_—.Classifying Organisms

Reading Preview gloflnaeb Discover ActivityKey Concepts \”0 Why do biologists organize living Can YOU Organlze a

things into groups? Junk Drawer?

' What do the levels 0f 1. Your teacher will give you someclassification indicate about the items that you might find inrelationship between organisms? the junk drawer of a desk Your

0 What characteristics are used to job is to organize the items.classify organisms into domains 2' Examine the objects and decideaNd kingdoms-7 on three groups into which you

can sort them.3. Place each object into one of

the groups, based on how theitem's features match thecharacteristics of the group.

4. Compare your grouping system with those of your classmates.{0) Target Reading Skill Think It Over

Asking Questions Before you Classifying Which of your classmates’ grouping systems seemedread, preview the red headings. In most useful? Why?a graphic organizer like the onebelow, ask a what, why, or howquestion for each heading. As youread, write the answers to yourquestions.

Key Terms0 classification 0 taxonomy0 binomial nomenclature0 genus 0 species 0 prokaryote0 nucleus 0 eukaryote

Suppose you had only ten minutes to run into a supermarketto get what you needed—milk and tomatoes. Could you do it?In most supermarkets this would be an easy task. You’d proba-Classifying Organisms bl . .y find out where the dalry and produce sect1ons are, and headstraight to those areas. Now imagine if you had to shop forthese same items in a market where things were randomly because . . .

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classify?

———v- — r placed throughout the store. Where would you begin? You’dt" have to search through a lot of things before you found what

you needed. You could be there for a long time!'\.(r

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FIGURE 6Classifying VegetablesVegetables in the produce sectionof a supermarket are neatlyorganized.

JWhyDo Scientists Classify?

Just as shopping can be a problem in a disorganized store, find-ing information about a specific organism can also be a prob-lem. So far, scientists have identified more than one millionkinds of organisms on Earth. That’s a large number, and it iscontinually growing as scientists discover new organisms.Imagine how difficult it would be to find information aboutone particular organism if you had no idea even where tobegin. It would be a lot easier if similar organisms were placedinto groups.

Organizing living things into groups is exactly what biolo-gists have done. Biologists group organisms based on similari-ties, just as grocers group milk with dairy products andtomatoes with produce. Classification is the process of group-ing things based on their similarities.

Biologists use classification to organize living things intogroups so that the organisms are easier to study. The scientificstudy of how living things are classified is called taxonomy (takSAHN uh mee). Taxonomy is useful because once an organism isclassified, a scientist knows a lot about that organism. Forexample, if you know that a crow is classified as a bird, then youknow that a crow has wings, feathers, and a beak.

Read v ~ V What is the scientific study of how living things are.Cbe-uv '2 A classified called?

FIGURE 7Classifying BeetlesThese beetles belong to a largeinsect collection in a natural his-tory museum. They have been clas-sified according to characteristicsthey share. Observing Whatcharacteristics may have been usedto group these beetles?

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LEWconcolor (Puma)Concolor means "the same color."Notice that this animal's coat ismostly the same color.

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The Naming System of LinnaeusTaxonomy also involves naming organisms. In the 17503, theSwedish naturalist Carolus Linnaeus devised a system of nam-ing organisms that is still used today. Linnaeus placed organ-isms in groups based on their observable features. Based on hisobservations, Linnaeus gave each organism a unique, two—partscientific name. This naming system Linnaeus used is calledbinomial nomenclature (by NOH mee ul NOH men klay chur).The word binomial means “two names.”

Genus and Species The first word in an organism’s scien-tific name is its genus. A genus (IEE nus) (plural genera) is aclassification grouping that contains similar, closely relatedorganisms. For example, pumas, marbled cats, and house catsare all classified in the genus Felis. Organisms that are classifiedin the genus Felis share characteristics such as sharp, retract-able claws and behaviors such as hunting other animals.

The second word in a scientific name often describes a dis-tinctive feature of an organism, such as where it lives or itsappearance. Together, the two words indicate a unique species.A species (SPEE sheez) is a group of similar organisms that canmate with each other and produce offspring that can also mateand reproduce.

Reading » What kind of name did Linnaeus give eachm Ch°°k_.p-.°.",_"J‘ Organism?

names Binomial NomenclatureThese three species of cats belong to the same genus.Their scientific names, written in Latin, share the samefirst word, Felis. The second word of their namesdescribes a feature of the animal. Classifying Whatcharacteristics do these species share?

Felis marmorata (Marbled cat)Notice the marbled pattern of thisanimal's coat. Marmorata means"marble."

Felis domesticus(House cat)Domesticus means"of the house."

Using Binomial Nomenclature Notice in Figure8 that a FIGURE9complete scientific name is written in italics. Only the first let— Marmota monaxter of the first word is capitalized. Notice also that scientific Although there are many common

names for this animal, it has onlynames contain Latin words. Linnaeus used Latin because It was i one scientific name, Marmotathe language that scientists used during that time.

Binomial nomenclature makes it easy for scientists to com—municate because everyone uses the same name for the sameorganism. Using different names can get confusing. Forinstance, people call the animal in Figure9 a woodchuck,groundhog, or whistlepig. Fortunately, it has only one scien—tific name—Marmara monax.

i‘ monax.

Levels of ClassificationThe classification system that scientists use today is based onthe contributions of Linnaeus. But today’s classification systemuses a series of many levels to classify organisms.

To help you understand the levels in classification, imagine ra room filled with everybody from your state. First, all of the .people from your town raise their hands. Then, those fromyour neighborhood raise their hands. Then, those from your lstreet raise their hands. Finally, those from your house raisetheir hands. Each time, fewer people raise their hands. But iyou’d be in all of the groups. The most general group you ‘.belong to is the state. The most specific group is the house. The ‘more levels you share with others, the more you have in com-mon with them. Of course, organisms are not grouped by wherethey live, but rather by their shared characteristics.

The Major Levels of Classification Most biologists todayclassify organisms into eight levels. First, an organism is placedin a broad group, which in turn is divided into more specificgroups. The more classification levels that two organismsshare, the more characteristics they have in common.

Here are the eight classification levels that biologistscommonly use.

° A domain is the highest level of organization.- Within a domain, there are kingdoms.° Within kingdoms, there are phyla (FY luh) (singular

phylum).° Within phyla are classes.- Within classes are orders.° Within orders are families.- Each family contains one or more genera.° Each genus contains one or more species.

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For: Links on kingdomsVisit: www.SciLinks.orgWeb Code: scn-0113

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Classifying an Owl Look at Figure 10 tOSsaeweihdoewvtahrieetgreat

horned owl is classified. The t)op row shONWOtice that as y oforganisms that share the owls domam. d of or anismygumove down the levels, there are fewer km s g s In

. m 'each group The organisms 1n each new groAuP 11.31231 dore 11H° 5 1 u escommon, however. For example> the Class V6 a1birds. The order Strigiformes includes only owls.

KingdomAnimalia

FIGURE 10

Classifying an OwlAs you move down the levelsof classification, the number oforganisms decreases. Theorganisms at lower levels sharemore characteristics with eachother. Interpreting Diagrams Dorobins have more in common withlions or with owls?

OrderStrigiformes

SpeciesBubovirginianus

Domains and KingdomsToday, a three—domain system of classification is commonlyused. Shown in Figure 11, the three domains are Bacteria,Archaea, and Eukarya. Within the domains are kingdoms.Organisms are placed into domains and kingdoms based ontheir cell type, their ability to make food, and the number ofcells in their bodies.

@ClassifyingTest your classifying skillsusing Figure 10. Lookcarefully at the organismspictured together at thekingdom level. Make a list ofthe characteristics that theorganisms share. Then maketwo more lists of sharedcharacteristics—one for theorganisms at the class leveland the other for those atthe genus level. How doesthe number of sharedcharacteristics on your listschange at each level?

Bacteria Although you may not know it, members of thedomain Bacteria are all around you. You can find them in theyogurt you eat, on every surface you touch, and inside yourbody, both when you are healthy and sick. Some bacteria areautotrophs, while others are heterotrophs.

Members of the domain Bacteria are prokaryotes (proh KAree ohtz). Prokaryotes are organisms whose cells lack anucleus. A nucleus (NOO klee us) (plural nuclei) is a dense areain a cell that contains nucleic acids—the chemical instructionsthat direct the cell’s activities. In prokaryotes, nucleic acids arenot contained within a nucleus.

Archaea Deep in the Pacific Ocean, hot gases and moltenrock spew out from a vent in the ocean floor. Surprisingly, agroup of tiny organisms thrives there. They are members of thedomain Archaea (ahr KEE uh), whose name comes from theGreek word for “ancient.” Archaea can be found in some of themost extreme environments on Earth, including hot springs,very salty water, swamps, and the intestines of cows! Scientiststhink that the harsh conditions in which archaea live are simi—lar to those of ancient Earth.

Like bacteria, archaea are unicellular prokaryotes. And likebacteria, some archaea are autotrophs while others are het— Ierotrophs. Archaea are classified in their own domain, how— iever, because their structure and chemical makeup differ from Ithat of bacteria.

Ch"; ' ' What is a nucleus?

' . ; w..~_w__...m........--...w...- FIGURE 11' 'F ”" :‘é‘fiffiboma‘I—ns of Life Three Domains

" ' ' ' In the three—domainsystem of classification,all known organisms

g belong to one of three' domains—Bacteria,

n: Archaea, or Eukarya.

Archaea l

li Protists Fungi Plants Animals

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A Protists: Paramecium

FIGURE 12

Domain EukaryaYou can encounter organisms fromall four kingdoms of Eukarya on ahike through the woods.Making Generalizations Whatcharacteristic do all Eukarya share?

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A Fungi: MushroomsDomain EukaryaWhat do seaweeds, mushrooms, tomatoes, and dogs have incommon? They are all members of the domain Eukarya.Organisms in this domain are eukaryotes (yoo KA ree ohtz)—organisms with cells that contain nuclei. Scientists classifyorganisms m' the domam' Eukarya m'to one of four km'gdoms:protists, fungi, plants, or animals.

Protists A protist (PROH tist) is any eukaryotic organism thatcannot be classified as an animal, plant, or fungus. Because itsmembers are so different from one another, the protist king-dom is sometimes called the “odds and ends” kingdom. Forexample, some protists are autotrophs, while other protists areheterotrophs. Most protists are unicellular, but some, such asseaweeds, are large multicellular organisms.

Fungi If you have eaten mushrooms, then you have eatenfungi (FUN jy). Mushrooms, molds, and mildew are all fungi.Most fungi are multicellular eukaryotes. A few, such as theyeast you use for baking, are unicellular eukaryotes. Fungi arefound almost everywhere on land, but only a few live in freshwater. All fungi are heterotrophs. Most fungi feed by absorbingnutrients from dead or decaying organisms.

Plants Dandelions on a lawn, mosses in a forest, and peas ina garden are familiar members of the plant kingdom. Plants areall multicellular eukaryotes and most live on land. In addition,plants are autotrophs that make their own food. Plants providefood for most of the heterotrophs on land.

The plant kingdom includes a great variety of organisms.Some plants produce flowers, while others do not. Someplants, such as giant redwood trees, can grow very tall. Others,like mosses, never grow taller than a few centimeters.

_————-—JAPlants: Moss

A Animals: Salamander

Animals A dog, a flea on the dog‘s ear, and a cat that the dogchases have much in common because all are animals. All ani- 3'mals are multicellular eulx'aryotes. In addition, all animals are iheterotrophs. Animals have difle‘rent adaptations that allowthem to locate food, capture it, eat it, and digest it. Members ofthe animal kingdom live in diverse environments throughoutliarth. Animals can be tound from ocean depths to mountain-tops, from hot, scalding deserts to cold, icy landscapes.

ReadingJ, Checkpoint Which two kingdoms consist only of heterotrophs?

section ‘ 2 Assessment

)rTarget Reading Skill Asking Questions Usethe answers to the questions you wrote about theheadings to help you answer the questions below.

Reviewing Key Concepts1. a. Why do biologists classify?

b. llll.’-'-‘ ru" 'r Suppose someone tells you that a

C.

2. a.

b.

jaguarundi is classilied in the same genus asa house cat. What characteristics do youthink a iaguarundi might have?Pl What genus name would youexpect a iaguarundi to have? Explain.l ~ , List in order the levels ofclassifi—cation, beginning with domain.

A < Woodchucks areclassified in the same family as squirrels, butin a ditl‘e‘rent lamily than mice. Do wood-chucks have more characteristics in corn—mon with squirrels or mice? Explain.

3. a. Identifying What are the three domainsinto which organisms are classified?

b. Classifying Which two domains includeonly organisms that are prokaryotes?

c. Comparing and Contrasting How do themembers of the two domains of prokaryotesdiffer?

,Volaneb At-Hio'yme Activity\“

Kitchen Classification With a family member,go on a "classification hunt” in the kitchen.Look in your refrigerator, cabinets, anddrawers to discover what classificationsystems your family uses to organize items.Then explain to your family member theimportance of classification in biology.

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