La 12: Dichotomous Key Page 1 of 10 STUDENT LABORATORY PACKET La #12 Dichotomous Key Activity Student s Full Name Instructor La # 12: Dichotomous Key La Date Ojectives: Students will e ale to: 1. Create a flow chart dichotomous key 2. Use a dichotomous key to identify fish in NYS 3. Create a dichotomous key of shells Portions of this la were adapted from dichotomous key las from Mr. Comet, a teacher at South Lewis High School in Turin, NY and Ms. Foglia from Division Avenue High School, Levittown. ---------------------------------------------Pre La (Do Before Coming to La)------------------------------------------- In taxonomy, a dichotomous key is used to help sort the diversity of organisms on Earth y their physical characteristics. With newer scientific advancements, other characteristics are added to the key, such as their genetic similarities. To create the dichotomous key, one asks a series of questions with either a yes or no answer, until there is only one item in an answer to a question. The last question leads to the identification of a specific organism. Below is an example of a dichotomous key in a flow chart format that can e used to identify an insect, dog, snail and worm. Snail Worm Insect Dog http://www.oldschool.com.sg/modpu/41602544e1a71d88dfae
La 12: Dichotomous Key Page 2 of 10 In the ox elow, create your own dichotomous flow chart (see example on page 1) using 8 items that you can find in your house. For example, select 8 different foods or 8 writing utensils or 8 pieces of clothing to classify.
La 12: Dichotomous Key Page 3 of 10 --------------------------------------------------------------Laoratory Exercise------------------------------------------------------------------------- Materials: ruler, colored images of NYS fish Procedure/Oservations: Note: Please do not damage the fish pictures so they can e reused each year. PART A: 1. Review the anatomical terms, the fish characteristics and the laeled fish elow. Anterior: towards the head Posterior: Towards the ack Broad part of the fish: height of thickest part of the fish from top to ottom, not including the fin. Use a ruler to measure the road part, then use a ruler to measure the length of the fish. Compare the two numers as a ratio. See image elow. Hinge: Where the corners of the mouth meet; can e in front of the eye, elow the eye, or in ack of the eye. Barel: a fleshy projection from the lip or head (like on a catfish) Concave: curving inward FINS: Fins can e single (separate), elongated (one type of fin, for example a dorsal fin that stretches along part of the length of the ody) or continuous (cannot distinguish separate fins, stretch along the entire length of fish as one fin) o Adipose: a small fin on the top mid-line of the ody near the tail fin (not pictured elow). o Anal: a fin along the lower mid-line of the ody near the tail fin. o Caudal: tail fin. Can e forked: looks like a sideways V, partially forked or unforked. o Dorsal: the fin or fins along the top mid-line of the ody. o Pectoral: the paired fins nearest the head, corresponding to front legs or arms. o Pelvic: the paired fins nearest the tail, corresponding to hind legs. o Scales: overlapping outgrowths of the skin. How to measure the road (top to ottom arrow) part of the fish as compared to the length of the fish (left to right arrow). 2. Closely examine fish #2 on the NYS Fish sheet. 3. Refer to the dichotomous key on page 4 of the la. Note that each numered item on the key presents two possiilities. Read oth statements listed under numer 1 in the classification key. One of these statements descries the characteristics of fish #2; the other does not. You can see that fish #2 has no scales, or at least we cannot see any. So choose item l. This refers us to numer 12. Go down to numer 12 in the dichotomous key. The fish is not elongated or snakelike (item 12), so go to numer 13 of the key. The fish we are classifying has arels growing from its lips and the top of its head (item 13a), so go to numer 14 of the key. Since the fish has a caudal fin that is rounded, and a lunt head, we see that it is the Bullhead catfish. On page 5 of the la, under the column Identified as write Bullhead catfish. In the column laeled Identification pathway write 1, 12, 13a, 14 4. Identify the remaining fish using the dichotomous key. Terms on the dichotomous key that are in old are defined aove.
La 12: Dichotomous Key Page 4 of 10 Classification Key for Common Freshwater Fish of New York State Questions Identify/Go To 1a. Body noticealy covered with scales 2 1. Scales not covering ody or too small to e seen 12 2a. Dorsal fin single 3 2. Dorsal fins two or more, joined or separated 6 3a. Body more than four times as long as road; front edge of dorsal fin far ack on 4 ody; mouth large, hinge of mouth in ack of eye 3. Body less than four times as long as road; front edge of dorsal fin aout midway etween head and tail; mouth not large, hinge in front of eye. 4a. Dark lines forming netted design on ody: fins not spotted Pickerel 4. Body covered with yellow spots; fins spotted Northern Pike 5a. Mouth turned downward: arels asent; dorsal fin not elongated White Sucker 5. Mouth not turned downward: arels present; dorsal fin elongated Carp 6a. Two dorsal fins separated, the anterior spiny and the posterior soft (not spiny) 7 6. Two dorsal fins united, forming an anterior spiny portion and a posterior soft 8 portion 7a. Top of head concave, farming a hump in front of dorsal fin; dark vertical ars on Yellow Perch ody 7. Top of head not concave, ody sloping to dorsal fin and not forming a hump; dark Walleye lotches on ody 8a. Body more than three times as long as road 9 8. Body less than three times as long as road 10 9a. Hinge of jaws ehind the eye: notch etween spiny and soft dorsal fin deep and Large Mouthed ass nearly separating into two fins 9. Hinge of jaws elow the eye; notch etween spiny and soft dorsal fin not nearly Small Mouthed Bass separating into two fins 10a. Mouth large, hinge elow or ehind eye 11 10. Mouth small, hinge in front of eye Bluegill 11a. Five to seven spines in dorsal fin; dark spots forming road vertical ars on sides, Pumpkinseed Red/orange earspot on gill covering (see picture) 11. Ten or more spines in dorsal fin: sides flecked with dark spots Rock Bass 12a. Body elongated and snakelike: dorsal, caudal, and anal fins continuous (cannot American Eel distinguish separate fins) 12. Body not elongated and snakelike: dorsal, caudal, and anal fins separate; adipose 13 fin present 13a. Barels growing from lips or top of head; head large and road 14 13. Barels lacking; head not large and road 16 14a. Caudal fin deeply forked(looks like a sideways v ); head tapering 15 14. Caudal fin rounded or slightly indented ut not forked: head lunt Bullhead Catfish 15a. Dorsal fin rounded at top: ody silvery, speckled with lack markings Channel Catfish 15. Dorsal fin long and pointed at top: ody luish-gray without speckles Blue Catfish 16a. Caudal fin deeply forked; ack not mottled (spotted) or with few spots Atlantic Salmon 16. Caudal fin square or slightly indented; ack mottled or spotted 17 17a. Back and caudal fin spotted: road horizontal and along sides Rainow Trout 17. Back mottled with dark lines: caudal fin not spotted; fins edged with white Brook Trout 5
La 12: Dichotomous Key Page 5 of 10 NYS Fish Identification Fish # Identified as Identification pathway 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
La 12: Dichotomous Key Page 6 of 10 -------------------------------------------------SECOND WEEK----------------------------------------------------- PART B: 1. You will create your own dichotomous key with one partner from your group. Select 10 random shells from the container. When you have created the final step that leads to the identification of a shell, create a scientific name for that shell in a genus species format: Genus species. Notice the g in genus is capitalized, the species name is all lower case, and the entire name is italicized. Try to make the name of your shell sound Latin. For example, the shell that looks like the horn of a unicorn can e called Shellaus unicornus. 2. Hints when creating your key: a. Use the most general traits that can e used to divide organisms up into two categories. These two categories will ecome 1a and 1. These two categories will ecome 1a and 1. Example: 1a... Go to 2 1... Go to 3. Now look at one of the groups and find a trait that will divide it into 2 more sugroups. Write the two distinguishing characteristics on step 2a and 2. c. There should e one less step then the total numer of organisms to e identified in your key so you will write 9 steps. d. The more similarities the group of organisms has, the more difficult it is to develop the key. Try to choose characteristics that are different to make classifying the organisms easier. e. Continue until you get all of the shells listed and named. f. Swap dichotomous keys with your partner and see if you can identify their shells correctly. 1 a 2 a 3 a 4 a 5 a 6 a 7 a 8 a 9 a Shell Dichotomous Key Step Go to Step
La 12: Dichotomous Key Page 7 of 10 Conclusion Questions: 1. LE Regents January 2010 question 55 2. LE Regents June 2009 question 50
La 12: Dichotomous Key Page 8 of 10 3. LE Regents January 2011 Questions 66 and 67. Copy your la onto the Student Answer Packet. Only these sheets will e collected and graded.
La 12: Dichotomous Key Page 9 of 10 Student Answer Packet LAB 12: Dichotomous Key Student s Full Name La Instructor Date Points FINAL GRADE Pre-La Completed as homework: Max. value 2 pt. pt. Procedure/Oservations: Max. value 18 pts. pts. PART A: NYS Fish Identification Fish # Identified as Identification pathway 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
La 12: Dichotomous Key Page 10 of 10 PART B: Shell Dichotomous Key Step Go to Step 1 a 2 a 3 a 4 a 5 a 6 a 7 a 8 a 9 a Conclusion Questions: 1. LE Regents January 2010 question 55. Organism identified as. 2. LE Regents June 2009 question 50 3. LE Regents January 2011 Questions 66 and 67.