Chapter 18: Classification
There are millions of different _______ on Earth.
To study this great diversity of organisms, biolgists must give each organism a ________.
Biolgists also must ______ living things into groups in a ______ way.
Therefore, biolgists need a _______ system.
_________ is the discipline of naming and classifying organisms.
To be useful, the names that are assigned should be _______ accepted.
A good classification system should also grou together organisms that are more _______ to each other than they are to organisms in other groups.
Common names for organisms vary by ________ and ______. This creates confusion.
By the 1700s, scientists had tried to solve this problem by agreeing to use a _________ for each species.
At first, the names they used were very ______.
carolus linnaeus, binomial nomenclature
Then, ____________ devoloped a two-word naming system called ____________.
This ______ is still used today.
In bionomial nomenclature, each species is assigned a ________ scientific name.
The first partof the name refers to ________ (plural:genera).
A ______ is a group of closely related species.
For example, the genus ______ contains six bear species.
The second part of the name, along with the genus name, refers to a single _______ (plural: species).
Recall that species consist of individuals who can ___________.
The name __________, for example, refers to the species polar bear.
Linnaeus’s system of classification has ______ different levels.
genus, family, order, class, phylum, kingdom
From smallest to largest, the levels are species, _____, _______, ______, ______, ________, and ___________.
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.
Linnaeus named two kingdoms of living things, the _______ (animal) and _______ (plant).
Linnaeus and other taxonomists have always tried to group organisms according to _________ important characteristics.
However, they have not always agreed upon which characteristics are most _________.
Early classifications were based on ___________.
Biologists now grou organisms according to _______________.
The study of evolutionary relationships among organisms is called ____________.
Classification based on evolutionary relationships is called __________________.
Species within one genus are more closely __________ to each other than to species in another genus.
This is because all members of a genus share a recent common ________.
All _______ in a family also share a common ancestor
However, this common ancestor is farther in the ______ than the common ancestor of species within a genus.
The higher the level of the _____, the father back in time is the common ancestor of all the organisms in that taxon.
Many biologists now use a method called ________________ to determine evolutionary relationships.
Cladistic analysis is based on _______________.
Derived characters are new _______ that arise as a group evolves over time.
Derived traits are therefore found in closely related _______ but not in their distant ancestors.
Derived characters can be used to construct a ___________.
A cladogram is a ________ that shows the evolutionary relationships among a group of organisms.
A cladogram is basically an ______________, much like a family tree.
All organisms have ______ and ______.
Because DNA and RNA are so ________ across all forms of life, these molecules ca be compared to different species.
The more similar the molecules are in different species; the more recently the species shared a ______________.
Therefore, the more closely __________ they are.
Comparisons of DNA can also be used to estimate the _______ that two species have been evolving independently.
A model called a __________ can be used for this purpose.
The model asumes that ________________, which do not afect phenotype, acccumulate in gene pools.
_____________ evolving independently from each other will accumulate different neutral mutations through time.
The more there are of these different neutral mutations, the _______ the two species have been evolving independently.
As biologists learned more aboutthe natural world, they realized that Linnaeus’s two kingdoms, _______ and ________, did not represent all life forms.
First, microorganisms, such as ________, were discovered.
Microorganisms did not seem to fit into either kingdom, so they were placed in their own kingdom, called _______.
Then, mushrooms, yeast, and molds were separated from plants and placed in their own kingdom, called _______.
Later, bacteria were separated from other Protista and placed in another new kingdom, called _______.
Finally, the Monera were divided into two kingdoms: __________ and ____________.
eubacteria, archaebacteria, protista, fungi, plantae, animalia
It includes the kingdoms ___________, __________, ________, __________, ___________, and __________.
By the 1990s, a ______________ system of classification was proposed.
A new taxon, called the ________, is now used by many biologists.
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 __________.
These organisms have cell walls that do not contain __________.
The domain Archaea corresponds to the kingdom ___________.
protista, fungi, plantae, animalia
THe domian Eukarya includes the four remaining kingdoms: _________, __________, __________, and ______________.
All members of the domain __________ have cells with a nucleus.
Most members of the kingdom __________ are unicellular organisms.
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 ____________.
The domain Bacteria corresponds to the Kingdom _________.
The domain _________ also includes unicellular organisms witohout a nucleus.
All members of the kingdom Plantae are ___________ autotrophs.
move about, cell walls
Most plants cannot __________ and their cells have _________.
All members of teh kingdom _______ are multicellular heterotrophs.
Most animals can move about, and their cells lack ____________.
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