CHAPTER 1 Classifying Life’s Diversity · related to biodiversity (1.1, 1.4) • B2.4 create and apply a dichotomous key to identify and classify organisms from each of the kingdoms

Specifi c Expectations In this chapter you will learn how to . . .

• B1.1 analyze some of the risks and benefi ts of human intervention to the biodiversity of aquatic and terrestrial ecosystems (1.4)

• B2.1 use appropriate terminology related to biodiversity (1.1, 1.4)

• B2.4 create and apply a dichotomous key to identify and classify organisms from each of the kingdoms (1.3)

• B3.1 explain the fundamental principles of taxonomy and phylogeny (1.1, 1.2)

• B3.2 compare and contrast the structure and function of diff erent types of prokaryotes, eukaryotes, and viruses (1.3)

• B3.5 explain why biodiversity is important to maintaining viable ecosystems (1.4)

This blind, white crab, known as the yeti crab (Kiwa hirsuta), is covered in hair-like structures that are home to millions of bacteria. Living more than 2 km under the ocean’s surface, this crab is a new species discovered during the Census of Marine Life. Th e Census is a 10-year project with the goal of learning more about the diversity and distribution of marine life.

Th e yeti crab is one example of that diversity. Based on genetic analysis, it is so diff erent from other crabs that a new family, Kiwaidea, was created to help classify it. Identifying and classifying this crab, along with more than 5000 other new species discovered by the Census, helps scientists learn more about the history and biodiversity of life on Earth. It also helps people make decisions about how to ensure that ocean biodiversity endures for the future.

CHAPTER

1Classifying Life’s Diversity

8 MHR • Unit 1 Diversity of Living Things

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Launch Activity

Organizing LifeWhen you think of biodiversity, you may think of the ocean or a rainforest. However, biodiversity exists in your area as well. Th ink about the diff erent types of birds, insects, or plants that you see when you are outside in your neighbourhood. How many diff erent kinds of organisms live in your neighbourhood? In this activity, you will list and classify local species.

Procedure1. Make a list of all the diff erent plants, animals, and fungi that you

observe during a 15-minute trip around your school or home. Include indirect evidence of organisms as well, such as tracks, animal droppings, nests, and sounds. Aim for at least 15 species in your list.

2. Organize your list into three main groups: plants, animals, and fungi. Within each main group, create subgroups based on the similarities and diff erences you observe or infer among the various kinds of organisms. Begin by choosing a characteristic that lets you divide each group into two subgroups: one that has the characteristic and one that does not. For example, one characteristic could be wings and no wings.

3. Next, decide if you can divide any of your groups and subgroups further using another characteristic. If so, list the organisms in each new group or subgroup.

4. Continue dividing your lists until you cannot see another way to do so.

Questions 1. What characteristics did you use to defi ne your groups? How many

diff erent subgroups did you make? 2. Exchange your lists with a partner. Interpret and discuss each other’s

system of classifi cation. 3. Compare the similarities and diff erences among the classifi cation

systems in the class. Why were so many systems invented?

Chapter 1 Classifying Life’s Diversity • MHR 9

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A B

SECTION

1.1Identifying, Naming, and Classifying Species

Key Terms

species

morphology

phylogeny

taxonomy

binomial nomenclature

genus

classifi cation

hierarchical classifi cation

rank

taxon

Take a moment to think about the great variety of organisms that inhabit Earth. From microscopic bacteria to carnivorous plants that capture insects, whales that migrate thousands of kilometres, and fungi that help break down dead trees, there are millions of species on Earth. To date, scientists have identifi ed about 2 million species on Earth. Although 2 million is a large number and new species are discovered every day, it is thought that this is just a fraction of the total number of species on Earth. Scientists estimate that the total number of species on Earth ranges from 5 million to 20 million.

Knowing the identity of Earth’s species is important not just to biologists or other scientists, but to everyone in society. Farmers and gardeners need to be able to identify weeds that might be growing next to their crop plants. Doctors need to know which species of bacteria a patient is infected with in order to prescribe the correct medication for treatment. Many people, including Aboriginal peoples, collect plants for medicinal use. It is critical for them to correctly identify the species they need. Border inspection offi cials must check incoming goods to prevent the introduction of an invasive species. Because species have been identifi ed, defi ned, and named by scientists, people worldwide can communicate about all of the diff erent organisms that live on Earth.

Identifying and Naming New SpeciesSuppose you are a scientist who discovers a new species, such as the woolly rat found in the crater of a volcano in New Guinea or the pink iguana found on only one of the Galapagos Islands, both of which are shown in Figure 1.1. Although it seems obvious that the rat is a mammal and the iguana is a reptile, how would you determine exactly what species these organisms are? What methods would you use to determine how closely they are related to other species? What methods would you use to classify them and give them scientifi c names? Th roughout history, scientists have used diff erent methods, and examined and compared diff erent characteristics, to defi ne and classify a species.

species a group of organisms that can interbreed in nature and produce fertile offspring

Figure 1.1 (A) The Bosavi woolly rat, about 1.5 kg in mass and 80 cm in length, is one of the largest rats in the world. Despite its size, it is closely related to the rats and mice most people are familiar with. (B) This pink iguana is found only in the crater of Wolf Volcano on Isabela Island in the Galapagos Islands.

Apply How might scientists determine whether this pink iguana is a different species from other iguanas living on the same island?


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Identifying Species: Using Species ConceptsDespite centuries of thought and research, scientists have been unable to agree on a single defi nition of what a species is. Instead, they have proposed various defi nitions of species, which are called species concepts. Table 1.1 describes three commonly used species concepts, along with advantages and disadvantages for each. Notice that each species concept focuses on a diff erent aspect of organisms. • Th e morphological species concept focuses on morphology—body shape, size, and

other structural features. • Th e biological species concept defi nes species on the basis of whether two organisms

can produce fertile off spring. • Th e phylogenetic species concept examines the phylogeny, or evolutionary history,

of organisms.

Table 1.1 Species Concepts

Species Concept Description Advantages and Disadvantages

Morphological species concept Th e morphological species concept focuses on the morphology of an organism. Th is species concept relies on comparing measurements and descriptions of similar organisms, taking into account that species change over time and that they have variation. Aft er comparisons are completed, scientists decide whether similar organisms represent diff erent species.

Advantage: Th e relative simplicity of this species concept makes it the most widely used, particularly for plants.Disadvantage: Th e challenge in applying this species concept comes from having to decide how much diff erence between individuals is too much variation. Almost all populations are made up of non-identical individuals.

Biological species concept Th e biological species concept focuses on similar characteristics and the ability of organisms to interbreed in nature and produce viable, fertile off spring. Th is means that if two individual organisms can mate under natural circumstances and they produce off spring that can successfully live and reproduce, then those two individuals are the same species.

Advantage: Th is species concept is widely used by scientists. Disadvantages: Th is species concept cannot be applied in all cases. For example, when two populations are physically separated, they never have the opportunity to interbreed in nature. Th is means that the viable, fertile off spring requirement cannot be tested. Also, this species concept cannot be applied to organisms that reproduce asexually, nor can it be applied to fossil species, which are no longer reproducing.

Phylogenetic species concept

Bacteria

CommonAncestor

Archaea

Th e phylogenetic species concept focuses on evolutionary relationships among organisms. A species is defi ned as a cluster of organisms that is distinct from other clusters and shows a pattern of relationship among organisms. For example, when a prehistoric species branches into two species over time, it becomes two diff erent phylogenetic species. Th is concept has become increasingly popular as biologists have obtained more evidence through DNA analysis about how species are related.

Advantages: Th e phylogenetic species concept can be applied to extinct species. It also considers information about relationships among organisms learned from DNA analysis, a method scientists are using more and more. For example, it was through DNA analysis that scientists were able to classify the pink iguana from the Galapagos Islands as a new species.Disadvantage: Evolutionary histories are not known for all species.

morphology the branch of biology that deals with the structure or form of organisms

phylogeny the evolutionary history of a species


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Naming SpeciesOnce researchers have decided which organisms qualify as a separate species, a name must be assigned to the species. Most familiar organisms have been given several—and sometimes many more—names that diff er from continent to continent, country to country, and oft en from region to region within the same country. For example, in English-speaking North America alone, the animal in Figure 1.2 may be known to diff erent people as a groundhog, a woodchuck, a whistle pig, or a forest marmot. Using so many names for the same type of organism can cause confusion. Th us, having a standard system for naming organisms, understood by any scientist, anywhere in the world, is essential.

A System of Standard Names for Species: Binomial NomenclatureTaxonomy is the branch of biology that identifi es, names, and classifi es species. Swedish scientist Carl von Linné, who is better known by the Latinized version of his name, Carolus Linnaeus, is oft en referred to as the Father of Taxonomy. He is credited with developing the system for naming species: binomial nomenclature. Binomial refers to something with two parts, and nomenclature means a naming system. Th us, in this system, each species has a two-part name. Th e two-part name is known as the species name, although it is oft en referred to as the scientifi c name as well.

Th e fi rst word in the scientifi c name is the genus name. Th e second word in the scientifi c name identifi es the particular species. Th e scientifi c name is italicized when typed, with the genus name capitalized and the species in lower case. For example, the scientifi c name for humans is Homo sapiens. When the scientifi c name is written by hand, both parts of the name are underlined.

taxonomy the branch of biology that identifies, names, and classifies species based on natural features

binomial nomenclature the system of giving a two-word Latin name to each species—the first part is the genus and the second part is the species

genus (plural genera) taxonomic group of a closely related species

Figure 1.2 This animal, made famous every February 2 in Canada and the United States, is known in English by many names. To biologists around the world, however, it is known only by one name: Marmota monax.


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1. Explain why it is important to everyone in society for scientists to identify, defi ne, and name species.

2. Explain why there are several diff erent species concepts, rather than a single defi nition for a species.

3. State which presentation of the scientifi c name for the domesticated dog is correct. Th en explain why it is correct and why the other three are incorrect.

a. Canis familiaris c. Canis familiaris b. Canis familiaris d. Canis Familiaris

4. Explain the advantages of using binomial nomenclature rather than common names to refer to organisms.

5. Use a graphic organizer to compare and contrast the types, advantages, and disadvantages of the species concepts described in Table 1.1.

6. Th e off spring of a horse and a donkey is a mule. Mules are unable to reproduce. Are horses and donkeys members of the same species? Why or why not? Use the biological species concept to explain why or why not.

Learning Check

Classifying SpeciesSpecies concepts allow scientists to determine what groups of organisms make up a species. Binomial nomenclature allows scientists to apply a formal name for each of those species. But millions of species currently live on Earth, and many other extinct species have been identifi ed from fossils. However, to understand, demonstrate, and communicate the relationships in life’s diversity, scientists need a set of agreed-upon rules or criteria to help them classify species. Again, it was Linnaeus who developed the basis of the system of classifi cation we use today.

classification the grouping of organisms based on a set of criteria that helps to organize and indicate evolutionary relationships

Suppose that you observe a reptile like the one shown in the photograph below. The reptile has no legs. However, that does not mean that it is a snake, because legless lizards also exist. How could you determine whether this reptile is a snake or a lizard?

Procedure 1. Use the information in the table on the right to

determine whether your specimen is a snake or a lizard.

Questions 1. What type of reptile do you think the organism is?

Explain your reasoning.

2. Which species concept did you use to help classify your specimen? Explain your reasoning.

3. What other data could you collect or analyze to provide additional evidence to help you confi rm your decision?

Morphological Characteristics of Snakes and Lizards

Organisms EyelidsEar

Openings

Tail Tip Breaks

Off When Handled Legs

Snakes Cannot move

No No No

Lizards Movable Yes Yes Yes/No

Your specimen

Movable Yes Yes No

Activity 1.1 You Decide: Snake or Lizard?

This legless reptile is known as Ophisaurus attenuatus.


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Hockey Golf

Sports

Soccer Tennis

Un-nested Classific tion

Nested Classific tion

Hockey Golf

Sports

Soccer Tennis

Non-team SportsTeam Sports

Hierarchical Classifi cationImagine a world in which there are just four sports: golf, tennis, hockey, and soccer. Any sports competition could then be classifi ed in one of four categories—a very simple, un-nested system, such as the fi rst one in Figure 1.3. Notice, however, that this simple system can be modifi ed by rearranging the sports into categories based on the characteristic of team sports versus non-team sports. Th e resulting classifi cation scheme is known as a nested system, because there is a hierarchy of categories. Th at is, the four specifi c sports are clustered into two more general categories. A hierarchy is an arrangement of items in which the items are identifi ed as being above, below, or at the same level compared to other items. Because nested classifi cation systems have categories arranged in hierarchies, this method of organization is called hierarchical classifi cation.

hierarchical classification the method of classifying organisms in which species are arranged in categories from most general to most specific

Taxonomic Categories Used To Classify OrganismsTaxonomic categories are the groupings, arranged in a hierarchy, that are used to classify organisms that have been named and identifi ed. In most cases, a species is classifi ed by assigning it membership in eight nested categories. Each of the eight taxonomic categories is known as a rank. Th e name of each rank is called a taxon.

Table 1.2 shows how the species Canis lupus, the grey wolf, is classifi ed using taxonomic categories. To start, based on the morphology and complexity of its cells, the grey wolf is placed in the domain Eukarya. A domain is the broadest of the ranks (categories). All large organisms have similar cells, so the grey wolf shares that domain with millions of other species, including those that do not have obviously similar characteristics, such as sugar maples and mushrooms.

rank a level in a classification scheme, such as phylum or order

taxon (plural taxa) a named group of organisms such as phylum Chordata or order Rodentia

Figure 1.3 Both of the classification systems shown here recognize the four activities as sports, but the nested classification provides more information. As more items (in this case, sports) are added, nesting becomes increasingly important for making classification as clear and detailed as possible.


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Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Canidae

Canis

Canis lupus

4–10 million

2 million

50 000

5 000

270

34

7

1

Number ofSpeciesin Taxon

Examples of Species in TaxonGrey WolfTaxon

Rank(TaxonomicCategory)

The Grey Wolf: Kingdom to SpeciesWithin the domain Eukarya are four kingdoms, and the grey wolf is placed in the animal kingdom. Th e kingdom has fewer species in it than a domain. However, because the animal kingdom includes insects and all other animals, it still contains more than a million species. As you can see from Table 1.2, within the animal kingdom is the chordate phylum. A phylum further narrows an organism’s classifi cation. Wolves are classifi ed in the chordate phylum. Th e chordate phylum does not include animals such as insects and worms, but it still includes other groups, such as fi sh and birds.

As classifi cation of the grey wolf continues to be narrowed down, the ranks become more specifi c and the number of members in each taxon becomes fewer. A major chordate class is the mammals—warm-blooded animals that have fur or hair and that nurse their young. Within the mammals is the order Carnivora, a group adapted for meat-eating, which includes weasels, cats, dogs, and seals. Within that order is the family Canidae, the dogs, including foxes, jackals, and the domestic dog. Th e Canis genus includes the grey wolf, shown in Figure 1.4, as well as the coyote and fi ve other species. Finally, the only kind of animal that remains at the species level is the grey wolf—Canis lupus.

Figure 1.4 Wolves are carnivores, a characteristic that distinguishes them from other types of mammals.

SuggestedInvestigationThoughtLab Investigation 1-A, Classifying Aquatic Species

Table 1.2 Taxonomic Classification of the Grey Wolf (Canis lupus)


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Section 1.1 R E V I E W

Review Questions 1. C Make a Venn diagram to compare and contrast

the morphological species concept and the phylogenetic species concept.

2. A In northwestern Ontario, there are two similar-looking garter snakes: the red-sided garter snake and the eastern garter snake. Th e two interbreed successfully in nature in that part of Ontario, producing off spring that have a mix of the physical traits of the two. Th e eastern garter snake also co-exists in southern Ontario with another very similar snake, the eastern ribbon snake. However, these two snakes are not known to interbreed successfully. Infer whether these three snakes are the same species or not. Explain your reasoning.

3. K/U What is binomial nomenclature? 4. K/U Two terms can be used to describe the

organization of organisms into hierarchies that help scientists understand the relationships among living things: classifi cation and taxonomy. Explain why both terms can be used correctly for this purpose.

5. A Design a diff erent nested classifi cation for the four sports in Figure 1.3.

6. C A mnemonic is something to help people remember things. Help yourself remember the eight taxonomic ranks by making an eight-word mnemonic sentence using the fi rst letter of each rank as the fi rst letter of each word in the sentence. An example is Does Kim Play Chess Or Fix Great Sandwiches?

7. C Distinguish between the terms rank and taxon. Include an example in your answer.

8. K/U Two organisms belong to the same family in the modern classifi cation system. List the other ranks in which these two organisms would also be placed within this system.

9. K/U Compare the number and variety of organisms placed in a kingdom taxon to the number and variety of organisms found in a species taxon.

10. A Th e table below shows the classifi cation of a praying mantis, an insect that preys on smaller insects.

a. What is the scientifi c name for the praying mantis? b. Which is the broadest category of classifi cation for

the praying mantis? c. What is the narrowest rank and taxon that the

praying mantis and the grey wolf have in common? Do you think these two organisms are closely related? Why or why not?

Classification of the Praying Mantis

Category Praying Mantis

Domain Eukarya

Kingdom Animalia

Phylum Arthropoda

Class Insecta

Order Mantodea

Family Mantidae

Genus Stagmomantis

Species Stagmomantis carolina

A praying mantis feeds on ants, bees, and spiders.

11. T/I In one naming system used before Linnaeus developed his, the European honeybee had a name with 11 descriptive words, all in Latin (Apis pubescens, thorace subriseo, abdomine fusco, pedibus posticis glabris untrinque margine ciliatis). In the system developed by Linnaeus, this bee’s scientifi c name became Apis mellifera. Evaluate the advantages of the current naming system compared to the earlier system.

Section Summary• Biologists use the morphological species concept,

the biological species concept, and the phylogenetic species concept to defi ne species.

• Species oft en have common names. However, they are formally known by two-part scientifi c names.

• All species are classifi ed by being placed in eight nested ranks. Th e broadest category is the domain, continuing to narrow to kingdom, phylum, class, order, family, genus, and fi nally species, which is the narrowest category.

• Each named rank is known as a taxon.


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common ancestor

red panda

raccoon

giant panda

other bears

SECTION

1.2Determining How Species Are Related

Key Terms

ancestor

anatomy

physiology

phylogenetic tree

Th e goal of modern classifi cation is to assign species to taxa so that the classifi cation refl ects both morphological similarities among organisms as well as hypotheses about their phylogeny (evolutionary history). To do this, biologists use the concept of shared evolutionary history. If two species share much of the same evolutionary history, it means they have a fairly recent common ancestor. In other words, the more a species shares its evolutionary history with another, the more closely related they are thought to be.

Consider the example of the animals in the family Canidae, which includes wolves, coyotes, jackals, foxes, and domestic dogs. Members of this family have morphological characteristics in common, including having fi ve toes on the front feet and four toes on the back feet. Th ey are not able to retract, or pull closer to the body, their claws, unlike other carnivores such as cats. Th ey also have elongated snouts. Aside from morphology, what other types of evidence do scientists examine to determine relationships among species? In terms of phylogeny, it is hypothesized that organisms in family Canidae share a common ancestor. In particular, based on DNA evidence, scientists believe that the grey wolf is the ancestor of the domestic dog.

Evidence of Relationships Among SpeciesDo you think that the giant panda in Figure 1.5 is more closely related to bears or raccoons? Giant pandas have characteristics of both groups, and scientists debated the puzzle of how to classify them for more than 100 years. How do scientists determine how much of the evolutionary histories of two species is shared? In modern taxonomy, three main types of evidence that are used include anatomical, physiological, and DNA. Th e information is then interpreted to make hypotheses about evolutionary history and how closely related diff erent species are. In the case of the giant panda, both physiological and DNA evidence placed this species closer to bears than raccoons.

ancestor an organism (or organisms) from which other groups of organisms are descended

Figure 1.5 This branching tree diagram shows the relationships among giant pandas, bears, and raccoons.


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A C

Whale Bat Horse Human

B

Anatomical Evidence of RelationshipsRecall that morphology refers to the body size, shape, and other physical features of organisms. Studying morphology helps scientists learn more about how an organism develops and functions structurally. Studying morphology also helps scientists determine evolutionary relationships among species. Anatomy, which is the study of the structure of organisms, is a branch of morphology. Study the oviraptor and the New Guinean cassowary shown in Figure 1.6.

At fi rst glance, it may not seem that these two organisms—one a dinosaur, the other a bird—are closely related. In fact, biologists used to think that modern reptiles shared a much closer evolutionary relationship with dinosaurs than birds did. However, detailed studies over the past several decades provide convincing evidence that dinosaurs and birds share a surprising number of anatomical features. For example, both have bones with large hollow spaces, whereas living reptiles have dense bones. Also, the arrangement of dinosaur bones in the hip, leg, wrist, and shoulder structures show stronger similarities to birds than to living reptiles. Some small dinosaur fossils, calculated to be about 150 million years old, have feathers, as you can see in Figure 1.6 (C). Th ese are some of the kinds of anatomical evidence that biologists have used to hypothesize a close evolutionary relationship between modern birds and dinosaurs.

anatomy the branch of biology that deals with structure and form, including internal systems

Another example of using anatomical evidence to determine relationships among organisms comes not from fossils, but from living species. Compare the bones in Figure 1.7 from a whale fl ipper, a bat wing, a horse leg, and a human arm. Even though these species look diff erent on the outside, they have similar bone structures on the inside. Over millions of years, the size and the proportions of the bones have been modifi ed for diff erent purposes (swimming, fl ying, running, and grasping). However, the overall arrangement and similarities indicate a shared evolutionary history.

Figure 1.6 (A) This artist’s conception of Oviraptor philoceratops might not appear to be related to the cassowary (B), a bird from New Guinea, but these animals have many similar characteristics that indicate a shared evolutionary history. (C) This fossil shows the remains of Archaeopteryx, an animal from about 150 million years ago that had many dinosaur features as well as feathers.

Infer Which similarities might prompt you to think that the oviraptor and the cassowary are more closely related than was commonly thought?

Figure 1.7 The same bones are found in the forelimbs of these four mammals. The matching sets of bones are colour-coded in this illustration.


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A B

Physiological Evidence of RelationshipsPhysiology is the study of the functioning of organisms—how they work. Physiology includes studying the biochemistry of organisms, including the proteins they make. Whether as enzymes or as parts of cells and tissues, an organism’s proteins are determined by the organism’s genes, since genes are coded instructions for making proteins. By comparing proteins among diff erent species, the degree of genetic similarity or diff erence can be determined. Modern technology has provided new tools for comparing species at this level, which has led to some organisms being reclassifi ed.

physiology the branch of biology dealing with the physical and chemical functions of organisms, including internal processes

For example, do you think the guinea pig and the mouse in Figure 1.8 are closely related? In the past, both mammals were classifi ed in the order Rodentia, the rodents. However, an analysis of several proteins, including insulin, caused scientists to rethink this classifi cation. Guinea pig insulin is so diff erent from that of typical rodents that guinea pigs were reclassifi ed into a taxon of their own. What about the horseshoe crab in Figure 1.9? Although it has the word crab in its common name, studies of blood proteins in the horseshoe crab have shown that this animal is more closely related to modern spiders than to crabs.

Figure 1.8 Guinea pigs (Cavia porcellus) (A) were once considered to be in the rodent order, like mice (B). Studies of protein structure suggest that guinea pigs are sufficiently different from other rodents that they should be placed in a separate order.

7. What is the main goal of modern classifi cation? 8. Use a graphic organizer, such as a fl owchart or a

main idea web, to show clearly how the following words are related: morphology, anatomy, and physiology.

9. Scientists oft en reclassify organisms as new information is discovered. Why is it important for scientists to continue to classify and reclassify organisms?

10. Sharks and dolphins have similar morphological characteristics. Th ey both have fi ns and bodies shaped for swimming. How could examining their anatomy and physiology help to further classify these two organisms?

11. Refer to Figure 1.5. Which pair of organisms in the diagram do you think is more closely related—Pair A: a giant panda and a red panda or Pair B: a red panda and a raccoon? Explain your reasoning.

12. Many animal species have red blood cells that contain the oxygen-carrying protein hemoglobin. Chickens (45), dogs (15), gorillas (1), frogs (57), and humans are included in this list. Th e numbers in brackets represent the number of amino acid diff erences between human hemoglobin and the hemoglobin of the other species. Based on this information, rank these animals from most closely to least closely related to humans.

Learning Check

Figure 1.9 Horseshoe crabs have pincher-like appendages and lack jaws.


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A

Animals PlantsFungi

Common Ancestor

Tim

e

B

DNA Evidence of RelationshipsStudy the diagram in Figure 1.10. Are you surprised that it shows that fungi are more closely related to animals than to plants? Genetic analysis suggests that this is the case. Genes are sections of DNA made of long chains of molecules called nucleotides. (You will learn more about genes, their composition, and their function in Unit 3.) Technological advances over the past few decades have made it increasingly possible to determine the sequence of the nucleotides of specifi c genes. Just as anatomical and physiological evidence can be compared among species, so too can these DNA sequences. Th is research has been a great benefi t to our understanding of evolutionary history and its application to classifi cation.

In some cases, new DNA evidence has meant that prior classifi cations based on morphological, physiological, or other evidence have to be dramatically restructured. Sometimes DNA evidence indicates unexpected relationships. For example, fungi and plants are superfi cially similar in that they do not move and they grow out of the ground. However, DNA evidence suggests that fungi are more closely related to animals than to plants. Th e diagram in Figure 1.10 refl ects this evidence. Similarly, Canada’s only vulture, the turkey vulture shown in Figure 1.11, appears similar to vultures from Asia and Africa. However, DNA indicates the turkey vultures may be more closely related to the storks, which are large wading birds.

Phylogenetic TreesOnce scientists have studied the features of organisms and learned more about their evolutionary histories, they oft en use a tool called a phylogenetic tree to represent a hypothesis about the evolutionary relationships among groups of organisms. You saw an example of a phylogenetic tree in Figure 1.5, when you considered the relationships among giant pandas, bears, and raccoons.

phylogenetic tree a branching diagram used to show the evolutionary relationships among species

Figure 1.10 Based on analysis of DNA, scientists hypothesize that animals and fungi are more closely related to each other than plants and fungi.

Figure 1.11 DNA evidence suggests that the turkey vulture (A) is really more closely related to the wading stork (B) than it is to the vultures of Asia and Africa. Both turkey vultures and storks are the only birds known to urinate on their legs, which they do to help keep their bodies cool during hot weather as well as to kill bacteria and other pathogens that cling to their legs.


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Aepyceros melampus(impala)

Oryx gazella(oryx)

Cervus elaphus(red deer)

Rangifer tarandus(reindeer)

Aepyceros Oryx Cervus Rangifer

Bovidae Cervidae

Artiodactyla

Species

Order

Family

Genus

Order ArtiodactylaFigure 1.12 shows another example of a phylogenetic tree—this time, one that illustrates the phylogeny of hooved mammals. Like a family tree, the roots or the base of the phylogenetic tree represents the oldest ancestral species. Th e upper ends of the branches represent present-day species that are related to the ancestral species. Forks in each branch represent the points in the past at which an ancestral species split—evolved, or changed over time—to become two new species.

In Figure 1.12, these four species have a common ancestor, and this common ancestor has general characteristics that it shares with all the species that evolved from it. Members of the order Artiodactyla typically have an even number of hooved toes on each foot and have specialized teeth and digestive systems adapted to eat plants. Th ere are about 150 members of this order worldwide, including goats, deer, cattle, antelopes, and pigs.

Family BovidaeNew species that evolve from a common ancestor have some characteristics in common with the common ancestor, as well as new features. Biologists use these new features to defi ne each family level of classifi cation on this tree. For example, members of the family Bovidae (cows and antelopes) are artiodactyls that have the anatomical feature of horns. Members of the family Cervidae (deer) are artiodactyls that have the anatomical features of antlers. Th ere are about 110 species of Bovidae and 40 species of Cervidae.

With continuing evolution, further new characteristics develop. On the time scale of the tree, members of diff erent genera have split apart from one another more recently than members of diff erent families. Smaller diff erences help distinguish one genus from another. For example, the family Cervidae includes 16 genera. Th e genus Cervus includes deer with highly branched antlers, while animals in the genus Rangifer are deer with broad, palmate antlers (having the shape of a hand).

Figure 1.12 This phylogenetic tree shows the evolutionary relationships among various species of plant-eating hooved mammals.

Interpret To which other organism shown in the phylogenetic tree is Cervus elaphus most closely related?


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A B

The Importance of Classification to Technology, Society, and the EnvironmentUnderstanding the evolutionary relationships among species and groups of organisms can have important consequences in the medical fi eld, as well as in agriculture and in the conservation of biodiversity. Consider the following examples: • When scientists are looking for sources of pharmaceutical drugs, hormones, and

other important medical products, they can narrow their search to species closely related to organisms already known to produce valuable proteins or chemicals.

• Understanding phylogeny can help scientists trace the transmission of disease and develop and test possible treatments. Diseases can spread more rapidly between species that share certain genetic characteristics. For example, Creutzfeldt-Jakob disease, a disease that aff ects the nervous system, may be transmitted from cows to people.

• In agriculture, ways to increase crop yields and disease resistance have already been developed by cross-breeding closely related species. Biological control through the use of natural predators, parasites, and diseases also depends on a knowledge of diff erent taxa and their particular characteristics.

• Sometimes, fi nding a new species or reclassifying an organism as a separate species has implications for environmental conservation. For example, in 2001, based on morphological and DNA analysis, scientists reclassifi ed the forest-dwelling elephants in Africa as a new species, Loxodonta cyclotis. Th ese elephants, shown in Figure 1.13, had previously been considered the same species as the African bush elephant, Loxodonta africana. Conservationists worried about the status of the new species. Loxodonta africana is classifi ed as threatened and protected by anti-poaching and anti-trading laws. Now that Loxodonta cyclotis was a separate species, it was potentially no longer protected. However, an international agreement that helps protect species from illegal trading gives Loxodonta cyclotis the highest category of protection.

Figure 1.13 The forest-dwelling elephant (Loxodonta cyclotis) (A) have smaller bodies, smaller ears, and longer tusks than the African bush elephant (Loxodonta africana) (B).


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Review Questions 1. C Construct a chart that diff erentiates the three

main types of evidence scientists use to determine relationships among species. Include an example of each type of evidence.

2. K/U Explain why knowing the shared evolutionary history of organisms is useful to each of the following:

a. a biologist b. a biology student c. a pharmaceutical laboratory assistant d. a conservation ecologist

3. K/U List three anatomical features scientists have used to hypothesize the relationship between modern birds and dinosaurs.

4. K/U What do the nucleotide sequences in the genes of turkey vultures suggest about their relatedness to vultures of Asia and Africa?

5. A You are comparing three species (A, B, and C) and you face a dilemma. Morphologically, species A and B are very similar, but they are both diff erent from species C. However, you have sequenced some genes in all three and the gene sequences indicate a high degree of similarity between species B and C. How would you resolve this situation?

6. T/I Use the phylogenetic tree below to justify the conclusion that the leopard is more closely related to the domestic cat than it is to the wolf.

Wolf Leopard Domestic Cat

Common Ancestor

7. A Refer to Figure 1.12. Explain why a reindeer (Rangifer tarandus) is more closely related to a red deer (Cervus elaphus) than it is to an oryx (Oryx gazella).

8. A Invasive species can out-compete native species when they are introduced outside of their natural environment. Th is can threaten a region’s ecosystems, economy, and society. Recently, Canadian researchers helped identify 15 new bird species through genetic analysis. Scientists were able to identify so many new species by analyzing and comparing the DNA of over 600 North American bird species. Explain how you think the use of genetic analysis could help prevent the introduction of new invasive species into Canada.

9. C Th ere is growing concern worldwide about the number of species that are going extinct. Conservation organizations work to protect endangered species, but there may be a disagreement about exactly what a species is.

a. How can classifying an organism infl uence our attitudes about that organism? For example, is a fi sh more likely to be protected if it is known to be an endangered species, or if it is newly discovered and diff erent from all known species of fi sh?

b. Suppose you had been working for a conservation group when the forest-dwelling elephants (Loxodonta cyclotis) were reclassifi ed as a separate species. Write a letter urging the Convention on International Trade of Endangered Species to consider the new species as endangered.

10. C Construct a graphic organizer of your choice to show the importance of classifi cation to technology, society, and the environment.

Section Summary• Modern classifi cation organizes diversity according to

evolutionary relationships.• Taxonomists rely on morphological, physiological, and

DNA evidence to identify and classify species.• Anatomical evidence includes comparing the structure

and form of organisms, including bones.

• Physiological evidence includes comparing the biochemistry of organisms, including proteins. DNA evidence includes comparing organisms’ DNA sequences.

• Understanding phylogeny can help scientists trace the transmission of disease and develop and test possible treatments.


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SECTION

1.3Kingdoms and Domains

All of the millions of species on Earth share certain fundamental similarities, such as being made of cells and having DNA. Despite these similarities, however, the structural diversity of Earth’s species—diversity that is based on variety of both external and internal structural forms in living things—is so great that it is almost impossible to imagine. Examining all of life’s structural diversity at the species level would be impractical, so biologists look for similarities and diff erences at a much higher taxonomic rank, such as kingdoms and even domains.

The Six Kingdoms Until the 1800s, the highest category for classifying organisms was the kingdom and there were only two: Plants and Animals. Table 1.3 summarizes how the number of kingdoms has changed since that time. In the 1800s, single-celled organisms were added to the classifi cation system through the creation of the kingdom Protista, bringing the total to three. In the fi rst half of the 1900s, some single-celled organisms were found to be extremely small and without a cell nucleus, so a new kingdom, Bacteria, was created for them, bringing the total to four. By the 1960s, it was known that fungi were so diff erent that they also needed their own kingdom, bringing the total to fi ve. During the 1990s, with new genetic information, the bacterial kingdom was divided in two, giving the current six-kingdom system.

In Chapters 2 and 3, you will examine each of the six kingdoms in more detail. As you study the remainder of this chapter, keep the following three important ideas in mind:• Th ere are two main cell types that are signifi cant for classifi cation at the upper

ranks, such as kingdom.• Th e study of cell types and genes has led scientists to add a rank higher than

kingdom—the domain.• It is important to understand how biologists think the domains and kingdoms

are connected in their evolutionary history.

Table 1.3 Changes in Classification Systems for Life’s Kingdoms

Original 1860s 1930s 1960s 1990s

Animals Animals Animals Animals Animals

Plants

Plants Plants Plants Fungi

Plants Fungi Protists

Protists Protists Protists Bacteria

Bacteria Bacteria Archaea

structural diversity a type of biological diversity that is exhibited in the variety of structural forms in living things, from internal cell structure to body morphology

Key Terms

structural diversity

prokaryotic

eukaryotic

dichotomous key

autotroph

heterotroph


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Prokaryotic cell

Eukaryotic cell

A

B

cell wallcell membraneDNA

capsule

flagellum

nucleus

cell membrane

chromosomes

ribosomes

Figure 1.14 Species are made of one of two kinds of cells. Compared to eukaryotic cells, prokaryotic cells are small, less complicated, and without a membrane-bound nucleus.

Describe one other difference between the prokaryotic cell and eukaryotic cell shown above.

Two Major Cell TypesIf an organism is made up of one cell only, it is described as being single-celled or unicellular. If an organism is made up of more than one cell, it is multicellular. Th ere is substantial variation among the cells of unicellular and multicelluar organisms. However, aft er centuries of study, biologists agree that there are two major types of cells: prokaryotic cells and eukaryotic cells.

Prokaryotic cells, such as the bacterial cell shown in Figure 1.14, are the most ancient cell type, though they remain abundant today. Th ey do not have a membrane-bound nucleus. Th e name prokaryotic refl ects this important distinction in the two cell types, because it means “before the nucleus.” Eukaryotic, on the other hand, means “true nucleus.” Eukaryotic cells do have a membrane-bound nucleus. Th ere are other diff erences as well. Eukaryotic cells, also shown in Figure 1.14, have a much more complex internal structure, and on average they are about 1000 times larger than prokaryotic cells. Th us, the two cell types represent a major division in the structural diversity of life. You will read more about diff erences between prokaryotes and eukaryotes in Chapter 2.

prokaryotic a smaller, simple type of cell that does not have a membrane-bound nucleus

eukaryotic a larger, complex type of cell that does have a membrane-bound nucleus


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Domains

Traditional eukaryotic kingdoms

Bacteria Archaea Eukarya

Protista Fungi Plantae Animalia

Dichotomous KeysEven when taxonomists have put together logical classifi cations, biologists still face a practical challenge. Imagine having a specimen whose identity is completely unknown. How could sorting through all the names and ranks in various classifi cations assist in determining what it is? Th e short answer is: it cannot. As a result, taxonomists use another tool to identify individuals or species: the dichotomous key.

A dichotomous key [dih-KAW-ta-mus kee] is a system for narrowing down the identifi cation of a specimen, one step at a time. Th e word key is used as a solution, and a dichotomy is a two-pronged fork, where there are two choices. So, a dichotomous key is an identifi cation solution that uses many two-part choices to narrow down the solution. An example of a two-part choice could be something as simple as red and not red.

dichotomous key an identification tool consisting of a series of two-part choices that lead the user to a correct identification

Figure 1.15 There are six major categories in the classification system for living and extinct organisms.

The Three DomainsAs scientists continued to analyze organisms in the kingdoms Bacteria and Archaea, the category of domain was added to the classifi cation system. Scientists found that the diff erences between these two groups at the genetic and cellular levels were so great that each group was elevated to a rank higher than kingdom—domain. So Bacteria and Archaea are two of the three domains.

As a result of reclassifying these kingdoms as domains, biologists reclassifi ed the remaining kingdoms in a domain of their own, Eukarya. Th is makes sense, since the other four kingdoms represent all the organisms with eukaryotic cells. Organisms in the two prokaryotic domains are unicellular, whereas both unicellular and multicellular organisms occur in the Eukarya. Figure 1.15 shows the current classifi cation at the level of domain and kingdom.

13. Explain how scientists overcome the impractical task of studying the structural diversity of life at the species level.

14. What led scientists to add the category called domain to modern classifi cation systems?

15. Make a table to compare and contrast prokaryotic cells and eukaryotic cells. Include the following categories in your table: Meaning of Name, Presence of Nucleus, Size, and Internal Structure.

16. Draw a fl owchart or other graphic organizer illustrating the relationship between the domains and the kingdoms found in each domain.

17. Th e following is the fi rst step in a tool used by taxonomists to classify vertebrate animals. Identify this tool and describe how it works.

1a. Hair present . . . . . . . . . . . . . . . . . . . . . . . . . Class Mammalia 1b. Hair absent . . . . . . . . . . . . . . . . . . . . . . . . . . go to Step 2

Learning Check


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Using a Dichotomous KeyTh e ultimate goal of many taxonomists is to make an identifi cation at the species level. Table 1.4 shows a small key that could be used to distinguish among just eight species: the frogs and toads in central Ontario.

Table 1.4 Dichotomous Key—Frogs and Toads of Algonquin Park

1a. Skin dry and warty .. . . . . . . . . . . American toad 1b. Skin not dry and warty .. . . . . . . . . . . . . . . . go to 2

2a. Toes with “sticky pads” .. . . . . . . . . . . . . . . . go to 3 2b. Toes without sticky pads .. . . . . . . . . . . . . . go to 4

3a. Brown, < 2 cm, a darker X-shaped mark on the back .. . . . . . . . . . . . . . . . . . . . spring peeper

3b. Grey or green, yellow under the legs . . . . . . . . . . eastern grey treefrog

4a. Back without a pair of ridges . . . . . . . . . . go to 5 4b. Back with a pair of ridges . . . . . . . . . . . . . . go to 6

5a. Mottled pattern, with a mammal-like odour .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mink frog

5b. Unmottled green pattern; to 15 cm ... . . . . . . . . . bullfrog

6a. Back with large round or squarish spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . go to 7

6b. Back unspotted (or with a few small spots) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . go to 8

7a. Spots round .. . . . . . . . . . . . . . . . . . . . . . . . leopard frog 7b. Spots squarish .. . . . . . . . . . . . . . . . . . pickerel frog

8a. Predominantly green colour .. . . . . . . . . . . . . . . . . . . .green frog

8b. Brown, with a dark mask through the eye .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . wood frog

Assume you are trying to identify the species in Figure 1.16. Before you begin, since you do not actually have the specimen in your hand, be aware that it has smooth, moist skin and it does not have “sticky pads” on its toes. To use a dichotomous key, always begin by choosing from the fi rst pair of descriptions (1a and 1b). In this case, because the skin is not dry and warty, you proceed to the next description within the fi rst pair of choices, 1b. If the skin had been dry and warty, you would have concluded the animal is an American toad, and your use of the key would be complete.

At the second set of choices (2a and 2b), since the toes are not sticky, you are directed to the fourth pair of choices (4a and 4b). Here, because you can see from Figure1.16 that the back has a pair of ridges, you move on to the sixth pair of choices (6a and 6b). Check Figure1.16 again to see if the back is spotted or unspotted. Because it is unspotted, you then move to the eighth pair of choices (8a and 8b). Finally, here you decide, based on its brown back and dark mask, that it is a wood frog (8b).

Figure 1.16 Use the dichotomous key in Table 1.4 to identify this species.


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Dichotomous keys are very helpful to identify and classify organisms. In this activity, you will develop a dichotomous key as you group familiar objects based on their characteristics.

Possible Materials• several diff erent types of an object or material, such as

backpacks, shoes, pens, or notebooks

Procedure 1. Choose an object for which you will create a

dichotomous key.

2. Place a collection of the object in a pile. For example, you may have your group members all place their backpacks or their notebooks in a pile.

3. Examine the objects and write the fi rst question for your dichotomous key. The question should focus on a distinguishing characteristic among the objects. Divide the objects into two groups based on that distinguishing characteristic.

4. Examine the characteristics of the objects in each subgroup. Write a second question that focuses on a characteristic that distinguishes the objects in one of the groups. Divide that group into two smaller groups based on this distinguishing characteristic.

5. Continue adding questions to your key and dividing the objects until there is only one object in each group. Make a branching diagram to identify each object with a distinct name.

6. Use your diagram to classify the same type of object from a diff erent source.

Questions 1. Relate the groups you used to classify your object to taxa.

How do your groups relate to the groups of kingdom, phyla, and the remaining six taxa in the modern classifi cation system?

2. How did you use your dichotomous key to classify the object from a diff erent source in step 6? For example, did you have to revise your key? Explain.

3. How could you modify your dichotomous key so that the user could more eff ectively identify an object of this type?

Activity 1.2 Create a Dichotomous Key

SuggestedInvestigationInquiry Investigation 1-C, Creating a Dichotomous Key to Identify Species of Beetles

A Dichotomous Key for KingdomsTo design a key to make identifi cations at the species level, appropriate choices of characteristics must be made. For instance, to identify the species of wildfl owers growing on a lawn, it would be logical to focus on things like the number and arrangement of leaves, fl ower colour, plant size, and branching pattern.

But keys are not always designed to identify species. If you are instead designing a key to determine what kingdom an organism is in, the focus has to be diff erent. Here, it is more useful to consider fundamental diff erences, such as the following: cell type and cell structure; whether the organism is multicellular; and methods of reproduction and obtaining nutrition.


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Main Characteristics of KingdomsTable 1.5 summarizes some of the main characteristics of kingdoms and, below it, Figure 1.17 shows some examples of organisms in each kingdom. A distinction has already been made between prokaryotic and eukaryotic cells based on size, the presence of a nucleus, and internal complexity. Another cell-level distinction is the cell wall, a tough structure that surrounds most cells. Cell walls are absent in animals, but in other organisms the composition of the cell wall varies. With respect to nutrition, an autotroph is an organism that obtains energy by making its own food, usually using sunlight. A heterotroph must consume other organisms to obtain energy-yielding food. Finally, asexual reproduction can be found in all kingdoms. However, sexual reproduction, in which genetic material from two parents combines to form off spring with a unique combination of genes, is a trait that only occurs in the Eukarya. Th e data in Table 1.5 are all that is needed to make a dichotomous key that can assign any species to its kingdom.

Table 1.5 Characteristics That Differentiate the Six Kingdoms

autotroph an organism that captures energy from sunlight (or sometimes non-living substances) to produce its own energy-yielding food

heterotroph an organism that cannot make its own food and gets its nutrients and energy from consuming other organisms

Domain Bacteria Archaea Eukarya

Kingdom Bacteria Archaea Protista Plantae Fungi Animalia

Example Staphylococcus Sulfolobus archaea Amoeba Maple tree Mushroom Rabbit

Cell type Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote

Number of cells Unicellular Unicellular Unicellular and multicellular

Multicellular Mostly multicellular

Multicellular

Cell wall material Peptidoglycan Not peptidoglycan; occasionally no cell wall

Cellulose in some; occasionally no cell wall

Cellulose Chitin No cell wall

Nutrition Autotrophs and heterotrophs

Autotrophs and heterotrophs

Autotrophs and heterotrophs

Autotrophs Heterotrophs Heterotrophs

Primary means of reproduction

Asexual Asexual Asexual and sexual

Sexual Sexual Sexual

Figure 1.17 Organisms from each of the six kingdoms represent Earth’s biodiversity.

Staphylococcus 4800×

Maple tree

Sulfolobus archaea 5000×

Mushroom

Amoeba 160×

Rabbit


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Review Questions 1. C Make a Venn diagram to compare and contrast

prokaryotic and eukaryotic cells. 2. K/U Identify the three domains and the kingdoms

within each domain. 3. K/U Refer to Figure 1.15. Explain, in your own words,

how scientists arrived at the three-domain system. 4. C Explain how a dichotomous key works. 5. K/U Distinguish between autotrophs and

heterotrophs. 6. A Refer to Table 1.5 to answer the following

questions. a. What form or forms of nutrition do eukaryotes use? b. What type of reproduction is used primarily by

prokaryotes? c. Describe the cells of organisms in domain Archaea. d. What is one characteristic that is unique to all

animals? 7. A Cyanobacteria, commonly called blue-green

algae, are classifi ed in the kingdom Bacteria. Cyanobacteria make their own food using carbon dioxide, water, and energy from sunlight. Th ey contain the pigment chlorophyll and another pigment that is blue. Explain why scientists in the early days of taxonomy would likely have classifi ed cyanobacteria in the kingdom Plantae.

8. T/I Refer to Table 1.5. A student was looking at some pond water under a microscope and noticed a single-celled organism in the fi eld of view. Th is organism had a nucleus as well as chloroplasts in its cytoplasm. Th e organism was enclosed by a cell wall. Aft er looking through a dichotomous key, the student determined this organism was a green alga. Predict the domain and kingdom of this organism. Explain the basis for your prediction.

9. A Use the dichotomous key in the table below to identify the organism in the image.

Dichotomous Key—Salamanders of Algonquin Park

1a. Skin without spots . . . . . . . . . . . . . . . . . . . . . go to 2

1b. Skin with spots . . . . . . . . . . . . . . . . . . . . . go to 4

2a. Found under cover in or beside streams .. . . . . . . . . . . two-lined salamander

2b. Found in forests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . go to 3

3a. Red stripe down back .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . red-backed salamander

3b. Grey-black overall . . . . . . . red-backed salamander (black variant)

4a. Bright red small spots . . . . . . . . . . . . . . . . . . . . . go to 5

4b. Blue or yellow spots . . . . . . . . . . . . . . . . . . . . . go to 6

5a. Green overall, found in aquatic ecosystems .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . red-spotted newt

5b. Reddish overall, found in terrestrial ecosystems .. . . . . . . red-spotted newt juvenile (“red eft ”)

6a. Many irregular blue spots . . . . . . . . . . . . . . . . . . . . . . . . blue-spotted salamander

6b. Large yellow spots . . . . . . . yellow-spotted salamander

10. C Use a graphic organizer to compare the characteristics of the kingdom Plantae to those of the kingdom Animalia.

Section Summary• Th e variety of internal and external forms exhibited

by species represents structural diversity.• Th ere are two cell types: prokaryotic and eukaryotic.

Prokaryotic cells do not have a membrane-bound nucleus. Eukaryotic cells are more complex and do have a membrane-bound nucleus.

• Organisms in the domains Bacteria and Archaea are unicellular and prokaryotic.

• Organisms in the domain Eukarya have eukaryotic cells and are unicellular or multicellular. Th ere are four kingdoms in the domain Eukarya: Protista, Plantae, Fungi, and Animalia.

• Taxonomists use dichotomous keys to make choices between pairs of options to narrow down identifi cations.


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C

A B

SECTION

1.4Classifying Types of Biodiversity

Key Terms

species diversity

genetic diversity

ecosystem diversity

gene pool

population

resilience

When you hear or read the word biodiversity, you probably think fi rst about species diversity. Species diversity is the variety and abundance of species in a given area. However, there are other ways of thinking about diversity other than species diversity, and they are just as important. Genetic diversity is evident in the variety of inherited traits within a species. Th e patterns on the tails of humpback whales, such as the one shown in Figure 1.18, are evidence of genetic diversity within this species. Ecosystem diversity is the rich diversity of ecosystems found on Earth, each of which contains many species. In this section, you will learn about the importance of all three of these types of diversity.

species diversity the variety and abundance of species in a given area

genetic diversity the variety of heritable characteristics (genes) in a population of interbreeding individuals

ecosystem diversity the variety of ecosystems in the biosphere

Figure 1.18 Biological diversity exists at different levels. (A) Within species there is genetic diversity, as evident in the different tail patterns of humpback whales. (B) Within ecosystems, like this alpine meadow, is species diversity. (C) Finally, a variety of ecosystems, such as this one in Algonquin Park, make up ecosystem diversity.

Describe one example of genetic diversity and one example of ecosystem diversity.


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Genetic DiversitySince 1996, Tasmanian devils (Sarcophilis harrisii), shown in Figure 1.19, have been suff ering from a contagious cancer that causes tumours on the face and mouth of the animals. Th e disease, spread from one individual to another by biting, eventually results in death. Th e population of Tasmanian devils has been reduced so extensively, from about 150 000 in 1996 to between 20 000 and 50 000 by 2006, that the species was classifi ed as endangered. Research has shown that a lack of genetic diversity in the Tasmanian devil population is a key factor in the impact of the disease.

Genes are the genetic material that controls the expression and inheritance of traits, such as sugar content in blueberries, pattern arrangement in ladybeetles, and human height. Th e variation among individuals in a population is largely a result of the diff erences in their genes. Genetic diversity within a population is known as the gene pool. In other words, the gene pool is the sum of all the versions of all the genes in a population. Th e genetic diversity within a species is typically greater than that within a population, because the gene pools of separate populations exposed to diff erent environmental conditions usually contain diff erent types or combinations of the diff erent versions of genes.

Genetic Diversity Provides Resistance to DiseaseGenetic diversity is especially important in disease resistance. As illustrated by the Tasmanian devil example, populations that lack genetic diversity are more susceptible to disease than those that have high diversity. If none of the individuals in a population have the ability to survive the disease, the entire population could be eliminated. If populations of the same species continue to be eliminated, it can lead to the extinction of the species.

Resistance to disease is just one example of why genetic diversity is important. Genetic diversity also allows populations and species to survive changing environmental conditions, such as a change in resource availability, climate change, a change in a predator population, or the introduction of a non-native species.

Genetic Diversity Supports Conservation BiologyAs scientists have learned more about the importance of genetic diversity and its relationship to species survival, they have begun to use their knowledge to help struggling populations. For example, in 1995 the population of Florida panthers, shown in Figure 1.20, had been reduced to between 30 and 50 individuals, partially due to a lack of genetic diversity. As part of the recovery plan for this endangered species, scientists introduced eight female panthers taken from a population of panthers in Texas. Th e eff ort was considered a success, and in 2009 the population had risen to about 100 individuals.

gene pool all the genes of all the individuals in a population

population a group of individuals of the same species in a specific area at a specific time

Figure 1.19 The Tasmanian devil is native to Tasmania, the island that is the southernmost state of Australia.

Figure 1.20 The Florida panther (Felis concolor coryi) population continues to be threatened by habitat loss and collisions with vehicles.


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Ecosystem DiversityIf the smallest scale at which scientists consider biodiversity is genetic diversity, then the largest scale is ecosystem diversity. Ecosystem diversity refers to the variety of ecosystems in the biosphere. Recall that ecosystems are made up of two components—biotic factors and abiotic factors. Biotic factors include interacting populations of species. Examples of abiotic factors include altitude, latitude, geology, soil nutrients, climate, and light levels. Because of the diversity of relationships among organisms and the variety of abiotic factors, Earth’s surface is highly varied physically and chemically, making ecosystem diversity very rich. Ecosystems can range in size from a small plant that grows on another plant to an entire biome, such as a tropical rainforest or Canada’s vast boreal forest.

18. Describe the diff erence among the three types of biodiversity.

19. Refer to Figure 1.18 (C). Identify three ecosystems you might fi nd in Algonquin Park.

20. What is a gene pool? 21. Explain why genetic diversity within a species is

always greater than the genetic diversity within an individual population.

22. Explain why genetic diversity is important to the survival of a species.

23. In the case of the Florida panther, humans intervened to save the species. Do you agree or disagree that humans should intervene to save endangered species? Explain your answer.

Learning Check

Sustainable agriculture must balance the risks of technology with the benefi ts. For example, atrazine is a herbicide used in agriculture to prevent the growth of weeds. Crops that have atrazine applied early in the growing season show a 25 percent increase in weed control, an 8 percent increase in corn yield, and an increase in profi t of $20 per hectare.

On the other hand, the herbicide is applied to crops early in the spring and can run off into nearby lakes and rivers. Studies have shown that atrazine and other chemicals can reduce reproductive success in many freshwater organisms. The timing of atrazine contamination of water sources directly coincides with amphibian breeding activities, since many amphibians reproduce during early spring rains.

In several European nations, atrazine has been banned because of environmental concerns. However, atrazine is approved for use in Canada. Alternative forms of weed control in corn crops are being investigated and include the use of bacteria and low-growing plants that block weeds from growing. Should the use of atrazine be banned completely worldwide?

Procedure 1. Read the introductory text and make a T-chart to list the

benefi ts and risks of using atrazine on corn crops.

2. Examine the graph on the right and add information to your chart.

3. Discuss the benefi ts and risks of using atrazine on corn crops with classmates.

Questions 1. Why is the timing of atrazine application such an

important factor?

2. Draw an illustration that shows the steps involved in how atrazine reaches aquatic ecosystems.

3. What is the direct impact of atrazine use on the leopard frog? Why is this something to be concerned about?

4. Name fi ve other species that would be aff ected by reduced frog reproduction. Sketch a food web to show the eff ects of atrazine on the biodiversity in ponds.

5. Analyze your T-chart. Do the benefi ts of using atrazine outweigh the risks? Explain your reasoning.

The graph shows the results of an experiment in which male northern leopard frogs were exposed to atrazine during development. The levels of testosterone in the atrazine-treated frogs were then compared to testosterone levels in non-treated male and female frogs.

Test

oste

ron

e (N

g/m

L)

Treatment Group

Testosterone Levels inNorthern Leopard Frogs

(Rana pipiens)

5

4

3

2

1

0

Atrazin

e-treated

Males

Non-treated

Males

Non-treated

Females

Activity 1.3 Sustainability and Diversity—Find a Balance?


S14_BIO11.indd 33 12/05/10 8:08 PM

Ecosystem ServicesEcosystem services are the benefi ts experienced by organisms, including humans, which are provided by sustainable ecosystems. Without ecosystem diversity, Earth would lose most of the services that ecosystems provide, which are shown in Table 1.6. Forests, for instance, take up carbon dioxide and maintain soil fertility. Ecosystems also maintain populations of organisms that are necessary for pest control, pollination, waste management, and other processes benefi cial to people.

In particular, wetlands provide several important ecosystem services, including storing water, which reduces the risk of fl oods; fi ltering water, which removes pollutants; and providing habitat for commercially important species of fi sh and shellfi sh. Because wetlands are so valuable, government agencies and non-governmental organizations oft en work together to preserve and protect them. For example, between 2000 and 2005, acting under the Great Lakes Wetlands Conservation Action Plan, more than 12 000 hectares of wetlands around the Great Lakes region were preserved. During that same time period government agencies worked with private organizations to restore another 4400 hectares of wetlands that had been disrupted by human activities such as agriculture and development.

Table 1.6 Examples of the World’s Ecosystem Services

Ecosystem Service Example

Atmospheric gas supply Regulation of carbon dioxide, ozone, and oxygen levels

Climate regulation Regulation of carbon dioxide, nitrogen dioxide, and methane levels

Water supply Irrigation, water for industry

Pollination Pollination of crops such as apples, blueberries, and clover

Ecological control Pest population regulation

Wilderness Habitat for wildlife

Food production Crops, livestock

Raw materials Fossil fuels, timber

Genetic resources Medicines, genes for disease resistance in plants

Recreation Ecotourism

Cultural benefi ts Aesthetic and educational value

Waste treatment Sewage purifi cation

Soil erosion control Retention of topsoil

Nutrient recycling Nitrogen, phosphorus, carbon, and sulfur cycles

Ecosystem Function and Species DiversityEcologists have long had the sense that ecosystems with greater species diversity were more likely to provide important services reliably. As well, there has also been a belief that such ecosystems exhibit resilience, the ability of an ecosystem to maintain an equilibrium, or balance, even in the face of signifi cant outside disturbances. Field research conducted by scientists from the University of Minnesota in the 1980s and 1990s has provided convincing evidence that this is the case.

Experiments came from a long-term project using many growing plots, each with a specifi c number of native plant species, ranging from 1 to 24. In all cases, the more species present in the plot, the more effi cient the ecosystem. Th e plots with more native species produced more biomass, which means they trapped more carbon dioxide. Th ey also consumed more nitrate, which can be toxic in high quantities. Th e more diverse plots were better able to resist the invasion of non-native species and exhibited reduced disease. Th e results of these experiments are shown in the graphs in Figure 1.21.

resilience the ability of an ecosystem to remain functional and stable in the presence of disturbances to its parts

SuggestedInvestigationThoughtLab Investigation 1-B, Resilience of a Grassland Ecosystem


S14_BIO11.indd 34 12/05/10 8:08 PM

65

60

55

50

45

40

35

30

25

0 5 10 15 20 25

Tota

l Pla

nt C

over

(%)

Plant Species Diversity

Plant Species Diversity andPercentage of Plant Coverage

Plant Species Diversity andNumber of Invasive Species

Plant Species Diversity andDisease Severity

4

3

2

1

0 4 8 12 16 20Plant Species Diversity

8

6

4

2

0 5 10 15 20 25

Num

ber

of I

nvas

ive

Spec

ies

(%)

Plant Species Diversity

Dis

ease

Sev

erit

y In

dex

Ecosystem Services and Human ActionsSometimes humans make changes to an ecosystem to enhance the services of the ecosystem. For example, wildlife offi cials may stock a lake with fi sh to provide recreation for fi shing enthusiasts. But what eff ects could this action have on the natural ecosystem of the lake? Th e results of a four-year study conducted by wildlife biologists in California showed that the introduction of non-native trout to mountain lakes in the western United States led to reduced population numbers of several amphibian species and changes in the number and variety of aquatic insect species. In particular, trout consume aquatic insects in the larval stage. Other organisms, including amphibians and other fi sh, also rely on insect larvae as a food source. As well, birds and bats that live near the lakes eat adult insects. All of these species must now compete with the non-native trout for food. Th e presence of trout has been linked with a decrease in the number of birds and in the activity of some types of bats.

In Ontario, the most successfully stocked fi sh is the smallmouth bass, shown in Figure 1.22. Introductions to previously bass-free lakes have greatly increased its Ontario range northward. Th is has enhanced recreational fi shing, but ecologists have documented resulting changes to lake ecology. One consequence is the loss of some native fi sh species such as stickleback and dace. Th is leads to a decline in species diversity and aff ects ecosystem diversity because the system loses complexity.

Where the bass are introduced into lakes with lake trout, the situation is worse. Trout are commonly top predators, but the reduced numbers of small fi sh caused by the introduced bass aff ect trout populations. With fewer small fi sh, trout must then consume less nourishing food, resulting in slower growth, smaller ultimate size, and decreased population numbers. Th is is a further impact on ecosystem diversity because of the food web alteration. Research documenting the negative eff ects of bass introductions has greatly reduced the practice. In Chapter 3, you will read more about how human actions aff ect biodiversity, particularly species diversity and ecosystem diversity.

Figure 1.21 In experiments conducted at the University of Minnesota from 1982 to 1993, researchers concluded that greater biodiversity in an ecosystem results in at least three beneficial patterns: increased plant cover, more resistance to invasive species, and more disease resistance.

Figure 1.22 Widespread introductions of the smallmouth bass in thousands of Ontario lakes have increased recreational fishing opportunities, but there have been negative consequences for species and ecosystem diversity.


S14_BIO11.indd 35 12/05/10 8:08 PM

BIOLOGY ConnectionsS T S E

DNA Bar Codes

Connect to the Environment

One benefi t of DNA bar code technology might be that farmers could identify pests and use species-specifi c methods for their removal. Do some research to fi nd out what is meant by “species-specifi c methods” and assess whether they are less harmful to the environment than other methods of pest removal.

Most people would fi nd it odd if their friend collected vials containing muscles from 940 diff erent species of fi sh—but then again most people haven’t undertaken a project as ambitious as this one.

DNA UPC Paul Hebert, a geneticist at the University of Guelph, in Ontario, is trying to gather cell samples from all of the world’s organisms. With small pieces of tissue no larger than the head of a pin, Hebert and his colleagues are working to assign DNA bar codes to every living species. Hebert has shown that the segment of mitochondrial DNA, called cytochrome c oxidase I, or COI, can be used as a diagnostic tool to tell animal species apart. Th e COI gene is easy to isolate and allows for identifi cation of an animal. A diff erent gene would need to be used for plants. Just like the Universal Product Codes (UPC) that appear on product packaging, the DNA segment sequence could be stored in a master database that would allow for easy access to the material. A hand scanner, when supplied with a small piece of tissue, such as a scale, a hair, or a feather, could identify the species almost instantly.

POTENTIAL BENEFITS Th is technology has several potential benefi ts. A doctor might use it to pinpoint disease-causing organisms quickly to prevent epidemics or to determine what antidote to give a victim of a snake bite. Health inspectors could scan foods for plant and animal contaminants. People who are curious about their surroundings could learn what lives around them. Farmers would be able to identify pests and use species-specifi c methods for their removal.

A NEW WAY TO CLASSIFY Using bioinformatics—a fi eld of science in which biology, computer science, and information technology merge—to create a database of DNA bar codes allows taxonomists to classify more organisms quickly. Currently, taxonomists have identifi ed approximately two million species. Scientists estimate that anywhere between 5 and 20 million species exist. Historically, species have been classifi ed using morphology, genetics, phylogeny, habitat, and behaviour. While the bar codes would not replace classic taxonomic methods, they could supplement them by giving scientists another tool to use.

This representation of DNA bar codes shows that the more closely related two species are, the more similar their bar codes are.

Honeybee American robin

Bumble bee Hermit thrush


031-037_S14_BIO11.indd 36 14/05/10 6:18 AM


Review Questions 1. C Use a graphic organizer to show the relationship

between the terms biodiversity, species diversity, genetic diversity, and ecosystem diversity.

2. A A pitcher plant (Sarracenia purpurea), shown on the right, is an Ontario bog plant with leaves that hold water in which various organisms live. Is a pitcher plant a species or an ecosystem? Explain your answer.

3. K/U Identify which of the following are ecosystems and explain what your answers tell you about ecosystem diversity.

a. fl ower basket b. surface of your skin c. schoolyard d. Lake Ontario e. the tundra

4. K/U Explain how the relationship between genetic diversity and disease resistance is similar to the relationship between species diversity within an ecosystem and disease resistance.

5. K/U Using examples from Table 1.6, explain why it is important to conserve ecosystem diversity.

6. K/U Why is it important to protect species diversity within an ecosystem?

7. C Summarize the information shown in the graphs in Figure 1.21.

8. T/I A microhabitat is an identifi ably diff erent portion of a larger discrete habitat such as a forest. Microhabitats off er a variety of microclimates, food, camoufl age, and shelter. Th e northern fl icker is a woodpecker that fi nds shelter in a hole in a tree, while a millipede fi nds food and shelter in the leaf litter at the base of the tree. Based on this information, predict the relationship between structural diversity and species diversity of an ecosystem.

9. A Attempts to calculate the cash value of diverse ecosystems have been made. One 1997 estimate placed Earth’s ecosystem services at more than 33 trillion dollars per year. Use the table below to answer the following questions.

a. Which ecosystem has the greatest global economic value? Why do you think this is?

b. Which ecosystem has the least global economic value? What is diff erent about this ecosystem compared to the others?

c. In your opinion, which ecosystem provides the most important ecosystem service? Why?

Value of the World’s Ecosystem Services

Ecosystem

Total Global Value (trillions

of dollars)Ecosystem

Service

Coastal shelf 4283 Nutrient cycling

Coral reef 375 Recreation

Cropland 128 Food production

Estuaries 4100 Nutrient cycling

Grasslands 906 Waste treatment/food production

Lakes and rivers 1700 Water regulation

Open ocean 8381 Nutrient cycling

Swamps 3231 Water supply

Temperate forest 894 Climate regulation/timber

Tropical forest 3813 Nutrient cycling/raw materials

10. K/U Explain the statement, “Maintaining the diversity of Earth’s ecosystems is important for species diversity.”

11. C Make a concept map that organizes the results of the study by biologists in which non-native trout were introduced to mountain lakes in the western United States.

Section Summary• Too little genetic diversity reduces a population’s ability

to resist disease or other changing environmental conditions.

• Ecosystems are diverse due to variations in abiotic and biotic factors.

• Ecosystems provide services, such as recycling nutrients and regulating gases in the atmosphere.

• Ecosystems with greater species diversity have higher resilience.


S14_BIO11.indd 37 12/05/10 8:08 PM

ThoughtLabI N V E S T I G AT I O N

S k i l l C h e c k

Initiating and Planning

✓ Performing and Recording

✓ Analyzing and Interpreting

✓ Communicating

Materials• reference books• computer with Internet access

Classifying Aquatic SpeciesIn the same way that marine organisms are mixed up in seafood stew, the names of the taxa that identify fi ve species are mixed up in the table below. In this lab, you will place each organism in its proper taxon at each level of the hierarchy.

Organisms in Seafood Stew

Common name Market squid, American lobster, blue mussel, Virginia oyster, European oyster

Phylum Arthropoda, Mollusca, Mollusca, Mollusca, Mollusca

Class Malacostraca, Bivalvia, Bivalvia, Bivalvia, Cephalopoda

Order Decapoda, Decapoda, Mytiloida, Pterioida, Pterioida

Family Ostreidae, Ostreidae, Nephropidae, Mytilidae, Loliginidae

Genus Homarus, Mytilus, Ostrea, Loligo, Crassostrea

Species americanus, virginica, edulis, edulis, opalescens

Pre-Lab Questions1. What is the order of classifi cation for organisms?2. Why is it useful to have a classifi cation system for organisms?

QuestionWhich organisms are closely related to each other? Which are not?

Organize the Data1. Draw a table with six columns and seven rows. At the top of the fi rst

column, write “Taxon.” At the top of each of the other columns, write the common name of each organism. Label the rows Phylum, Class, Order, Family, Genus, and Species.

2. Use reference books or the Internet to classify each organism at each taxon level.

Analyze and Interpret 1. Which order name is found in both the Arthropoda and Mollusca phyla

(plural of phylum)? What does this name mean? 2. Which two genera (plural of genus) have species with names containing the

same word? What does this word mean?

Conclude and Communicate 3. Which two organisms are most closely related to each other? Explain why. 4. Which organism is least closely related to the other four? Explain why.

Extend Further

5. INQUIRY Place fi ve organisms from your neighbourhood in the proper taxon at each level of the hierarchy.

6. RESEARCH How are names for the levels in the hierarchy determined?

1-A

The American lobster and the blue mussels shown here are both members of the animal kingdom.

Go to Organizing Data in a Table in Appendix A for help with making your table.


038-049_REV_BIO11.indd 38 14/05/10 6:25 AM

S k i l l C h e c k




✓ Communicating

Materials• graph paper• ruler

Resilience of a Grassland EcosystemResilience is the ability of an ecosystem to maintain an equilibrium, or balance, despite signifi cant outside disturbances. Results of studies conducted using experimental plots of plants showed that increased biodiversity in the experimental plots led to increased resistance to the invasion of non-native species and decreased incidence of disease. Th e scientists who reported these results also recorded data about the ability of grassland plants to resist drought conditions in relation to species diversity. Th ey measured the change in biomass of the plants from 1986, the year before the drought began, to 1988, the peak of the drought. Th e data collected are shown in the table below. Resistance values closer to zero imply greater resistance to the drought.

Pre-Lab Questions 1. What is resilience? 2. How is resilience related to species diversity within an ecosystem? 3. Why is it important to maintain biodiversity in ecosystems?

QuestionHow does species diversity aff ect the resilience of an ecosystem?

Organize the Data 1. Make a line graph of the data in the table. Note that the values on the

y-axis begin with zero and decrease to negative values. 2. Label the axes of your graph and give your graph a title.

Analyze and Interpret 1. Explain the relationship between resilience and species diversity in the

grassland plots used in this experiment. 2. Another factor that scientists analyze when determining the stability of an

ecosystem is the amount of time it takes for the ecosystem to return to the conditions that existed before the disturbance. Predict which plots returned to the pre-drought conditions more quickly—those with high species diversity or those with low species diversity. Explain your reasoning.

Conclude and Communicate 3. How does species diversity aff ect the resilience of an ecosystem?

Extend Further

4. INQUIRY Describe another experiment to gather more evidence about the relationship between the resilience of an ecosystem and its biodiversity.

5. RESEARCH Find out more about how planting native species in a disturbed area can help improve the ecosystem. Use the Internet or library to fi nd an example of how the resilience of a disturbed ecosystem was improved aft er native plants were planted.

ThoughtLabI N V E S T I G AT I O N 1-B

Resilience of a Plant Community During a Drought

Number of Plant Species

Resistance to Drought (change

in biomass/yr)

0 0.002 -1.104 -0.806 -0.758 -0.65

10 -0.5012 -0.4214 -0.4016 -0.4018 -0.4020 -0.3822 -0.3824 -0.38

Go to Constructing Graphs in Appendix A for help with making your graph.


038-049_REV_BIO11.indd 39 14/05/10 6:27 AM

InquiryI N V E S T I G AT I O N

S k i l l C h e c k




✓ Communicating

Materials• illustration of 18 beetles• sample dichotomous keys

Creating a Dichotomous Key To Identify Species of BeetlesIf you fi nd an insect you have never seen before, how could you discover its identity? Many fi eld guides help you match up the characteristics of your specimen with those of similar organisms using a dichotomous key. Th is identifi cation key uses a series of paired comparisons to sort organisms into smaller and smaller groups. In this investigation, you will learn how to make your own keys to identifi cation.

Pre-Lab Questions 1. What characteristics do all insects have in common? 2. Name two characteristics that scientists use to tell diff erent insects apart. 3. How can you use the characteristics of beetles to classify them?

QuestionHow do you make a dichotomous key?

PredictionPredict which characteristics of insects will be most useful in creating an identifi cation key.

Procedure 1. Copy the diagram of a dichotomous tree shown here onto a separate

piece of paper.group 7

group 8

group 3

group 4

group 9

group 10

group 1

group 2

group 11

group 12

group 5

group 6

group 13

group 14

Allbeetles

2. Study the illustration of 18 beetles shown on the next page. 3. Select one characteristic and sort the beetles into two groups based on

whether they have the characteristic or not. 4. List each beetle’s number under either group 1 or group 2 on your diagram.

1-C

A dichotomous key can help you identify beetles such as these.


REV_BIO11.indd 40 12/05/10 8:04 PM

1

Variegated mud-loving beetle

2

Mycetaeid beetle

3

Apricot borer

4

Water tiger

5

Predaceousdiving beetle

6

Crawlingwater beetle

7

Flathead apple borer

8

Red-neckedcane borer

9

Cucumbersnout beetle

10

Whirligig beetle

11

Ironclad beetle

12

Broad-hornedflour beetl

13

Red flour beetl

14

Blindant-beetle

15

False wirewormbeetle

16

White-markedspider beetle

17

Montereycyprus beetle

18

Drug storebeetle

5. Record the characteristic that identifi es each group. 6. Select another characteristic of each subgroup, and

repeat steps 4 and 5 for the next level down on your diagram.

7. Continue to subdivide the groups until you have 18 groups with one beetle in each.

8. Using the characteristics shown on your diagram, construct a dichotomous key that someone could use to identify any beetle from the original large group.

a. To do this, create a series of numbered steps with the fi rst step showing the fi rst characteristic you used.

b. At each step, off er two choices for classifying the beetle based on a single characteristic. For example, you may have used the characteristic “antennae longer than front legs” as your fi rst dividing characteristic. Th e fi rst numbered step in your key would be (1a) antennae longer than front legs or (1b) antennae not longer than front legs.

c. Use the sample keys provided by your teacher to help you.

9. Exchange your key with a partner. Use your partner’s key to classify a beetle, and record all the characteristics of the species you chose.

Analyze and Interpret 1. Did your partner produce a dichotomous key identical

to yours? Explain why or why not. 2. Which beetle characteristics were not useful for

creating your key? Explain why.

Conclude and Communicate 3. Why does a key off er two choices at each step and not

more than two? 4. In your own words, defi ne dichotomous key.

Extend Further

5. INQUIRY Your teacher will provide you with several diff erent “mystery” beetles. Use your dichotomous key to see if you can identify what species they are. You may be unable to completely identify your beetles using your key. If this is the case, how far could you go with your key?

6. RESEARCH Visit the library or the Internet and get a fi eld guide to beetles. Use this to identify the mystery beetles. What characteristics would you have needed in your key in order to fully identify them?


REV_BIO11.indd 41 12/05/10 8:04 PM

S T S E

Case Study

This large monoculture operation shows regularly spaced eucalyptus trees in Brazil. The regular, unobstructed spacing makes planting and harvesting easier than in a natural eucalyptus forest, but monocultures are at risk if a pest or disease attacks the crops.

Tree PlantationsThe root of the problem or the solution to deforestation?

You have joined the International Youth Delegation (IYD), an international coalition of youth working on urgent ecological issues, such as deforestation. The Food and Agriculture Organization of the United Nations (FAO) reports that approximately 13 million hectares of forests worldwide are cut down every year. Much of that land, particularly in the tropics, is cleared to increase arable land so people can grow food. A possible solution is to encourage the planting of fast-growing and economically important tree species, such as eucalyptus, as crops to be harvested. These managed tree plantations would provide income to local landowners and, at the same time, discourage ongoing deforestation. Your IYD group has been asked to assess the viability of monoculture tree plantations as a solution to deforestation. Many large organizations, including the United Nations and the World Bank, support the practice of monoculture tree plantations. Members of the IYD are divided on the issue. The members who agree with the UN and the World Bank have summarized their position on the issue. The key points of this summary include the following:• Tree plantations can be planted on cleared and deforested

land. These “re-created” forest areas provide habitats for many plant and animal species, some of which are at risk of extinction due to habitat loss.

• Forests reduce the potential for damage from drought and fl oods. As well, forests reduce soil erosion, which dramatically benefi ts local water quality in streams and rivers.

• Tree plantations bring many social and economic benefi ts to local farmers, including providing income and opportunities for other agricultural activities in the plantation, such as livestock grazing.

• Aside from providing the raw materials for the lumber industry, tree plantations also provide the waste wood that remains after harvesting. The waste wood can be used to produce renewable energy in the form of biofuels.

• The tree plantations act as a carbon sink, storing carbon in the wood of the trees and helping to keep it out of the atmosphere. Forests are known to store more carbon than they emit, so increasing forest cover means reducing net emissions of greenhouse gases.

Other members of the IYD have a diff erent opinion. They do not agree that planting trees as part of monoculture tree plantations is a solution to the problem of deforestation. Rather, they believe these plantations will increase the problems associated with loss of forest biodiversity, particularly in tropical countries. IYD members who oppose monoculture tree plantations have compiled a list of their concerns about tree plantations in a memo to the FAO, shown in the next page.

42 MHR • Unit 1 Diversity of Living Things42 MHR • Unit 1 Diversity of Living Things

REV_BIO11.indd 42 12/05/10 8:04 PM

Research and Analyze 1. There are tree plantations in

Canada, and one of the key species planted is red pine. The purpose of these tree plantations varies from helping the recovery of accidentally destroyed forests, such as those aff ected by forest fi re, to replacing the stock of wood harvested by pulp and paper companies. Research and analyze the similarities and diff erences between tree plantations in Canada and tree plantations in tropical countries as described in the scenario.

2. Tree plantations are considered to be a key factor in the fi ght against climate change because forests capture carbon. The United Nations Framework Convention on Climate Change (UNFCCC) is promoting a program to subsidize tree plantations in order to trap carbon and create “carbon credits” for the plantation owners. These credits can then be sold in international carbon markets, such as the European Union Emission Trading Systems (EU ETS). Research these programs and consider whether you agree that tree plantations are an important part of fi ghting climate change.

3. Make a Venn diagram to compare and contrast monoculture tree plantations and natural forests. What is your opinion of monoculture tree plantations? What questions do you have regarding tree plantations?

Take Action 1. Plan In a group, discuss the concerns related to

the issue of monoculture tree plantations. Based on research and the information in the scenario, what are the diff ering points of view in your group with respect to the practice? What are the diff erences, if any, between tree plantations in Canada and tree plantations in other, less developed countries? Share the results of the research and analysis you conducted in questions 1 to 3 above.

2. Act Prepare a letter to be submitted to the FOA outlining your recommendations about the viability of monoculture tree plantations as a solution to deforestation. Support your position with information from credible sources.

From: International Youth Delegation

To: United Nations Food and Agriculture Organization

RE: Concerns About the Practice of Tree Plantations

We believe that encouraging landowners to plant desirable tree

species, such as eucalyptus and mahogany, for later harvesting is

counterproductive in the fi ght against deforestation. Th e economic

benefi ts of tree plantations actually encourage local farmers to clear

existing stands of natural forests in order to plant large tracts of

monoculture trees.

Th e practice of developing tree plantations in order to make up for

the loss of natural ecosystems does not recognize that tree plantations

have no relationship to natural forests—the only similarity between

them is that they both contain trees. Natural forests contain many

diff erent species of trees and other plants that form the basis

for supporting a huge diversity of other organisms, including

insects, reptiles, and mammals. Monocultures may support some

biodiversity, but they provide a limited number of habitats compared

to naturally occurring forests, which are able to support ecosystems

rich in biodiversity. For example, a natural forest ecosystem in

Nigeria has between 40 and 55 species of trees, and each provides

habitat and resources for other species, such as birds and mammals.

A tree plantation has only a single species of tree.

Th e benefi ts of natural forests include providing many ecosystem

services, such as regulating water supply and reducing soil

erosion. Th ese ecosystem services cannot be replaced by planting

monocultures of tree species destined for harvest.

Monocultures are highly vulnerable to pests, disease, and natural

disasters. If any of these threats occurs, entire crops will be wiped

out. Farmers will be devastated and have no other crop to support

them as they replant and wait for new crops to mature.


REV_BIO11.indd 43 12/05/10 8:05 PM

SUMMARYChapter 1

Classifying and Naming SpeciesSection 1.1

Taxonomists classify species by using two-part scientifi c names and by using hierarchical classifi cation based on eight ranks.

KEY TERMSbinomial nomenclatureclassifi cationgenushierarchical classifi cationmorphology

phylogenyrankspeciestaxontaxonomy

KEY CONCEPTS• Biologists use the morphological species concept, the

biological species concept, and the phylogenetic species concept to defi ne species.

• Species often have common names. However, they are formally known by two-part scientifi c names.

• All species are classifi ed by being placed in eight nested ranks. The broadest category is the domain, continuing to narrow to kingdom, phylum, class, order, family, genus, and fi nally species, which is the narrowest category.

• Each named rank is known as a taxon.

Determining How Species Are RelatedSection 1.2

Modern classifi cation uses a variety of types of evidence to classify and determine relationships among species, but genetic information is currently a strong infl uence in our understanding of how to classify.

KEY TERMSanatomyancestor

phylogenetic treephysiology

KEY CONCEPTS• Modern classifi cation organizes diversity according to

evolutionary relationships.

• Taxonomists rely on morphological, physiological, and DNA evidence to identify and classify species.

• Anatomical evidence includes comparing the structure and form of organisms, including bones.

• Physiological evidence includes comparing the biochemistry of organisms, including proteins. DNA evidence includes comparing organisms’ DNA sequences.

• Understanding phylogeny can help scientists trace the transmission of disease and develop and test possible treatments.

Kingdoms and DomainsSection 1.3

All species are placed in three domains that contain six kingdoms, and taxonomists use dichotomous keys to identify species.

KEY TERMSautotrophdichotomous keyeukaryotic

heterotrophprokaryoticstructural diversity

KEY CONCEPTS• The variety of internal and external forms exhibited by

species represents structural diversity.

• There are two cell types: prokaryotic and eukaryotic. Prokaryotic cells do not have a membrane-bound nucleus. Eukaryotic cells are more complex and do have a membrane-bound nucleus.

• Organisms in the domains Bacteria and Archaea are unicellular and prokaryotic.

• Organisms in the domain Eukarya have eukaryotic cells and are unicellular or multicellular. There are four kingdoms in the domain Eukarya: Protista, Plantae, Fungi, and Animalia.

• Taxonomists use dichotomous keys to make choices between pairs of options to narrow down identifi cations.

Classifying Types of BiodiversitySection 1.4

Species diversity, genetic diversity, and ecosystem diversity are three types of biodiversity. Each is important to the health of a population, a species, and an ecosystem.

KEY TERMSecosystem diversitygene poolgenetic diversity

populationresiliencespecies diversity

KEY CONCEPTS• Too little genetic diversity reduces a population’s ability to

resist disease or other changing environmental conditions.

• Ecosystems are diverse due to variations in abiotic and biotic factors.

• Ecosystems provide services, such as recycling nutrients and regulating gases in the atmosphere.

• Ecosystems with greater species diversity have higher resilience.


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REVIEWChapter 1

Knowledge and UnderstandingSelect the letter of the best answer below. 1. Which kingdom has species whose cells do not have

cell walls? a. Animalia d. Plantae b. Archaea e. Protista c. Bacteria

Use this table to answer questions 2 and 3.Classification of Selected Mammals

Kingdom Animalia Animalia Animalia Animalia

Phylum Chordata Chordata Chordata Chordata

Class Mammalia Mammalia Mammalia Mammalia

Order Carnivora Perissodactyla Perissodactyla Perissodactyla

Family Phocidae Rhinocerotidae Equidae Equidae

Genus Halichoerus Diceros Equus Equus

Species Halichoerus grypus

Diceros bicornis

Equus caballus

Equus grevyi

Common Name

Grey seal Rhinoceros Horse Zebra

2. Which animal is the most distant relative to the others? a. E. grevyi d. rhinoceros b. grey seal e. zebra c. horse

3. At which level does the rhinoceros split from the zebra?

a. class d. order b. genus e. species c. family

4. Which term describes an identifi cation tool that uses a series of two-part choices?

a. binomial nomenclature b. dichotomous key c. phylogenetic tree d. phylogenetic key e. taxonomic key

5. Which type of diversity describes the variety of heritable characteristics in a population of interbreeding individuals?

a. biodiversity b. ecosystem diversity c. evolutionary diversity d. genetic diversity e. species diversity

6. Which species concept focuses on the evolutionary relationships among organisms?

a. morphological species concept b. biological species concept c. phylogenetic species concept d. taxonomic species concept e. hierarchical species concept

7. In which kingdom would you place an organism that is multicellular, has a cell wall made of cellulose, and is autotrophic?

a. Bacteria b. Archaea c. Protista d. Plantae e. Fungi

8. Which structure that makes up genes is of most interest to modern taxonomists?

a. glucose b. chitin c. cellulose d. eukaryote e. DNA

Answer the questions below. 9. What is the main benefi t of scientists using the same

system to classify living things? 10. Explain the meaning of the term binomial

nomenclature. 11. What is a domain? Give an example of a domain. 12. Which organisms are more closely related, those in the

same genus or those in the same family? 13. In your notebook, state whether each of the following

statements is true or false. If the statement is false, rewrite it so that it is true.

a. Some species of bacterium are eukaryotes. b. Species in the same family are more closely related

to one another than species in the same class. c. Th e morphological species concept classifi es

organisms based on their evolutionary histories. 14. Th e little brown bat (Myotis lucifugus) is common

throughout northwestern Ontario. Th e northern long-eared bat (Myotis septentrionalis) is also found in many regions of Canada. Explain the taxonomic relationship between these two mammals.

15. Identify fi ve ecosystem services that sustainable ecosystems provide.


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REVIEWChapter 1Chapter 1

16. Describe how anatomical evidence can be used to indicate the shared evolutionary history of whales, bats, horses, and humans.

Thinking and Investigation 17. You have discovered an unknown organism while on a

fi eld trip. You think it is a new species of protist. How could you test to identify this species as a protist? What data would you need to classify it in kingdom Protista?

18. You have found a heterotrophic species with cell walls made of chitin. What resources could you use from this chapter to determine in which kingdom it belongs? Identify the kingdom to which it belongs.

19. Many agricultural crops are known as monocultures, in which a single species is cultivated in a large fi eld. Identify some problems that might occur in monocultures, given experiments that show the relationship between species diversity and ecosystem effi ciency.

20. All living things can be classifi ed according to their anatomical and physiological

characteristics. Study the organisms shown below. Create a dichotomous key to identify them. Give the key to another person to use to identify the organisms. Make revisions to your key as needed.

21. Th e scientifi c name of a Bengal tiger is Panthera tigris tigris, and the Siberian tiger’s scientifi c name is Panthera tigris altaica. Th e third term in each name identifi es the subspecies of these animals. Why do you think taxonomists added the third term to the scientifi c names of these animals?

22. Infer the relatedness of the vertebrate animals shown in this phylogenetic tree. Explain your reasoning.

CommonAncestor

Snakes Lizards

Crocodiles Birds

Communication 23. Create a graphic organizer such as a main idea web to

show the diff erent domains and kingdoms. For each grouping, include a list of the characteristics that defi ne the grouping.

24. Create a handout to compare and contrast prokaryotic and eukaryotic cells. If you were to teach this material to students in a lower grade, what information would be the most important to teach them the basic diff erences between the two cell types?

25. Human activities aff ect the diversity of living things in ecosystems. Th ere are many

examples of plants that are harvested for medicinal use, such as the Pacifi c yew, which is used to make medication used in the treatment of certain cancers. In some areas, native plants used for medicinal purposes have been overharvested. Th ink about the possible eff ects that overharvesting of medicinal plants could have on biodiversity within an ecosystem. Make an argument for regulating the number of plants that can be harvested from a particular ecosystem.

26. Over 100 billion Cavendish bananas are consumed worldwide annually. As a result of agricultural practices, each Cavendish is genetically identical to all others. Write an e-mail to the owner of a banana plantation outlining your concerns about the lack of genetic diversity found in this important food source.

27. Biological diversity exists at diff erent levels. Draw a pyramid diagram showing the relationship between the three widely accepted levels of biodiversity.

28. Summarize your learning in this chapter using a graphic organizer. To help you, the Chapter 1 Summary lists the Key Terms and Key Concepts. Go to Using Graphic Organizers in Appendix A to help you decide which graphic organizer to use.


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Application 29. Taxonomists rely on more than anatomical,

physiological, and DNA evidence to classify. With animals, they also compare behaviour patterns between diff erent species to determine the degree of relatedness.

a. How valuable do you think this type of evidence is? Explain.

b. Provide an example of a type of behaviour that may be helpful to a taxonomist, and give reasons to support your answer.

30. Use the information in the table below to answer the following questions.

Ontario Reptiles

Common Name Scientifi c Name Family

Eastern garter snake Th amnophis sirtalis Colubridae

Painted turtle Chrysemys picta Emydidae

Eastern massasauga rattlesnake

Sistrurus catenatus Viperidae

Snapping turtle Chelydra serpentine Chelydridae

Spotted turtle Clemmys guttata Emydidae

Five-lined skink Eumeces fasciatus Scincidae

Smooth green snake Opheodrys vernalis Colubridae

Musk turtle Sternotherus odoratus

Kinosternidae

Ringneck snake Diadophis punctatus

Colubridae

Eastern ribbon snake

Th amnophis sauritus

Colubridae

a. Which pair of species is the most closely related pair? Explain.

b. How many families are represented by the four turtle species? Explain.

c. How many families are represented by the fi ve snake species? Explain.

d. Is the spotted turtle more closely related to the painted turtle or the musk turtle? Why?

31. Canadian researchers have helped uncover 15 new bird species through a process of genetic testing that they say will pave the way for cataloguing the world’s organisms. Th e discovery of so many new species was made possible by analyzing and comparing the DNA genetic bar codes of 643 North American bird species. Predict what the use of DNA genetic bar codes will have on the current taxonomic systems.

32. In 2005, a hunter shot what he thought was a polar bear in the Canadian Arctic. Th e bear was brownish white and had some other features not typical of polar bears. Genetic tests proved it was a hybrid, the off spring of a grizzly bear and a polar bear mating. Your friend says that this is evidence that polar bears and grizzly bears are the same species. Do you agree? What other information might you want to know before you agree or disagree? Explain your reasoning.

33. Use the dichotomous key below to answer the following questions.

A

B

1a. Front and hind wings similar in size and shape, and folded parallel to the body when at rest . . . . . . . . . . . . . . . . damselfly

1b. Hind wings wider than front wings near base, and extend on either side of the body when at rest. . . . . . . . . . . . . . . . dragonfly

a. Identify the organisms shown in the diagrams. Explain how you came to your decision.

b. From the key and the diagrams above, explain why you could conclude that dragonfl ies and damselfl ies evolved from a common ancestor.

34. Use the Internet or the print resources in your school’s library to research the common names of the animal Puma concolor. Based on your research, explain why scientists prefer to use binomial nomenclature rather than the common names of organisms.

35. Scientists are racing to discover new species that live just below the ice in the Arctic Ocean. However, the sea ice is disappearing and many of these unique organisms may become extinct. Use the Internet or print resources to research the services provided by this ecosystem. Based on this information, predict how the loss of sea ice will aff ect these services.


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Chapter 1 SELF-ASSESSMENT

Select the letter of the best answer below. 1. K/U Which is the correct order of the categories of

classifi cation, from most diverse to most specifi c? a. Kingdom, Domain, Phylum, Family, Class, Order,

Species, Genus b. Species, Genus, Family, Order, Class, Phylum,

Kingdom, Domain c. Kingdom, Family, Domain, Species, Genus, Phylum,

Class, Order d. Domain, Kingdom, Phylum, Class, Order, Family,

Genus, Species e. Domain, Kingdom, Phylum, Family, Class, Order,

Species, Genus 2. K/U Of the organisms listed below, which is the

closest relative of the snowy owl (Bubo scandiacus)? a. barn owl (Tyto alba) b. great horned owl (Bubo virginianus) c. saw-whet owl (Aegolius acadicus) d. eastern screech owl (Megascops asio) e. burrowing owl (Athene cunicularia)

3. K/U Which two kingdoms are not classifi ed in Domain Eukarya?

a. Protista and Fungi b. Plantae and Animalia c. Bacteria and Fungi d. Archaea and Protista e. Bacteria and Archaea

4. K/U Th e monarch butterfl y (Danaus plexippus) and viceroy butterfl y (Limenitis archippus) look almost identical. Which species concept might have led taxonomists to classify them as the same species?

a. phylogenetic species concept b. Linnaean species concept c. biological species concept d. morphological species concept e. binomial species concept

5. K/U An autotrophic prokaryote with no cell wall would be found in which kingdom?

a. Archaea d. Fungi b. Bacteria e. Plantae c. Protista

6. K/U Which species concept focuses on the ability of organisms to interbreed in nature and produce viable, fertile off spring?

a. morphological species concept b. biological species concept c. phylogenetic species concept d. taxonomic species concept e. hierarchical species concept

7. K/U Which statement about binomial nomenclature is false?

a. An organism’s scientifi c name is made up of two words.

b. Th e fi rst word of an organism’s scientifi c name is its genus, and the second word is its species.

c. Th e scientifi c name is italicized if typed. d. Th e scientifi c name is underlined if handwritten. e. Both the genus and species names are capitalized.

8. K/U Th e following is an example of a tool used by taxonomists to divide Order Cetacea (whales, dolphins, and porpoises) into two suborders.

1a. have baleen plates for fi ltering food from water . . . . . . Suborder Mysticeti: baleen whales

1b. have teeth .. . . . . . . . . . Suborder Odontoceti: toothed whales

What is the name of this taxonomic tool? a. scientifi c name b. binomial nomenclature c. phylogenetic species concept d. dichotomous key e. hierarchical classifi cation

9. K/U Identify the level of diversity that is evident in the variety of inherited traits within a species.

a. species diversity b. genetic diversity c. ecosystem diversity d. taxonomic diversity e. phylogenetic diversity

10. K/U Which is not a benefi t of understanding the evolutionary relationships among species?

a. discovering the source of new medicines b. discovering new proteins or chemicals c. identifying biological controls through use of

natural predators d. protecting and conserving existing species e. determining the number of wolves in an area


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Self-Check

If you missed question ... 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Review section(s) ... 1.1 1.1 1.3 1.1 1.3 1.1 1.1 1.3 1.4 1.2 1.3 1.1 1.1 1.3 1.4 1.2 1.1 1.4 1.3 1.3 1.4 1.3 1.2

Use sentences and diagrams as appropriate to answer the questions below. 11. K/U Identify the kingdom in which you would place

a single-celled, eukaryotic organism that makes it own food.

Use the table below to answer questions 12 and 13.Classification of a Coyote and a Dog

Rank Coyote DogDomain Eukarya EukaryaKingdom Animalia AnimaliaPhylum Chordata ChordataClass Mammalia MammaliaOrder Carnivora CarnivoraFamily Canidae CanidaeGenus Canis CanisSpecies Canis latrans Canis familiaris

12. A Use the scientifi c name of the coyote to explain binomial nomenclature.

13. T/I Predict the family into which the red wolf (Canis rufus) would be classifi ed. Explain, in terms of the hierarchical classifi cation system, your prediction.

14. C Construct a dichotomous key you could use to classify the music of 10 performers on a personal digital audio player.

15. C A group of concerned students is developing a plan to increase the biodiversity of their school’s grounds. Currently, the school ground is primarily a large open grass fi eld with a handful of trees planted near the chain-link fence that surrounds the grounds. Make a list of at least fi ve actions the students could include in their plan to increase the biodiversity of their school’s grounds.

16. T/I Two scientists, working independently, produce the phylogenetic trees shown below for the same group of organisms. Explain why the two scientists could come up with the two diff erent phylogenetic trees.

Common Ancestor

Phylogenetic Tree A

NML

Common Ancestor

Phylogenetic Tree B

MLN

17. A Th e clouded leopard is a medium-sized wildcat found in the forests of Asia. In a study comparing diff erences in clouded leopard coat patterns and coloration throughout the cat’s range, researchers concluded that individuals found on the islands of Borneo and Sumatra are markedly diff erent from animals found on the Southeast Asian mainland. Th ese observations have been supported by genetic testing. Based on this information, are the clouded leopards of Borneo and Sumatra the same species as those on the mainland, or are the two groups diff erent species? Explain your reasoning.

18. A In the 1800s, Irish farmers planted a large number of potatoes that were genetically identical to one another. When a potato disease swept through the country in the 1840s, the potatoes, and the people who depended on them for food, were devastated. Explain how the lack of genetic diversity of the potatoes grown in Ireland could have contributed to a period of low or no crop yield and widespread starvation.

19. T/I Rhizopus stolonifer can be found growing on an old loaf of bread or a piece of fruit that has been sitting on the counter for several days. Members of this species cannot make their own food, and they have a cell wall. Is there enough information provided above to defi nitively place this species in one of the six kingdoms? Explain why or why not.

20. K/U List the characteristics of eukaryotic cells and prokaryotic cells.

21. K/U Defi ne the term ecosystem services and list fi ve examples of the world’s ecosystem services.

22. T/I While hiking in the Hudson Bay Lowlands, you fi nd a multicellular organism growing on the bark of a dying black spruce tree. Under a microscope, you observe that its cells are eukaryotic, have cells walls, and do not contain chloroplasts. Into what kingdom would you classify this organism? Explain why.

23. C Suppose you had to explain the phylogenetic tree shown in Figure 1.5 to a class of Grade 6 students. Write a short paragraph explaining what the diagram shows and how scientists use other diagrams like it to help classify organisms.


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Documents

CHAPTER 1 Classifying Life’s Diversity · related to biodiversity (1.1, 1.4) • B2.4 create and apply a dichotomous key to identify and classify organisms from each of the kingdoms