Classification of Living Things Program...

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Interactive Biology Multimedia Courseware Copyright 2001 CyberEd, Inc.

Classification of Living Things

Program Supplement

Cyber Ed® Multimedia Courseware – Classification of Living Things Program Supplement

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Classification of Living Things Table of Contents

Subject: (Jump to Page #) Page # Scenes 1-12 2 Introduction and History of Classification Scenes 13-21 9 Criteria for Classification Scenes 22-32 14 The Five-Kingdom Classification Scheme Scenes 33-38 19 The Six-Kingdom and Three-Domain Classification Schemes Scenes 39-51 22 Taxonomic Keys, Systematics, and Conclusion Quizzes 28 Keys to Quizzes 38 Multiple Choice Exam 39 Exam Key 46 Glossary 47


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Scenes 1-12

Introduction and History of Classification (Scene Number)

I. Introduction 1 A. Importance of classification 1 II. History of classification 2 A. Early humans classified organisms 2 B. Aristotle 3

C. John Ray 4 D. Carolus Linnaeus 4 E. Ernst Haeckel 11 F. R. H. Whittaker/ Lynn Margulis 12


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Scene 1:

Imagine that you want to purchase a particular book, perhaps a copy of the latest novel by your favorite author. You go to your local bookstore and begin searching, but unfortunately, the books are not arranged in any particular order. The novel you want is nowhere in sight, and as you look at the random stacks and piles of books surrounding you, you begin to lose hope of ever finding what you are looking for. Fortunately, most bookstores are better organized than the one in this example. Books are usually classified into different categories such as fiction, history, and self-help. Just as classification helps you organize and make sense of your everyday world, biologists rely on classification to make sense of the incredible diversity of life on this planet. Scientists have classified about 1.7 million different living species, and experts estimate that there may be another 5-100 million species that have not yet been discovered or categorized. Clearly, then, biologists need some sort of system to keep track of all these different species Scene 2:

For as long as humans have existed, some form of classification has existed as well. Making sense of the world through classification seems to be a universal human behavior. Our distant ancestors had to classify organisms as a matter of necessity. Edible plants had to be distinguished from poisonous ones. Likewise, some animals could be hunted for food, while others were dangerous predators that needed to be avoided. Such information was passed down orally from generation to generation. Classification of this sort was essential for survival. Scene 3:

One of the first widely recognized attempts at a systematic classification scheme for living organisms was developed by Aristotle , a Greek philosopher who lived over two thousand years ago. Although he focused his classification efforts primarily on animals, Aristotle divided the organisms of the world into two broad kingdoms: Animalia, the animals, and Plantae, the plants. He divided the animals into water dwellers, land dwellers, and air dwellers, categories that were further subdivided to indicate more subtle distinctions between organisms. For instance, Aristotle distinguished between permanent water dwellers such as fish, and air breathing organisms such as crocodiles and beavers that spend a great deal of time in the water. Aristotle based his classification primarily on the physical characteristics of animals, as well as on their behavior. For example, he noted that some organisms are gregarious, or social, while others tend to be solitary. Aristotle's division of living things into two main groups remained unchanged until the late 1800's.


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Scene 4: During the 17th and 18th centuries, John Ray and Carolus Linnaeus were

responsible for many of the advances made in taxonomy, the field of biology that deals with classifying and naming organisms. In the late 1600's, John Ray, a British naturalist, worked on devising an effective system of classification. Ray made his classifications by looking at the structure of entire plants. In other words, he grouped plants according to similarities in their overall morphology. Morphology is the study of physical form, or structure. Coloration, leaf shape, and flower structure are all examples of morphological data used by Ray. Scene 5:

Born in the early 1700's, Carl Von Linné, or as he eventually came to call himself, Carolus Linnaeus , is considered by many to be the father of modern taxonomy. Linnaeus, a Swedish botanist, was primarily concerned with plants, and like Ray before him, he based his classifications almost entirely upon morphology. Unlike Ray, however, he relied only on the structure of flowers to make his classifications, not the structure of the who le plant. Linnaeus made two very significant contributions to modern taxonomy: the hierarchical classification scheme and binomial nomenclature, both of which are still in use by biologists today. The hierarchical classification scheme consists of seven decreasingly inclusive categories, or taxonomic groupings: kingdom, phylum, class, order, family, genus, and species, though Linnaeus himself did not include the family grouping; it was added later. In plants and fungi, "phylum" is replaced with "division". A handy mnemonic, or memory, device to help you remember the different categories is the sentence, "King Philip came over for good soup". Notice that the first letter of each word in the sentence is the same as the first letter of one of the categories in the classification scheme, and that the letters appear in the same order. Note that in plants and fungi, however, the taxonomic grouping phylum is replaced with the grouping division.


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Scene 6:

Organisms of the same species, the most specific category, are very closely related. Many biologists define a species as a group of organisms that is genetically similar enough to interbreed and produce fertile offspring. For example, although they can vary greatly in appearance, all humans belong to the same species because they can produce fertile offspring. Closely related species are grouped together into a genus. Similar genera are grouped together into a family, and so forth, until the kingdom level is reached. Organisms in the same kingdom may share only broad similarities while organisms at the family and genus level share many specific similarities. The seven levels of classification are further subdivided into sublevels when biologists wish to differentiate subtle distinctions between closely related organisms. Scene 7:

Here is a brief look at the hierarchical classification system using Homo sapiens, or humans, as an example. Humans belong to the kingdom Animalia, along with tigers, elephants, insects, birds, sponges, and many other organisms. Humans belong to the phylum Chordata, along with all other animals with backbones. They are members of the class Mammalia, the mammals, along with other warm-blooded animals. They belong to the order Primates, which includes the apes and monkeys as well. Humans are the only living members of the family Hominidae, genus Homo, and species, Homo sapiens. All early ancestors of humans from the family level down are extinct, meaning none are alive today. As you can see, at each level, humans are grouped with far fewer organisms. At the kingdom level, they are grouped with many other species, but at the species level, it has been narrowed down to just one, Homo sapiens. Scene 8:

Here is another example of the hierarchical classification system, starting with species and working up to the kingdom level. Apis mellifera is the species name of the common honeybee. The genus, Apis, consists of several species of honeybees. Family Apidae contains both honeybees and bumblebees. Honeybees belong to the order Hymenoptera, which consists of bees, wasps, and ants. They are members of the class Insecta, which contains a vast number of insect species, such as butterflies and beetles. Honeybees are members of the phylum Arthropoda, to which crabs, lobsters, spiders, and scorpions belong as well. Finally, they are members of the kingdom Animalia, the same kingdom to which humans belong.


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Scene 9:

In addition to the hierarchical classification system, Linnaeus devised a method of naming organisms called binomial nomenclature. You have already seen two examples of binomial nomenclature, Homo sapiens, and Apis mellifera. In this system, each organism is assigned a two part name, usually in Latin, though sometimes in Greek or other languages. Latin was the language of education in Europe during the time of Linnaeus, and the convention of giving species Latin names has remained in effect to this day. In binomial nomenclature, the first name indicates the genus of the organism, and the second name is the specific epithet, or most precise description of the organism. A species is identified by both the genus name and the specific epithet. For example, humans are most precisely described as Homo sapiens, not just sapiens. The first letter of the genus name is always capitalized while the specific epithet begins with a lowercase letter. These two part names, or scientific names as they are often called, are italicized when written. When you see a name written in this fashion, you will know that it is the most specific designation of an organism. Scene 10:

You might wonder why scientific names are still written in Latin since it's no longer spoken and is no longer the European language of education. One advantage to using Latin is that having a universal scientific language improves communication among scientists, both locally and internationally. Common names of organisms are often misleading. For example, a sea horse is not a horse, nor is a jellyfish a fish. In addition, one organism can have several different common names, or many organisms can be known by a single name. For instance, when a person says, "pine tree", they could be referring to a white pine, Austrian pine, or Bishop pine. However, when they refer to the organism in question as Pinus muricata, the scientific name for the Bishop pine, there is no confusion.


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Scene 11:

In the late 1600's, the development of the light microscope led to the observation of microscopic organisms not visible to the naked eye. These organisms didn't fit neatly into either of the broad kingdoms established by Aristotle; they were not easily classified as either plant or animal. It wasn't until the late 1800's that Ernst Haeckel, a German biologist, proposed a third kingdom, Protoctista, or as it is more commonly called, Protista, to accommodate these microscopic multicellular and unicellular organisms. Multicellular organisms are comprised of more than one cell, while unicellular organisms are single cells. Scene 12:

During the 1960's, R.H. Whittaker developed the concept of a five-kingdom classification system, an idea that was further developed by Lynn Margulis. To the three existing kingdom classifications of Plantae, Animalia, and Protista, Whittaker added two more kingdoms: Monera, the bacteria and cyanobacteria; and Fungi, the mushrooms and yeasts. The five-kingdom classification scheme is still in use today, though many in the scientific community are beginning to favor a six-or-more-kingdom classification scheme, or a scheme composed of three broad domains, or as they are also known, empires. Domains are recognized by some biologists as taxonomic groupings that exist above the kingdom level. These classification schemes will be explored in greater detail later in this program.


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Scenes 13-21 Criteria for Classification

III. Criteria for classification 13 A. Morphology 13 B. Behavior 13 C. Evolution/Phylogeny 14 D. Fossil Record 18 E. Embryology 19 F. DNA Analysis 20 1. Molecular Clocks 20 2. DNA Hybridization 21


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Scene 13: Early taxonomists such as Aristotle, Ray, and Linnaeus relied primarily on

morphological data, as do many modern taxonomists. They also relied on behavioral observations, such as Aristotle's distinction between social animals and solitary animals. Behavioral data can include such things as how organisms obtain nutrition and how they reproduce. Keep in mind that current technology such as light microscopy, electron microscopy, and genetic analysis was not available to these early pioneers in the field of classification. They constructed the best classification schemes they could with the technology and data at their disposal. Scene 14:

Books, organisms, or anything else can be grouped or classified according to a variety of criteria. There is no right way to classify things, but some systems of classification may lend themselves to certain applications more readily than do others. Biologists could choose to classify organisms according to the month in which they were discovered. They could also classify them according to size, color, or a variety of other characteristics. Are such classification schemes valid? Certainly, but would they be of any value to biologists? The fact that a particular organism was discovered in December tells very little about how it fits in with the rest of the known species. How do biologists decide on a system of classification? A classification of living things can function as more than just an arbitrary grouping of organisms. If properly constructed, it can also tell biologists something about how organisms are related to each other, not just in terms of physical similarities, but in terms of descent and common ancestry as well. The study of these evolutionary lines of descent is called phylogeny. Scene 15:

English naturalists Charles Darwin and Alfred Wallace, who arrived independently at many of the same conclusions, synthesized existing ideas about evolution and brought the concept to the attention of the scientific community. Before evolution was widely accepted, it was assumed that all species had existed in their present forms since they first appeared on the planet. In the mid-1800's, Darwin and Wallace popularized the notion that this was not the case, and that species change over time. With the development of Darwin's theory of evolution, taxonomists became increasingly aware of the evolutionary relationships among organisms.


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Scene 16:

In brief, Darwin's theory suggests that all life originated from a common ancestor, and diverged over time into a variety of species. The diversity of life we now see arises from natural variations that occur among populations. Some variations, such as eye color in humans, have little or no effect on survival. Others, however, such as wing coloration that serves to camouflage moths from predators, can affect the fitness, or overall chance of survival, of an organism. Those variations that better allow organisms to survive in their environment will probably be passed on to future generations because organisms possessing those variations have a better chance of maturing and reproducing. In this manner, variations or adaptations that confer a survival advantage are passed on to new generations. Over time, the accumulation of variations can lead to the development of new species. Scene 17:

Ernst Haeckel, who proposed the kingdom Protista, was one of the first biologists to call attention to the phylogenetic, or evolutionary, connections between the various species of organisms. He was one of the first biologists to draw a family tree of sorts to map these phylogenetic relationships. Just as your own family has a family tree, it is possible to construct a family tree for all living things, past and present. If you have a brother or sister, then you and your sibling share your parents as common ancestors. Some people are able to trace these ancestral family relationships back for many centuries. Likewise, somewhat similar relationships exist between species, only on a much broader evolutionary level than in direct family relationships. If a system of classification is designed to reflect these relationships, it can allow biologists to see how existing species are related to each other, as well as where newly discovered species should fit into the overall classification scheme. Scene 18:

As Darwin's theory of evolution gained acceptance within the scientific community, people began to look at the fossil record differently. It became apparent that some fossils represented earlier ancestors of organisms found today, while others seemed to have no living counterparts in the modern world because those species are now extinct. All of this supports the theory that species change over time. Although useful, the fossil record presents biologists with a number of challenges. Fossils are only formed under certain conditions. Many soft tissued organisms decay before they form fossils, while organisms with shells or other hard body parts are more likely to leave fossils. Add to this the fact that fossils must end up in a location where someone can actually find them, and you can begin to see how difficult it is to reconstruct patterns of descent through fossil evidence. In spite of these difficulties, fossil evidence has provided biologists with some valuable clues. It can help to establish the approximate date at which a species first appeared, and in some cases, fossil evidence can be used to reconstruct a lineage of descent.


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Scene 19:

Another area of interest for taxonomists is embryology, or the study of the early development of organisms. Ernst Haeckel observed that the embryological development of some organisms seems to recapitulate, or replay to a certain extent, the phylogeny of those organisms. In other words, during their development, some organisms go through stages in which they resemble ancestral organisms. For example, some early ancestors of humans and other vertebrates possessed gills and tails. Humans possess vestigial gills and a tail during certain phases of their embryological development, which are lost before birth. Modern biologists recognize that some sort of a connection between phylogeny and embryological development exists, and they are still attempting to understand its significance. Scene 20:

One of the more recent tools to become available to the taxonomist is genetic analysis. DNA is the spiraled, or helical, double-stranded molecule through which genetic information is passed from generation to generation. It is essential to all life, and provides the blueprint for the growth and development of organisms. DNA changes gradually over time through the process of mutation, or the occurrence of random changes and variations in the DNA sequence. Some DNA sequences mutate at a more rapid rate than others, but the rate for a particular sequence tends to remain fairly constant over time, which allows biologists to use these changes as a sort of molecular clock. This molecular clock is useful in determining the relationships among organisms. By comparing the DNA of an ancestral species with that of its descendants, biologists can estimate when the descendants split from the ancestral species, based on the amount of difference between specific DNA sequences. Scene 21:

DNA hybridization experiments allow biologists to determine the level of similarity between DNA sequences in different organisms. When double-stranded DNA is heated in solution, the bonds that form the rungs of the twisted DNA ladder dissolve, and the two long strands come apart. When the solution is cooled, the two strands bond completely to form once again the original double helix, or twisted ladder shape. In DNA hybridization experiments, double-stranded DNA from two different organisms is heated to separate the strands, and single strands from each


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organism are combined in a separate container. If the DNA sequences of the strands are similar, they will bond more completely than if they are different. In other words, the degree of bonding that takes place between the strands indicates the degree of similarity between them, and indirectly, the degree of similarity between the organisms from which the strands were taken.


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Scenes 22-32 The Five-Kingdom Classification Scheme

IV. The Five-Kingdom Classification Scheme 22 A. Introduction 22 B. Monera 23 C. Protista 25 D. Fungi 27 E. Plantae 29 F. Animalia 31


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Scene 22:

Whether they base their classifications primarily on morphology and fossil evidence or on the more recent techniques of embryology and DNA analysis, all taxonomists classify organisms according to a particular classification scheme. Although more and more biologists are leaning towards a six-plus-kingdom classification scheme, a three-domain classification scheme, or some combination thereof, the five-kingdom classification scheme proposed by R. H. Whittaker is still widely used. This system groups all known living organisms into five broad kingdoms, or categories, based primarily on their cellular organization, as well as on how they obtain their nutrition. Keep in mind that within the five-kingdom classification scheme, the kingdom is the broadest taxonomic grouping. Each kingdom contains a vast number of different species. Scene 23:

The kingdom Monera consists of unicellular organisms. In other words, each individual organism is comprised of a single cell. Monerans are prokaryotic, meaning that their DNA is not contained within a membrane-bound nucleus. Instead, a single large circular strand of DNA floats freely in the cytoplasm in a dense area called the nucleoid region. Most of the monerans are aerobic organisms, meaning they need oxygen to grow, but some are obligate anaerobes, meaning that they need anaerobic, or oxygen-free, conditions to survive. Monerans generally display one of three basic shapes. The first of these shapes is the rod. The second is a spherical shape called a coccus. The third is the spirillum, or spiral shape.


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Scene 24: The primary groups within Kingdom Monera are the eubacteria, or "true

bacteria", and the cyanobacteria. Many of the eubacteria are heterotrophic, meaning that they cannot photosynthesize or produce their own nourishment through chemical means and therefore have to rely on a food source. Most monerans feed on decomposing matter such as leaves and dead animals. The cyanobacteria, or as they were once called, the blue green algae, were originally classified with eukaryotic algae, but it is now known that they are prokaryotic. Cyanobacteria are autotrophs, or "self feeders", and obtain their nourishment through photosynthesis, a process where energy from the sun is used to convert carbon dioxide and water to sugars. In the five-kingdom classification scheme, the archaebacteria are placed in the kingdom Monera as well. Archaebacteria, or as they are more properly called, archaea, are prokaryotic organisms that appear similar to bacteria. As you will see, however, there is a growing dispute over grouping the archaea with the monerans. This will be discussed in greater detail in the sections on the six-kingdom classification scheme and the three-domain classification scheme. Scene 25:

The kingdom Protista consists of the algae, which are plant-like; the protozoa, or animal-like protists; water molds; and slime molds. The protists are all eukaryotic, meaning that they possess a membrane-bound nucleus in which genetic information is stored. They are typically unicellular organisms, though some, such as seaweed, are multicellular. The classification of organisms within this kingdom, particularly the multicellular organisms, is being debated by biologists. The fact that protists are so diverse indicates that the kingdom Protista may need to be split into several different taxonomic groups. Scene 26:

Algae produce their own nourishment through the process of photosynthesis, and their cells are usually surrounded by a cell wall. Whereas the algae are primarily plantlike, the protozoa, a name that literally means "first animals", are more animal-like. The protozoa are usually found in water, but can be found in moist soil and in other organisms as well. Some protozoa are heterotrophic, feeding on other organisms or on decaying matter. Still others are parasitic, meaning that they obtain their nourishment from a living host organism. In addition, the kingdom protista contains the slime molds and water molds. Slime molds are mobile during certain life stages. They typically engulf their food or prey for internal digestion. Water molds have a body composed of filaments, and their cells are surrounded by a cell wall composed of a compound known as cellulose. Most water molds are parasitic. They differ from fungi in their reproductive cycle.


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Scene 27: All members of Kingdom Fungi are eukaryotic, and most are multicellular.

One noteworthy exception is yeasts, single celled organisms often used in the production of bread and alcoholic beverages. All fungi are heterotrophs, and most are saprotrophs, which means they obtain their nourishment from decaying matter. They digest their food externally, and then absorb the resulting nutrients through their cell wall and plasma membrane. Almost all fungi are filamentous in nature. The cells of most fungi are surrounded by cell walls composed of a compound known as chitin. Fungi are non-motile, meaning that they cannot move under their own power. They obtain their nourishment by gradually growing towards a food source. Scene 28:

The kingdom Fungi contains a wide variety of organisms, which are divided into four main divisions. Division zygomycota includes bread mold, which you may see if you leave bread out on the counter. Ascomycota, the sac fungi, includes the previously mentioned yeasts, as well as morels and truffles, both of which are prized by many as delicacies. Basidiomycota includes the edible mushrooms found in the produce section of your local grocery store, as well as the potentially poisonous mushrooms on your lawn. Division deuteromycota, the imperfect fungi, includes the fungus responsible for athlete's foot. Unlike the other fungi, which can exhibit both sexual and asexual reproduction, the deuteromycota have only been observed to reproduce through asexual means. Scene 29:

The kingdom Plantae is comprised of multicellular eukaryotes. The cells of plants are surrounded by cell walls composed of cellulose. Most plants have well-differentiated tissues, or groups of similar cells that perform a specific function, such as transporting minerals and water. In addition, most plants have specialized structures in the form of roots, stems, and leaves. Roots allow plants to absorb water and nutrients from the soil. Stems provide structural support for leaves and allow for the transport of water and nutrients throughout the plant. Leaves contain structures called chloroplasts, which allow plants to harness the energy of the sun to produce their own nourishment through photosynthesis. Therefore, plants are autotrophs.


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Scene 30: Plants can be divided into three very broad categories: nonvascular

plants, seedless vascular plants, and seed vascular plants. Nonvascular plants lack vascular tissue. Vascular plants, on the other hand, possess vascular tissue consisting of xylem, which transports water and minerals from the soil into the plant, and phloem, which transports nutrients from one part of the plant to another. The seed vascular plants are further subdivided into gymnosperms and angiosperms. Gymnosperm literally means "naked seed", and as the name suggests, the seeds of gymnosperms are not covered by any sort of fruit. The seeds of angiosperms, on the other hand, are enclosed within fruits. Angiosperms are further divided into two classes: magnoliopsida, the dicotyledons, and liliopsida, the monocotyledons. The distinction between the two is based on the number of cotyledons, or seed leaves, present when the seed germinates. Dicotyledons, or dicots, have two cotyledons while monocotyledons, or monocots, have one. Scene 31:

The kingdom Animalia is comprised of multicellular eukaryotic organisms. Most animals have specific tissues and organs, which are groupings of tissues that perform a specific function. All animals are heterotrophic, and most digest their food within a central body cavity. Most are motile, meaning that they can move about under their own power. In addition, animals can usually reproduce sexually. When you think of animals, you probably think of cats or dogs, or perhaps farm animals such as cows and horses. While these are indeed animals, vertebrates, or animals with backbones, such as the ones just mentioned, comprise only a small percentage of the animal kingdom. Only about five percent of animals are vertebrates. The remaining 95 percent or so are invertebrates, or organisms that lack a backbone. Scene 32:

In addition to the presence or absence of a backbone, biologists use several other criteria to classify animals. One such criterion is body symmetry. Animals display one of three types of symmetry. They can be asymmetrical, which means that they lack any sort of symmetry. They can also display radial, or circular symmetry. In addition, some animals display bilateral symmetry, meaning that they have a distinct right and left side. Animals can also be classified on the basis of how many tissue layers they have. Some animals, such as sponges, lack distinct tissue layers. Others have two distinct tissue layers that arise during the development of the embryo, while some have three tissue layers. These tissue layers give rise to another means of animal classification, the presence or absence of a coelom, a specially lined body cavity within which internal organs are located. Only animals with three tissue layers develop a true coelom. Finally, animals can be classified based on whether or not they are segmented. Segments are similar repeating units, such as those found in an earthworm.


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Scenes 33-38 The Six-Kingdom and Three-Domain Classification Schemes

V. The Six-Kingdom Classification Scheme 33 A. Characteristics of Archaea 33 B. Splitting of Kingdom Monera 34 C. Differences Between Archaea and Bacteria 34 VI. The Three-Domain Classification Scheme 37 A. Problems with the Six-Kingdom Classification Scheme 37 B. The Three Domains 37 C. Controversy Over Protista 38


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Scene 33:

As mentioned earlier during the discussion of the kingdom Monera, the archaea, or as they were formerly called, the archaebacteria, are at the center of a controversy regarding the five and six-kingdom classification systems. Most archaea are extremophiles, which means that they live in extreme environments. Some of the archaea are thermophiles, or heat loving organisms. They are found in hot springs as well as in thermal vents on the ocean floor, and some can thrive in water temperatures exceeding 100° Celsius. Others are halophiles, or salt loving organisms, and can survive in extremely salty water. Still others are acidophiles, which thrive under extremely acidic conditions. Scene 34:

Until fairly recently, the archaea were classified in the kingdom Monera along with the bacteria and cyanobacteria, and were viewed as a peculiar form of bacteria. In 1977, Carl Woese proposed that the archaea were different enough from other monerans that they belonged in a separate taxonomic group. Some biologists establish this taxonomic group at the kingdom level, by splitting the kingdom monera into two new kingdoms, Archaebacteria and Eubacteria, for a total of six kingdoms. Woese based his proposal on his analysis of single-stranded genetic material called RNA that is important in protein synthesis and is also found in cellular structures called ribosomes. He found that in terms of ribosomal RNA, the archaea have as much, or perhaps even more in common with eukaryotic organisms than they do with bacteria. Scene 35:

While both archaea and bacteria are unicellular prokaryotic organisms, there are a number of differences between the two. In addition to the differences in ribosomal RNA, the ribosomal proteins of archaea are more similar to those of eukaryotic organisms than they are to those of bacteria. Furthermore, the way in which archaea initiate the process of making copies of their DNA, a process known as transcription, bears more in common with transcription in eukaryotic organisms than in bacteria. Archaea also differ from bacteria in the chemical composition of their plasma membranes and cell walls. Finally, although most archaea are autotrophic, they do not photosynthesize. Instead, they rely on chemical processes to produce their own nourishment.


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Scene 36: The simple solution to the classification riddle posed by the archaea is to

split the kingdom Monera into two new kingdoms, placing the archaea and the bacteria in their own kingdoms. The rest of the five-kingdom classification scheme remains unchanged. However, Woese's research suggests that the solution might not be so simple. As you just learned, the archaea, though they are prokaryotic organisms, share much in common with eukaryotes. Woese has suggested that the archaea and the bacteria split from a common ancestor very early on in the evolution of life on earth, and that the eukaryotes actually evolved from the archaea at a later date. Scene 37:

It is possible that placing the archaea in their own kingdom does not adequately acknowledge their evolutionary significance. Woese has suggested that a new taxonomic grouping above the kingdom level should be established. This grouping is called the domain, or empire. He proposed three domains: Archaea; Eubacteria, which consists of the bacteria and the cyanobacteria; and Eukarya, which consists of the kingdoms Protista, Fungi, Plantae, and Animalia. The domain Archaea is further divided into two kingdoms: Euryarchaeota and Crenarchaeota. Euryarchaeota consists of the methanogens, or methane producing and tolerating organisms, halophiles, and thermophiles. Crenarchaeota consists of hyperthermophiles, or extreme heat lovers, as well as some non-thermophilic archaea. Scene 38:

In addition, the attempt to establish a system of classification based on three domains has further aggravated the controversy surrounding classification of organisms within the kingdom Protista, which you learned about earlier. Some biologists suggest that the kingdom protista should be divided into three new kingdoms: Ciliata, Flagellata, and Microsporidia. Still others feel that there should be six kingdoms under the domain Eukarya: Protozoa, Slime Molds, Algae, Fungi, Plantae, and Animalia. As you can see, there are many opinions about how organisms should be organized within this new classification system. Debate on the subject is likely to continue for quite some time, and it is certainly possible, in fact probable, that new classification schemes will arise in the future.


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Scenes 39-51 Taxonomic Keys, Systematics, and Conclusion

VII. Taxonomic Keys 39 A. Definition 40 B. Example 40 VIII. Systematics 41 A. Definition 41 B. Traditiona l School of Systematics 42 1. Phylogenetic Trees 42 C. Cladistics 44 1. Criteria 44 a. Synapomorphies 44 2. Cladograms 46 D. Phenetics 48 IX. Summary 50 X. Conclusion 51


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Scene 39:

Regardless of which classification scheme taxonomists choose to follow, they all utilize a similar approach to identify an unrecognized organism. You are probably familiar with the game 20 questions, where one player thinks of an object, and the other players try to guess the identity of the object by asking questions that narrow down the possibilities. Suppose your first question is whether or not the object is a person. If the answer is yes, then your next logical question might be whether the person is female or male. If the answer to the first question is no, however, it will probably lead you to ask a different set of questions. When biologists wish to identify organisms they don't immediately recognize, they play their own version of 20 questions to narrow down the possibilities. Instead of making up their own questions as they go along, biologists rely on an organized series of questions called a taxonomic key. These keys are primarily useful in identifying organisms that have already been classified. If a key doesn't lead to a positive identification, then the taxonomist has either made a mistake, or perhaps discovered a new species. Scene 40:

Taxonomic keys consist of a series of choices. Most keys are dichotomous, meaning that at each step in the process, there are two divergent choices, such as whether an organism is multicellular or unicellular. Just as each question might lead you to a different set of questions in a game of 20 questions, each choice in a taxonomic key leads to a different section of the key, which contains more specific choices to further narrow down the identity of the organism in question. Taxonomic keys can be fairly broad, such as a key for identifying the different classes of vertebrate animals, or they can be very specific, such as a key for identifying the various subspecies of a particular insect. The first question in a key for identifying vertebrates might be whether or not the animal in question has a backbone. If the answer is no , then a key for vertebrates is of little use in identifying the animal. If the answer is yes, however, the key directs the user to the next section. The next section might ask whether or not the animal has gills and fins. If the answer is yes, then the animal is a fish. If the answer is no, the key will direct the user to the next section. This process continues until a positive identification is made.


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Scene 41: The terms systematics and taxonomy are often used interchangeably,

but taxonomy is actually a subdivision of systematics. Systematics is the study of living organisms, both in terms of their diversity and in terms of their interrelationships from the global level to the level of the individual organism. Systematics, which has a much broader focus than taxonomy, includes such other areas of biology as ecology, biochemistry, and genetics. There are three main schools of systematics: the traditional school of systematics, cladistics, and phenetics. As you'll learn during the next few scenes, each of these groups approaches the problem of studying the diversity and interrelationships of organisms in a slightly different fashion. Scene 42:

The traditional school of systematics stresses common ancestry of organisms, as well as the degree of morphological, or structural, similarity between organisms in its approach to taxonomy. In this system, an organism that shows a high degree of evolutionary change or adaptation to a new environment may not be grouped with the common ancestor from which it evolved. The ancestral relationships of organisms are often visually represented in the form of a phylogenetic tree, a branching diagram that can be read as a sort of flow chart. Species that have evolved more recently are placed at the tips of the branches. The forks where branches split represent ancestral species evolving to form more recent species. Following the main trunk down to the roots of the phylogenetic tree leads to earlier organisms such as cyanobacteria and archaea. The deepest roots of the universal phylogenetic tree are still a mystery. Biologists have not yet determined the nature of the first common ancestor of all life. Scene 43:

On your screen is an example of a phylogenetic tree showing the ancestry of the giant panda and the red panda. Both species are found in China, and both feed exclusively on bamboo. However, the giant panda possesses an opposable thumb, while the red panda lacks this characteristic. Notice that while the red panda and the giant panda share a distant common carnivorous ancestor, the giant panda actually shares a more recent common ancestor with bears than with the red panda. The red panda, on the other hand, actually shares a more recent common ancestor with the raccoon than it does with the giant panda. Scene 44:

The second school of systematics is called cladistics. Cladistics is favored by many biologists because it takes evolutionary theory into account. Cladists, or people who study cladistics, base their classification of organisms on common ancestry. The way they determine this ancestry is through the analysis of a particular form of characteristic, called a shared derived characteristic, or synapomorphy. Synapomorphies are characteristics that arise in a common ancestor and are passed on to all of its descendant species. They are called


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shared derived characteristics because they are shared by closely related species, and are derived from a common ancestor. Note that synapomorphies arise as new traits in a common ancestor and are subsequently passed on to its descendants instead of being inherited by that ancestor and then passed on to its descendants. Scene 45:

An example of a synapomorphy is retractable claws. It can be inferred that retractable claws, a trait not all mammals possess, developed at some point in an ancestor common to both cougars and housecats, and were not found in any mammals before this point. This characteristic was derived in both housecats and cougars from the common ancestor. In this case, the presence of a shared derived characteristic allows cladists to classify the various felines as being more related to each other than they are to other mammals, such as bears and humans which lack the characteristic. If retractable claws had existed in a more distant ancestral mammal before the common ancestor of housecats and cougars evolved, then it is quite probable that more mammals would have inherited retractable claws. Scene 46:

Cladists look at a wide variety of synapomorphies in an attempt to create what are known as monophyletic groupings of organisms. A monophyletic grouping of organisms consists of a common ancestor and all its descendants. Cladists refer to these groupings as clades. Ideally, organisms in a clade should be more closely related to each other than they are to any other organisms. The branching diagrams cladists construct as a visual representation of these ancestral relationships are called cladograms. Each branching point on a cladogram represents a synapomorphy. Organisms on one side of the branch share the synapomorphy, while those on the other side lack it. The construction of cladograms can be fairly involved. For this reason, cladists usually rely on computers to assist in their construction. Although the branching patterns of cladograms resemble those of phylogenetic trees, the two differ in that cladograms are more objective because each branching point is defined by the presence or absence of a particular shared derived characteristic. Phylogenetic trees show relationships between organisms, but not the data used to determine such relationships.


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Scene 47: On the screen is a simplified version of a cladogram. Notice that each

branching point indicates a synapomorphy, or shared derived characteristic. The first shared derived characteristic, the presence of bilateral symmetry, distinguishes the clade of eel, lizard, horse, and human from starfish. The presence of four limbs distinguishes the clade of lizard, horse, and human from eels and starfish. The presence of fur distinguishes the clade of horse and human from starfish, eels, and lizards, while the final synapomorphy, the presence of an opposable thumb, distinguishes humans from all other organisms in the cladogram. Keep in mind that cladograms are normally constructed using a wide variety of characteristics, as opposed to just four as in this simplified example. Scene 48:

The third approach to systematics is called phenetics, or numerical phenetics. Pheneticists feel that it is impossible to reconstruct phylogenetic relationships, so they don’t take them into account when classifying organisms. Phentics has fewer supporters than the other schools of systematics because most taxonomists are primarily interested in phylogenetic relationships. In phenetics, species are grouped according to the overall number of similar character traits they share. The more traits two organisms share, the more closely they are grouped together. Whereas cladists rely only on shared derived characteristics in the construction of cladograms, pheneticists look at as many characteristics as possible. These results are then averaged, usually by a computer, to provide an overall measure of similarity between organisms. By looking at as wide a variety of characteristics as possible and averaging the results, pheneticists hope to arrive at an accurate classification scheme. The results of phenetic analysis are portrayed in a form of tree called a phenogram. Scene 49:

In the phenogram on your screen, the lion and tiger are grouped together not because they share a recent common ancestor, but because they share a large number of traits. Likewise, the housecat is closer to the lion and tiger not because they share a closer phylogenetic relationship with each other than they do with the other organisms in the phenogram, but because they share a greater number of traits. Pheneticists argue that such classifications are more objective than either cladistics or traditional systematics because they rely entirely on data in the form of characteristics instead of relying on presumed phylogenetic relationships. However, the same set of data can produce very different phenograms depending on how it is handled.


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Scene 50: In this program, you learned that biologists have probably only classified a

small percentage of the estimated number of species living on this planet. You also learned that classification is a dynamic study. Classification schemes are constantly revised and updated as new data becomes available and as new ideas emerge. In addition, advances in technology such as light microscopy and more recently, genetic analysis, can lead to new classification schemes as well. Our current classification schemes utilize evolutionary relationships based on the best available data. Classification is very important because it allows biologists to keep track of and make sense of the incredible diversity of living organisms. Scene 51:

As biologists arrive at a better understanding of the roles different organisms play in the biosphere, classification will become an increasingly valuable tool. Tropical rainforests throughout the world, which contain many undiscovered species, are being rapidly deforested. Many of these species may become extinct before biologists become aware of their existence. Sadly, little emphasis has been placed on classification in recent years, and some biologists fear that it will become a lost art. As our current generation of taxonomists begins to retire, there may be no one to continue their work. Classification provides a broad framework within which details about the individual species can be placed. If biologists lose this framework, they may lose a great deal of understanding as well. Hopefully, though, new generations of biologists, perhaps even you, will see the importance of classification, and will continue the process which began with Aristotle, and which continues to this day.


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Quiz One Introduction and History of Classification

1. Early humans relied on classification for entertainment purposes only. A. True B. False 2. Biologists have classified roughly how many different species? A. one thousand B. ten billion C. over one million D. None of the above 3. Aristotle divided living organisms into two categories:__________. A. Plantae and Animalia B. Animalia and Protista C. Protista and Monera D. Animalia and Monera 4. Linnaeus made two significant contributions to modern taxonomy: binomial

nomenclature and __________. A. cladistics B. the five-kingdom classification scheme C. DNA hybridization D. the hierarchical classification scheme 5. In binomial nomenclature__________. A. organisms are always named in Greek B. several organisms can share the same name C. organisms are assigned a two part name, usually in Latin D. names are never italicized when written 6. The most specific taxonomic grouping in the hierarchical classification

scheme is __________. A. phylum B. species C. genus D. kingdom 7. Aristotle based his classification of living things primarily on phylogeny. A. True B. False


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8. Taxonomy is the field of biology that deals with__________. A. classifying and naming organisms B. evolution C. ecology D. morphology 9. In binomial nomenclature, what is the correct way to write the species name

for human beings? A. homo sapiens B. Homo Sapiens C. homo Sapiens D. Homo sapiens 10. Both Linnaeus and John Ray focused their classification efforts primarily on

__________. A. bacteria B. plants C. archaea D. animals


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Quiz Two Criteria for Classification

1. Morphology is the study of the evolutionary relationships between organisms. A. True B. False 2. Embryology is__________. A. the study of the evolutionary relationships of organisms B. the study of the early development of organisms C. the study of the behavior of organisms D. none of the above 3. Which of the following is true about phylogeny? A. it involves the study of the evolutionary relationships between organisms. B. it relies primarily on synapomorphies to classify organisms. C. both A and B are true. D. neither A nor B are true. 4. Mutation is the occurrence of __________. A. new species B. eukaryotic organisms C. random changes or variations in a DNA sequence D. the transformation of DNA into RNA 5. In DNA hybridization experiments, DNA from one organism is combined with

ribosomes from another organism. A. True B. False 6. Fossils__________. A. are only formed under certain conditions B. are more likely to form from the remains of soft-bodied organisms C. are too different from organisms found today to be of any use to biologists D. all of the above are true 7. Early taxonomists relied primarily on__________. A. phylogenetic data B. genetic data C. morphological data D. biochemical data


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8. Which of the following are examples of morphological data? A. leaf shape B. flower coloration C. both A and B D. neither A nor B 9. Some DNA sequences change at a more rapid rate than others, but the rate

of change for a particular sequence of DNA tends to remain fairly constant over time.

A. True B. False 10. Charles Darwin and Alfred Wallace worked together to develop the theory of

evolution. A. True B. False


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Quiz Three The Five-Kingdom Classification Scheme

1. The kingdom Protista is comprised of__________. A. both multicellular and unicellular organisms B. unicellular organisms C. multicellular organisms D. none of the above 2. Autotrophs are organisms that__________. A. lack DNA and RNA B. produce their own nourishment through photosynthesis or other means C. always possess a membrane-bound nucleus D. All of the above 3. Eukaryotic organisms__________. A. lack a membrane bound nucleus that contains genetic information B. possess a membrane bound nucleus that contains genetic information C. belong to the kingdom Monera D. are always unicellular 4. Fungi do not carry out photosynthesis. A. True B. False 5. Vertebrates comprise roughly what percentage of animals? A. ninety five percent B. five percent C. fifty percent D. all animals are vertebrates. 6. Plants can be divided into what three broad categories? A. eukaryotic, prokaryotic, and dikaryotic B. autotrophic, heterotrophic, and saprotrophic C. radial, bilateral, and asymmetrical D. nonvascular, seedless vascular, and seed vascular 7. Slime molds belong to the kingdom__________. A. Animalia B. Fungi C. Protista D. Monera


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8. Humans possess vestigial gills and a tail during certain phases of their embryological development.

A. True B. False 9. All animals are multicellular. A. True B. False 10. In the five-kingdom classification scheme, archaea are placed in which

kingdom? A. Protista B. Fungi C. Cyanobacteria D. Monera


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Quiz Four The Six-Kingdom and Three-Domain Classification Schemes

1. The three domains in the three-domain classification scheme consist of

Archaea, Eukarya and__________. A. Plantae B. Animalia C. Mammalia D. Eubacteria 2. Many of the archaea are__________. A. vertebrates B. extremophiles C. eukaryotic D. fungi 3. In order to survive, aerobic organisms require__________. A. oxygen B. sunlight C. Both A and B are correct D. Neither A nor B is correct 4. In the six-kingdom classification scheme, kingdom monera is split into which

two kingdoms? A. Plantae and Animalia B. Protista and Eukarya C. Autotrophae and Heterotrophae D. Eubacteria and Archaebacteria 5. Halophiles thrive under conditions of extreme__________. A. heat B. salt concentration C. acidity D. cold 6. Carl Woese based his research on RNA found in what cellular structures? A. DNA B. ribosomes C. cell walls D. plasma membranes 7. Many biologists suggest that the kingdom Plantae is diverse enough that it

needs to be split into several kingdoms. A. True B. false


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8. Archaea differ from bacteria in that_________. A. they have different ribosomal RNA B. the chemical composition of their plasma membranes is different C. they initiate transcription in a different fashion D. all of the above 9. Carl Woese suggested that eukaryotic organisms evolved from__________. A. bacteria B. archaea C. fungi D. plants 10. Domains are also known as__________. A. empires B. townships C. kingdoms D. areas


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Quiz Five Taxonomic Keys, Systematics, and Conclusion

1. Phylogenetic trees are visual representations of__________. A. systematics B. cladistics C. ancestral relationships of organisms D. metabolic pathways 2. A clade consists of__________. A. prokaryotic organisms B. a common ancestor and all its descendants C. eukaryotic organisms D. none of the above 3. Synapomorphies are __________. A. distant relatives of bacteria B. not useful in determining phylogenetic relationships C. eukaryotic D. none of the above 4. Cladograms _________. A. contain the data used to determine phylogenetic relationships B. lack the data used to determine phylogenetic relationships C. are the same as phylogenetic trees D. are only useful when classifying fungi 5. Taxonomic keys can only be used with the five-kingdom classification

scheme. A. True B. False 6. In a phylogenetic tree, more recent species are placed__________. A. in the trunk B. in the roots C. at the tips of the branches D. none of the above 7. In phenetics, classification is based on__________. A. shared derived characteristics only B. as many characteristics as possible C. phylogenetic relationships D. the month in which organisms were discovered


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8. Cladograms are constructed using__________. A. synapomorphies B. DNA C. phenetics D. all of the above 9. Which school of systematics takes evolutionary theory into account? A. taxonomy B. phenetics C. the traditional school of systematics D. cladistics 10. Taxonomic keys are usually__________. A. monochotomous B. trichotomous C. dichotomous D. transchotomous


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Key to Quizzes Quiz One Quiz Two Quiz Three Quiz Four Quiz Five 1. B 1. B 1. A 1. D 1. C 2. C 2. B 2. B 2. B 2. B 3. A 3. A 3. B 3. A 3. D 4. D 4. C 4. A 4. D 4. A 5. C 5. B 5. B 5. B 5. B 6. B 6. A 6. D 6. B 6. C 7. B 7. C 7. C 7. B 7. B 8. A 8. C 8. A 8. D 8. A 9. D 9. A 9. A 9. B 9. D 10. B 10. B 10. D 10. A 10. C


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Comprehensive Multiple Choice Exam

1. Early humans relied on classification for entertainment purposes only. A. True B. False 2. Biologists have classified roughly how many different species? A. one thousand B. ten billion C. over one million D. None of the above 3. Aristotle divided living organisms into two categories:__________. A. Plantae and Animalia B. Animalia and Protista C. Protista and Monera D. Animalia and Monera 4. Morphology is the study of the evolutionary relationships between organisms. A. True B. False 5. Linnaeus made two significant contributions to modern taxonomy: binomial

nomenclature and __________. A. cladistics B. the five-kingdom classification scheme C. DNA hybridization D. the hierarchical classification scheme 6. In binomial nomenclature__________. A. organisms are always named in Greek B. several organisms can share the same name C. organisms are assigned a two part name, usually in Latin D. names are never italicized when written 7. The kingdom Protista is comprised of__________. A. both multicellular and unicellular organisms B. unicellular organisms C. multicellular organisms D. none of the above


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8. Which of the following is true about phylogeny? A. it involves the study of the evolutionary relationships between organisms. B. it relies primarily on synapomorphies to classify organisms. C. both A and B are true. D. neither A nor B are true. 9. Mutation is the occurrence of __________. A. new species B. eukaryotic organisms C. random changes or variations in a DNA sequence D. the transformation of DNA into RNA 10. In DNA hybridization experiments, DNA from one organism is combined with

ribosomes from another organism. A. True B. False 11. Autotrophs are organisms that__________. A. lack DNA and RNA B. produce their own nourishment through photosynthesis or other means C. always possess a membrane-bound nucleus D. All of the above 12. Eukaryotic organisms__________. A. lack a membrane bound nucleus that contains genetic information B. possess a membrane bound nucleus that contains genetic information C. belong to the kingdom Monera D. are a lways unicellular 13. Fungi do not carry out photosynthesis. A. True B. False 14. Vertebrates comprise roughly what percentage of animals? A. ninety five percent B. five percent C. fifty percent D. all animals are vertebrates. 15. Plants can be divided into what three broad categories? A. eukaryotic, prokaryotic, and dikaryotic B. autotrophic, heterotrophic, and saprotrophic C. radial, bilateral, and asymmetrical D. nonvascular, seedless vascular, and seed vascular


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16. The three domains in the three-domain classification scheme consist of Archaea, Eukarya and__________.

A. Plantae B. Animalia C. Mammalia D. Eubacteria 17. Slime molds belong to the kingdom__________. A. Animalia B. Fungi C. Protista D. Monera 18. The most specific taxonomic grouping in the hierarchical classification

scheme is __________. A. phylum B. species C. genus D. kingdom 19. Many of the archaea are__________. A. vertebrates B. extremophiles C. eukaryotic D. fungi 20. Fossils__________. A. are only formed under certain conditions B. are more likely to form from the remains of soft-bodied organisms C. are too different from organisms found today to be of any use to biologists D. all of the above are true 21. Humans possess vestigial gills and a tail during certain phases of their

embryological development. A. True B. False 22. In order to survive, aerobic organisms require__________. A. oxygen B. sunlight C. Both A and B are correct D. Neither A nor B is correct


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23. In the six-kingdom classification scheme, kingdom monera is split into which two kingdoms?

A. Plantae and Animalia B. Protista and Eukarya C. Autotrophae and Heterotrophae D. Eubacteria and Archaebacteria 24. Halophiles thrive under conditions of extreme__________. A. heat B. salt concentration C. acidity D. cold 25. Phylogenetic trees are visual representations of__________. A. systematics B. cladistics C. ancestral relationships of organisms D. metabolic pathways 26. A clade consists of__________. A. prokaryotic organisms B. a common ancestor and all its descendants C. eukaryotic organisms D. none of the above 27. Synapomorphies are __________. A. distant relatives of bacteria B. not useful in determining phylogenetic relationships C. eukaryotic D. none of the above 28. Cladograms _________. A. contain the data used to determine phylogenetic relationships B. lack the data used to determine phylogenetic relationships C. are the same as phylogenetic trees D. are only useful when classifying fungi 29. Taxonomic keys can only be used with the five-kingdom classification

scheme. A. True B. False


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30. In a phylogenetic tree, more recent species are placed__________. A. in the trunk B. in the roots C. at the tips of the branches D. none of the above 31. In phenetics, classification is based on__________. A. shared derived characteristics only B. as many characteristics as possible C. phylogenetic relationships D. the month in which organisms were discovered 32. All animals are multicellular. A. True B. False 33. In prokaryotic organisms, DNA is found__________. A. freely in the cell B. in the nucleus C. in the coelom D. prokaryotic organisms do not possess DNA. 34. In the five-kingdom classification scheme, archaea are placed in which

kingdom? A. Protista B. Fungi C. Cyanobacteria D. Monera 35. Algae carry out photosynthesis. A. True B. False 36. Insects belong to the kingdom__________. A. Protista B. Monera C. Archaebacteria D. Animalia 37. Carl Woese based his research on RNA found in what cellular structures? A. DNA B. ribosomes C. cell walls D. plasma membranes


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38. Cladograms are constructed using__________. A. synapomorphies B. DNA C. phenetics D. all of the above 39. Which school of systematics takes evolutionary theory into account? A. taxonomy B. phenetics C. the traditional school of systematics D. cladistics 40. Aristotle based his classification of living things primarily on phylogeny. A. True B. False 41. Taxonomy is the field of biology that deals with__________. A. classifying and naming organisms B. evolution C. ecology D. morphology 42. In binomial nomenclature, what is the correct way to write the species name

for human beings? A. homo sapiens B. Homo Sapiens C. homo Sapiens D. Homo sapiens 43. Early taxonomists relied primarily on__________. A. phylogenetic data B. genetic data C. morphological data D. biochemical data 44. Many biologists suggest that the kingdom Plantae is diverse enough that it

needs to be split into several kingdoms. A. True B. false 45. Taxonomic keys are usually__________. A. monochotomous B. trichotomous C. dichotomous D. transchotomous


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46. Both Linnaeus and John Ray focused their classification efforts primarily on __________.

A. bacteria B. plants C. archaea D. animals 47. Which of the following are examples of morphological data? A. leaf shape B. flower coloration C. both A and B D. neither A nor B 48. Some DNA sequences change at a more rapid rate than others, but the rate

of change for a particular sequence of DNA tends to remain fairly constant over time.

A. True B. False 49. Archaea differ from bacteria in that_________. A. they have different ribosomal RNA B. the chemical composition of their plasma membranes is different C. they initiate transcription in a different fashion D. all of the above 50. The presence of retractable claws among felines is an example

of__________. A. a synapomorphy B. a cladogram C. mutation D. phenetics


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Comprehensive Exam key

1. B 11. B 21. A 31. B 41. A 2. C 12. B 22. A 32. A 42. D 3. A 13. A 23. D 33. A 43. C 4. B 14. B 24. B 34. D 44. B 5. D 15. D 25. C 35. A 45. C 6. C 16. D 26. B 36. D 46. B 7. A 17. C 27. D 37. B 47. C 8. A 18. B 28. A 38. A 48. A 9. C 19. B 29. B 39. D 49. D 10. B 20. A 30. C 40. B 50. A


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Classification of Living Things Glossary aerobic: organisms or processes requiring the presence of oxygen. Animalia: one of the five broad kingdoms of life in the five -kingdom classification

scheme. All members of kingdom Animalia are heterotrophic multicellular eukaryotes.

archaea: single celled prokaryotic organisms that share similarities with other

prokaryotic organisms, such as bacteria, as well as with eukaryotic organisms. Some taxonomists place archaea in the kingdom Monera, while others assign them to their own kingdom or domain.

archaebacteria: another name for archaea. Archaebacteria is also a kindgom

under the six-plus-kingdom classification scheme. asexual reproduction: reproduction where offspring are produced from only one

parent; offspring are genetically identical to their parent. asymmetrical: lacking a recognizable pattern of symmetry. autotroph: an organism that produces its own nourishment through

photosynthesis or other processes. bacteria: prokaryotic unicellular organisms. bilateral symmetry: pattern of symmetry where an organism displays a distinct

right and left side. binomial nomenclature: a system of naming organisms developed by Carolus

Linnaeus. Each organism is assigned a two part name composed of the genus and specific epithet.

cell wall: a rigid structure that can be composed of various substances,

surrounding individual plant and fungi cells. chloroplast: cellular structure where photosynthesis takes place in eukaryotes. clade: group of organisms composed of a common ancestor and all its

descendants. cladistics: a school of systematics where classification of organisms is based on

shared common ancestry.


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cladogram: a diagram used to visually represent cladistic data. Organisms are grouped in a cladogram on the basis of synapomorphies, or shared derived characteristics.

class: a taxonomic grouping narrower than phylum and broader than order. coccus, (pl) cocci: a round or spherical shaped bacterium. coelom: specially lined body cavity where internal organs are located. Found in

some animals. common ancestry: descent from a shared, or common, ancestor. cyanobacteria: unicellular prokaryotes that carry out photosynthesis, also known

as blue-green algae. cytoplasm: the contents of a cell between the nuclear envelope and the cell

membrane. dichotomous key: a tool designed to assist in the classification of organisms.

Consists of a series of divergent choices. DNA: the double stranded helix shaped macro-molecule that carries hereditary

information from generation to generation. DNA hybridization: an experiment where single strands of DNA from two

different organisms are combined and allowed to reform double strands. The degree of bonding indicates the degree of similarity between the different strands.

domain: taxonomic grouping recognized by some biologists as existing above

the kingdom level. electron microscope: a device that uses a beam of electrons to form images of

objects. electron microscopy: the use of an electron microscope to view organisms or

details of organisms not visible to the naked eye. embryology: the study of the early development of organisms. embryo: a multicellular organism in the early stages of prenatal development. empire: another name for domain. eubacteria: "true" bacteria, as distinguished from archaebacteria.


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eukaryotic: possessing a membrane bound nucleus in which genetic information

is stored. evolution: change over time. Evolution in populations can give rise to new

species. extremophile: an organism that can survive in extreme conditions such as high

heat, high acidity, or high salt concentrations. family: a taxonomic grouping narrower than order and broader than genus. filament: long cellular structure containing more than one nucleus in fungi and

water molds. fitness: in biological terms, a measure of an organism's overall ability to survive

and reproduce. five-kingdom classification scheme: an assignment of organisms into one of five

broad kingdoms, Monera, Protista, Fungi, Plantae, or Animalia. fossil record: preserved remains of organisms as they relate to the history of life

on this planet. Fungi: one of the five broad kingdoms of life in the five-kingdom classification

scheme. Most members of kingdom Fungi are multicellular; all are eukaryotic, and most are saprotrophs.

gamete: the reproductive cells of an organism; sperm and egg cells. genetic analysis: the study of DNA and RNA composition genus: a taxonomic grouping narrower than family and broader than species. helical: possessing a spiral shape. heterotroph: an organism that does not produce its own nourishment through

photosynthesis or other means. Heterotrophic organisms rely on external food sources.

hierarchical classification scheme: system of taxonomic groupings devised by

Linnaeus, consisting of kingdom, phylum, class, order, family, genus, and species. The taxonomic grouping family was not utilized by Linnaeus, but was added later.

invertebrate: organism that lacks a backbone.


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kingdom: the broadest, most inclusive taxonomic grouping in the five and six-

kingdom classification schemes. light microscope: an optical device used to view organisms or details of

organisms not visible to the naked eye. light microscopy: the process of employing optical devices to view organisms or

details of organisms not visible to the naked eye. Monera: one of the five broad kingdoms of life in the five -kingdom classification

scheme. All members of kingdom Monera are single-celled and prokaryotic. monophyletic group: in cladistics, a group of organisms composed of a common

ancestor and all its descendants. morphology: the study of form or structure. multicellular: composed of more than one cell. Most members of Kingdom Fungi

are multicellular, and all members of Plantae and Animalia are multicellular. mutation: changes or variations in a DNA sequence. nonvascular plant: plant that lack vascular tissue. nucleoid region: area in the cytoplasm of prokaryotes where DNA is located. numerical phenetics: also known as phenetics, the school of systematics where

classifications are based solely on the number of traits shared by organisms. Phenetics does not take into account common ancestry.

obligate anaerobe: an organism that cannot survive in the presence of oxygen. order: a taxonomic grouping narrower than class and broader than family. parasite: an organism that obtains its nourishment from a living host organism. phenetics: Also known as numerical phenetics. The school of systematics

where classifications are based on the number of traits shared by organisms. Phenetics does not take into account common ancestry.

phenogram: a type of phylogenetic tree used to visually represent phenetic data.

Organisms are grouped in a phenogram according to the number of character traits they share.


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phloem: vascular tissue found in some plants that transports nutrients from one part of the plant to another.

photosynthesis: the process through which plants and some members of the

kingdoms monera and protista utilize solar energy to produce their own nourishment in the form of sugars from carbon dioxide and water.

phylogenetic tree: branching diagram used to represent phylogeny. phylogeny: the study of the evolutionary relationships of organisms. phylum: a taxonomic grouping narrower than kingdom and broader than class. Plantae: one of the five broad kingdoms of life in the five -kingdom classification

scheme. All members of kingdom Plantae are autotrophic, multicellular eukaryotes.

plasma membrane: membrane that surrounds an entire cell and which regulates

the flow of substances to and from the cell. prenatal: prior to birth. prokaryotic: an organism lacking a membrane bound nucleus in which genetic

information is stored. Protista: one of the five broad kingdoms of life in the five -kingdom classification

scheme, comprised of algae, protozoa, slime molds, and water molds. All members of kingdom Protista are eukaryotic.

radial symmetry: pattern of symmetry where an organism can be split in half by

any line bisecting the vertical axis ribosome: cellular structure involved in protein synthesis. Ribosomes contain

genetic material in the form of RNA, and the analysis of this RNA led to the concept of a three-domain classification scheme.

RNA: a single stranded macro-molecule that carries genetic information and is

involved in protein synthesis. rod: a bar shaped or elongated bacterium. saprotroph: an organism that feeds on dead or decaying organic matter. seed vascular plant: plant possessing vascular tissue in the form of xylem and

phloem, and which propagates through the dispersal of seeds.


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seedless vascular plant: plant possessing vascular tissue in the form of xylem and phloem, which does not produce seeds. Seed vascular plants propagate through the dispersal of airborn spores.

sexual reproduction: reproduction where new offspring are produced by the

combination of genetic material from two gametes, usually from two different parents.

six-kingdom classification scheme: an assignment of organisms to six broad

kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, or Animalia. The six kingdom scheme differs from the five kingdom classification scheme in that kingdom Monera is split into two separate kingdoms, Eubacteria and Archaebacteria.

species: the narrowest or most specific taxonomic grouping. Also defined as a

genetically similar population of organisms capable of reproducing with other members of their own species.

spirillum: a spiral or helical shaped bacterium. synapomorphy: shared derived characteristic. Synapomorphies are

characteristics that arise in a common ancestor and are passed on to all its descendants.

systematics: the study of living organisms in terms of their diversity and

interrelationships. Taxonomy is a sub-discipline of systematics. taxonomic key: an organized set of choices that allows a taxonomist to identify

an unknown organism. taxonomy: the study of classifying and naming organisms. three-domain classification scheme: classification scheme in which organisms

are assigned to one of three broad domains, Archaea, Eubacteria, or Eukarya, based on cellular structure, genetics, and nutritional mode.

traditional school of systematics: a school of systematics where classifications

are based on morphological similarities as well as common ancestry among organisms.

transcription: a cellular process in which a section of double stranded DNA is

copied in the form of a single strand of RNA. unicellular: comprised of a single cell.


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vascular tissue: in plants, specialized groupings of cells in the form of xylem and phloem that conduct minerals, water, and nutrients throughout the plant.

vertebrate: an animal that possesses a backbone. vestigial: non-functional structures in an organism that are remnants of

structures that were once func tional in ancestral species of that organism. xylem: vascular tissue found in some plants that conducts water and minerals

from the roots to the rest of the plant.

Classification of Living Things Program...

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