved to need that cold, wet period to germinate. So we’d talk a little bit about evolution, and about the adaptive value of something that makes it harder to propagate plants. It seems like a pain in the neck that you have to stick the seeds in your refrigerator for several months, but really it has evolutionary adaptive value. So they’re there with their hands in the dirt, and they’re dealing with moisture and all these tactile things, and we’re talking the whole time. A lot of kids can’t learn if they’re sitting still. They have to be physically moving to learn, they have to be physically engaged.

For instance, for a seed that requires stratification (long exposure to cold temperatures), the class could refrigerate seeds for different lengths of time and see which artificial winter produces the highest germination rate. There may be a tradeoff between germination rate and time invested: “if you get 90 percent with three months and 85 percent with two months, is it worth the extra month?”

For a seed that requires scarification (penetration of the shell), the class could abrade some seeds with a file and crack other seeds with pliers. (Sulfuric acid can also be used to penetrate seed shells, but that treatment could not be performed in the classroom.) Then the germination rates of the filed seeds and cracked seeds could be compared. Seeds that require scarification include Kentucky coffee tree and thornless honey locust seeds. A plant propagation encyclopedia would list other examples. If you have difficulty obtaining appropriate seeds, Dyson suggests contacting the nearest land grant university (NC State University or NC A&T State University), a local 4H service, or your local cooperative extension agent, listed in the blue pages under cooperative extension service.

Fruit salad

One class period the students particularly enjoyed was the day they made fruit salad. Dyson used this day to discuss propagation of the various fruits, but she points out that fruit could also be used to talk about seed distribution methods, differences between wild and domesticated plants, or sexual reproduction in plants. “I brought in a lot of fruits that were pretty exotic, that you could propagate at home, and we made a fruit salad. I also brought in avocados and we made guacamole.” The fruits included star fruit, papayas, and kumquats, all of which have seeds that can be sown, and pineapples, which can be propagated using the spiky top.

“I had the kids busy cutting and mashing, so they were physically engaged. So we’re all sitting around a big round table talking. And we learned how to propagate every single one of the fruits while we were making the food and eating it. Some kids got to go home with an avocado seed to sprout, and I thought everyone did this in preschool, but believe it or not, some of these kids did not know you could sprout avocado seeds.” Everyone went home with something to try to grow. “They’re so excited, because you’re giving them food, which always ramps up the happiness level, and they’re learning. So that was a really successful day.”

When you have less time

In a more general biology class, one or more of these activities might be useful in tying together several themes, such as ecology, evolution, and botany. While examining window plants or seeding fruit, the class could review ecological challenges plants face, how they have evolved to answer those challenges, and the resulting botany. “I think that these types of classes are really good at introducing principles, or at reinforcing principles, or at getting excitement built around principles,” Dyson says. “One kid’s going to get an introduction, and one kid’s going to get a reinforcement, and one kid’s going to get excitement. All out of the same class.” Hands-on biology lessons can engage and motivate students who have trouble mastering concepts through reading and students whose learning process is aided by physical movement or social interaction. And doesn’t every class have students like that?