18.3 Building the Tree of Life

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Lesson Objectives Name the six kingdoms of life as they are currently identified. Explain what the tree of life represents. Lesson Summary Changing Ideas About Kingdoms As biologists learned more about the natural world, they realized that Linnaeus’s two kingdoms, Animalia and Plantae, did not represent all life. ▶ Researchers found that microorganisms were very different from plants and animals. They were placed in their own kingdom, called Protista. ▶ Then, yeast, molds, and mushrooms were separated from plants and placed in their own kingdom, called Fungi. ▶ Because bacteria lack nuclei, mitochondria, and chloroplasts, they were separated from Protista and placed in another new kingdom, called Monera. ▶ In the 1990s, kingdom Monera was divided into two kingdoms: Eubacteria and Archaebacteria. The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia. ▶ Genetic analysis revealed that two prokaryotic groups are even more different from each other, and from Eukaryotes, than previously thought. This discovery lead to the creation of a new taxon, called the domain. The domain is a larger, more inclusive category than a kingdom. The three domain system consists of: Bacteria, Archaea, and Eukarya. ▶ Domain Bacteria corresponds to the kingdom Eubacteria. Domain Archaea corresponds to the kingdom Archaebacteria. Domain Eukarya corresponds tokingdoms Fungi, Plantae, Animalia, and “Protista.” ▶ Quotations are used for the old kingdom Protista to signify that it is not a valid clade.

The Tree of All Life The tree of life shows current hypotheses regarding evolutionary rela- tionships among taxa within the three domains of life. ▶ The domain Bacteria includes unicellular organisms without a nucleus. They have cell walls containing a substance called peptidoglycan. ▶ The domain Archaea also includes unicellular organisms without a nucleus. These organisms have cell walls that do not contain peptidoglycan. ▶ The domain Eukarya includes the four remaining kingdoms: “Protista,” Fungi, Plantae, and Animalia. All members of the domain Eukarya have cells with a nucleus. • Most members of the kingdom “Protista,” are unicellular organisms. Some Protista are photosynthetic; others are heterotrophs. • Most members of the kingdom Fungi are multicellular, and all members of this kingdom are heterotrophs with cell walls containing chitin. • All members of the kingdom Plantae are multicellular and photosynthetic. Most plants cannot move about, and their cells have cell walls. • All members of the kingdom Animalia are multicellular heterotrophs. Most animals can move about, and their cells lack cell walls.

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Changing Ideas About Kingdoms 1. What fundamental traits did Linnaeus use to separate plants from animals? Animals were mobile organisms that used food for energy. Plants were green organisms that did not move and got their energy from the sun.

2. What types of organisms were first placed in the kingdom Protista? At first, all microorganisms were placed in the kingdom Protista. 3. What types of organisms were placed into the kingdom Fungi? mushrooms, yeast, and molds 4. Why did scientists place bacteria in their own kingdom, the Monera? Bacteria lack the nuclei, mitochondria, and chloroplasts found in other forms of life.

5. What two kingdoms was kingdom Monera separated into? Eubacteria and Archaebacteria 6. Complete the concept map.

The Six-Kingdom System

includes

Animalia Plantae Fungi Protista Eubacteria Archae- bacteria

7. What is a domain? A domain is a larger, more inclusive category than a kingdom.

8. What did genomic analysis reveal about the two prokaryotic groups? They were more different from each other and from eukaryotes than previously thought.

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The Tree of All Life 9. Complete the chart below.

Classification of Living Things Domain Kingdom Examples

Bacteria Eubacteria Salmonella typhimurium

Archaea Archaebacteria Sulfolobus archaea

Eukarya “Protista” Ciliates, brown algae

Fungi mushrooms, yeasts

Plantae Mosses, ferns, cone-bearing plants, flowering plants

Animalia Sponges, worms, insects, fishes, mammals

Match the kingdom with the description that applies to members of that kingdom.

Kingdom Description C 10. “Protista” A. They feed on dead or decaying organic A 11. Fungi matter. D 12. Plantae B. They have no cell walls and they move about. B 13. Animalia C. They are a “catchall” group of eukaryotes. D. They include mosses and ferns.

14. What characteristics led camels to be classified in the same domain, kingdom, phylum, and class as dogs? Camels and dogs are members of the Eukarya domain because their cells have nuclei. They are members of the kingdom Animalia because they are multicellular heterotrophs that move from place to place. Camels and dogs are both members of the phylum chordata because they both share important body plan features including a nerve cord. Finally, they are both members of the same class, Mammalia, because they are warmblooded, have body hair, and produce milk for their young. Lesson 18.3 • Workbook A • Copyright © by Pearson Education, Inc., or its afﬁ liates. All Rights Reserved. 295

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Chapter Vocabulary Review Match the term with its deﬁ nition.

Term Definition H 1. phylogeny A. The domain containing all organisms that have a B 2. Bacteria nucleus E 3. order B. The domain containing organisms that are prokaryotic and unicellular C 4. phylum C. A group of classes F 5. clade D. A group of orders D 6. class E. A group of families A 7. Eukarya F. A group of species that includes a single common G 8. domain ancestor and all descendents of that ancestor G. A larger, more inclusive category than a kingdom H. The study of how living and extinct organisms are related to one another For Questions 9–18, complete each statement by writing the correct word or words. 9. Members of the domain Archaea live in some of the most extreme environments on Earth. 10. A(n) derived character is a trait that arose in the most recent common ancestor of a particular lineage, and was passed along to its descendants. 11. Multicellular organisms that move about are placed in the kingdom Animalia. 12. Under Linnaeus’ classification system, similar genera were placed into a larger category called a(n) family . 13. Families, Orders, Classes, and Phyla are all taxa . 14. The science of naming and grouping organisms is called systematics . 15. A(n) cladogram shows relative degrees of relatedness among lineages. 16. The name Ursus arctos is an example of the two-part scientific name given in the binomial nomenclature system. 17. A(n) genus is a group of similar species. 18. A clade is made up of a(n) monophyletic group .

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As you learned from solving the mystery, the question of what defines a species is sometimes hard to answer. The distinction is GRIN AND BEAR IT not just important to scientists. It can also have legal ramifications.

Learning

Legal Protection for a Threatened Species WASHINGTON, D.C.—On May 14, 2008, the Secretary of the Interior Dirk Kempthorne announced that he would accept the recommendation of U.S. Fish and Wildlife Service to list the polar bear as a threatened species under the Endangered Species Act (ESA). Section 3 of the 1973 Endangered Species Act defines an endangered species as any species “which is in danger of extinction throughout all or a significant portion of its range.” The opening para- graph of the rule is shown below.

Continued on next page ▶

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Themes Science and Civic Literacy 1. Who wrote the document and who ruled on its findings? The U.S. Fish and Wildlife Service made the recommendation. The Secretary of the Interior accepted the recommendation. 2. How does the U.S. Government define an endangered species? An endangered species is any species “which is in danger of extinction throughout all or a significant portion of its range.”

3. In making its ruling, the U.S. Government considered not only scientific information but also commercial information. What do you think this means? SAMPLE ANSWER: When deciding whether an animal should be protected, the government also considers the impact this would have on commercial interests in the area.

4. What is the reason for listing the polar as a threatened species? SAMPLE ANSWER: Because sea ice is melting, polar bears are losing their habitat.

5. The Government lists the polar bear as a threatened species, not an endangered one. What is the threat facing a species that is listed as threatened? The threat facing threatened species is that the species will become endangered in the foreseeable future.

Update: Status of Polar Bears The skills used in this activity include information and media literacy, communication skills, and critical thinking and systems thinking.

Working with a small group, report back to the class on what has happened to the status of the polar bear since the U.S. Government made its initial ruling in May 2008. Find out if the status of the polar bear has changed and comment on whether the Government was right to make the ruling when it did.

Present your ﬁ ndings to the class using a digital slide show. Evaluate students’ work for completeness, accuracy, and reliability of sources. Students’ points of view on the status of polar bears should be logically argued and supported with facts.

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