Mints Under The Microscope
GRADE LEVELS 3rd-5th; California Content Standards for 3rd-5th SUBJECTS Investigation and Experimentation, Life Sciences DURATION Preparation: 20 minutes Activity: 60 minutes SETTING Classroom, Lab
Objectives
In this activity, students will: 1. use close observation and sketching to learn about characteristics of the mint family. 2. practice the scientific method.
Materials
microscopes samples of different plants in the mint family (examples include thyme, basil, sage, spearmint, rosemary, lavender, and oregano); flowers not necessary science notebooks (or paper) pens or pencils mint notebook example
Vocabulary
family: a group of closely related organisms ranking above a genus and below an order root: a plant part that usually grows underground, secures the plant in place, absorbs minerals and water, and stores food manufactured by leaves and other plant parts leaf: an appendage growing from the stem of a plant leaf margin: the edge of a leaf stem: the main, often long or slender part of a plant that usually grows upward above the ground and supports other parts, such as branches and leaves shoot: the part of a vascular plant that is above ground, including the stem and leaves node: a point on a stem where a leaf is or has been attached internode: a segment of a stem between two nodes petiole: the slender stalk by which a leaf is attached to the stem bud: a small swelling on a branch or stem, containing an undeveloped shoot, leaf, or flower flower: the reproductive part of a seed-bearing plant venation: the distribution or arrangement of a system of veins, as in an insect's wing or a leaf blade
Teacher Background
Science Skills: This lesson combines learning about plants with practicing the scientific method. One of the most important scientific skills is close observation. In this activity, students will look at a number of different plants from the mint family. They will use sketching to document their careful observations. They will also record questions that come up as they observe – a crucial
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Mints Under The Microscope
(and often unpracticed) scientific skill. Although the lesson covers the whole science process, the skills of careful observation and developing questions are particular focuses. Plants: Below are a list and a chart that show important characteristics of leaves. Simple leaf: a leaf that is composed of a single part Compound leaf: a leaf that is divided into distinct parts or leaflets Arrangement of leaves on stem: alternate: leaves arranged one per node opposite: leaves arranged two per node whorled: leaves arranged three or more per node
Chart of leaf morphology characteristics from Wikipedia Commons
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Mints Under The Microscope
The Mint Family: Many of our common herbs, including basil, thyme, lavender, lemon balm, oregano, marjoram, rosemary, sage, anise, are all from the mint family. (For more specific information about many of these plants, please see the Resources section of this lesson.) All of the herb plants in the mint family are native to the Mediterranean (except sweet basil, which is from tropical Africa and Asia). Although there are clear differences between these plants, they are all in the same family and share some of the same characteristics. Many of these characteristics can be observed by examining the leaves and stems. These are the attributes your students will be looking to discover through their scientific investigation. Stems are often square Leaves are simple (not compound) Leaves are in pairs up the stem Leaves are frequently hairy and/or have scent glands Foliage is aromatic If the plants are in bloom, there are additional shared characteristics that can be observed; however, it is not necessary to use plants that are in bloom for this investigation. Flowers have two lips, one of which protrudes more than the other Flowers appear in circles around the stem
Activity
Preparation 1. Collect samples of various plants in the mint family. 2. Set up microscopes. Introduction Tell your students that they are going to be scientists, observing plants under a microscope. Like scientists, they will record their observations in their science notebooks. Procedure 1. Place one large specimen of each plant type on each table. 2. Tell students to examine the plants on their tables. Explain that these plants all belong to the mint family. Being in the same family often means that organisms have characteristics in common. 3. Have students write the following focus question in their notebooks. Focus Question: What are the characteristics that these plants share? 4. Have students look at the plants again and write a prediction. Prediction: Based on your initial observations, write a prediction to the focus question. 5. As a class, develop a plan for addressing this question. Since you have microscopes, you can develop a plan for carefully observing the mints under the microscopes. A possible plan follows. Pick two of the plants to study in detail.
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Mints Under The Microscope
Quickly sketch the stems of each plant. (Pay attention to the pattern of leaf attachment to the stem and the shape of the stem.) Make a life-sized sketch of a leaf from each plant. Place the leaves under the microscope (one at a time) and sketch the details of the leaves. (Look at the underside of the leaf, the leaf shape, leaf margin, the arrangement of the veins, hairiness, glands) Once you have a detailed plan, go ahead and execute it. Follow your plan, collect data, and record everything in the science notebooks. In addition to sketches of the plants, include answers to the following questions. What do the plants have in common? What is different between the two plants? Write down at least three questions you have? (Optional: show students the mint notebook example so they can see the kinds of sketches and written observations you are looking for.) As a class, discuss your conclusions. Discuss the similarities between the various plants as a group. Collect information on all the different plants and document it in a matrix on the board. Have students write their conclusions in their notebooks. What did you find? Answer the focus question and respond to the prediction. Have students write a reflection. Possible reflection prompts include: What surprised you about this investigation? Which of your questions do you really want to know the answer to?
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Wrap-Up Discuss with the students: How could we find the answers to our questions? Categorize your questions into 3 categories: 1. Questions to look up (library, internet) 2. Questions to ponder (no one knows or will know the answer) 3. Questions to investigate (testable)
Extensions
Test your ability to distinguish the scents of different mints. Cut up little pieces of rosemary, basil, mint, sage, and lavender and put them in their own jars. Mark each jar with numbers so that you know which is which. Without looking have students smell each sample and try to determine which is which. As a celebratory extension, you can feast on various mint family treats. Examples include mint tea, rosemary bread, and pizza with oregano.
Resources
Lawton, B.B. (2002). The fragrant mint family dominates the herb word. The Christian Science Monitor. Retrieved May 12, 2009 from http://www.csmonitor.com/2002/0515/p18s02liga.htm.
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Mints Under The Microscope References
LAMIACEAE (formerly LABIATAE) - The Mint Family. Retrieved May 12, 2009 from http://theseedsite.co.uk/lamiaceae.html
Correlated California Content Standards
Grade Three Life Sciences 3a. Students know plants and animals have structures that serve different functions in growth, survival, and reproduction. Investigation and Experimentation 5e. Collect data in an investigation and analyze those data to develop a logical conclusion. Grade Four Investigation and Experimentation 6a. Differentiate observation from inference (interpretation) and know scientists’ explanations come partly from what they observe and partly from how they interpret their observations. Grade Five Investigation and Experimentation 6b. Develop a testable question. 6c. Plan and conduct a simple investigation based on a student-developed question and write instructions others can follow to carry out the procedure.
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