Taxonomy: Classification of
Organisms
LEARNING OBJECTIVE 1
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Define taxonomy & evolution
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Explain why the assignment of a
scientific name to each species is
important for biologists
Gophers & Turtles
Camminalcules Project
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KEY TERMS
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TAXONOMY
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Science of describing, naming, and classifying
organisms
EVOLUTION
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The change in the inherited characteristics of
biological populations over successive
generations.
Evolutionary processes give rise to diversity
at every level of biological organization,
including species, individual organisms
Scientific Names
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Biologists use scientific names to precisely
identify organisms
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Each organism has only one scientific name
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Avoids confusion of many common names
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Gophers & Turtles
LEARNING OBJECTIVE 2
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Identify the biologist who originated the
binomial system of nomenclature
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Describe the general scheme of the
system
KEY TERMS
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BINOMIAL NOMENCLATURE
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System for giving each organism a two-word
scientific name
First used consistently by Carolus Linnaeus
Linnaeus
Binomial Nomenclature
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Species
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The basic unit of classification
The scientific name of each species has
two parts:
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generic name (genus)
specific epithet (species)
• Eg. Homo sapiens
Tradescantia virginiana
LEARNING OBJECTIVE 3
•
List and describe the hierarchical
groupings of classification
Classification
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Hierarchical groups (most to least inclusive)
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domain
kingdom
phylum
class
order
family
genus
species
Classification of Ginger
Domain
Kingdom
Eukarya
Plantae
Animalia
Protista
Fungi
5 other
kingdoms
Eubacteria
Phylum
Anthophyta
9 other phyla
Class
Monocotyledones
1 other main
class
Order
Zingiberales
18 other
orders
Family
Zingiberaceae
4 other
families
Genus
Zingiber
(ginger genus)
48 other
genera
Fungi
(b) Each taxonomic level is
more inclusive than the one
below it. For example, the
order Zingiberales consists
of 5 families. The family
Zingiberaceae contains 49
genera and a total of about
1300 species.
Fig. 18-5b, p. 356
A Dichotomous Key
Organized set of couplets of mutually exclusive characteristics of biological
organisms.
Identifying beans using a dichotomous key. Use the key to identify the beans
depicted here.
Black Bean, Garbanzo Bean, Kidney Bean, Pinto Bean, White Northern Bean
Dichotomous Key for Beans
1a. Bean round
Garbanzo bean
1b. Bean elliptical or oblong
Go to 2
2a. Bean white
White northern
2b. Bean has dark pigments
Go to 3
3a. Bean evenly pigmented
Go to 4
3b. Bean pigmentation mottled
Pinto bean
4a. Bean black
Black bean
4b. Bean reddish-brown
Kidney bean
Once a characteristics applied, it cannot be represented in the
future samples.
Identifying beans using a dichotomous key. Use the key to identify the beans
depicted here.
Black bean
Kidney bean
White northern
Pinto bean
Garbanzo bean
LEARNING OBJECTIVE 4
•
Define systematics
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Describe the cladistic approach to
systematics
KEY TERMS
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SYSTEMATICS
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Scientific study of the diversity of organisms
and their natural (evolutionary) relationships
A systematist seeks to reconstruct phylogeny
KEY TERMS
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PHYLOGENY
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Evolutionary history of a species or other
taxonomic group
MONOPHYLETIC
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Said of a group consisting of organisms that
evolved from a common ancestor
KEY TERMS
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CLADISTICS
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Classification of organisms based on recency
of common ancestry rather than degree of
structural similarity
Cladistics
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Cladists emphasize phylogeny by focusing
on when evolutionary lineages (lines of
descent) divide into two branches
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Cladists develop cladograms
KEY TERMS
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CLADOGRAM
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A diagram that illustrates evolutionary
relationships based on the principles of
cladistics
Building a Cladogram
Characters
TAXON
VASCULAR TISSUES
SEEDS
FLOWERS
Moss
A
A
A
Fern
P
A
A
Pine
P
P
A
Daisy
P
P
P
Fig. 18-7 (1), p. 358
Daisy
Pine
Moss
Fern
Node
1
Common ancestor
with vascular tissues
Common plant
ancestor
(a) All of the plant groups shown here except mosses
have vascular
Fig. 18-7a, p. 358
Daisy
Pine
Moss
Fern
Node
2
Node
1
Common ancestor
with vascular tissues
Common plant
ancestor
(b) Seeds are a shared character for all plant groups
shown here except mosses and ferns.
Fig. 18-7b, p. 358
Daisy
Pine
Moss
Fern
Node
3
Common
seedproducing
ancestor
Node
2
Node
1
Common ancestor
with vascular tissues
Common plant
ancestor
(c) Of the plant groups shown here, only the daisy
produces flowers.
Fig. 18-7c, p. 358
LEARNING OBJECTIVE 5
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List and briefly describe the three
domains and six kingdoms recognized
by many biologists
KEY TERMS
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DOMAIN BACTERIA
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Domain of metabolically diverse, unicellular,
prokaryotic organisms
KEY TERMS
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DOMAIN ARCHAEA
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Domain of unicellular, prokaryotic organisms
adapted to extreme conditions (such as very
hot or very salty environments)
KEY TERMS
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DOMAIN EUKARYA
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Includes all eukaryotic organisms (protists,
plants, fungi, and animals)
The Three Domains
Domain
Bacteria
Domain
Archaea
Domain
Eukarya
Common ancestor
of all living organisms
Fig. 18-9, p. 360
Six-Kingdom Classification
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Kingdom Bacteria (domain Bacteria)
Kingdom Archaea (domain Archaea)
Kingdom Protista (domain Eukarya)
Kingdom Fungi (domain Eukarya)
Kingdom Plantae (domain Eukarya)
Kingdom Animalia (domain Eukarya)
The Six Kingdoms
Bacteria
Archaea
Protista
Plantae
Protista
Animalia
Fungi
Common ancestor
of all eukaryotes
Common ancestor
of all living organisms
Fig. 18-8, p. 360
LEARNING OBJECTIVE 6
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Summarize the scientific limitations of
the kingdom Protista
KEY TERMS
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PARAPHYLETIC
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Said of a group consisting of a common
ancestor and some, but not all, of its
descendants
Kingdom Protista
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Ideally, all members of a kingdom should
have a common ancestor
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Members of kingdom Protista are
paraphyletic
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Some biologists think protists should not
be grouped in a single kingdom