Above Image: A collection of fruits from various categories. © Serg_Velusceac, iStockphoto.com
Students will use a basic dichotomous key and practice their skills of observation, comparing and contrasting, and decision-making to classify a variety of common fleshy fruits.
Inquiry Skill Development
- To increase awareness of the biodiversity of fruit
- To introduce the botanical names of types of fruit
- To introduce and practice using a dichotomous key to classify types of common fruits
Prior Knowledge and Skills
- Basic plant anatomy
- Definition of a fruit
- Understands the mechanics of a basic tree diagram (e.g., family tree)
- Students engage in discussions
- Students collaborate to problem–solve
- Students understand the purpose of a dichotomous key and can use it accurately to identify different types of fleshy fruit
- 40 – 50 minutes in class
- Preparation of fruit images prior to class (photocopying and cutting)
- Time may be required prior to lesson to purchase fruit if Materials Option A is chosen
Note: The fruit images and dichotomous key placemats can be prepared once and reused from year to year.
Materials Option A: A selection of real fruit (See BLM1: Fruit Pictures for Classification for ideas of fruit to collect/purchase)
Materials Option B: BLM1: Fruit Pictures for Classification - 1 set per group pdf
BLM2: Dichotomous Key for Classifying Fleshy Fruits - 1 place mat per table group pdf
BLM3: Answers to Dichotomous Key for Classifying Fleshy Fruits (Teacher resource) pdf
BLM4: Fruit Classification Results Summary Chart - 1 per student doc pdf
Tomato Taxonomy - (Tomatosphere™ backgrounder)
Optional: Video 1: Dichotomous Key - Mark Drollinger (Video on YouTube) This video demonstrates the function of a basic dichotomous key, using examples of birds.
Tips for Success
- Organizing working partners and/or discussion groups prior to the lesson is highly recommended to save time.
Introduce the concept of a dichotomous key
Note: Students should be familiar with the botanical definition of a fruit before starting to brainstorm. A fruit is a part of a plant that develops from a flower’s ovary and contains seeds.
NOS Alert: Science involves many methods and tools that have been developed and changed over time.
As a whole class or in table groups, have students use the Brainstorming learning strategy on ideapark.letstalkscience.ca to identify and list as many different fruits as possible. Students can generate lists on paper at each table, on chart paper, on a black/white board or using the presentation technology that is available in your classroom.
Introduce the concept of dichotomous key. You can use the definition provided below to help introduce this concept. Tell students that they will be using a dichotomous key to determine the botanical classification and names of different types of fleshy fruit.
What is a dichotomous key?
Note: The dichotomous key used for this inquiry is quite simple and relies on making choices based on observable differences. Therefore, it does not include differentiation choices for all types of fruit.
A dichotomous key is a tool created by scientists, called Taxonomists, to help identify and name or group different species of organisms. This tool consists of a series of choices, usually based on the observable physical features of an organism. These choices can help determine an organism’s scientific name (species and genus). Sometimes a dichotomous key can help sort types of organisms. The process of classifying and naming living things is known as taxonomy.
Optional: Have students watch Video 1: Dichotomous Key to help introduce the concept of a dichotomous key by demonstrating how familiar birds are classified. The dichotomous key in the video is represented as a vertical list of choices, instead of tree diagram format that is used for this inquiry. Explain to your students that both styles of keys have them make a series choices in order to classify items, despite their differences in appearance.
Use a dichotomous key to classify common fruit
Note: If possible, bring in a real banana and grapes with seeds. Since banana seeds are very small and many grapes these days are seedless cultivars, students may not realize there are seeds in these fruit.
Provide each table group with the selection of real fruit you have collected (Materials Option A) or a set of fruit images (Materials Option B).
Optional Step: (Time permitting). Ask students how they would sort the fruit based on their observations. Provide students with a few minutes to observe the fruit and do their sorting. Follow up by having student groups describe their classification system to the rest of the class.
Provide students with the BLM2: Dichotomous Key for Classifying Fleshy Fruits. Using the key, model how the key is used before the student use it themselves.
Students conduct their classification using the dichotomous key provided and the real fruit or pictures of fruit.
Summarizing Classification Results
Students may summarize the results of their classification inquiry by writing the common names of the fruit they have classified in the spaces provided on BLM2.
Students can also conduct detailed summaries of their inquiry results, using BLM4: Fruit Classification Results Summary Chart. This page asks students to identify the key characteristics that contribute to each item’s classification. Refer to BLM3: Answers to Dichotomous Key for Classifying Fleshy Fruits to check student classification results.
Follow-up by having students read the backgrounder Tomato Taxonomy to learn more about tomato classification, as well as some of the challenges of naming species.
Optional: Students can continue to add onto these summaries as they identify and classify other fleshy fruits they encounter in their daily lives.
NOS Alert: New methods in science, such as DNA Barcoding, can enhance and work with older methods, like traditional Linnaean taxonomy, to build understanding and make classification tasks easier.
- Get students to think of other types of fruit not included on the image page. Have them try to classify these fruit using the dichotomous key provided. Have students do online research to find out more about the different types of fruits that are not included on this dichotomous key.
- View this short video, Barcode of Life (Video on CurioCity) and introduce your students to DNA Barcoding. This is a newer and faster method of identifying species using the DNA from an organism’s cells. This biotechnology technique, developed in Canada, is now being used hand-in-hand with traditional taxonomy to identify species correctly. This video created by the International Barcode of Life at the University of Guelph describes how the technique of DNA Barcoding is becoming valuable method of identifying existing and new living organisms around the world.
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