To understand the fundamental methods of plant classification and to become familiar with their applications in science.
"...as scientists are better able to assess the conservation status of the species that compose an ecosystem, the more they will understand the health of that ecosystem. It is time to accelerate taxonomy and scientific natural history, two of the most vital but neglected disciplines of biology." Stuart et al., Science 328:177 (2010).
This is the second lesson in a two-part series on plant identification and classification.The first lesson, Grassland Plants: Plant Identification, provides students with an opportunity to explore how plant structures can be used in plant identification.
Grassland Plants: Plant Classification provides students with an opportunity to explore how plant structures can be used to build phylogenetic trees, a skill important in the taxonomy and natural history disciplines. Any group of organisms can be used to develop classification skills; however, in this lesson, grassland plants are the focus of the examples used.
Research involving ecosystems and interactions between the species that inhabit them has played an important role in their conservation. Determination of a species' conservation status plays an integral part in maintaining ecosystem biodiversity. Two important goals set by the Convention on Biological Diversity are to: (1) decrease degradation of habitats and (2) address the decline of species. (Stokstad, Science 329:1272 (2010).) In order to catalog the world's plants, assess the conservation status of a species, and characterize natural habitats, it is necessary to have a strong working knowledge of classification systems; in other words, an understanding of taxonomy. Taxonomy, broadly defined, is the scientific discipline which involves naming, describing, and classifying species. Biologists classify organisms into a hierarchy of groups based on similarities and differences in their structure. (Science for All Americans, p. 60.) Since the focus of this lesson is on classification, you will look at the evolutionary relatedness of plants found growing around your school.
Animals and plants have a great variety of body plans, with different overall structures and arrangements of internal parts to perform the basic operations of making or finding food, deriving energy and materials from it, synthesizing new materials, and reproducing. When scientists identify and classify organisms, they consider details of anatomy to be more relevant than behavior or general appearance. (Science for All Americans, p. 60.)
Students often have misconceptions about classification; therefore, it is important for you to query your students to discover these misconceptions.
Note: As a precautionary measure and to minimize risk, you should make yourself aware of any students who may have allergies to bee stings. Bees are found in the grasslands and pollinate flowers; the risk for a student to be stung is something to consider.
These resources provide good background information for this lesson:
- Stuart S.N., Wilson E.O., McNeely J.A., Mittermeier R.A., Rodríguez J.P. "The barometer of life." Science 328:177. (2010)
- Stokstad, E. "Despite Progress, Biodiversity Declines." Science 329:1272. (2010)
- Read a review of A Tour of the Flowing Plants in Science Books & Films
Since an understanding of evolutionary history (how organisms are related to one another) is essential in biology, plant classification is an important concept to understand in budding biology students. You should begin with a brainstorming session to assess what your students know about classification and to identify any misconceptions they might have about evolutionary relationships among organisms and how this is connected to classification. You can easily begin the brainstorming session by directly asking your students what they know about the relationships between different plant species. You may have already discussed the general classification scheme (Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species) in class.
Start by bringing a couple of plants or plant parts to class which students would commonly eat (e.g., apples, celery, peaches) and some local "wild" plants they would normally see (e.g., trees, weeds). You could perform this activity outside in the field too. If possible, include flowers and other reproductive parts when collecting plant material. Use the materials along with the following prompt to get the lesson started and write out students' answers in a field notebook (in the field) or on a chart (in the classroom):
- If you were to sort these plants into groups, what characteristics would you use to sort them into groups?
- (Students may or may not know plants can be grouped into families as is done in animal classification. Traditionally, plant taxonomists have relied more on reproductive structure [e.g., flowers, inflorescences, fruits] in grouping plants into taxonomic categories. Today, plant taxonomists also use additional molecular evidence such as gene sequence comparisons to classify plants. Asking your students this question is a good opportunity for you to determine if they know anything at all about relatedness among plants.)
Plant structure will be used to infer relatedness and classification in this lesson and plant names will enhance the understanding of this lesson; therefore, it is assumed your students will have some familiarity with plant names. If your students are completely unfamiliar with any of the plant structures and/or with the names of any of these plants, it might be best to start with a lesson on plant identification first (see Grassland Plants: Plant Identification).
Next, have your students look at a wide variety of plant structures and their arrangement outside in the field (preferably) or provided in lab. The best order of observing structures are usually from the least to most complex. Therefore, consider starting with organs (roots, stems, leaves), then flowers; then inflorescences (clusters of flowers); then fruits (the products of flower parts). This is your chance to connect structural terms (vocabulary) with living examples. The Botanical Society of America's Apple Poster provides an excellent resource to model the timed sequence of leaves and flowers emerging from a bud through fruit maturation. The observation of these structures will hopefully spark interest in your students to further explore how plants are constructed, grow, and develop. For now, however, you are interested in how plant structures can be used to group or classify plants. Knowing some basic plant (especially reproductive) structure is fundamental to understanding how plants have been traditionally classified.
Begin this section by having students use their Classification of Plants student esheet to view the Plant Identification and Classification video. In this video, your students will gain an understanding of the processes of plant identification and classification and why the two disciplines are important to scientific research. The main focus of this lesson is to provide students with an opportunity to think about how plants are related. After viewing the video, discuss these questions with your students:
- There are eight major taxonomic ranks. How do scientists classify an individual plant using these ranks?
- (The eight major taxa are Domain, Kingdom, Phyllum, Class, Order, Family, Genus, and Species. They can analyze physical structures, chemistry, and/or DNA sequences to observe similarities and differences.)
- What more advanced method is now available to classify a plant specimen?
- (A more advanced method is analyzing similarities and differences in DNA sequences.)
Your students should understand the process of classification and its importance to research.
Next, your students will have the opportunity to practice sorting local plants into groups. Before bringing your students out to the field to complete this activity, you should explore the school grounds or surrounding area and find a location where biodiversity is high and students can sample 10-15 plant species. Use the field guide to identify several of the plant species in your study area. Then bring your students outside to gather their plant specimens. Students should follow the directions on their Plant Classification student sheet to do this activity. You can use the Plant Classification teacher sheet to check student work.
Once students have gathered their plant specimens, bring them back inside and demonstrate the use of the Encyclopedia of Life website and where the data students need to collect can be found. Students should follow the steps explained in the video when classifying their specimens and record their data in the table provided.
Next, begin discussing the processes of evaluating evolutionary history and constructing evolutionary trees explained on the Evolutionary History student sheet. You may want to have your students re-view the Plant Identification and Classification video before answering the corresponding questions. After students finish answering the questions for the video, discuss the introductory paragraph, the video, and student responses as a class. (You can refer to the Evolutionary History teacher sheet for answers to the questions.) It is important that your students understand that classification systems are built on similarities and differences between species and that these similarities are not simply due to coincidence, but result from a shared evolutionary history and common ancestry. In this activity, your students will have the opportunity to gain a further understanding of how all of the plant life around them is related by creating a phylogenetic tree.
Once your class discussion is complete, you should introduce the evolutionary history activity to your students. Students should follow the steps explained in the Evolutionary History student sheet to complete this activity.
- First, you should start by asking students questions about how to set up the activity. A suggested question includes: What information is gained by understanding a plant's relatedness to other plant species?
- One potential activity layout:
- Take photos of the plants you use for this activity. If a camera is not an available resource, sketch each specimen or collect a sample and press to preserve it.
- Find family and scientific names of specimens to determine their classification using Encyclopedia of Life online.
- Determine relatedness of specimens using classification data.
- Create a well-organized phylogenetic tree showing relatedness of specimens. Include family name, scientific name, and visual of specimen.
This lesson provides an opportunity for students to complete a classification table and build a phylogenetic tree. These two items can be graded separately or included in a lab report about classification. Focus your assessment on student understanding of how identification and classification are complementary to one another, how closely their phylogenetic trees matched those of their classmates, and how these skills might be applied in scientific research.
Grocery store botany: You can have students look at a variety of commonly eaten fruits, vegetables, and other plants/plant products they might find in the local grocery store. Use the questions in the "Motivation" section as prompts for a discussion of how different food plants are related to one another. A good place to start is having students identify the families which include our major crops. Here are some examples:
- Grass family (Poaceae) includes: rice, corn, wheat, oats, barley
- Legume family (Fabaceae) includes: lentils, kidney beans, green beans, peas
- Rose family (Rosaceae) includes: apple, pear, strawberry, blackberry
Species Concepts: What constitutes a species? There is not one set definition for a "species." In fact, plant taxonomists usually recognize taxonomic species as opposed to biological species. The species concept would make for an interesting class topic, especially one which leads to a discussion of biodiversity.
You should consider the potential this activity has for getting students more involved with research. There are many good avenues for student research presentations available through venues such as JSHS and Intel Science Talent Search.
Literacy Connection: The formalized K-W-L method can be used with A Tour of the Flowering Plants science trade book by Priscilla Spears.