1. Interest Grabber
Section 18-1
Order From Chaos
When you need a new pair of shoes, what do you do? You probably walk confidently into a shoe store, past the tens or hundreds of pairs of shoes you don’t want and straight to the kind you do want. How do you find them? Shoes are organized in the store in categories. People organize objects by grouping similar objects together.
Go to Section:

2. Interest Grabber continued
Section 18-1
1. Consider the task facing early biologists who attempted to organize living things. How might they have begun?
2. Suppose that you have been given a green plant, stringy brown seaweed, a rabbit, a mushroom, a worm, and a grasshopper. You’ve been asked to organize these things into categories that make sense. How would you do it?
3. Decide on your categories and write each on a sheet of paper. Next to each category, write the defining characteristics of that category. Then, write in the organisms that fall into each category.
Go to Section:

3. Answers
Order From Chaos
1. Students may say that early biologists attempted to formulate logical systems for organizing the diversity of life.
2. Students may group the plantlike, sessile organisms (the plant, seaweed, and mushroom) together, grouping the others as animals.
3. Remind students that organizational systems are human-made, and there are no right or wrong ones. Some, however, are more useful than others.

4. 18–1 Finding Order in Diversity A. Why Classify?
Section Outline
Section 18-1
18–1 Finding Order in Diversity
A. Why Classify?
B. Assigning Scientific Names
1. Early Efforts at Naming Organisms
2. Binomial Nomenclature
C. Linnaeus’s System of Classification
Go to Section:

5. Words to Know
Taxonomy – classifying organisms and assigning each organism a universally accepted name
Carolus Linnaeus – Swedish botanist who developed a two-word naming system called binomial nomenclature
The scientific name:
The first word is the genus and it is capitalized
The second word is the species and it is lowercased
It is always written in italics

6. Examples
Felis concolor – mountain lion, puma, cougar, panther
Ursus arctos (grizzly bear) and Ursus maritimus (polar bear) belong to the same genus, but not the same species

7. Taxonomic Categories (Taxa) {Singular: taxon}
Kingdom, Phylum, Class, Order, Family, Genus, Species (Larger category to more specific)
Genera that share many characteristics are grouped in a larger category, the family
An order is a broad taxon composed of similar families
A class is composed of similar orders
Several different classes make up a phylum

8. Flowchart Linnaeus’s System of Classification Kingdom Phylum Class
Section 18-1
Linnaeus’s System of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Go to Section:

9. Figure 18-5 Classification of Ursus arctos
Section 18-1
Grizzly bear
Black bear
Giant panda
Red fox
Abert squirrel
Coral snake
Sea star
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
SPECIES Ursus arctos
Go to Section:

10. Interest Grabber
Section 18-2
One Big Family?
How can you determine if one organism is closely related to another? It may seem easy, but it isn’t, and looks are often deceiving. For example, roses and orchids are both flowering plants, but roses grow on bushes or vines and have thorns. Many orchids don’t even grow in soil—they can grow in trees! Rose and orchid blossoms look very different, and roses and orchids cannot produce hybrids, or offspring of crosses between parents with different traits.
Go to Section:

11. Interest Grabber continued
Section 18-2
1. Do you think roses and orchids are closely related? Explain your answer.
2. Now, apply the same logic to dogs. Different breeds of dogs—such as a Labrador retriever and a collie—can breed and produce offspring. So what is the difference between the rose-orchid combination and the Lab-collie combination?
3. What defines a species? Is appearance important? What other factors might be considered?
Go to Section:

12. Answers
One Big Family?
Students may say that their different growth habits and inability to hybridize indicate that they are not closely related.
2. Students may know that all domestic dogs are a single species.
3. Students may suggest that a species is defined by its members’ ability to interbreed, regardless of appearance.

13. 18–2 Modern Evolutionary Classification
Section Outline
Section 18-2
18–2 Modern Evolutionary Classification
A. Problems With Traditional Classification
B. Evolutionary Classification
C. Classification Using Cladograms
D. Similarities in DNA and RNA
E. Molecular Clocks
Go to Section:

14. Words to Know
Traditional classification – organisms were grouped according to similarities in appearance
Evolutionary classification – grouping organisms based on their evolutionary history
Cladistic analysis – identifies and considers only those characteristics of organisms that are evolutionary innovations (new characteristics that arise as lineages evolve over time)
Derived characters – characteristics that appear in recent parts of a lineage but not in its older members

15. Cladogram – a diagram that shows the evolutionary relationships among a group of organisms (derived characters such as free-swimming larva and segmentation)
The genes of many organisms show important similarities at the molecular level. (American vultures are more closely related to storks than to African vultures. A gene that codes for myosin protein indicates that humans and yeast have a common ancestry.)
Molecular clock – uses DNA comparisons to estimate the length of time that two species have been evolving independently (Longer=more different)

16. TRADITIONAL CLASSIFICATION
Traditional Classification Versus Cladogram
Section 18-2
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL CLASSIFICATION
CLADOGRAM
Go to Section:

17. TRADITIONAL CLASSIFICATION
Traditional Classification Versus Cladogram
Section 18-2
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL CLASSIFICATION
CLADOGRAM
Go to Section:

18. Interest Grabber
Section 18-3
My Way or the Highway
Categories that are used to organize an assortment of things should be valid. That is, they should be based on real information. However, categories should be useful, too. Suppose that you are taking a survey of traffic. You sit at the side of a busy intersection and record the vehicles you see in one hour.
Go to Section:

19. 1.What categories could you use to organize your count of vehicles?
Interest Grabber continued
Section 18-3
1.What categories could you use to organize your count of vehicles?
2. Look at your list of categories. Are all of them equally useful?
3. Is there more than one valid and useful way to organize living things?
Go to Section:

20. Interest Grabber
My Way or the Highway
Students’ answers may include, type of vehicle, color, age, or manufacturer.
2. Students may suggest that the usefulness of the criteria depends on the intent of the study.
3. Students should conclude that the same set of living things could be categorized in several ways, depending upon the criteria used.

21. A.The Tree of Life Evolves B.The Three-Domain System
Section Outline
Section 18-3
18–3 Kingdoms and Domains
A.The Tree of Life Evolves
B.The Three-Domain System
C .Domain Bacteria
D .Domain Archaea
E .Domain Eukarya
1. Protista
2. Fungi
3. Plantae
4. Animalia
Go to Section:

22. Two Kingdoms – animals and plants (1700s)
Three Kingdoms – animals, plants, and protists (microorganisms) [Late 1800s]
Four Kingdoms – animals, plants, protists, fungi (mushrooms, yeasts, molds)
Five Kingdoms – monera, protista, fungi, plantae, and animalia (1950s)
Six Kingdoms – Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia
Three Domains – Bacteria, Archaea (live in extreme environments), Eukarya

23. Concept Map Section 18-3 Living Things Go to Section: Eukaryotic cells
Prokaryotic cells
are characterized by
Important characteristics
and differing
which place them in
Domain Eukarya
Cell wall structures
such as
which is subdivided into
which place them in
Kingdom Plantae
Kingdom Protista
Kingdom Fungi
Kingdom Animalia
Domain Bacteria
Domain Archaea
which coincides with
which coincides with
Kingdom Eubacteria
Kingdom Archaebacteria
Go to Section:

24. Classification of Living Things
Figure Key Characteristics of Kingdoms and Domains
Section 18-3
Classification of Living Things
DOMAIN
KINGDOM
CELL TYPE
CELL STRUCTURES
NUMBER OF CELLS
MODE OF NUTRITION
EXAMPLES
Bacteria
Eubacteria
Prokaryote
Cell walls with peptidoglycan
Unicellular
Autotroph or heterotroph
Streptococcus, Escherichia coli
Archaea
Archaebacteria
Prokaryote
Cell walls without peptidoglycan
Unicellular
Autotroph or heterotroph
Methanogens, halophiles
Protista
Eukaryote
Cell walls of cellulose in some; some have chloroplasts
Most unicellular; some colonial; some multicellular
Autotroph or heterotroph
Amoeba, Paramecium, slime molds, giant kelp
Fungi
Eukaryote
Cell walls of chitin
Most multicellular; some unicellular
Heterotroph
Mushrooms, yeasts
Eukarya
Plantae
Eukaryote
Cell walls of cellulose; chloroplasts
Multicellular
Autotroph
Mosses, ferns, flowering plants
Animalia
Eukaryote
No cell walls or chloroplasts
Multicellular
Heterotroph
Sponges, worms, insects, fishes, mammals
Monera - Eubacteria and Archaebacteria
Methanogens: produce methane as a byproduct
Halophiles: “salt loving”
Go to Section:

25. Figure 18-13 Cladogram of Six Kingdoms and Three Domains
Section 18-3
DOMAIN ARCHAEA
DOMAIN EUKARYA
Kingdoms
Eubacteria
Archaebacteria
Protista
Plantae
Fungi
Animalia
DOMAIN BACTERIA
Go to Section: