Lesson Title: Dichotomous KeyGrade Level: 6Designer:

Learning Outcomes/IntentionsFormal Unit Outcome(s): Outcome: DL6.2Examine how humans organize understanding of the diversity of living things. [CP, SI] 

Knowledge & Understandings:Use morphology and a dichotomous key to classify/identify different organisms and objects..A dichotomous key is a tool that allows the user to determine the identity of items and organisms in the natural world. A dichotomous key always gives two choices in each step

Essential Questions: What is a dichotomous key and how is it useful?How do we classify organisms into groups?

Skills:Construct and use a classification system to organize living things into groups and subgroups according to student-developed criteria.

“I can . . .” statements:I can explain how dichotomous keys are used to identify organisms.I can use a dichotomous key to identify unknown organisms.

Assessment EvidenceFormative Assessments (Assessment for Learning):

Peer assessment of the completed dichotomous key - See Peer Assessment Sheet - Attached.

Insect Discovery Activity - Feedback to be given during class or handed in for summative evaluation.

SafetyBe aware of safety at all times .No safety concerns for this lesson.

Materials

Dichotomous Key Worksheet (ATTACHED)Set of assorted screws, nails, nuts, and bolts for each group.Butcher paper or Large sheets of white paperLCD projectorPower pointPeer Assessment form (Attached)Insect Discovery Activity (Attached)

Learning PlanLearning Experiences & Instruction:Have each group describe for the rest of the class how they sorted their grasshoppers.ASK:How did you organize your grasshoppers?Was the key in table form or tabular form?What traits or characteristics did you use to sort them? Were the characteristics measurable?*Stress that the way to best sort items is with a yes or no question.

Power point presentation Discuss how to create a dichotomous key and how to use a dichotomous key. EXPLORE:Have the students work in groups to create a dichotomous key with the set of assorted screws, nails, nuts, and bolts.

Once all the groups have completed their keys have them exchange the key with another group for peer assessment. Each group must give feedback to at least two other groups.

ELABORATE:Assign - Insect Discovery Activity (This can be used as an additional formative assessment or as a summative assessment).

Name:_______________________ Period:__________ Purpose: To create a dichotomous key Materials: Set of assorted screws, nuts and bolts (wood screws have a pointed end)Procedure: 1. Obtain one set of the assorted screws, nuts and bolts.2. Examine the items and look for similarities and differences. 3. Create a dichotomous key on a large sheet of paper. 4. Continue adding information to the dichotomous key until all 12 items have been used. 5. Look over your dichotomous key and determine if it makes sense. 6. Hand over your dichotomous key to another student and see if he/she can identify all 12 items correctly. 7. Put all 12 items into the baggie. 8. Count to be sure you have all 12 items 9. Place the baggie back into the tub you got the materials from.

Example: 1. Does the creature have antlers……………………….. Deer 1. Does the creature not have antlers……………………. Go to 2 2. Does the creature walk on 4 legs……………………... Polar Bear 2. Does the creature walk on less than 4 legs…………… Go to 3 3. Does the creature have a beak………………………… Ostrich 3. Does the creature not have a beak……………………. Sasquatch

3" Robertson head 3/4" Robertson head3/4" Flat head11/4" Nail1" Roofing Nail4" Nail1" Flat head bolthexagon nutsquare nut1" Wood screw with a Robertson head4" Bolt½" Brass flat head screw

Insect Discovery

Introduction:Do you remember the first time you saw an insect? You may have asked yourself, “What is it?” You may still be curious to know the names of the insects and other organisms you see. In this activity, you are going to learn how to classify insects based on their distinguishing characteristics in to their Order, not Genus name. You will use a key to identify different adult species of insects. Safety: There are no safety concerns in this activity. If using live organisms, handle them with care.Materials:

A dichotomous key pictures or actually organisms being classified

Using a dichotomous key for Insects:1. Study the dichotomous key (graph or sentence format) and pictures for

the insects. What do you notice about the branching network used in the key?

2. Make a list of similarities and differences in characteristics that you can observe about the different insects from the pictures, such as, texture of wings, number of legs, spines on legs and body shape.

3. Look at figure 1 to identify the insect parts used in the key. 4. Examine the Insect 1 picture in figure 2 closely for it’s characteristics.

Look at the dichotomous key, either the sentence format or the graph format. Identify the characteristics in 1a and 1b, which of these characteristics does Insect 1 have?

5. Follow the pathway or numbers along the dichotomous key that correspond to the characteristics of Insect 1. For example, if Insect 1 has wings (1a), then go to 5. Read all the characteristics for 5a, 5b, 5c and 5d, until you find the correct characteristic for Insect 1. If the Insect 1 does not have wings (1b), then go to 2. Read all the characteristics for 2a and 2b, until you find the correct characteristic for Insect 1.

6. Continue following the pathway or numbers until an order name (in red) for Insect 1 is determined.

7. Repeat steps 4-6 for all of the other Insects 2-10 until all the insects have been identified. Write the family name on the line below each insect picture.

8. In the table, write down the distinguishing characteristics of each insect.

Insect Order Name

List of identifying characteristicsIsoptera

HymenopteraCollembolaImmature

InsectDipteraOdonata

Ephemeroptera

HemipteraHomopteraOrthopteraMantodea

Figure 1: Insect Diagram

Figure 2: Insect Identification

Graph Format of a Dichotomous key for Insects

Sentence format Dichotomous Key for Adult Insects1a. With wings................................................................................................................. 51b. Without wings........................................................................................................... 22a. Ant-like body………………………………………......................................... 32b. Not an Ant-like body .............................................................................................. 43a. Ant-like body with a narrow waist (ants)........................................Hymenoptera 3b. Ant-like with a wide waist (termites) ........................................................Isoptera 4a. With an 2 antennae-like appendages located at the end of the abdomen which isused .as a "spring" (springtails) ...................................................................Collembola 4b. Has 3 pair of legs, but no wings, and no springy legs..............Immature insect5a. With only a single pair of wings; the second pair of wings modified into a pairof knob-like organs known as halteres (flies) ..................................................Diptera5b. With two pair of wings ............................................................................................ 65c. With piercing, sucking mouthparts (like a straw)..................................................75d. Forewings leathery, but not hard; hindwings membranous and folded under

the forewings....................................................................................................................86a. The wings are equal in size with a long slender abdomen…………………….(dragonflies and damselflies)............................................................................ Odonata6b. The first pair of wings much larger than second and held straight up over thebody; with two or three long, antennae-like appendages at the end of theabdomen(mayflies) ................................................................................Ephemeroptera7a. Forewings half leathery, half membranous, while hindwings entirely membranous;wings makes an “X” when folded on the back (true bugs) .......................Hemiptera 7b. Forewings either entirely membranous or entirely leathery; held rooflike overthe body (aphids, scales, leafhoppers, and cicadas) ..................................Homoptera8a. Chewing mouthparts; hind legs often enlarged, adapted for jumping………….(grasshoppers, katydids, and crickets)..........................................................Orthoptera8b. Hind legs are not enlarged and adapted for jumping.........................................99a. Front legs have many spines and are held in front of them in a bent “prayer like”position; with large eyes (praying mantids) ...................................................Mantodea

Answer Key for Insect Discovery

Insect Order Name

List of identifying characteristicsIsoptera Ant-like in body shape, but with wider waists

Hymenoptera Two pairs of thin, often see-through wings - ant-like in body shape

Collembola Two appendages located at the end of the abdomenImmature

InsectDiptera One pair of membranous wingsOdonata Two pairs of long wings of approximately the same

sizeEphemeropte

raTwo pairs of somewhat triangular-shaped wings.The front pair of wings is much larger than the hind pair

Hemiptera Forewings half leathery, half membranous, wings makes an “X” when folded on the back (true bugs)

Homoptera Two pairs of wings, which it holds angled up to look like a little roof over its back.

Orthoptera Hind legs often enlarged, adapted for jumpingMantodea Triangular-shaped head. Front legs bent “prayer

like”.Insect # 1 - EphemeropteraInsect # 2 - HemipteraInsect # 3 - HymenopteraInsect # 4 - DipteraInsect # 5 - CollembolaInsect # 6 - HomopteraInsect # 7 - OrthopteraInsect # 8 - MantodeaInsect # 9 - OdonataInsect # 10 - Isoptera

Group doing the assessing:

Group being assessed:

1. Were you able to identify all 12 items?

2. Was the key in table form or tabular form?

3. Were the characteristics used to describe the objects constant?

4. Were the characteristics measurable?

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