27.5 Systematics (Naming Organisms)
Learning goals:
1. Discuss how phylogenetics is used to classify organisms
2. Cite the differences between a five-kingdom and a three-domain system
Systematics: seeks to understand evolutionary history of live. It is very analytical and relies on a
combination of data from the fossil record and comparative anatomy and development, and molecular
data to reconstruct phylogeny (the evolutionary history of a group or organisms). Classification is ONE
PART of systematics.
1. Linnean Classification
a. Taxonomy: ___________________________________________________________
b. Binomial system of _______________ (naming) of genus and species e.g. Homo sapien
c. Linnean Levels: ________________________________________________________
d. New addition: domain (higher than kingdom)
e. Each level/category can be subdivided into three additional levels (superorder, order,
suborder, infraorder)
f. More than 30 levels/category of classification
g. This is STILL how we name organisms
2. Polygenetics
a. Modern way to _________________________________________
b. Arrange species and higher classification categories into _____________
c. Clades: contain a most recent common ancestor and all its descendent species;
pictured in a ______________
d. Convergent evolution: (converge = to come together)
i. the acquisition of the same or similar traits in distantly related lines of descent
ii. analogous structures: (e.g. bat wings and insect wings) ___________________
________________________________________________________________
iii. homologous structures: (e.g. Figure 27.8 on p.549)_______________________
________________________________________________________________
e. Parsimony:
i. ____________ method of classifying with phylogenetics
ii. the pattern that requires the ___________ evolutionary changes is most likely
f.
Decisions today about how closely organisms are related is based on ______ or ______
sequences
g. Linnean Classification vs. Phylogenetics
i. Traditional Linnean classification is often ______________________________
(based on DNA and rRNA sequences) of phylogenetics
ii. New classification system proposed: “International Colde of Phylogenetic
Nomenclature” or “____________” for short
1. Naming based on ___________________________________________
iii. Other option: modify Linnean classification to be consistent with new findings
from phylogenetics
h. Two major unsolvable problems:
i. Clades are hierarchically arranged as are Linnean categories, but ___________
________________________________________________________________
ii. Taxonomic groups are not necessarily equivalent in the Linnean system
3. Three Domain Classification System
a. Traditionally, five kingdom system used (________ , ________ , ________ , _______,
________)
b. ____________ designation based on:
i. cell type (prokaryote vs. eukaryote)
ii. Level of organization (multicellular or unicellular)
iii. Type of nutrition
c. DNA sequencing lead to questions as to this classification system
i. Two groups of prokaryotes: __________ and __________  given new
classification of domain
d. Domain is a ____________________________
e. New levels: (from lowest to highest) species, genus, family, order, class, phylum, and
kingdom, domain
f. Three Domains:
i. _________
ii. _________
iii. _________ (contains protists, animals, fungi, and plants)
Check Your Progress p.565 #1-3
27.5 Systematics (Naming Organisms) - ANSWERS
Systematics: seeks to understand evolutionary history of live. It is very analytical and relies on a
combination of data from the fossil record and comparative anatomy and development, and molecular
data to reconstruct phylogeny (the evolutionary history of a group or organisms). Classification is ONE
PART of systematics.
1. Linnean Classification
a. Taxonomy: the branch of biology concerned with identifying, naming, and classifying
organisms
b. Binomial system of nomenclature (naming) of genus and species e.g. Homo sapien
c. Linnean Levels: species, genus, family, order, class, phylum, and kingdom
d. New addition: domain (higher than kingdom)
e. Each level/category can be subdivided into three additional levels (superorder, order,
suborder, infraorder)
f. More than 30 levels/category of classification
g. This is STILL how we name organisms
2. Polygenetics
a. Modern way to classify animals and build evolutionary trees
b. Arrange species and higher classification categories into clades
c. Clades: contain a most recent common ancestor and all its descendent species;
pictured in a cladogram
d. Convergent evolution: (converge = to come together)
i. the acquisition of the same or similar traits in distantly related lines of descent
ii. analogous structures: (e.g. bat wings and insect wings) have the same function
but the two organisms do NOT share a common ancestor
iii. homologous structures: structure that is similar in two or more organisms due
to common ancestry (e.g. Figure 27.8 on p.549)
e. Parsimony:
i. Traditional method of classifying with phylogenetics
ii. the pattern that requires the fewest evolutionary changes is most likely
f.
Decisions today about how closely organisms are related is based on DNA or rRNA
sequences
g. Linnean Classification vs. Phylogenetics
i. Traditional Linnean classification is often inconsistent with new understandings
(based on DNA and rRNA sequences) of phylogenetics
ii. New classification system proposed: “International Colde of Phylogenetic
Nomenclature” or “PhyloCode” for short
1. Naming based on clades instead of traditional Linnean levels
iii. Other option: modify Linnean classification to be consistent with new findings
from phylogenetics
h. Two major unsolvable problems:
i. Clades are hierarchically arranged as are Linnean categories, but there are
MANY more clades than Linnean taxonomic categories
ii. Taxonomic groups are not necessarily equivalent in the Linnean system
3. Three Domain Classification System
a. Traditionally, five kingdom system used (animals, plants, fungi, protists, and monerans)
b. Kingdom designation based on:
i. cell type (prokaryote vs. eukaryote)
ii. Level of organization (multicellular or unicellular)
iii. Type of nutrition
c. DNA sequencing lead to questions as to this classification system
i. Two groups of prokaryotes: archaea and bacteria  given new classification of
domain
d. Domain is a higher classification than Kingdom
e. New levels: (from lowest to highest) species, genus, family, order, class, phylum, and
kingdom, domain
f. Three Domains:
i. Archaea
ii. Bacteria
iii. Eukarya (contains protists, animals, fungi, and plants)