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Teacher’s Corner Lesson Plans Helping Teachers and Students Make the Most of their Outdoor Classroom www.evergreen.ca Bringing Nature to our Cities Using a Dichotomous Key∗† Judy Olacke Grade level: Grade 11. Provincial curriculum links: Ontario. Subject: Science; Biology. Keywords: Dichotomous key, tree, coniferous, leaves, human interaction, leaf. Description Using a dichotomous key and observation skills, students will classify various specimens of trees. Curriculum Framework Specific Lesson Goals Classify specimens by applying the principles of taxonomy Use a dichotomous key as part of the data collection to describe and evaluate an ecosystem Preparation Preparation time: 1 hour Preparation time includes: Copy, laminate and assemble the tree key “wheels” Copy and laminate cards with pictures of leaf characteristics Put out numbered stakes beside the trees to be identified. There should be at least 5 different types of trees. ∗ Source of Lesson Plan: Written by Judy Olacke and based on lessons originally found in: Ministry of Natural Resources. Focus On Forests. Toronto: Ontario Ministry of Natural Resources. 1989. † Submitted by: Judy Olacke <[email protected]> Using a Dichotomous Key 2 Length of lesson: 2 hours. One hour for the introductory lesson on the role of taxonomy as well as constructing and using simple dichotomous keys. One hour for learning the terms used for leaf characteristics. Resources required: Cards with pictures showing the terms used on keys to describe leaf characteristics (pp 27 & 28, Focus on Forests - see Resource Required below) – Leaf Types (compound, simple, scale-like, needle-like, in bundles or singly on twigs) – Arrangement on Twig (opposite, whorled, alternate) – Leaf Margins (smooth, toothed, wavy) – Leaf Shapes (linear, oval, reversed oval, chordate, connate, heart-shaped) Copies of a few varieties of dichotomous keys (insects, whales, flowers) (see Gr. 11 Biology texts - any publisher) One coniferous tree “wheel” key per student (pp 32, 33 Focus on Forests) Numbered stakes for indicating the trees to be identified Ruler (cm) Pencil and record sheet Procedure Part I (1 hour) 1. In class, introduce the students to the importance and purpose of classifying things (telephone book, CD collection, etc). Relate classifying things to the role of a taxonomist and the “tools” they use. 2. Construct a dichotomous key using 8 of the students’ shoes. 3. Give the students an opportunity to use a variety of dichotomous keys for different species. Part II (1 hour) 1. As a whole group activity, have the students observe and describe leaf characteristics using common scientific terms. Distribute leaf cards that show examples of each characteristic. (See resources) 2. Write the leaf characteristic terms on the chalkboard. Have students stick their leaf card under the appropriate term and discuss. 3. Students can then write the leaf characteristics in notebooks and sketch an example of each. 4. Outside, distribute tree wheels. Walk through how to identify a tree with all students. 5. Individually, students will then use the tree key and identify each of the designated trees. Students will record their results in their science notebooks. Teacher’s Corner — www.evergreen.ca Using a Dichotomous Key 3 Discussion and Questions Discuss identifications. What characteristics were difficult to decide between? What were some easy characteristics to decide between? Are there other characteristics that could have been used in the key? Would all groups of species in an ecosystem be as easy to identify (e.g. insects)? What job or careers would involve the use of dichotomous keys? For what purposes? Why is it important to know what species exist in an ecosystem? What human interactions can have an impact on the variety of species (diversity) and the population of individual species in an ecosystem? Student Evaluation Rubric or rating scale for students to determine how well they completed the goals of the lesson. Enrichment and Extension Activities Students could classify and identify other species in the naturalized area (e.g. Flowers, shrubs, deciduous trees or insects). Students could also extend their dichotomous keys to other areas of interest such as music, or video games. Educator Notes This lesson plan should be used after teaching the binomial naming system and the Classification Levels and species. This will develop a greater understanding of the need for taxonomy and its related career opportunities. Other keys may be used if there is not a wide variety of coniferous trees in the outdoor area (e.g. shrubs, flowers). References Focus on Forests: A Resource Manual for Intermediate and Senior Teachers on Forest and Forest Management. Minister of Supply and Services, Canada. 1989. Ministry of Natural Resources. http://www.oforest.on.ca/programs/Focus/indexM.html Teacher’s Corner — www.evergreen.ca