the “key” to leaf identification

Noble Research Institute, LLC • 2510 Sam Noble Parkway • Ardmore, OK 73401 • www.noble.org • 580-223-5810

An education and outreach program of:

TEACHERGUIDE

LESSON OBJECTIVES:Students will be able to:

1. Define terms associated with leaf anatomy.

2. Explain what a dichotomous key is and how it is used.

3. Use a dichotomous key to identify tree species by their leaves.

ESSENTIAL QUESTION: How are organisms classified?

TOPICAL ESSENTIAL QUESTION:What leaf characteristics are used to identify trees?

NOTE TO THE TEACHER: 1. Have enough copies of the insect and arachnid dichotomous key

(found at the end of the teacher’s guide) for each student or pair of students.

2. It is recommended to have the students count the number of plastic insects/arachnids prior to starting the activity and again at the end to be certain they are all there.

3. It is recommended to spread the leaves out around the room and allow students to get up and move to each leaf.

MATERIALS• 13 leaf samples (Flinn Scientific Leaf

ID Super Kit Set B)

• Leaf dichotomous key

• Student Guide

• Copies of Insect and arachnid dichotomous key

• Plastic insects and arachnids (each group should have the same)

SAFETY PRECAUTIONS• Please do not eat or drink in

the laboratory.

TOTAL DURATION 45 - 60 min. class time

THE “KEY” TO LEAFIDENTIFICATION


TEACHER GUIDE


KEY VOCABULARY:Margin Classification TaxonomySerrated Simple CompoundVein Blade PetioleDichotomous Parallel Lobe Downy

LESSON BACKGROUND INFORMATION: (TEACHER VERSION)

NOTE: This is background information for the teacher to assist in facilitating learning and will be explained to the students after the explore lab activity.

Students often have a difficult time learning scientific classification because it can be abstract and seem irrel-evant to their current lives. One way to connect students to the scientific classification system is to compare it to a library. Hopefully all students have been to a library and have an understanding of how to find books. There are many similarities between library classification and biological classification. Library book collec-tions are organized based on categories that start broad and become more and more specific. Libraries use a specific classification system to organize those collections. It is also a system that is used worldwide. A student can walk into any library in more than 135 countries and find a book just as they would at their home library.

THE "KEY" TO LEAF IDENTIFICATION

STANDARDS:Middle SchoolMS-LS1-6From Molecules to Organisms: Structures and Pro-cessesStudents who demonstrate understanding can: Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of mat-ter and flow of energy into and out of organisms.

High SchoolHS-LS1-2From Molecules to Organisms: Structures and Pro-cesses Students who demonstrate understanding can: Develop and use a model to illustrate the hierarchi-cal organization of interacting systems that provide specific functions within multicellular organisms.

Science and Engineering Practices1. Asking questions

2. Developing and using models

3. Analyzing and interpreting data

4. Obtaining, evaluating, and communicating information

Crosscutting concepts1. Structure and function


TEACHER GUIDE


ENGAGE:This engagement activity uses plastic insects and arachnids to help students understand a dichotomous key. Try not to answer questions from students while they are grouping insects. The goal is to guide them to answer their own questions.

1. Hand out the plastic insects and arachnids to each group along with an Insect and Arachnid Dichoto-mous Key (found at the end of the teacher guide).

2. Instruct students to empty the bag on their desk.

3. Ask students to organize the insects into groups. (They should choose how to do this on their own.) Discuss how or what characteristics groups used to organize. Were there commonalities among groups? Place all organisms back into one group.

4. Ask students to group based on the presence of wings. Compare results. Many groups will have different numbers because they will group the insects that only have wings outlined on their body as non-winged. Point out that characteristics aren’t always easy to identify, so it’s important to look closely. Place all organisms back into one group.

5. Ask students to group based on the number of legs. Compare results. Again, students will have differing number of groups. Ask students if there was any piece of information that could have made the group-ing easier. Students should say something about knowing what is considered a leg. Point out that while the scorpion and the preying mantis appear to have six legs and “hands” they actually have eight legs. The two front legs are modified for catching prey or eating. Place all organisms back into one group.

6. Now ask students to use the dichotomous key to identify several insects in order to practice using the key.



TEACHER GUIDE


EXPLORE:Activity 1: Identifying Leaf AnatomyUnderstanding the meaning of the anatomical terms used in the dichotomous key is necessary to successful-ly identify each leaf. If you are not sure of the meaning of a term, use the definitions and leaf figures below to help you. Never guess, as this could lead to the wrong classification term.

Blade - Thin, flat part of leaf important in photosynthesis

Petiole - The stalk attaching the leaf blade to the stem

Simple leaf - Consists of a single blade on a petiole

Compound leaf - Composed of two or more leaflets on a common leaf stem

Margin - The edge of the leaf

Veins - Vascular tissues of a leaf that carry water and nutrients, and support the blade, much as the metal ribs support the fabric of an open umbrella. The main vein is the main or central vein that runs from the leaf stem to the tip of the leaf or to the tips of the leaf lobes (in this case, the leaf will have more than one main vein). Secondary or lateral leaf veins may branch off of the main vein.

Lobe - Distinct protrusion and may be either rounded or pointed

Scale-like - Leaf has leaves that look like scales

Needle-like - Leaf has long, thin leaves that look like needles

Serrated - Leaf has a margin notched like a saw with teeth pointing toward the tip of the leaf

Lobes

Vein

Petiole

Margin

Blade



TEACHER GUIDE



Identify the leaves below as one of the following: Compound Leaf Simple Leaf Needle-like Scale-Like Serrated

Simple Leaf Compound Leaf

Scale-like Leaf Serrated

Needle-like


TEACHER GUIDE



PROCEDUREUsing the dichotomous key at each station, identify each unknown leaf.

1. Always begin with step 1 of the dichotomous key.

2. When looking at the key, there are two options for each step. For example:

1a. Leaves are scale-like or needlelike …………….. 2

1b. Leaves are not scale-like or needlelike ..……. 3

3. Choose the option that best describes the leaf and continue to the indicated step (in the example above you would either continue to step 2 or 3).

4. As you work your way through the key, the choices will eventually lead to the name of the leaf.

5. Record the identity of the leaf on the “Leaf Identification Worksheet.”

6. Move to the next station and repeat, always beginning with step 1 of the dichotomous key.

7. Continue classifying until all of the unknown samples have been identified.

LEAF IDENTIFICATION WORKSHEET

Name: ____________________________________________

Unknown Leaf # Name of Leaf

1 American Sycamore

2 Eastern Redbud

3 Siberian Elm

4 Eastern Cottonwood

5 Osage Orange

6 Silver Maple

7 Scotch Pine

8 Gingko

9 Norway Maple

10 Honey Locust

11 Eastern Hemlock

12 Little Leaf Linden

13 Northern Red Oak


TEACHER GUIDE



EXPLAIN:(see student guide background)

EXTEND:1. Students could collect leaves from their homes and bring them in to identify them using the dichoto-

mous key.

2. Download the “Leaf Snap” app on a phone, and use the app to identify the leaves.

3. Use a bag of plastic assorted insects, dinosaurs, buttons, etc., and have students create a dichotomous key to classify those items.

EVALUATE:The “Key” to Leaf Identification Assessment QuestionsHave students answer questions at the end of the student guide.

1. ___Classification___ is an important way of organizing information to understand the natural world.

2. Scientist use ___Latin___ as a common language in order to be able to communicate with other scientist around the world.

3. ___D___ The field of biology identifying and classifying organisms into categories is calledA. Biology

B. Endocrinology

C. Virology

D. Taxonomy

4. A ___Dichotomous___ key is a guide for classifying and identifying something by asking a series of ques-tions to which there are only two possible answers.

5. What is a dichotomous key used for?a. A dichotomous key is used to identify organisms and/or objects

6. What does the word “dichotomous” mean? a. Divided into two parts

7. What are some of the identifiable features used to classify the unknown leaves? a. Answers will vary but should include leaf parts explicitly outlined in the investigation. E.g. Leaf shape,

vein structure, leaf margins, etc.

8. Explain how to use a dichotomous key to identify unknown organisms/objects.a. Answers will vary but should provide enough description about the proper use of a dichotomous key.


TEACHER GUIDE



9. Match the common name of each tree to its scientific name. You may need to use another resource.

__D__ 1. American Sycamore

__L__ 2. Eastern Cottonwood

__F__ 3. Eastern hemlock

__G__ 4. Eastern redbud

__E__ 5. Gingko

__M__ 6. Honey Locust

__B__ 7. Little Leaf Linden

__H__ 8. Norway Maple

__C__ 9. Northern Red Oak

__I__ 10.Osage Orange

__J__ 11. Scotch Pine

__A__ 12. Siberian Elm

__K__ 13. Silver Maple

A. Ulmus pumila

B. Tilia cordata

C. Quercus rubra

D. Platanus occidentalis

E. Kinkgo biloba

F. Tsuga candensis

G. Cercis candensis

H. Acer platanoides

I. Macular pomifera

J. Pinus sylvestris

K. Acer saccharinum

L. Populus deltoides

M. Gleditsia triacanthos


TEACHER GUIDE



INSECT AND ARACHNID DICHOTOMOUS KEY

1a. Organism has six (6) legs ............................................................................................................ go to 51b. Organism has more than six legs ............................................................................................ go to 2

2a. Organism has eight (8) legs ..................................................................................................... go to 32b. Organism has more than eight legs ..................................................................................... Centipede

3a. Organism has long, cylindrical green and yellow body .............................................. Green Caterpillar3b. Organism does not have long, cylindrical body ............................................................. go to 4

4a. Organism has a hard exterior black/brown skeleton with yellow lines ............... Garden Spider4b. Organism is red with pinchers on the first pair of legs ............................................... Red Bark Scorpion

5a. Organism has wings ..................................................................................................................... go to 75b. Organism does not have wings .............................................................................................. go to 6

6a. Organism has long cylindrical brown body ...................................................................... Rock Crawler6b. Organism has black body with a thin waist ..................................................................... Carpenter Ant

7a. Organism has clear wings ......................................................................................................... go to 87b. Organism has solid colored wings ........................................................................................ go to 9

8a. Organism is has four wings and is red ................................................................................ Dragon Fly8b. Organism has two wings and is black ................................................................................ Horse Fly

9a. Organism has a two protrusions coming from the back end .................................. go to 109b. Organism does not have any protrusions from the rear ............................................ go to 11

10a. Organism has bent rear legs for jumping, brown in color ....................................... Cricket10b. Organism has no jumping legs, red in color .................................................................. Cockroach

11a. Organism has modified front legs with serrations ....................................................... Praying mantis11b. Organism has brown rear legs .............................................................................................. Grasshopper



STUDENTGUIDE

MATERIALS

• 13 leaf samples

• Leaf dichotomous key

• Leaf identification worksheet

• Bag of plastic insects and arachnids

• Insect and arachnid dichotomous key

SAFETY PRECAUTIONS:• Do not eat or drink in the laboratory.

ESSENTIAL QUESTION:How are organisms classified?

TOPICAL ESSENTIAL QUESTION:What leaf characteristics are used to identify trees?

OBJECTIVES:1. Students will learn leaf anatomy.

2. Students will use a dichotomous key to identify trees.

INTRODUCTION:This lab activity will demonstrate how a dichotomous key can be used to identify unknown trees based on their leaves.

THE “KEY” TO LEAFIDENTIFICATION


STUDENT GUIDE



KEY VOCABULARY:Margin Classification TaxonomySerrated Simple CompoundVein Blade PetioleDichotomous Parallel LobeDowny

ENGAGE:Follow your teacher’s instructions while using the bag of plastic insects and arachnids and the dichotomous key.

What types of information are important to know before working with a dichotomous key?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

Why would you use a dichotomous key?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________


STUDENT GUIDE



EXPLORE:Activity 1: Identifying Leaf AnatomyUnderstanding the meaning of the anatomical terms used in the dichotomous key is necessary to successfully identify each leaf. If you are not sure of the meaning of a term, use the definitions and leaf figures below to help you. Never guess, as this could lead to the wrong classification term.

Blade - Thin, flat part of leaf important in photosynthesis

Petiole - The stalk attaching the leaf blade to the stem

Simple leaf - Consists of a single blade on a petiole

Compound leaf - Composed of two or more leaflets on a common leaf stem

Margin - The edge of the leaf

Veins - Vascular tissues of a leaf that carry water and nutrients, and support the blade, much as the metal ribs support the fabric of an open umbrella. The main vein is the main or central vein that runs from the leaf stem to the tip of the leaf or to the tips of the leaf lobes (in this case, the leaf will have more than one main vein). Secondary or lateral leaf veins may branch off of the main vein.Lobe - Distinct protrusion and may be either rounded or pointed

Scalelike - Leaf has leaves that look like scales

Needle-like - Leaf has long, thin leaves that look like needles

Serrated - Leaf has a margin notched like a saw with teeth pointing toward the tip of the leaf

Lobes

Vein

Petiole

Margin

Blade


STUDENT GUIDE



Identify the leaves below as one of the following: Compound Leaf Simple Leaf Needle-like Scale-Like Serrated


STUDENT GUIDE



PROCEDURE:Using the dichotomous key at each station, identify each unknown leaf.

1. Always begin with step 1 of the dichotomous key.

2. When looking at the key, there are two options for each step. For example:

1a. Leaves are scalelike or needlelike ……………... 2

1b. Leaves are not scalelike or needlelike …...…. 3

3. Choose the option that best describes the leaf and continue to the indicated step (in the example above you would either continue to step 2 or 3).

4. As you work your way through the key, the choices will eventually lead to the name of the leaf.

5. Record the identity of the leaf on the “Leaf Identification Worksheet.”

6. Move to the next station and repeat, always beginning with step 1 of the dichotomous key.

7. Continue classifying until all of the unknown samples have been identified.

LEAF IDENTIFICATION WORKSHEETName: ____________________________________________

Unknown Leaf # Name of Leaf

1

2

3

4

5

6

7

8

9

10

11

12

13


STUDENT GUIDE



LEAF DICHOTOMOUS KEY 1a. Leaves are scale-like or needlelike .......................................................................................................... 21b. Leaves are not scale-like or needlelike ................................................................................................. 3

2a. Leaves are 1/2” long or shorter and have a narrow base ............................................................ Eastern Hemlock2b. Leaves are long and narrow, and needles are united at base to form bundles ............... Scotch Pine

3a. Leaves are finely serrated ......................................................................................................................... 43b. Leaves are not finely serrated ................................................................................................................ 6

4a. Leaf has a single main vein with smaller side veins ...................................................................... 54b. Leaf has main veins radiating from one point, base is not symmetrical ............................. Little Leaf Linden

5a. Leaf has a wide main vein .......................................................................................................................... Eastern Cottonwood5b. Leaf has straight, parallel, seldom branched veins ........................................................................ Siberian Elm

6a. Leaves are lobed ............................................................................................................................................ 76b. Leaves are not lobed ................................................................................................................................... 10

7a. Leaf has one main vein ............................................................................................................................... Northern Red Oak7b. Leaf has three to seven main veins radiating from one point at or near the base ........ 8

8a. Leaf has three distinct main veins ........................................................................................................ American Sycamore8b. Leaf has more than three distinct main veins ................................................................................. 9

9a. Notches between lobes are deep and the under-surface is white downy ....................... Silver Maple9b. Leaf is usually wider than long and base of leaf is not curved .............................................. Norway Maple

10a. Compound leaflets are present ........................................................................................................... Honey Locust10b. Compound leaflets are not present ................................................................................................... 11

11a. Leaf is fan-shaped ........................................................................................................................................ Ginkgo11b. Leaf is not fan-shaped ................................................................................................................................ 12

12a. Leaf is heart-shaped with veins branching from the base ....................................................... Eastern Redbud12b. Leaf is not heart-shaped .......................................................................................................................... Osage Orange


STUDENT GUIDE



EXPLAIN:Classification is simply a method of organization. While it may seem that biological classification doesn’t have much to do with your everyday life, it is very similar to another classification system that you’ve used before: library classification. Libraries organize their book collections using specific organizational systems that are used all over the world. If you were to walk into a library in England you could find a book just as easily as you can in your school library!

Just like biological classification, books are organized into broad categories that contain more specific categories, which con-tain even more specific categories and so on. If you walk into a library, you will find that books are initially organized based on target readers. You’ll find children’s books, adult books and teenage books in different sections, or categories. Within each of these categories, there are additional categories that become more specific, such as fiction and nonfiction. Fiction books are further categorized by topics like mystery, drama, comedy and science fiction. Fiction books are then further identified using the first three letters of the author’s last name. Nonfiction books use a more specific classification system. Perhaps you’ve heard of it: the Dewey Decimal Classification system? This system groups nonfiction books into topics like natural science, philosophy, literature, art and technology. Each topic is assigned a three digit value that includes 99 places (natural science is 500-599). Within each subject category, there are additional categories for different subjects within the broader category. For example, in the natural science category, there is biology, chemistry, physics and more. Each of these specific subjects gets another numerical identifier. The categories continue until every possible topic has a place.

In the same way that the library’s classification system organizes books so they can be found more easily, the biological clas-sification system organizes living organisms so we gain a more complete understanding of the natural world. With almost 9 million known species on Earth today, classification is an important science that helps us see the similarities and differences in the living things around us.

Within the field of biology there is a specific area of study called taxonomy that is responsible for identifying and classifying organisms. Taxonomists identify physical characteristics of living organisms and classify them based on their similarities. Bio-logical classification starts with the broadest categories (those that separate out the biggest differences among organisms), and each preceding level becomes more and more specific (organizing organisms that are more similar to each other). The goal of biological classification is to be able to give every individual type of organism a name (Genus species).

Biological classification is used all around the world. Scientists speak different languages but need to be able to share infor-mation and data with other scientists around the world. To solve this issue, biological classification uses Latin (a language that was common during the 1700s when the system was developed.) This allows scientist all over the world to know that Canus domesticus refers to a dog.

A dichotomous key is a tool used for identifying an unknown organism by asking a series of questions to which there are only two possible answers. Questions are answered until there is only one possible choice and the organism is identified. Dichoto-mous means “divided into two parts.” Many parts of the natural world have been classified, categorized and grouped and can be identified using a dichotomous key. Many different characteristics of organisms can be used for identification on a dichoto-mous key, for example in plants not only leaves; but bark, seeds, flowers, roots and twigs can be used for identification.


STUDENT GUIDE



EVALUATE:Answer the following questions.

1. _________________________ is an important way of organizing information to understand the natural world.

2. Scientist use ________________ as a common language in order to be able to communicate with other scientist around the world.

3. _________ The field of biology identifying and classifying organisms into categories is calledA. Biology

B. Endocrinology

C. Virology

D. Taxonomy

4. A __________________________ key is a guide for classifying and identifying something by asking a series of questions to which there are only two possible answers.

5. What is a dichotomous key used for?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

6. What does the word “dichotomous” mean?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

7. What are some of the identifiable features used to classify the unknown leaves?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________


STUDENT GUIDE



8. Explain how to use a dichotomous key to identify unknown organisms/objects.

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

9. Match the common name of each tree to its scientific name. You may need to use another resource.

_____ 1. American Sycamore A. Ulmus pumila

_____ 2. Eastern Cottonwood B. Tilia cordata

_____ 3. Eastern hemlock C. Quercus rubra

_____ 4. Eastern redbud D. Platanus occidentalis

_____ 5. Gingko E. Kinkgo biloba

_____ 6. Honey Locust F. Tsuga candensis

_____ 7. Little Leaf Linden G. Cercis candensis

_____ 8. Norway Maple H. Acer platanoides

_____ 9. Northern Red Oak I. Macular pomifera

_____ 10.Osage Orange J. Pinus sylvestris

_____ 11. Scotch Pine K. Acer saccharinum

_____ 12. Siberian Elm L. Populus deltoides

_____ 13. Silver Maple M. Gleditsia triacanthos

the “key” to leaf identification

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