Chapter 18: Classification

species
There are millions of different _______ on Earth.

name
To study this great diversity of organisms, biolgists must give each organism a ________.

organize, logical
Biolgists also must ______ living things into groups in a ______ way.

classification
Therefore, biolgists need a _______ system.

Taxonomy
_________ is the discipline of naming and classifying organisms.

universally
To be useful, the names that are assigned should be _______ accepted.

similar
A good classification system should also grou together organisms that are more _______ to each other than they are to organisms in other groups.

language, region
Common names for organisms vary by ________ and ______. This creates confusion.

single name
By the 1700s, scientists had tried to solve this problem by agreeing to use a _________ for each species.

long
At first, the names they used were very ______.

carolus linnaeus, binomial nomenclature
Then, ____________ devoloped a two-word naming system called ____________.

system
This ______ is still used today.

two-part
In bionomial nomenclature, each species is assigned a ________ scientific name.

genus
The first partof the name refers to ________ (plural:genera).

genus
A ______ is a group of closely related species.

ursus
For example, the genus ______ contains six bear species.

species
The second part of the name, along with the genus name, refers to a single _______ (plural: species).

interbreed
Recall that species consist of individuals who can ___________.

ursus maritimus
The name __________, for example, refers to the species polar bear.

seven
Linnaeus’s system of classification has ______ different levels.

genus, family, order, class, phylum, kingdom
From smallest to largest, the levels are species, _____, _______, ______, ______, ________, and ___________.

taxon
Each of the levels is called a ____ (plural:taxa).

family, order, class, phylum, kingdom
Just as a genus is a group of similar species, a _______ is a group of similar genera, an ______ a group of similar families, a ______ a group of similar orders, a ________ (plural:phyla) a group of similiar classes, and a ________ a group of similar phyla.

animalia, plantae
Linnaeus named two kingdoms of living things, the _______ (animal) and _______ (plant).

biologically
Linnaeus and other taxonomists have always tried to group organisms according to _________ important characteristics.

important
However, they have not always agreed upon which characteristics are most _________.

visible similarities
Early classifications were based on ___________.

evolutionary relationships
Biologists now grou organisms according to _______________.

phylogeny
The study of evolutionary relationships among organisms is called ____________.

evolutionary classification
Classification based on evolutionary relationships is called __________________.

related
Species within one genus are more closely __________ to each other than to species in another genus.

ancestor
This is because all members of a genus share a recent common ________.

genera
All _______ in a family also share a common ancestor

past
However, this common ancestor is farther in the ______ than the common ancestor of species within a genus.

taxon
The higher the level of the _____, the father back in time is the common ancestor of all the organisms in that taxon.

cladistic analysis
Many biologists now use a method called ________________ to determine evolutionary relationships.

derived characters
Cladistic analysis is based on _______________.

traits
Derived characters are new _______ that arise as a group evolves over time.

organisms
Derived traits are therefore found in closely related _______ but not in their distant ancestors.

cladogram
Derived characters can be used to construct a ___________.

diagram
A cladogram is a ________ that shows the evolutionary relationships among a group of organisms.

evolutionary tree
A cladogram is basically an ______________, much like a family tree.

DNA, RNA
All organisms have ______ and ______.

similar
Because DNA and RNA are so ________ across all forms of life, these molecules ca be compared to different species.

common ancestor
The more similar the molecules are in different species; the more recently the species shared a ______________.

related
Therefore, the more closely __________ they are.

length
Comparisons of DNA can also be used to estimate the _______ that two species have been evolving independently.

molecular clock
A model called a __________ can be used for this purpose.

neutral mutations
The model asumes that ________________, which do not afect phenotype, acccumulate in gene pools.

Two species
_____________ evolving independently from each other will accumulate different neutral mutations through time.

longer
The more there are of these different neutral mutations, the _______ the two species have been evolving independently.

animalia, plantae
As biologists learned more aboutthe natural world, they realized that Linnaeus’s two kingdoms, _______ and ________, did not represent all life forms.

bacteria
First, microorganisms, such as ________, were discovered.

protista
Microorganisms did not seem to fit into either kingdom, so they were placed in their own kingdom, called _______.

fungi
Then, mushrooms, yeast, and molds were separated from plants and placed in their own kingdom, called _______.

monera
Later, bacteria were separated from other Protista and placed in another new kingdom, called _______.

eubacteria, archaebacteria
Finally, the Monera were divided into two kingdoms: __________ and ____________.

eubacteria, archaebacteria, protista, fungi, plantae, animalia
It includes the kingdoms ___________, __________, ________, __________, ___________, and __________.

six-kingdom
By the 1990s, a ______________ system of classification was proposed.

domain
A new taxon, called the ________, is now used by many biologists.

one
The domain is _____ level higher than the kingdom.

bacteria, archaea, eukarya
Three domains are recognized: __________, _________, and _________.

unicellular, nucleus, peptidoglycan
The domain Bacteria includes _________ organisms without a __________. They have cell walls containing a substance called __________.

peptidoglycan
These organisms have cell walls that do not contain __________.

archaebacteria
The domain Archaea corresponds to the kingdom ___________.

protista, fungi, plantae, animalia
THe domian Eukarya includes the four remaining kingdoms: _________, __________, __________, and ______________.

Eukarya
All members of the domain __________ have cells with a nucleus.

Protista
Most members of the kingdom __________ are unicellular organisms.

autotrophs, heterotrophs
Some Protista are __________; others _________.

multicellular, heterotrophs, autotrophs
Most members of the kingdom Fungi are __________, and all are ___________. All members of the Kingdom Plantae are multicellular ____________.

Eubacteria
The domain Bacteria corresponds to the Kingdom _________.

Archaea
The domain _________ also includes unicellular organisms witohout a nucleus.

multicellular
All members of the kingdom Plantae are ___________ autotrophs.

move about, cell walls
Most plants cannot __________ and their cells have _________.

animalia
All members of teh kingdom _______ are multicellular heterotrophs.

cell walls
Most animals can move about, and their cells lack ____________.

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