Dichotomous Key Biology Lab

Transcription

1 Dichotomous Key Biology Lab Over 60,000 different tree species exist in out world. Identifying one species from another is as easy as answering a list of yes/no questions, called a dichotomous key. Answering the first question will lead to to another question, like choosing an action in an adventure book will take you to another page in the book, and so on. Let s see how a dichotomous key works. The Planet Pamishan On the next page is a photo array of different animals living on an imaginary planet. We can figure out the name of each animal by using the dichotomous key on the following page. Here s how we can identify Animal #1. The first trait we need to identify is head size. Since #1 has a narrow head, we are directed to question 11. That question asks whether the animal has antennae. It does, so we go to question 15, and determine whether it has a mouth. It does, so we move on to Question 16. Since the animal has spikes on its leg, we now know its name; Narrowus portus. We can repeat the process for all of the other species on the page. Make sure you start with Question #1 every time you want to identify a new species! dich /23/18

2 Biology Lab Boricua College Name: dich /23/18

3 Dichotomous Key Biology Lab 1. a. The creature has a large wide head go to 2 b. The creature has a small narrow head go to a. It has 3 eyes go to 3 b. It has 2 eyes go to 7 3. a. There is a star in the middle of its chest go to 4 b. There is no star in the middle of its chest go to 6 4. a. The creature has hair spikes Broadus hairus b. The creature has no hair spikes. go to 5 5. a. The bottom of the creature is arch-shaped Broadus archus b. The bottom of the creature is M-shaped. Broadus emmus 6. a. The creature has an arch-shaped bottom. Broadus plainus b. The creature has an M-shaped bottom. Broadus tritops 7. a. The creature has hairy spikes go to 8 b. The creature has no spikes go to a. There is a star in the middle of its body Broadus hairystarus b. The is no star in the middle of its body go to 9 9. a. The creature has an arch shaped bottom Broadus hairyemmus b. The creature has an M shaped bottom Broadus kiferus 10. a. The body is symmetrical Broadus walter b. The body is not symmetrical. Broadus anderson dich /23/18

4 Dichotomous Key Biology Lab 11. a. The creatrue has no antennae. go to 12 b. The creature has antennae go to a. There are spikes on the face. Narrowus wolfus b. There are no spikes on the face go to a. The creature has no spike anywhere Narrowus blankus b. There are spikes on the right leg Narrowus starboardus 14. a. The creature has 2 eyes go to 15 b. The creature has 1 eye Narrowus cyclops 15. a. The creature has a mouth go to 16 b. The creature has no mouth go to a. There are spikes on the left leg Narrowus portus b. There are no spikes at all. Narrowus plainus 17. a. The creature has spikes go to 18 b. The creature has no spikes Narrowus georginia 18. a. There are spikes on the head go to 19 b. There are spikes on the right leg Narrowus montanian 19. a. There are spikes covering the face Narrowus beardus b. There are spikes only on the outside edge of head Narrowus fuzzus dich /23/18

5 Dichotomous Key Biology Lab West Coast Trees We were able to name the Pamishan creatures by determining their characteristic traits (head shape, number of eyes, leg shape). We can apply the same procedure to identifying any tree on Earth. Each tree on our planet can be described by a short list of traits that all trees possess. You need to know how each trait is expressed before you use a tree identification dichotomous key. So let s start with some basic vocabulary. Tree Traits Go to the VCU website, and define the following terms. Coniferous Deciduous Simple leaf Compound leaf dich /23/18

6 Dichotomous Key Biology Lab Alternate leaves Opposite leaves Palmate leaf Pinnate leaf Lobed leaf Unlobed leaf dich /23/18

7 Dichotomous Key Biology Lab Now that we understand the various tree traits, let s use a dichotomous key to identify trees that grow in the western United States. You can use the dichotomous key on the next page, or the Oregon State tree app to identify the following trees. A -- Dogwood B -- Sweetgum C -- Spruce D -- Sequoia E -- Apple F -- Walnut G -- Juniper H -- Buckeye I -- Oak J -- Pine K -- Cedar L -- Maple M -- Cypress N -- Locust O -- Ash P -- Redwood R -- Cedar Write the letter of the correct tree for each picture number dich /23/18

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10 Dichotomous Key Biology Lab Back in the City We can apply the same West Coast tree technique to naming trees on our Brooklyn city blocks. On the next two pages is an array of the most common trees in our city. Use your materials to answer the following questions. 1) Describe one of the NYC tress using the following terms: simple/common, alternate/opposite, coniferous/deciduous, palmate/ pinnate. 2) Describe a second tree using the same vocabulary 3) And a third tree. 4) Can the dichotomous tree we used to identify trees in the western US be used to identify all NYC trees? Why or why not? dich /23/18

11 Dichotomous Key Biology Lab 5) The 2005 tree census, like our national Constitutional census, counts the number of trees in our city. Go to the NYC tree map website, and list the trees next to your residence. Describe their traits using the vocabulary listed on pages Extra Credit Go the University of WIsconsin Tree Identification website, and identify the trees. Click on the LEAF Dichotomous Tree Key button on left side of screen dich /23/18

12 Western US Tree Dichotomous Key 1. Is it a conifertree 2 Is it a deciduous tree Are the leaves needlelike 3 Are the leaves flat or scale like Are the needles clustered 4 Are the needles not clustered 6 4. Are the needles in clusters of 2-5 Pine Are the needles in clusters > Are the needles soft? Larch Are the needles stiff? Cedar 6. Are the needles short and sharp Sequoia Are the needles longer than 1/2 an inch 7 7. Are there tiny pegs on the branches 8 Are there no tiny pegs on the branches 9 8. Are the pegs square Spruce Are the pegs round Hemlock 9. Are the buds large and pointed Douglas Fir Are the buds not large and pointed Redwood 10. Are the leaves short and sharp Sequoia Are the leaves not short and sharp 11 dich /23/18

13 Western US Tree Dichotomous Key 11. Are the cones round 12 Are the cones not round Are the cones soft and leathery Juniper Are the cones woody Are the cones < 1/2 an inch in diameter cedar Are the cones > 1/2 an inch in diameter cypress 14. Do the cones look like rose buds Arbor vitae Do the cones look like a duck s bill Cedar 15. Are the leaves compound 16 Are the leaves simple Are they palmate leaves Buckeye Are they pinnate leaves Are the leaves alternate 18 Are the leaves opposite Ash 18. Are the leaflets < 3 inches 19 Are the leaflets > 3 inches Walnut 19. Are the leaflet edges smooth Locust Are the leaflet edges serrated Mountain ash 20. Are the leaves opposite 21 Are the leaves alternate 23 dich /23/18

14 Western US Tree Dichotomous Key 21. Are the leaves lobed Maple Are the leaves not lobed Are the leaves heart shaped Catalya Are the leaves not heart shaped Dogwood 23. Are the leaves deeply lobed 24 Are the leaves not deeply lobed??? 24. Are the leaves palmatively lobed 25 Are the leaves pinnately lobed Are the leaves star shaped Sweetgum Are the leaves not star shaped Sycamore 26. Are the branches without thorns 27 Are the branches with thorns Hawthorne 27. Do the leaves have <5 lobes 28 Do the leaves have >5 lobes Oak 28. Do the leaves have 4 lobes Poplar Do the leaves have <4 lobes Apple dich /23/18

15 VCU Materials Opposite vs Alternate The arrangement of leaves on the stem/branch can be opposite (in pairs, directly across from each other on the branch) or alternate (singly and alternate from one side of the stem/branch to the other) Choose the arrangement that is most like your tree. If you are having trouble determining whether the leaves are alternate or opposite, sometimes you can look at the twigs on a branch. As each twig originates from where a leaf used to be, their pattern should be the same as the leaf pattern. Always look at more then one leaf/ twig/branch as sometimes they can be broken off during growth and this can alter the pattern. Opposite Alternate Opposite - Compound vs Simple The next step is to look more closely at a single leaf to determine if it is compound or simple. This has more to do with the structure of the leaf itself than with the position of the leaf on the stem. One of the defining characterstics of a leaf is that at the base of the leaf stem (petiole) there is a small bud called the axillary bud. Sometimes this bud is covered by the petiole so make sure you look carefully. If there is no axillary bud at the base of the petiole, then the structure is not a leaf but rather a leaflet and the leaf, as a whole, is compound. Compound Simple dich /23/18

16 VCU Materials Alternate - Compound vs Simple The next step is to look more closely at a single leaf to determine if it is compound or simple. This has more to do with the structure of the leaf itself than with the position of the leaf on the stem. One of the defining characterstics of a leaf is that at the base of the leaf stem (petiole), there is a small bud called the axillary bud. Sometimes this bud is covered by the petiole so make sure you look carefully. If there is no axillary bud at the base of the petiole, then the structure is not a leaf but rather a leaflet and the leaf, as a whole, is compound. Compound leaves are composed of multiple leaflets, while simple leaves do not have leaflets at all. Compound Simple Opposite & Compound - Pinnate vs Palmate Pinnate means that the veins resemble a feather: one main vein with many smaller veins branching off. The palmate vein pattern looks roughly like the outspread fingers of your hand. All of the main veins in the leaf originate at the base of the leaf and fan outward. Pinnate Palmate dich /23/18

17 VCU Materials Opposite & Simple - Lobed vs Unlobe Lobes are large and distinct indentations of the margin of the leaf. The depth/degree of the lobe, referred to as the sinus, can be useful in identifying a plant, as can the number of lobes on the leaf. Leaves without lobes will have an edge devoid of major indentations. Lobed Unlobe dich /23/18

18 Answers Answer Key to Pamishan Creatures 1. Narrowus portus 2. Broadus archus 3. Narrowus plainus 4. Broadus hairyemmus 5. Broadus hairus 6. Broadus anderson 7. Narrowus montanian 8. Narrowus georginia 9. Narrowus blankus 10. Broadus emmus 11. Narrowus cyclops 12. Broadus hairystarus 13. Narrowus beardus 14. Broadus walter 15. Broadus plainus 16. Broadus kiferus 17. Narrowus starboardus 18. Broadus tritops 19. Narrowus wolfus 20. Narrowus fuzzus Answer Key for Western US Trees 1. K Cedar 2. H Buckeye 3. G Juniper 4. M Cypress 5. A Dogwood 6. N Locust 7. L Maple 8. O Ash 9. I Oak 10. J Pine 11. P Redwood 12. D Sequoiia 13. C Spruce 14. B Sweetgum 15. F Walnut dich /23/18

19 Answers Key to trees on LEAF Site: 1. Black Cherry 2. White Pine 3. Tamarack 4. White Birch 5. Jack Pine 6. Black Walnut 7. Scotch Pine 8. Sugar Maple 9. Red Oak 10. White Ash 11. Cottonwood 12. Balsam Fir 13. Basswood 14. Eastern Hemlock 15. American Beech 16. Trembling Aspen 17. Red Maple 18. Big Toothed Aspen 19. Northern White Cedar 20. White Oak 21. Black Spruce 22. Red Pine 23. White Spruce 24. Yellow Birch 25. Black Ash 26. Norway Spruce 27. Shagbark Hickory dich /23/18