ch 18: classification · ch 18: classification 18-1 finding order ... biologists use a...

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Big idea/Questions/Notes

CH 18: Classification

18-1 Finding Order in Diversity

A. Why Classify?

1. ________________________________ and other processes have led to a staggering diversity of organisms.

2. Biologists have identified and named about _________________________________________________ so far.

a. They estimate that 2–100 million additional species have yet to be discovered.

3. To study the diversity of life, biologists use a classification system to name organisms and group them in a

logical manner.

4. Discipline of _________________________________- scientists classify organisms and assign each organism a

_____________________________________________________________________________________.

B. Assigning Scientific Names

1. Common names of organisms vary, so scientists assign ___________________________________________.

2. Because 18th century scientists understood ________________________________, they used those languages for

scientific names.

3. This practice is still followed in naming new species.

4. Carolus ___________________ developed a naming system called ____________________________________.

5. In binomial nomenclature, each species is assigned a two-part scientific name.

a. 1st part of the name- the __________________ to which the organism belongs.

i. Genus- a group of closely related species. The genus name is __________________________.

ii. Example: grizzly bear is the genus ________________

b. 2nd part of the name is unique to each _____________________ within the genus.

i. This part of the name often describes an important trait or where the organism lives.

ii. The species name is ____________________.

iii. Example: grizzly bear Ursus maririmus (polar bear) or Ursus artos (brown bear)

6. Linnaeus's seven levels of classification are—from smallest to largest—

a. _________________________

b. _________________________

c. _________________________

d. _________________________

e. _________________________

f. _________________________

g. _________________________

18-2 Modern Evolutionary Classification

A. Which similarities are most important?

1. Early classification was based on _____________________________________________________________

How are evolutionary relationships important in classification?

2. _________________________________ the study of evolutionary relationships among organisms.

B. Evolutionary Classification

1. Biologists now ______________________________________________________________________________

_______________________________________________________ which is called evolutionary classification.

2. Species within one genus are more closely related to one another than to species in another genus.

3. All members of a genus share a __________________________________

4. The higher the level of the taxon, the further back in time is the common ancestor of all the organisms in the

taxon.

5. Organisms that ______________________________________________________________________________.

6. Superficial similarities once led barnacles and limpets to be grouped together.

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7. However, barnacles and crabs share an evolutionary ancestor that is more recent than the ancestor that barnacles

and limpets share.

8. Barnacles and crabs are classified as _____________________, and limpets are _____________________.

C. Classification Using Cladograms

1. Many biologists now use a method called ____________________________________.

2. Cladistic analysis identifies and considers only new characteristics that arise as lineages evolve.

3. Characteristics that appear in recent parts of a lineage but not in its older members are called

________________________________.

4. Derived characters can be used to construct a cladogram, a ___________________________________________

___________________________________________________________________________________________.

5. Cladograms help scientists understand how one lineage branched from another in the course of evolution.

a. Ex: A cladogram shows the evolutionary relationships between crabs, barnacles, and limpets.

Activity: Understanding Cladograms

- Color the organisms that have a molted external

skleton blue

- Color the organisms without a molted external

skeleton red

- Circle the point on the cladogram that shows the

most recent common ancestor of the crab and the

barnacle

- Mark an X on the point on the cladogram that

shows the most recent common ancestor of

mollusks and crustaceans

D. Similarities in DNA and RNA

How can DNA and RNA help scientists determine

evolutionary relationships?

1. ______________________________________

can be used to help determine classification and

evolutionary relationships.

2. DNA evidence shows ________________________________________________________________________.

3. The more similar the DNA of two species, the more recently they shared a common ancestor, and the more

closely they are related in evolutionary terms.

4. The more two species have ________________________ from each other, the less similar their DNA will be.

E. Molecular Clocks

1. Comparisons of DNA are used to mark the passage of evolutionary time.

2. A ______________________________ uses DNA comparisons to estimate the length of time that two species

have been evolving independently.

3. A molecular clock relies on _______________________________________________________________.

4. Simple mutations in DNA structure occur _____________.

5. Neutral mutations accumulate in different species at about the same rate.

6. Comparing sequences in two species shows how dissimilar the genes are, and shows when they shared a common

ancestor.

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Activity: Three Domains

Use the diagram to answer the questions

1. Which species is most closely related to Species B?

Species A or Species C

. Explain how you used the DNA sequences to answer

question 1. (2-3 sentences)

A: ______________________________________________

________________________________________________

________________________________________________

__

3. How can you tell that Species C developed from the

organism with gene 3?

A: ______________________________________________

________________________________________________

________________________________________________

_ .

18-3 Kingdoms and Domains

A. The Tree of Life Evolves

1. Systems of classification adapt to new discoveries.

2. Linnaeus classified organisms into two kingdoms — ______________________________________.

3. The only known differences among living things were the fundamental traits that separated animals from plants.

4. Scientists realized there were enough differences among organisms to make 5 kingdoms:

a. _______________________________

b. _______________________________

c. _______________________________

d. _______________________________

e. _______________________________

B. Six Kingdoms

1. Recently, biologists recognized that ______________________________ were composed of two distinct groups:

_______________________ and ______________________________.

What are the six kingdoms of life as they are now identified?

2. The six-kingdom system of classification includes:

a. ______________________________

b. Archaebacteria

c. ______________________________

d. Fungi

e. ______________________________

f. Animalia

C. The Three-Domain System

1. Molecular analyses have given rise to a new taxonomic category that is now recognized by many scientists.

2. The ___________________________ is a more inclusive category than any other—larger than a kingdom.

3. The three domains are:

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a. __________________ - which is composed of protists, fungi, plants, and animals.

i. All members have cells _________________________________________________

b. ______________________- which corresponds to the kingdom Eubacteria.

i. Unicellular organisms _______________________________

ii. Have cell wall _____________________________ peptidoglydan

c. ______________________- which corresponds to the kingdom Archaebacteria.

i. Unicellular organisms ________________________________

ii. Have cell walls _____________________ peptidoglydan

4. Modern classification is a rapidly changing science.

5. As new information is gained about organisms in the domains Bacteria and Archaea, they may be subdivided into

additional kingdoms.

D. Domain Bacteria

1. Members of the domain Bacteria are ________________________________.

2. Their cells have thick, rigid cell walls that surround a cell membrane.

3. Their cell walls contain peptidoglycan.

4. The domain Bacteria corresponds to the kingdom _______________________.

E. Domain Archaea

1. Members of the domain Archaea are ________________________________________.

2. They live in ___________________________________________________________.

3. Their cell walls lack peptidoglycan, and their cell membranes contain unusual lipids not found in any other

organism.

4. The domain Archaea corresponds to the kingdom Archaebacteria.

F. Domain Eukarya

1. The domain Eukarya consists of organisms that have a nucleus.

2. This domain is organized into four kingdoms:

a. Protista

i. Most members are unicellular

ii. Can be _____________________________________

b. Fungi

i. Are all _____________________

ii. Most fungi feed on dead or decaying organic matter by secreting digestive enzymes into it and

absorbing small food molecules into their bodies.

iii. They can be either multicellular (____________________) or unicellular (___________)

c. Plantae

i. are multicellular, photosynthetic autotrophs

ii. Plants are __________________ - they cannot move from place to place.

iii. Plants have cell walls that contain _______________________.

iv. The plant kingdom includes cone-bearing and flowering plants as well as mosses and ferns.

d. Animalia

i. Are __________________________________________________________.

ii. The cells of animals do not have cell walls.

iii. Most animals can move about.

Textbook p. 453…

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Answers for Analyze and Conclude:

1. ______________________________________________________________________________________________

________________________________________________________________________________________________

2. ______________________________________________________________________________________________

________________________________________________________________________________________________

3. ______________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________.

4. ______________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________.

Teaching Resources /Chapter 18 229

Compare/Contrast Table

Use the terms listed below to fill in the compare/contrast table. The terms may be used more than once, and some sections of the table may have more than one term.

Animalia; Eukaryotic; Cell walls with peptidoglycan; Varied types of cell walls and cells without walls; Eubacteria; Fungi; Multicellular; Plantae; Prokaryotic; Protista; Unicellular

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Characteristics of the Three Domains

Domain Bacteria Domain Archaea Domain Eukarya

Number of Cells 1. Unicellular 2.

Cell Type Prokaryotic 3. 4.

Cell Structures 5. Cell walls without 6.peptidoglycan

Kingdom(s) 7. Archaebacteria 8.

Completion On the lines provided, complete the following sentences.

1. In the discipline known as , biologists assign eachkind of organism a universally accepted name.

2. In , each species is assigned a two-part scientific name.

3. In taxonomy, each level of classification is referred to as a(an) .

4. The seven taxonomic categories in Linnaeus’s system of classification are:

Multiple Choice On the lines provided, write the letter of the answer that best completes thesentence or answers the question.

5. The method of grouping organisms into categoriesthat represent lines of evolutionary descent is called a. taxonomy. c. binomial nomenclature.b. cladistic analysis. d. evolutionary classification.

6. Comparison of DNA to determine how long different specieshave been evolving independently can be done usinga. cladograms. c. kingdoms.b. molecular clocks. d. domains.

7. Characteristics that appear in recent parts of a lineage but not in its oldermembers are called a. taxons. c. cladograms.b. derived characters. d. genes.

8. What type of model is shown below?a. binomial nomenclature c. cladogramb. molecular clock d. domain

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Chapter 18 Classification Chapter Vocabulary Review

226 Teaching Resources /Chapter 18

© Pearson Education, Inc. All rights reserved.

Barnacle

Moltedexoskeleton

Limpet

Segmentation

Tiny free-swimming larva

Crab

9. Which phylum includes humans, snakes, and sharks?a. Ursidae c. Mammaliab. Carnivora d. Chordata

10. The group of organisms that can be larger than akingdom is called aa. domain. c. phylum.b. species. d. class.

11. A prokaryote whose cell walls contain peptidoglycanbelongs to the domaina. Eukarya. c. Bacteria.b. Protista. d. Archaea.

12. Unicellular organisms sometimes found in hot springsare part of the domaina. Eubacteria. c. Protista.b. Archaea. d. Eukarya.

13. The domain Eukarya includes the kingdom(s)a. Protista, Plantae, Fungi, Animalia. c. Eubacteria.b. Protista, Plantae, Bacteria. d. Archaea, Bacteria.

14. The kingdom Protista contains a. only single-celled organisms.b. both single-celled and multi-celled organisms.c. only multi-celled organisms.d. neither single-celled nor multi-celled organisms.

15. Mushrooms belong to the kingdoma. Protista. c. Plantae.b. Bacteria. d. Fungi.

16. The kingdom Plantae contains primarily a. photosynthetic autotrophs. c. photosynthetic heterotrophs.b. single-celled autotrophs. d. protists.

17. The organisms found in the kingdom Animalia area. photosynthetic heterotrophs. c. multicellular heterotrophs.b. single-celled heterotrophs. d. protists.

18. Into how many domains are organisms divided?a. three c. fourb. five d. six

19. The unicellular prokaryotes that make up the domainBacteria are also classified in the kingdoma. Archaebacteria. c. Fungi.b. Eubacteria. d. Protista.

20. The prokaryotes that live in extreme environments are classifed in the kingdoma. Archaebacteria. c. Fungi.b. Eubacteria. d. Protista.

Teaching Resources /Chapter 18 227

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Chapter 18 Classification

Using and Constructing a Dichotomous KeyIntroductionAll cultures have developed names for the living things found in theirenvironments. When various everyday names are used for the sameorganism, confusion is possible. So, scientists have developed aninternational system for naming and classifying all organisms.Identification guides, called keys, have been developed to help all peoplesrecognize and identify organisms according to their scientific names.

The word dichotomous comes from the word dichotomy, meaning“two opposite parts or categories.” A dichotomous key gives thereader a series of opposing descriptions of basic features of anorganism. The reader studies the specimen and selects the descriptionsthat apply to it until reaching a statement that characterizes only onespecies and names it. In this investigation, you will use a typicaldichotomous key to identify the genus and species of several differentsalamanders. Then, you will create your own dichotomous key tocategorize a diverse group of wildflowers.

ProblemHow is a dichotomous key used to distinguish among similar organisms?

Pre-Lab Discussion Read the entire investigation. Then, work with a partner to answer the following questions.

1. How many choices does a dichotomous key provide at each step? There are two choices at each step.

2. What are some of the apparent differences among the salamanders illustrated?The size, color, shape, numbers and patterns of spots, and the presence or absence of external

gills are differences.

3. Based on the information in Figure 2, what is a distinguishingcharacteristic of the members of the genus Ambystoma? They all have a body coloring pattern with a black background and variable white spots.

4. What might be a good strategy for beginning to create a dichotomouskey for the six types of wildflowers shown in the diagram?Find a broad difference between them such as the number of petals in the flower or the number of

divisions in the leaf.

5. If you were to use live flowers instead of diagrams, what othercharacteristics could you use to identify the flowers?The color, scent, leaf size, and flower size could be compared.

Biology Laboratory Manual A/Chapter 18 147

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You may want to refer students to Chapter 18 in thetextbook for a discussion of the classification systemused in biology. Time required: 45 minutes

Students may work alone or with a partner, depending on your preference.

Procedure

Part A: Using a Dichotomous Key1. Examine the drawings of the salamanders in Figure 1. Choose one

salamander to identify by using the key.

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Figure 1

2. Use the dichotomous key (Figure 2) to determine the genus andspecies of that salamander. Begin by reading statements 1a and 1b.One of the statements describes the salamander; the other statementdoes not. Follow the directions for the statement that applies to thatsalamander and continue following the correct statements until youhave identified it. Record the scientific and common name of thesalamander in the Data Table on page 150.

3. Repeat step 2 for each of the other salamanders in Figure 1.

1 a Hind limbs absent Siren intermedia, siren

b Hind limbs present Go to 2

2 a External gills present in adults Necturus maculosus, mud puppy

b External gills absent in adults Go to 3

3 a Large size (over 7 cm long in Figure 1) Go to 4

b Small size (under 7 cm long in Figure 1) Go to 5

4 a Body background black, large white spots variable in size completely covering body and tail Ambystoma tigrinum, tiger salamander

b Body background black, small round white spots in a row along each side from eye to tip of tail Ambystoma maculatum, spotted salamander

5 a Body background black with white spots Go to 6

b Body background light color with dark spots and/or lines on body Go to 7

6 a Small white spots on black background in a row along each side from head to tip of tail Ambystoma jeffersonianum, Jefferson salamander

b Small white spots scattered throughout a black background from head to tip of tail Plethodon glutinosus, slimy salamander

7 a Large irregular white spots on a black background extending from head to tip of tail Ambystoma opacum, marbled salamander

b No large irregular black spots on a light background Go to 8

8 a Round spots scattered along back and sides of body, tail flattened like a tadpole Triturus viridescens, newt

b Without round spots and tail not flattened like a tadpole Go to 9

9 a Two dark lines bordering a broad light middorsal stripe with a narrow median dark line extending from the head onto the tail Eurycea bislineata, two-lined salamander

b Without two dark lines running the length of the body Go to 10

10 a A light stripe running the length of the body and bordered by dark pigment extending downward on the sides Plethodon cinereus, red-backed salamander

b A light stripe extending the length of the body withoutdark pigment on the sides Hemidactylium scutatum, four-toed salamander

Figure 2


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Data Table

Number Genus and species Common name

1 Plethodon glutinosus slimy salamander

2 Ambystoma jeffersonianum Jefferson salamander

3 Ambystoma maculatum spotted salamander

4 Triturus viridescens newt

5 Eurycea bislineata two-lined salamander

6 Necturus maculosus mud puppy

7 Ambystoma tigrinum tiger salamander

8 Plethodon cinereus red-backed salamander

9 Hemidactylium scutatum four-toed salamander

10 Siren intermedia siren

11 Ambystoma opacum marbled salamander

Part B. Constructing a Dichotomous Key1. Examine Figure 3, which shows some common North American

wildflowers. Note different characteristics in flower shape, numberof petals, and leaf number and shape.


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TrilliumMay apple

Arrowhead

Violet

Clover Bellwort

Figure 3

2. Use the space below to construct a dichotomous key for thewildflowers in Figure 3. Be sure to use enough pairs of statementsto have a final positive statement for each to identify each of the sixflowers shown. Use the key to salamanders as a model fordeveloping your wildflower key.

3. Check the usefulness of your wildflower key by letting anotherstudent see if he or she can use it to identify each pictured flower.

Wildflower Dichotomous Key

Analysis and Conclusions1. Analyzing Data What are some examples of basic differences

among the salamanders pictured? Adults with external gills and salamanders with hind limbs absent are two of the most basic differences.


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A possible key follows:1a Having numerous small petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clover1b Lacking numerous small petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 2

2a Having 3 separate petals only . . . . . . . . . . . . . . . . . . . . . . . . . . Arrowhead2b Having more than 3 separate petals . . . . . . . . . . . . . . . . . . . . . . . . Go to 3

3a Having 3 inner petals surrounded by 3 leaflike structures . . . . . . . . Trillium3b Having 5 or 6 petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 4

4a Having 5 petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Violet4b Having 6 petals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to 5

5a Having 6 petals that form a bell-like shape . . . . . . . . . . . . . . . . . . Bellwort5b Having 6 petals arranged in a flat circular shape . . . . . . . . . . . . May apple

2. Drawing Conclusions Do the dichotomous keys you have justworked with have any limitations in distinguishing betweenspecies? Yes, they are based only on appearance. There may be other important traits that distinguish species.

3. Comparing and Contrasting Do any of the wildflowers shown inFigure 3 appear to be similar enough to be in the same genus? No, the structures of the wildflowers are too different from each other.

4. Evaluating What characteristics should be very similar in order tosupport an inference that two plants are closely related? They should share strong similiarities in several basic structures such as flowers, leaves, and seeds

to be closely related. However, similar traits may be due to convergent evolution instead of a shared ancestry.

5. Drawing Conclusions Could the three salamanders from the genusAmbystoma be more closely related than Necturus, the mud puppy,and Triturus, the newt?Yes, but anatomical features are only one indicator of possible evolutionary relationships. Scientists would

have to compare the DNA of the five species to determine how closely they are related to one another.

Going FurtherConstruct an evolutionary tree diagram based on the physicalsimilarities and differences of the salamanders shown in Figure 1.Assume that those most similar share a recent ancestor and those thatare most different had a common ancestor long ago. Explain why yourevolutionary tree is a hypothesis, and describe what kind of evidencemight show whether your hypothesis is correct.


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Chapter 18 Classification

Identifying Vertebrates Using Dichotomous Keys

IntroductionOrganisms such as vertebrates (animals with backbones) are classified into groups according to certain characteristics. Using these 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 answer the 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 given

to 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?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

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You may want to refer students to Chapter 18 text andReal-World Lab in the textbook before performing thisinvestigation.Time required: 40 minutes

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.

132 Biology Laboratory Manual B/Chapter 18

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Pigeon

Fish (North America)

Bison

Figure 1

Dodo

Elk

Wolf

Tortoise


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Figure 1 continued

Data Table

Name of Animal Appendages Body Temperature BreathingCovering Regulation Mechanism

Tortoise X X X X X

Dodo X X X X

Fish (North America) X X X X

Wolf X X X X X

Pigeon X X X X

Elk X X X X X

Snake X X X

Frog X X X X X

Bison X X X X X X

Fish (New Zealand) X X X X


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Snake

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Fish (New Zealand)

Figure 1 continued

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2. 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 1

1a Is endothermic Go to 2

b Is ectothermic Go to 6

2a Has feathers Go to 3

b Has hair or fur Go to 4

3a Has narrow, straight beak Passenger pigeon

b Has wide, crooked beak Dodo

4a Has horns Go to 5

b Has no horns Texas red wolf

5a Horns may have many branches Eastern elk

b Horns have no branches Oregon bison

6a Breathes with gills Go to 7

b Breathes with lungs Go to 8

7a Has large, fan-shaped fins just behind the head Utah Lake sculpin

b Has small pectoral fins New Zealand grayling

8a Has scaly skin Go to 9

b Has smooth skin Palestinian painted frog

9a Has front and hind legs Domed tortoise

b Has no legs Round Island boa

Analysis and Conclusions1. Classifying Reptiles are ectothermic, have scaly skin, and breathe

with 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?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.


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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, and

breathe 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 human

PEGASUS: winged horse

CHIMERA: front part a combination of lion and goat,hind part a serpent, breathes fire

CENTAUR: human from head to waist, remainder ofbody a horse

GRIFFIN: body of a lion, head and wings of aneagle, back covered with feathers

UNICORN: body of a horse, head of a deer, feet ofan elephant, tail of a boar, a single blackhorn in the middle of its forehead

Dichotomous Key for Mythical Animals

1a Part of body is human Go to 2

b None of body is human Go to 3

2a Part lion Sphinx

b Part horse Centaur

3a Wings Go to 4

b No wings Go to 5

4a Feathers on back Griffin

b No feathers on back Pegasus

5a Horn Unicorn

b No horn Chimera

Going FurtherChoose 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.


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LABORATORY MANUAL CHAPTER 17 BIOLOGY: The Dynamics of Life 117

Name Date Class

??INVESTIGATIONINVESTIGATION How Can a Key Be Used toIdentify Organisms?

Lab

17-1Lab

Classification is a way of separating a large group of closely related organisms into smallersubgroups. The scientific names of organisms are based on the classification systems of liv-

ing organisms. The identification of an organism is easy with a classification system. To iden-tify an organism, scientists often use a key. A key is a listing of characteristics, such as structureand behavior, organized in such a way that an organism can be identified.

• Hypothesize how organisms can be identifiedwith a key.

• Use a key to identify fourteen shark families.• Examine the method used to make a key.• Construct your own key that will identify another

group of organisms.

goggles

1. Make a hypothesis to describe how sharks canbe identified using a key. Write your hypothesisin the space provided.

2. Use Figure 1 as a guide to the shark parts used inthe key on page 119.

3. Read statements 1A and 1B of the key. Theydescribe a shark characteristic that can be used toseparate the sharks into two major groups. Thenstudy Shark 1 in Figure 2 for the characteristicreferred to in 1A and 1B. Follow the directions inthese statements and continue until a family

name for Shark 1 is determined. For example, tokey a shark that has a body that is not kite shapedand has a pelvic fin and six gill slits, follow thedirections of 1B and go directly to statements 2.Follow statement 2B to statements 3. At state-ment 3A, identify the shark as belonging toFamily Hexanchidae.

4. Continue keying each shark until all have beenidentified. Write the family name on the linebelow each shark in Figure 2.

5. Have the teacher check your answers.

OBJECTIVESOBJECTIVES MATERIALSMATERIALS

PROCEDUREPROCEDURE

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HYPOTHESISHYPOTHESIS

Figure 1

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118 CHAPTER 17 BIOLOGY: The Dynamics of Life LABORATORY MANUAL

How Can a Key Be Used to Identify Organisms?Lab17-1Lab

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Figure 2

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LABORATORY MANUAL CHAPTER 17 BIOLOGY: The Dynamics of Life 119


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1. A. Body kitelike in shape (if viewed from above) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 12B. Body not kitelike in shape (if viewed from above) . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 2

2. A. Pelvic fin absent and nose sawlike . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family PristophoridaeB. Pelvic fin present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 3

3. A. Six gill slits present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family HexanchidaeB. Five gill slits present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 4

4. A. Only one dorsal fin present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family ScyliorhinidaeB. Two dorsal fins present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 5

5. A. Mouth at front of head rather than back along underside of head . . . . . . Family RhinocodontidaeB. Mouth back along underside of head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 6

6. A. Head expanded on side with eyes at end of expansion . . . . . . . . . . . . . . . . . . . . . Family SphyrnidaeB. Head not expanded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 7

7. A. Top half of caudal fin exactly same size and shape as bottom half . . . . . . . . . . . . . . Family IsuridaeB. Top half of caudal fin different in size and shape from bottom half . . . . . . . . . . . . Go to statement 8

8. A. First dorsal fin very long, almost half total length of body . . . . . . . . . . . . . Family PseudotriakidaeB. First dorsal fin length much less than half total length of body . . . . . . . . . . . . . . . Go to statement 9

9. A. Caudal fin very long, almost as long as entire body . . . . . . . . . . . . . . . . . . . . . . . . Family AlopiidaeB. Caudal fin length much less than length of entire body . . . . . . . . . . . . . . . . . . . . . Go to statement 10

10. A. Nose with long needlelike point on end . . . . . . . . . . . . . . . . . . . . . . . . . Family ScapanorhynchidaeB. Nose without needlelike point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 11

11. A. Anal fin absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Family SqualidaeB. Anal fin present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family Carcharhinidae

12. A. Small dorsal fin present near tip of tail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family RajidaeB. Small dorsal fin absent near tip of tail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Go to statement 13

13. A. Hornlike appendages at front of shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family MobulidaeB. Hornlike appendages not present at front of shark . . . . . . . . . . . . . . . . . . . . . . . Family Dasyatidae

1. What is a classification key and how is it used?

2. List four different characteristics that were used in the shark key.

3. a. Which main characteristic could be used to distinguish shark 4 from shark 8?

b. Which main characteristic could be used to distinguish shark 4 from shark 7?

ANALYSISANALYSIS

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120 CHAPTER 17 BIOLOGY: The Dynamics of Life LABORATORY MANUAL


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Key

1. A.

B.

2. A.

B.

3. A.

B.

4. A.

B.

Did your hypothesis describe the key correctly?

CHECKING YOUR HYPOTHESISCHECKING YOUR HYPOTHESIS

1. Exchange keys with a classmate. Work through it to identify the fish. Is the key correct?2. The library will have many books that include simple keys to different plants and animals, as well as to

rocks, fossils, and stars. Select a book that includes keys to local plants or animals. Take a walk andpractice using the key to identify some of the organisms that live in your area.

FURTHER INVESTIGATIONSFURTHER INVESTIGATIONS

Figure 3

4. Prepare your own key for the five fish in Figure 3. Use the same format as on page 119.The family names to be used are the numbers I, II, III, IV, and V. Your key should correctlyuse traits that will lead to each fish family. To help you get started, the first statements aregiven. Statement 1 divides the five fish into two main groups, based on body shape. Next,choose another characteristic that will divide the fish not having a tubelike body into twogroups. Continue to choose characteristics that will separate a group into smaller groups.Write your key in the space below.

1. A. Fish with long tubelike bodyB. Fish with body shape not tubelike

ANALYSISANALYSIS continued

ch 18: classification · ch 18: classification 18-1 finding order ... biologists use a...

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