131 Laboratory Manual B/Chapter 18 Biology

NameChapter 18ClassDateClassificationIdentifying VertebratesUsing Dichotomous KeysYou may want to refer students to Chapter 18 text andReal-World Lab in the textbook before performing thisinvestigation.Time required: 40 minutesIntroductionOrganisms such as vertebrates (animals with backbones) areclassified into groups according to certain characteristics. Usingthese characteristics, dichotomous keys can be developed. Biologistsdevelop these dichotomous keys so they can be used to identifyunfamiliar organisms. Such keys are also useful in studying commoncharacteristics and relationships among organisms.In this investigation, you will learn to use a simple dichotomouskey to identify some organisms.ProblemHow is a dichotomous key used to identify various animals?Pre-Lab DiscussionRead the entire investigation. Then, work with a partner to answerthe following questions.1. Into which five basic groups will you be classifying vertebrates?Fishes, amphibians, reptiles, birds, and mammals.2. What information do you need in order to classify the animals shown inFigure 1? Where will you find this information?Students will need to have a completed Data Table on page 134. This information will either be givento students in the Procedure or students will obtain it by observing the pictures of the animals in Figure 1.3. What is a dichotomous key? Prentice-Hall, Inc.Students may say that a dichotomous key is a list of characteristics that can be used to identify organisms.4. What do the a and b statements in the dichotomous key describe?They are contrasting characteristics, only one of which can apply to the vertebrate being considered.5. Read statement 1b in the Dichotomous Key for the Extinct Animalsshown in Figure 1. If an animal is ectothermic, what is the next stepin the key? Explain.If an animal is ectothermic, you skip statements 2–5 and go directly to statement 6 as directed.Statements 2–5 describe characteristics of endotherms.Biology Laboratory Manual B/Chapter 18 131

Procedure1. Vertebrates can be divided into five major groups: fishes,amphibians, reptiles, birds, and mammals. (These are not all formaltaxonomic groups.) Fishes have gills. The other vertebratesmentioned have lungs. Fishes, amphibians, and reptiles are calledectothermic because they derive body heat mainly from theirenvironment. (Ecto- means outside; -therm means heat.) Birds andmammals are called endothermic because they derive body heatmainly from metabolism. (Endo- means inside.) Some species ineach vertebrate group have become extinct. Ten extinct animals arepictured in Figure 1 on pages 132–134. Study the characteristics ofthese animals by completing the Data Table on page 134.Fish (North America) Prentice-Hall, Inc.PigeonBisonFigure 1132 Biology Laboratory Manual B/Chapter 18

NameClassDateDodo Prentice-Hall, Inc.ElkWolfFigure 1 continuedTortoiseBiology Laboratory Manual B/Chapter 18 133

FrogFish (New Zealand)SnakeFigure 1 continuedData TableElkXXXXXSnakeXFrogXXBisonXXX134 Biology Laboratory Manual B/Chapter XXWolfFish (New Zealand)ScalesSmooth skinXHornsHindlegsXTemperatureRegulationXXXX Prentice-Hall, Inc.DodoForelegsWings, 2 LegsTortoiseFish (North America)BodyCoveringAppendagesFinsName of Animal

NameClassDate2. The following key is based on information from Figure 1 and theData Table. Examine how a key works by using it to identify eachanimal.Dichotomous Key for the Extinct Animals Shown in Figure 1123456789a Is endothermicGo to 2b Is ectothermicGo to 6a Has feathersGo to 3b Has hair or furGo to 4a Has narrow, straight beakPassenger pigeonb Has wide, crooked beakDodoa Has hornsGo to 5b Has no hornsTexas red wolfa Horns may have many branchesEastern elkb Horns have no branchesOregon bisona Breathes with gillsGo to 7b Breathes with lungsGo to 8a Has large, fan-shaped fins just behind the headUtah Lake sculpinb Has small pectoral finsNew Zealand graylinga Has scaly skinGo to 9b Has smooth skinPalestinian painted froga Has front and hind legsDomed tortoiseb Has no legsRound Island boaAnalysis and Conclusions1. Classifying Reptiles are ectothermic, have scaly skin, and breathewith lungs. Which of the animals in Figure 1 are reptiles?Domed tortoise, Round Island boa.2. Classifying The Palestinian painted frog is an amphibian. What isone difference between amphibians and reptiles? Prentice-Hall, Inc.Amphibians have smooth skin; reptiles have scaly skin.3. Classifying Mammals are endothermic, have hair or fur, breathewith lungs. (They also give birth to live young.) Which of theanimals in Figure 1 are mammals?Eastern elk, Oregon bison, Texas red wolf.4. Classifying Birds are endothermic vertebrates with feathers andwings. Which animals in Figure 1 are birds?Dodo, passenger pigeon.Biology Laboratory Manual B/Chapter 18 135

5. Drawing Conclusions To which vertebrate group do you belong?Explain.Mammals. Like all mammals, humans are endothermic, have two pairs of limbs, are covered with hair, andbreathe with lungs.6. Classifying Develop a dichotomous key for the following mythicalcreatures. The key has been started for you.SPHINX:body of lion, upper part a humanPEGASUS:winged horseCHIMERA:front part a combination of lion and goat,hind part a serpent, breathes fireCENTAUR:human from head to waist, remainder ofbody a horseGRIFFIN:body of a lion, head and wings of aneagle, back covered with feathersUNICORN:body of a horse, head of a deer, feet ofan elephant, tail of a boar, a single blackhorn in the middle of its foreheadDichotomous Key for Mythical Animals12345a Part of body is humanGo to 2b None of body is humanGo to 3a Part lionSphinxb Part horseCentaura WingsGo to 4b No wingsGo to 5a Feathers on backb No feathers on backGriffinPegasusa HornUnicornb No hornChimeraChoose an organism that you would like to study. Find out how theorganism is classified. Try to find out what characteristics are used toclassify the organism. Make a chart of your findings. The chart shouldhave columns headed with the terms “kingdom,” “phylum,” “class,”“order,” “family,” “genus,” and “species.” In each column, write thecharacteristics of the organism that belong under the heading.136 Biology Laboratory Manual B/Chapter 18 Prentice-Hall, Inc.Going Further

The following key is based on information from Figure 1 and the Data Table. Examine how a key works by using it to identify each animal. Dichotomous Key for the Extinct Animals Shown in Figure 1 1 a Is endothermic Go to 2 b Is ectothermic Go to 6 2 a Has feathers Go to 3 b Has hair or fur Go to 4 3 a Has narrow, straight beak Passenger pigeon b .