Chapter 18: Classification
Assigning Scientific Names
The first step in understanding and studying diversity is to __________ and ________ each species.
By using a __________________, biologists can be sure that they are discussing the ______ organism. Common
names can be _________ because they vary among languages and from place to place.
Binomial Nomenclature
In the 1730s, Swedish botanist _______________ developed a two-word naming system called ________
___________________.
The scientific name usually is _____. It is written in _____. The __________________________ letter, and the
second word is _________________.
ex. Homo sapiens
The polar bear, for example, is called Ursus maritimus.
The first part of the name—Ursus—is the _______ to which the organism belongs. A genus is a ___________
_______. The genus Ursus contains five other species of bears, including Ursus arctos, the brown bear or grizzly
bear.
The second part of a scientific name—maritimus for polar bears—___________________ and is often a
_____________________________ or of an important trait. The Latin word maritimus refers to the sea: polar
bears often live on pack ice that floats in the sea.
Linnaean Classification System
Linnaeus also developed a classification system that organized species into a hierarchy, or ranking.
In deciding how to place organisms into larger groups, Linnaeus grouped species according to ___________
__________________________________.
Seven Levels
1. ____________: the largest and most inclusive of Linnaeus’s taxonomic categories
2. _________: classes are grouped includes organisms that are different but that share important characteristics
3. _________: closely related orders are grouped into the next larger rank
4. _________: closely related families are grouped into the next larger rank
5. ________: genera that share many similarities are grouped into a larger category
6. _________: is a group of similar species
7. ___________: individual organism
Camel Classification
Species: Camelus bactrianus
Genus: Camelus
Family: Camelidae
Order: Artiodactyla
Class: Mammalia
Phylum: Chordata
Kingdom: Animalia
Evolutionary Classification
The concept of descent with modification led to _______________—the study of how living and
extinct organisms are related to one another.
A clade is a ________________________________________________________ and all descendants of
that ancestor—living and extinct.
Cladograms
This information is used to link clades together into a cladogram, which illustrates
_________________________are related to one another by showing how evolutionary lines, or ___________,
branched off from common ancestors.
Building Cladograms
This cladogram represents current hypotheses about evolutionary relationships among vertebrates.
Note that in terms of ancestry, amphibians are more closely related to mammals than they are to ray-finned
fish!
Devised Characters in Organisms
Organism
Devised Character
Backbone
Legs
Hair
Earthworm
Absent
Absent
Absent
Trout
Present
Absent
Absent
Lizard
Present
Present
Absent
Humans
Present
Present
Present
Constructing a Cladogram
1 Identify the organism in the table that is least closely related to the others.
2 Use the information in the table to construct a cladogram of these animals.
Analyze and Conclude
1. Interpret Tables What trait separates the least closely related animal from the other animals?
__________________________________________________________________________________________________
__________________________________________________________________________________________________
_______________________________________________________________________________________________.
2. Apply Concepts Do you have enough information to determine where a frog should be placed on the cladogram?
Explain your answer.
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
______________________________________________________________________________________________.
3. Draw Conclusions Does your cladogram indicate that lizards and humans share a more recent common ancestor than
either does with an earthworm? Explain your answer.
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
________________________________________________________________________________________________.
18.3 Building the Tree of Life
Changing Ideas About Kingdoms
During ____________ time, living things were classified as either __________________________.
Animals were organisms that moved from place to place and used food for energy.
Plants were green organisms that generally did not move and got their energy from the sun.
As biologists learned more about the natural world, they realized that Linnaeus’s two kingdoms—Animalia and
Plantae—did not reflect the full diversity of life.
Three Domains
Genetic analysis has revealed that the two main prokaryotic kingdoms are more different from each other, and
from eukaryotes, than previously thought. So, biologists established a new taxonomic category—the domain. A
domain is a _______, more inclusive category than a __________.
Under this system, there are three domains—domain Bacteria (corresponding to domain ___________), domain
Archaea (corresponding to kingdom ______________), and domain Eukarya (corresponding to kingdoms _____,
________, _________, and kingdom “________”).
Quotes are put around kingdom “Protista” to indicate that it is not a monophyletic group.
Domain Bacteria
Members of the domain Bacteria are ______________. This domain corresponds to the kingdom Eubacteria.
Their cells have thick, rigid walls that surround a cell membrane and contain a substance known as
___________________.
These bacteria are ______________, ranging from free-living soil organisms to deadly parasites. Some
photosynthesize, while others do not. Some need oxygen to survive, while others are killed by oxygen.
Domain Archaea
The domain Archaea corresponds to the kingdom Archaebacteria.
Members of the domain Archaea are __________________, and they live in some ____________—in volcanic
hot springs, brine pools, and black organic mud totally devoid of oxygen. Many of these bacteria can survive only
in the absence of oxygen.
Their cell walls ____________, and their cell membranes contain unusual lipids that are not found in any other
organism.
Domain Eukarya
The domain Eukarya consists of all organisms that have a nucleus. It comprises the four remaining kingdoms of
the six-kingdom system: “Protista,” Fungi, Plantae, and Animalia.
The “Protists”: Unicellular Eukaryotes
The kingdom Protista has long been viewed by biologists as a “catchall” group of ________ that could
not be classified as fungi, plants, or animals.
Most “protists” are _________, but one group, the brown algae, is multicellular.
Some “protists” are ____________, while others ____________________.
Some display characters that resemble those of fungi, plants, or animals.
Since these organisms cannot be properly placed into a single taxon, we refer to them as “protists.”
Fungi
Members of the kingdom Fungi are __________with cell walls containing _______.
Most fungi ____________________________. They secrete digestive enzymes into their food source,
which break the food down into smaller molecules. The fungi then absorb these smaller molecules into
their bodies.
Mushrooms and other recognizable fungi are _____________, like the ghost fungus shown. Some
fungi—yeasts, for example—are unicellular.
Plantae
Members of the kingdom Plantae are _____________, have ________________________, and are
___________________.
Autotrophic plants are able to carry on ____________________.
Plants are nonmotile—they ___________ from place to place.
The entire plant kingdom is the sister group to the red algae, which are “protists.” The plant kingdom,
therefore, includes the green algae along with mosses, ferns, cone-bearing plants, and flowering plants.
Animalia
Members of the kingdom Animalia are __________________________________________.
Animal cells ___________________________.
Most animals can ______________, at least for some part of their life cycle.
There is incredible diversity within the animal kingdom, and many species of animals exist in nearly
every part of the planet.