Chapter 1: Classifying Life's Diversity PDF

UNIT 1 Diversity of Living Things C anada’s Carolinian ecosystem, located in southern All living things can be classified...

UNIT 1 Diversity of Living Things C anada’s Carolinian ecosystem, located in southern All living things can be classified Ontario, is unique. With over 2000 species of plants according to their anatomical and physiological characteristics. and approximately 400 species of birds, it is one of Canada’s most diverse ecosystems. These baby opossums Human activities affect the diversity of living things in ecosystems. are just one of many animal species that live in Carolinian Canada. How are scientists able to identify and classify all of the organisms Overall Expectations that live in Carolinian Canada? They use a classification system that In this unit, you will... has been developed over the last 250 years. The system allows scientists to begin with a broad category and analyze the effects of various human activities on the diversity of living things continue to narrow down the classification of an organism based on its distinguishing characteristics. For example, you know these investigate through laboratory and/or field activities, or through simulations, opossums fit into one broad category, animals, but how could you the principles of scientific classification, narrow down the classification even more? Since they have hair and using appropriate sampling and glands that produce milk to nourish their young, they are mammals. classification techniques But what type of mammal? Did you know that, like kangaroos and demonstrate an understanding of the koala bears, opossums are pouched mammals? After the young are diversity of living organisms in terms born, they continue to develop in a pouch on the mother’s body. of the principles of taxonomy and What other characteristics might scientists use to classify these phylogeny opossums into more specific categories? As you study this unit, look ahead to the Unit 1 Project on pages Unit 1 Contents 142 and 143, which gives you an opportunity to demonstrate and Chapter 1 Classifying Life’s Diversity apply your new knowledge and skills. Keep a planning folder so you How do scientists classify life on Earth? can complete the project in stages as you progress through the unit. Chapter 2 Diversity: From Simple to Complex What are the characteristics of bacteria, archaea, and protists? Chapter 3 Multicellular Diversity How do plants, fungi, and animals differ? 2 3 UNIT 1 Preparation Sustainable Ecosystems An ecosystem includes all the interacting parts of a Climate change refers to changes in the long-term biological community and the non-living components trends of climate conditions experienced by a region. of its environment. Ecosystem services are the benefits experienced by Sustainable use of a resource is use that does not organisms, including humans, that are provided by cause long-term depletion of the resource or affect the sustainable ecosystems. Ecosystem services are the diversity of the ecosystem from which the resource is natural result of all the activities that occur in the obtained. biosphere. A sustainable ecosystem is one that is capable of Biodiversity is the number and variety of organisms withstanding pressure and giving support to a variety found in a specific region. The current accelerated rate of organisms. Sustainable ecosystems endure, and they of extinctions is often referred to as the biodiversity support a wide variety of organisms. All organisms crisis. Scientists hypothesize that the biodiversity crisis require sustainable ecosystems for survival. has resulted from the actions of humans. Photosynthesis and cellular respiration are reciprocal processes that cycle oxygen and carbon dioxide through the biosphere. 1. Which is a predicted impact of climate change? 5. Define the term ecosystem. Include a description of a. Sea ice coverage will increase in area. a terrestrial ecosystem and an aquatic ecosystem in b. Evaporation rates will decrease worldwide. your definition. c. Flow rate of ocean currents will increase. 6. Define the term sustainable ecosystem. d. Sea levels will rise. 7. What is meant by the statement, “All organisms e. The frequency and intensity of storms will decrease. require sustainable ecosystems for survival”? 2. Which is an example of an ecosystem service? 8. Explain why you agree or disagree with the statement a. the provision of food and clean water that consumers depend on producers for survival. b. the cycling of nutrients 9. Explain climate change in terms of rising average c. the conversion of atmospheric carbon into biomass temperatures, changing precipitation, and severity of d. the pollination of crops and natural vegetation storms. e. All of the above are true. 10. Explain how ecosystem services are linked to the 3. Which is a threat to biodiversity? concept of sustainable ecosystems. a. reforestation d. bioremediation 11. Explain the connection between biodiversity and b. wetland restoration e. bioaugmentation ecosystem sustainability. c. deforestation 12. Write a caption explaining what is displayed on the 4. The diagram below shows the processes of graph below. photosynthesis and cellular respiration in a plant leaf. Mass Extinctions O2 (families per million years) CO2 Photosynthesis 20 light (day) Late Permian- Ordovician Triassic Extinction Rate 15 Cretaceous- H2O glucose Late Tertiary Devonian Late energy 10 Triassic 5 Cellular Respiration H2O CO O2 (day and night) 2 Paleozoic Mesozoic 0 600 300 0 a. What is photosynthesis? Millions of Years Ago b. What is cellular respiration? 4 MHR Unit 1 Diversity of Living Things  Safe and Effective Use of the Microscope The light microscope is an optical instrument that A compound microscope consists of structural magnifies objects that are usually too small to be seen and optical components. The three basic structural with the unaided eye. components of a compound microscope are the tube, A compound light microscope uses a series of lenses base, and arm. There are two optical systems in a and a light source to view the object. compound microscope: the eyepiece lens and the objective lenses. A microscope is an expensive, precision instrument that must be handled properly and carefully. There are proper procedures to follow and skills required to use a microscope safely and effectively. 13. Which microscope is commonly found in most high 17. Make a table in your notebook that school science labs? a. identifies the parts of the microscope shown below a. compound light microscope b. describes the function of each component b. transmission electron microscope (TEM) c. scanning electron microscope (SEM) A d. phase contrast microscope e. fluorescence microscope K 14. Which statement is false with respect to using a microscope? B J a. The specimen appears upside down and backward. b. When you move your slide to the right, it appears to move to the left. I C c. When you switch from the low-power objective lens H to a higher-power objective lens, the field of view decreases. G D d. When you switch from the low-power objective lens to a higher-power objective lens, the amount of detail you observe decreases. e. The total magnification of the specimen you are E observing with a 10× eyepiece lens and a 40× objective lens is 400×. F 15. Explain why it is important to follow the proper procedures for handling and using a microscope. Include the proper way to carry a microscope from the storage area to your lab station. 18. When working with microscopic specimens, it is often 16. Which shows the proper way to calculate the total difficult to observe the structures in the specimens magnification of an object viewed under low power? clearly. You can use various stains to colour the (Assume the eyepiece magnification is 10× and the structures you want to see. Summarize the steps you low-power objective is 4×.) would use to stain onion epidermis cells and then a. 10 × 4 = 40× make a wet-mount slide of these cells. Assume you will use iodine solution to stain the cells. A piece of onion b. 10 ÷ 4 = 2.5× is lined on either side by a single layer of cells, which is c. 10 - 4 = 6× called an epidermis. d. 10 + 4 = 14× 19. Summarize the proper microscope procedures for e. 10 × 4 × 4 = 160× viewing the wet-mount slide that you described making in question 18. Unit 1 Preparation MHR 5  Cell Structure and Function The cell theory is one of the major theories in science. In plant and animal cells, specific functions to All cells have a cell membrane to control what enters support life are carried out by internal cell parts called and leaves the cell. The membrane separates the inside organelles. Examples of cellular organelles include of the cell from the outside environment. mitochondria, Golgi bodies, ribosomes, vesicles, vacuoles, chloroplasts, and a nucleus or multiple nuclei. The cytoplasm includes the organelles and other life-supporting materials, such as water, all of which are contained by the cell membrane. 20. Which statement about cell theory is false? 25. Which describes the function of a chloroplast? a. Cells are the structural and functional units of life. a. captures light energy for photosynthesis b. Cells divide to produce new cells. b. controls cell’s functions c. Cells can arise spontaneously out of inorganic matter. c. makes proteins d. All organisms are composed of one or more cells. d. packages proteins into vesicles e. Cells pass copies of their genetic material on to e. stores food daughter cells. 26. Identify the structures labelled in the diagram below. 21. What is the primary function of a cell membrane? Record your answers in your notebook. a. allows materials to move out of but not into the cell B b. allows materials to move into but not out of the cell A c. always uses energy to move materials into and out of the cell d. creates a separate, independently functioning environment in the cell e. controls what enters and leaves the nucleus 22. Mitochondria in both plant and animal cells carry out which function? a. producing glucose from sunlight b. converting glucose into usable energy c. manufacturing proteins d. packaging and secreting proteins C e. storing water and nutrients 23. Which statement about cells is true? F D a. Only plant cells have a cell wall and chloroplasts. b. Only animal cells have a cell wall and chloroplasts. E c. Only plant cells have a nucleus and mitochondria. 27. Identify the function of each organelle listed below. d. Only animal cells have a nucleus and mitochondria. a. ribosome e. There are no differences between plant and animal b. mitochondrion cells. c. vacuole 24. Which structure helps strengthen plant cells? d. vesicle a. cell wall 28. Describe a procedure to identify whether a sample of b. chloroplast cells was collected from an animal or from a plant. c. cytoplasm 29. Explain the relationships between the nucleus, d. endoplasmic reticulum ribosomes, and proteins. e. ribosome 6 MHR Unit 1 Diversity of Living Things  Diffusion and Osmosis The cell membrane controls what enters and leaves Diffusion is the net movement of particles from the cell. an area of high concentration to an area of lower Concentration is the quantity of a given substance in concentration. a given volume. Osmosis is the movement of water molecules across a cell membrane from an area of higher concentration of water to an area of lower concentration of water. 30. Which is an example of osmosis? 33. Explain the term selectively permeable as it applies to a. movement of oxygen from the alveoli in lungs into a cell membrane. capillaries of the circulatory system 34. Compare the processes of diffusion and osmosis in the b. movement of carbon dioxide from capillaries of the context of a cell membrane. circulatory system into the alveoli in lungs 35. Describe the importance of diffusion to a cell. c. absorption of nutrients from the villi of the small 36. An amoeba (Amoeba proteus) is a single-celled intestine into the capillaries of the circulatory protozoan that lives in fresh water. Water continually system moves into this organism by osmosis. Amoebas use d. absorption of water from the soil to plant root cells an organelle called a contractile vacuole to remove e. movement of sugar produced by photosynthesis excess water from the cell. from the leaves to other parts of a plant 31. Which plant cell shown below is in an environment contractile where there is a higher concentration of water vacuole molecules inside the cell than outside of the cell? H2O H2O H2O H2O H2O a. Describe what would happen to an Amoeba proteus if it did not have a contractile vacuole. b. Predict the effect of placing an Amoeba proteus in salt water. I II III IV 37. Dialysis tubing is a material used to make artificial a. I c. III membranes that are selectively permeable. A b. II d. IV photograph of a membrane model made with dialysis tubing is shown below. Imagine that the membrane 32. A dropper-full of ink is released into a beaker of water. model contains distilled water and is placed in the The three photographs below show how the ink diffused ink-and-water beaker from question 32. Assume that in the water over a period of time. Write one caption the ink has fully diffused through the water when the to go with this set of three photographs to explain membrane model is placed in it. Also assume that the what is happening. The following terms should appear dialysis tubing is permeable to water but not to ink in your caption: diffusion, high concentration, low particles. Describe what will happen as time passes, concentration, ink, water. and explain why it will happen. Unit 1 Preparation MHR 7  CHAPTER Classifying Life’s Diversity 1 Specific Expectations In this chapter you will learn how to... B1.1 analyze some of the risks and benefits 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 different 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. The Census is a 10-year project with the goal of learning more about the diversity and distribution of marine life. The yeti crab is one example of that diversity. Based on genetic analysis, it is so different 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. 8 MHR Unit 1 Diversity of Living Things  Launch Activity Organizing Life When you think of biodiversity, you may think of the ocean or a rainforest. However, biodiversity exists in your area as well. Think about the different types of birds, insects, or plants that you see when you are outside in your neighbourhood. How many different kinds of organisms live in your neighbourhood? In this activity, you will list and classify local species. Procedure 1. Make a list of all the different 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 differences 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 define your groups? How many different subgroups did you make? 2. Exchange your lists with a partner. Interpret and discuss each other’s system of classification. 3. Compare the similarities and differences among the classification systems in the class. Why were so many systems invented? Chapter 1 Classifying Life’s Diversity MHR 9  SECTION Identifying, Naming, and Classifying Species 1.1 Key Terms 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 species thousands of kilometres, and fungi that help break down dead trees, there are millions morphology of species on Earth. To date, scientists have identified about 2 million species on Earth. phylogeny Although 2 million is a large number and new species are discovered every day, it is taxonomy thought that this is just a fraction of the total number of species on Earth. Scientists binomial nomenclature estimate that the total number of species on Earth ranges from 5 million to 20 million. genus Knowing the identity of Earth’s species is important not just to biologists or other classification scientists, but to everyone in society. Farmers and gardeners need to be able to identify hierarchical classification weeds that might be growing next to their crop plants. Doctors need to know which rank species of bacteria a patient is infected with in order to prescribe the correct medication taxon 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 species a group of officials must check incoming goods to prevent the introduction of an invasive organisms that can species. Because species have been identified, defined, and named by scientists, people interbreed in nature and worldwide can communicate about all of the different organisms that live on Earth. produce fertile offspring Identifying and Naming New Species Suppose 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 scientific names? Throughout history, scientists have used different methods, and examined and compared different characteristics, to define and classify a species. A B 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? 10 MHR Unit 1 Diversity of Living Things Identifying Species: Using Species Concepts Despite centuries of thought and research, scientists have been unable to agree on a morphology the single definition of what a species is. Instead, they have proposed various definitions branch of biology that of species, which are called species concepts. Table 1.1 describes three commonly used deals with the structure species concepts, along with advantages and disadvantages for each. Notice that each or form of organisms species concept focuses on a different aspect of organisms. phylogeny the evolutionary history of The morphological species concept focuses on morphology—body shape, size, and a species other structural features. The biological species concept defines species on the basis of whether two organisms can produce fertile offspring. The 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 The morphological species concept Advantage: The relative simplicity of focuses on the morphology of an this species concept makes it the most organism. This species concept relies widely used, particularly for plants. on comparing measurements and Disadvantage: The challenge in descriptions of similar organisms, applying this species concept comes taking into account that species change from having to decide how much over time and that they have variation. difference between individuals is too After comparisons are completed, much variation. Almost all populations scientists decide whether similar are made up of non-identical organisms represent different species. individuals. Biological species concept The biological species concept focuses Advantage: This species concept is on similar characteristics and the widely used by scientists. ability of organisms to interbreed Disadvantages: This species concept in nature and produce viable, fertile cannot be applied in all cases. For offspring. This means that if two example, when two populations are individual organisms can mate under physically separated, they never have natural circumstances and they the opportunity to interbreed in produce offspring that can successfully nature. This means that the viable, live and reproduce, then those two fertile offspring requirement cannot individuals are the same species. 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 The phylogenetic species concept Advantages: The phylogenetic species focuses on evolutionary relationships concept can be applied to extinct Bacteria among organisms. A species is species. It also considers information defined as a cluster of organisms about relationships among organisms that is distinct from other clusters learned from DNA analysis, a method and shows a pattern of relationship scientists are using more and more. For among organisms. For example, when example, it was through DNA analysis a prehistoric species branches into that scientists were able to classify the Archaea two species over time, it becomes pink iguana from the Galapagos Islands two different phylogenetic species. as a new species. This concept has become increasingly Disadvantage: Evolutionary histories Common Ancestor popular as biologists have obtained are not known for all species. more evidence through DNA analysis about how species are related. Chapter 1 Classifying Life’s Diversity MHR 11  Naming Species Once 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 differ from continent to continent, country to country, and often 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 different 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. Thus, having a standard system for naming organisms, understood by any scientist, anywhere in the world, is essential. 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. A System of Standard Names for Species: Binomial Nomenclature taxonomy the branch of biology that identifies, Taxonomy is the branch of biology that identifies, names, and classifies species. names, and classifies Swedish scientist Carl von Linné, who is better known by the Latinized version of his species based on natural name, Carolus Linnaeus, is often referred to as the Father of Taxonomy. He is credited features with developing the system for naming species: binomial nomenclature. Binomial binomial refers to something with two parts, and nomenclature means a naming system. Thus, nomenclature the system of giving a in this system, each species has a two-part name. The two-part name is known as the two-word Latin name species name, although it is often referred to as the scientific name as well. to each species—the The first word in the scientific name is the genus name. The second word in the first part is the genus scientific name identifies the particular species. The scientific name is italicized when and the second part is typed, with the genus name capitalized and the species in lower case. For example, the the species scientific name for humans is Homo sapiens. When the scientific name is written by genus (plural genera) taxonomic group of hand, both parts of the name are underlined. a closely related species 12 MHR Unit 1 Diversity of Living Things  Learning Check 1. Explain why it is important to everyone in society 4. Explain the advantages of using binomial for scientists to identify, define, and name species. nomenclature rather than common names to refer 2. Explain why there are several different species to organisms. concepts, rather than a single definition for a species. 5. Use a graphic organizer to compare and contrast the 3. State which presentation of the scientific name for types, advantages, and disadvantages of the species the domesticated dog is correct. Then explain why it concepts described in Table 1.1. is correct and why the other three are incorrect. 6. The offspring of a horse and a donkey is a mule. a. Canis familiaris c. Canis familiaris Mules are unable to reproduce. Are horses and b. Canis familiaris d. Canis Familiaris donkeys members of the same species? Why or why not? Use the biological species concept to explain why or why not. Classifying Species Species concepts allow scientists to determine what groups of organisms make up a classification the species. Binomial nomenclature allows scientists to apply a formal name for each of grouping of organisms those species. But millions of species currently live on Earth, and many other extinct based on a set of species have been identified from fossils. However, to understand, demonstrate, and criteria that helps communicate the relationships in life’s diversity, scientists need a set of agreed-upon to organize and indicate evolutionary rules or criteria to help them classify species. Again, it was Linnaeus who developed relationships the basis of the system of classification we use today. Activity 1.1 You Decide: Snake or Lizard? Suppose that you observe a reptile like the one shown 3. What other data could you collect or analyze to provide in the photograph below. The reptile has no legs. However, additional evidence to help you confirm your decision? that does not mean that it is a snake, because legless lizards Morphological Characteristics of Snakes and Lizards also exist. How could you determine whether this reptile is a snake or a lizard? Tail Tip Breaks Procedure Ear Off When Organisms Eyelids Openings Handled Legs 1. Use the information in the table on the right to determine whether your specimen is a snake or a lizard. Snakes Cannot No No No move Questions Lizards Movable Yes Yes Yes/No 1. What type of reptile do you think the organism is? Explain your reasoning. Your Movable Yes Yes No specimen 2. Which species concept did you use to help classify your specimen? Explain your reasoning. This legless reptile is known as Ophisaurus attenuatus. Chapter 1 Classifying Life’s Diversity MHR 13  Hierarchical Classification Imagine a world in which there are just four sports: golf, tennis, hockey, and soccer. hierarchical classification the Any sports competition could then be classified in one of four categories—a very method of classifying simple, un-nested system, such as the first one in Figure 1.3. Notice, however, that organisms in which this simple system can be modified by rearranging the sports into categories based on species are arranged in the characteristic of team sports versus non-team sports. The resulting classification categories from most general to most specific scheme is known as a nested system, because there is a hierarchy of categories. That is, the four specific sports are clustered into two more general categories. A hierarchy is an arrangement of items in which the items are identified as being above, below, or at the same level compared to other items. Because nested classification systems have categories arranged in hierarchies, this method of organization is called hierarchical classification. Un-nested Classification Sports Hockey Soccer Tennis Golf Nested Classification Sports Team Sports Non-team Sports Hockey Soccer Tennis Golf 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. Taxonomic Categories Used To Classify Organisms Taxonomic categories are the groupings, arranged in a hierarchy, that are used to rank a level in a classification scheme, classify organisms that have been named and identified. In most cases, a species is such as phylum or order classified by assigning it membership in eight nested categories. Each of the eight taxon (plural taxa) taxonomic categories is known as a rank. The name of each rank is called a taxon. a named group of Table 1.2 shows how the species Canis lupus, the grey wolf, is classified using organisms such as taxonomic categories. To start, based on the morphology and complexity of its cells, phylum Chordata or order Rodentia 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. 14 MHR Unit 1 Diversity of Living Things Table 1.2 Taxonomic Classification of the Grey Wolf (Canis lupus) Rank Number of (Taxonomic Grey Wolf Species Examples of Species in Taxon Category) Taxon in Taxon Domain Eukarya 4–10 million Kingdom Animalia 2 million Phylum Chordata 50 000 Class Mammalia 5 000 Order Carnivora 270 Family Canidae 34 Genus Canis 7 Species Canis lupus 1 The Grey Wolf: Kingdom to Species Within the domain Eukarya are four kingdoms, and the grey wolf is placed in the animal SuggestedInvestigation kingdom. The kingdom has fewer species in it than a domain. However, because the ThoughtLab Investigation animal kingdom includes insects and all other animals, it still contains more than a 1-A, Classifying Aquatic million species. As you can see from Table 1.2, within the animal kingdom is the chordate Species phylum. A phylum further narrows an organism’s classification. Wolves are classified in the chordate phylum. The chordate phylum does not include animals such as insects and worms, but it still includes other groups, such as fish and birds. As classification of the grey wolf continues to be narrowed down, the ranks become more specific 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. The Canis genus includes the grey wolf, shown in Figure 1.4, as well as the coyote and five 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. Chapter 1 Classifying Life’s Diversity MHR 15  Section 1.1 RE V IE W Section Summary Biologists use the morphological species concept, All species are classified by being placed in eight nested the biological species concept, and the phylogenetic ranks. The broadest category is the domain, continuing to species concept to define species. narrow to kingdom, phylum, class, order, family, genus, Species often have common names. However, they are and finally species, which is the narrowest category. formally known by two-part scientific names. Each named rank is known as a taxon. Review Questions 1. C Make a Venn diagram to compare and contrast 10. A The table below shows the classification of a the morphological species concept and the praying mantis, an insect that preys on smaller insects. phylogenetic species concept. a. What is the scientific name for the praying mantis? 2. A In northwestern Ontario, there are two similar- b. Which is the broadest category of classification for looking garter snakes: the red-sided garter snake the praying mantis? and the eastern garter snake. The two interbreed c. What is the narrowest rank and taxon that the successfully in nature in that part of Ontario, praying mantis and the grey wolf have in common? producing offspring that have a mix of the physical Do you think these two organisms are closely traits of the two. The eastern garter snake also co-exists related? Why or why not? in southern Ontario with another very similar snake, Classification of the Praying Mantis the eastern ribbon snake. However, these two snakes Category Praying Mantis are not known to interbreed successfully. Infer whether these three snakes are the same species or not. Explain Domain Eukarya your reasoning. Kingdom Animalia 3. K/U What is binomial nomenclature? Phylum Arthropoda 4. K/U Two terms can be used to describe the Class Insecta organization of organisms into hierarchies that help Order Mantodea scientists understand the relationships among living Family Mantidae things: classification and taxonomy. Explain why both Genus Stagmomantis terms can be used correctly for this purpose. Species Stagmomantis carolina 5. A Design a different nested classification 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 first letter of each rank as the first 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 A praying mantis feeds on ants, bees, and spiders. modern classification system. List the other ranks in 11. T/I In one naming system used before Linnaeus which these two organisms would also be placed developed his, the European honeybee had a name within this system. with 11 descriptive words, all in Latin (Apis pubescens, 9. K/U Compare the number and variety of organisms thorace subriseo, abdomine fusco, pedibus posticis placed in a kingdom taxon to the number and variety glabris untrinque margine ciliatis). In the system of organisms found in a species taxon. developed by Linnaeus, this bee’s scientific name became Apis mellifera. Evaluate the advantages of the current naming system compared to the earlier system. 16 MHR Unit 1 Diversity of Living Things  SECTION Determining How Species Are Related 1.2 The goal of modern classification is to assign species to taxa so that the classification Key Terms reflects both morphological similarities among organisms as well as hypotheses about ancestor their phylogeny (evolutionary history). To do this, biologists use the concept of shared anatomy evolutionary history. If two species share much of the same evolutionary history, it means physiology they have a fairly recent common ancestor. In other words, the more a species shares phylogenetic tree 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 five toes on the front feet and four toes on the back feet. They are not able to retract, or pull closer to the body, their claws, unlike ancestor an organism other carnivores such as cats. They also have elongated snouts. Aside from morphology, (or organisms) from what other types of evidence do scientists examine to determine relationships among which other groups of organisms are species? In terms of phylogeny, it is hypothesized that organisms in family Canidae descended 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 Species Do 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. The information is then interpreted to make hypotheses about evolutionary history and how closely related different species are. In the case of the giant panda, both physiological and DNA evidence placed this species closer to bears than raccoons. giant panda raccoon other bears red panda common ancestor Figure 1.5 This branching tree diagram shows the relationships among giant pandas, bears, and raccoons. Chapter 1 Classifying Life’s Diversity MHR 17  Anatomical Evidence of Relationships Recall that morphology refers to the body size, shape, and other physical features of anatomy the branch of biology that deals organisms. Studying morphology helps scientists learn more about how an organism with structure and develops and functions structurally. Studying morphology also helps scientists form, including internal determine evolutionary relationships among species. Anatomy, which is the study of systems the structure of organisms, is a branch of morphology. Study the oviraptor and the New Guinean cassowary shown in Figure 1.6. At first 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). These are some of the kinds of anatomical evidence that biologists have used to hypothesize a close evolutionary relationship between modern birds and dinosaurs. A B C 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? 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 flipper, a bat wing, a horse leg, and a human arm. Even though these species look different 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 modified for different purposes (swimming, flying, running, and grasping). However, the overall arrangement and similarities indicate a shared evolutionary history. Figure 1.7 The same Whale Bat Horse Human bones are found in the forelimbs of these four mammals. The matching sets of bones are colour- coded in this illustration. 18 MHR Unit 1 Diversity of Living Things Physiological Evidence of Relationships Physiology is the study of the functioning of organisms—how they work. Physiology physiology the branch includes studying the biochemistry of organisms, including the proteins they make. of biology dealing Whether as enzymes or as parts of cells and tissues, an organism’s proteins are with the physical and determined by the organism’s genes, since genes are coded instructions for making chemical functions of proteins. By comparing proteins among different species, the degree of genetic organisms, including internal processes similarity or difference can be determined. Modern technology has provided new tools for comparing species at this level, which has led to some organisms being reclassified. A B 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. For example, do you think the guinea pig and the mouse in Figure 1.8 are closely related? In the past, both mammals were classified in the order Rodentia, the rodents. However, an analysis of several proteins, including insulin, caused scientists to rethink this classification. Guinea pig insulin is so different from that of typical rodents that guinea pigs were reclassified 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 Figure 1.9 Horseshoe crabs have pincher-like modern spiders than to crabs. appendages and lack jaws. Learning Check 7. What is the main goal of modern classification? 11. Refer to Figure 1.5. Which pair of organisms in 8. Use a graphic organizer, such as a flowchart or a the diagram do you think is more closely related— main idea web, to show clearly how the following Pair A: a giant panda and a red panda or Pair B: a words are related: morphology, anatomy, red panda and a raccoon? Explain your reasoning. and physiology. 12. Many animal species have red blood cells that 9. Scientists often reclassify organisms as new contain the oxygen-carrying protein hemoglobin. information is discovered. Why is it important Chickens (45), dogs (15), gorillas (1), frogs (57), for scientists to continue to classify and and humans are included in this list. The numbers reclassify organisms? in brackets represent the number of amino acid differences between human hemoglobin and the 10. Sharks and dolphins have similar morphological hemoglobin of the other species. Based on this characteristics. They both have fins and bodies information, rank these animals from most closely shaped for swimming. How could examining their to least closely related to humans. anatomy and physiology help to further classify these two organisms? Chapter 1 Classifying Life’s Diversity MHR 19 Figure 1.10 Based on Animals Fungi Plants analysis of DNA, scientists hypothesize that animals and fungi are more closely related to each other than plants and fungi. Time Common Ancestor DNA Evidence of Relationships Study 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 specific genes. Just as anatomical and physiological evidence can be compared among species, so too can these DNA sequences. This research has been a great benefit to our understanding of evolutionary history and its application to classification. In some cases, new DNA evidence has meant that prior classifications based on morphological, physiological, or other evidence have to be dramatically restructured. Sometimes DNA evidence indicates unexpected relationships. For example, fungi and plants are superficially 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. The diagram in Figure 1.10 reflects 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. Figure 1.11 DNA evidence suggests that the turkey A B 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. Phylogenetic Trees phylogenetic tree Once scientists have studied the features of organisms and learned more about their a branching diagram evolutionary histories, they often use a tool called a phylogenetic tree to represent a used to show the hypothesis about the evolutionary relationships among groups of organisms. You saw evolutionary relationships an example of a phylogenetic tree in Figure 1.5, when you considered the relationships among species among giant pandas, bears, and raccoons. 20 MHR Unit 1 Diversity of Living Things Order Artiodactyla Figure 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. The 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. There are about 150 members of this order worldwide, including goats, deer, cattle, antelopes, and pigs. Family Bovidae New 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 define each family level of classification 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. There 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 different genera have split apart from one another more recently than members of different families. Smaller differences help distinguish one genus from another. For example, the family Cervidae includes 16 genera. The 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). Aepyceros melampus Oryx gazella Cervus elaphus Rangifer tarandus (impala) (oryx) (red deer) (reindeer) Species Genus Aepyceros Oryx Cervus Rangifer Family Bovidae Cervidae Order Artiodactyla 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? Chapter 1 Classifying Life’s Diversity MHR 21  The Importance of Classification to Technology, Society, and the Environment Understanding the evolutionary relationships among species and groups of organisms can have important consequences in the medical field, 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 affects 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 different taxa and their particular characteristics. Sometimes, finding 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 reclassified the forest-dwelling elephants in Africa as a new species, Loxodonta cyclotis. These 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 classified 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. A B 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). 22 MHR Unit 1 Diversity of Living Things  Section 1.2 RE V IE W Section Summary Modern classification organizes diversity according to Physiological evidence includes comparing the evolutionary relationships. biochemistry of organisms, including proteins. DNA Taxonomists rely on morphological, physiological, and evidence includes comparing organisms’ DNA sequences. DNA evidence to identify and classify species. Understanding phylogeny can help scientists trace the Anatomical evidence includes comparing the structure transmission of disease and develop and test possible and form of organisms, including bones. treatments. Review Questions 1. C Construct a chart that differentiates the three 7. A Refer to Figure 1.12. Explain why a reindeer main types of evidence scientists use to determine (Rangifer tarandus) is more closely related to a red deer relationships among species. Include an example of (Cervus elaphus) than it is to an oryx (Oryx gazella). each type of evidence. 8. A Invasive species can out-compete native 2. K/U Explain why knowing the shared evolutionary species when they are introduced outside of their history of organisms is useful to each of the following: natural environment. This can threaten a region’s a. a biologist ecosystems, economy, and society. Recently, Canadian b. a biology student researchers helped identify 15 new bird species c. a pharmaceutical laboratory assistant through genetic analysis. Scientists were able to d. a conservation ecologist identify so many new species by analyzing and comparing the DNA of over 600 North American bird 3. K/U List three anatomical features scientists have species. Explain how you think the use of genetic used to hypothesize the relationship between modern analysis could help prevent the introduction of new birds and dinosaurs. invasive species into Canada. 4. K/U What do the nucleotide sequences in the genes 9. C There is growing concern worldwide about the of turkey vultures suggest about their relatedness to number of species that are going extinct. Conservation vultures of Asia and Africa? organizations work to protect endangered species, but 5. A You are comparing three species (A, B, and C) there may be a disagreement about exactly what a and you face a dilemma. Morphologically, species A species is. and B are very similar, but they are both different from a. How can classifying an organism influence our species C. However, you have sequenced some genes in attitudes about that organism? For example, is a fish all three and the gene sequences indicate a high degree more likely to be protected if it is known to be an of similarity between species B and C. How would you endangered species, or if it is newly discovered and resolve this situation? different from all known species of fish? 6. T/I Use the phylogenetic tree below to justify the b. Suppose you had been working for a conservation conclusion that the leopard is more closely related to group when the forest-dwelling elephants the domestic cat than it is to the wolf. (Loxodonta cyclotis) were reclassified as a separate species. Write a letter urging the Convention on Wolf Leopard Domestic Cat 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 classification to technology, society, and the environment. Common Ancestor Chapter 1 Classifying Life’s Diversity MHR 23  SECTION Kingdoms and Domains 1.3 Key Terms 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 structural diversity of Earth’s species—diversity that is based on variety of both prokaryotic external and internal structural forms in living things—is so great that it is almost eukaryotic impossible to imagine. Examining all of life’s structural diversity at the species level dichotomous key would be impractical, so biologists look for similarities and differences at a much autotroph higher taxonomic rank, such as kingdoms and even domains. heterotroph The Six Kingdoms Until the 1800s, the highest category for classifying organisms was the kingdom and structural diversity a type of biological there were only two: Plants and Animals. Table 1.3 summarizes how the number of diversity that is kingdoms has changed since that time. In the 1800s, single-celled organisms were exhibited in the variety added to the classification system through the creation of the kingdom Protista, of structural forms bringing the total to three. In the first half of the 1900s, some single-celled organisms in living things, from internal cell structure to were found to be extremely small and without a cell nucleus, so a new kingdom, body morphology Bacteria, was created for them, bringing the total to four. By the 1960s, it was known that fungi were so different that they also needed their own kingdom, bringing the total to five. 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: There are two main cell types that are significant for classification at the upper ranks, such as kingdom. The 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 24 MHR Unit 1 Diversity of Living Things Two Major Cell Types If 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. There is substantial variation among the cells of unicellular and multicelluar organisms. However, after 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 prokaryotic a smaller, ancient cell type, though they remain abundant today. They do not have a membrane- simple type of cell bound nucleus. The name prokaryotic reflects this important distinction in the two that does not have cell types, because it means “before the nucleus.” Eukaryotic, on the other hand, a membrane-bound means “true nucleus.” Eukaryotic cells do have a membrane-bound nucleus. There nucleus are other differences as well. Eukaryotic cells, also shown in Figure 1.14, have a much eukaryotic a larger, complex type of cell that more complex internal structure, and on average they are about 1000 times larger than does have a membrane- prokaryotic cells. Thus, the two cell types represent a major division in the structural bound nucleus diversity of life. You will read more about differences between prokaryotes and eukaryotes in Chapter 2. Prokaryotic cell A DNA cell membrane cell wall flagellum capsule Eukaryotic cell B cell membrane chromosomes nucleus 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. Chapter 1 Classifying Life’s Diversity MHR 25  The Three Domains As scientists continued to analyze organisms in the kingdoms Bacteria and Archaea, the category of domain was added to the classification system. Scientists found that the differences 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 reclassified the remaining kingdoms in a domain of their own, Eukarya. This 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 classification at the level of domain and kingdom. Domains Figure 1.15 There are six major categories in Bacteria Archaea Eukarya the classification system Protista Fungi Plantae Animalia for living and extinct organisms. Traditional eukaryotic kingdoms Dichotomous Keys Even when taxonomists have put together logical classifications, 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 classifications assist in determining what it is? The short answer is: it cannot. As a result, taxonomists use dichotomous key an another tool to identify individuals or species: the dichotomous key. identification tool A dichotomous key [dih-KAW-ta-mus kee] is a system for narrowing down the consisting of a series of identification of a specimen, one step at a time. The word key is used as a solution, and two-part choices that a dichotomy is a two-pronged fork, where there are two choices. So, a dichotomous lead the user to a correct key is an identification solution that uses many two-part choices to narrow down the identification solution. An example of a two-part choice could be something as simple as red and not red. Learning Check 13. Explain how scientists overcome the impractical 16. Draw a flowchart or other graphic organizer task of studying the structural diversity of life at the illustrating the relationship between the domains species level. and the kingdoms found in each domain. 14. What led scientists to add the category called 17. The following is the first step in a tool used by domain to modern classification systems? taxonomists to classify vertebrate animals. Identify 15. Make a table to compare and contrast prokaryotic this tool and describe how it works. cells and eukaryotic cells. Include the following 1a. Hair present......................... Class Mammalia categories in your table: Meaning of Name, Presence 1b. Hair absent.......................... go to Step 2 of Nucleus, Size, and Internal Structure. 26 MHR Unit 1 Diversity of Living Things Using a Dichotomous Key The ultimate goal of many taxonomists is to make an identification 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 3b. Grey or green, yellow under the legs.......... the back..................... spring peeper 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 5b. Unmottled green pattern; to 15 cm............................................. mink frog bullfrog 6a. Back with large round or squarish spots 6b. Back unspotted (or with a few small spots)................................. go to 7....................................... go to 8 7a. Spots round......................... leopard frog 7b. Spots squarish................... pickerel frog 8a. Predominantly green colour..................... 8b. Brown, with a dark mask through the eye green frog....................................... 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 first 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 first 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. Chapter 1 Classifying Life’s Diversity MHR 27  A Dichotomous Key for Kingdoms SuggestedInvestigation To design a key to make identifications at the species level, appropriate choices of characteristics must be made. For instance, to identify the species of wildflowers Inquiry Investigation 1-C, growing on a lawn, it would be logical to focus on things like the number and Creating a Dichotomous Key to Identify Species arrangement of leaves, flower colour, plant size, and branching pattern. of Beetles 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 different. Here, it is more useful to consider fundamental differences, such as the following: cell type and cell structure; whether the organism is multicellular; and methods of reproduction and obtaining nutrition. Activity 1.2 Create a Dichotomous Key Dichotomous keys are very helpful to identify and classify 4. Examine the characteristics of the objects in each organisms. In this activity, you will develop a dichotomous subgroup. Write a second question that focuses on a key as you group familiar objects based on their characteristic that distinguishes the objects in one of the characteristics. groups. Divide that group into two smaller groups based on this distinguishing characteristic. Possible Materials 5. Continue adding questions to your key and dividing several different types of an object or material, such as the objects until there is only one object in each group. backpacks, shoes, pens, or notebooks Make a branching diagram to identify each object with a distinct name. Procedure 1. Choose an object for which you will create a 6. Use your diagram to classify the same type of object dichotomous key. from a different source. 2. Place a collection of the object in a pile. For example, you Questions may have your group members all place their backpacks 1. Relate the groups you used to classify your object to taxa. or their notebooks in a pile. How do your groups relate to the groups of kingdom, 3. Examine the objects and write the first question for phyla, and the remaining six taxa in the modern your dichotomous key. The question should focus on a classification system? distinguishing characteristic among the objects. Divide 2. How did you use your dichotomous key to classify the the objects into two groups based on that distinguishing object from a different source in step 6? For example, did characteristic. you have to revise your key? Explain. 3. How could you modify your dichotomous key so that the user could more effectively identify an object of this type? 28 MHR Unit 1 Diversity of Living Things Main Characteristics of Kingdoms Table 1.5 summarizes some of the main characteristics of kingdoms and, below autotroph an organism it, Figure 1.17 shows some examples of organisms in each kingdom. A distinction that captures energy has already been made between prokaryotic and eukaryotic cells based on size, from sunlight (or the presence of a nucleus, and internal complexity. Another cell-level distinction sometimes non-living is the cell wall, a tough structure that surrounds most cells. Cell walls are absent substances) to produce its own energy-yielding in animals, but in other organisms the composition of the cell wall varies. With food respect to nutrition, an autotroph is an organism that obtains energy by making heterotroph an its own food, usually using sunlight. A heterotroph must consume other organisms organism that cannot to obtain energy-yielding food. Finally, asexual reproduction can be found in all make its own food and kingdoms. However, sexual reproduction, in which genetic materi