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CHAPTER 10
Taxonomy and Phylogeny of
Animals
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Linnaeus and Taxonomy
More than 1.5 million species of animals are named Estimated that these account for
Less than 20% of all animals currently alive
Less than 1% of extinct animals
Taxonomy (aka - Systematics) Formal system for naming and classifying species
Science of classifying organisms based on similarity, biogeography, etc.
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Systematics
3 types of Systematics/Taxonomy Evolutionary Systematics
Grouping organisms that resemble ancestors
Numerical Taxonomy Used mathematical models to group organisms
according to overall similarities
Phylogenetic Systematics (cladistics) Use “outgroups”, differences between taxa to make a
subset called a clade (Greek - branch)
Most commonly used, measures variety of characteristics. *Discussed later*
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Linnaeus and Taxonomy
Greek philosopher Aristotle first classified organisms (350 BC)
Carolus Linnaeus designed the current system of classification (1750)
Swedish botanist with extensive experience classifying objects, especially flowers
Used morphology (study of form and structure) to develop a classification system of animals and plants
Divided animal kingdom into species and gave each a distinctive name
Grouped species into genera, genera into orders, and orders into classes
His classification scheme has been drastically altered, but the basic principle is still followed
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Hierarchy of taxonomic ranks now includes 7 major groups
Kingdom, phylum, class, order, family, genus, and species
Now, the new level of Domain is also used.
All animals are placed in Kingdom Animalia, or Domain Eukarya
Taxa (Taxon) - Groups of animals that share a particular set of characteristics.
Example: True Flies “Diptera” - single pair of wings
Each rank can be subdivided into additional levels of taxa Superclass, suborder, etc.
Linnaeus and Taxonomy
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3 Domains - current proposal
Based on ribosomal RNA sequences
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Nomenclature: assignment of a distinctive name to each species
A scientific name of an animal consists of two words (binomial nomenclature) First word is the genus and is capitalized
Second is the species written in lower case
Scientific name should be printed in italics or underlined if handwritten Homo sapiens
Homo sapiens
Taxonomy
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Some animals are subspecies, usually caused by Geographic locations. They are referred to as trinomials (3 names) All three terms are in italics
Subspecies is also in lower case
Ex. Ensantina eschscholtzii (salamander) has many subspecies. E.e. plantens, E.e. picta, E.e.croceater
Taxonomy
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Species
Biological Species Concept Been refined and reworded several times
A species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature.
Ability to successfully interbreed is central to the concept
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Species
Biologists use certain criteria for identifying species
Common Descent
Reproductive Community
Member of a species must form a reproductive community that excludes members of other species
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Cladogram Diagram illustrating hierarchy of clades (groups
of animals with common ancestry)
To construct a Phylogenetic tree Additional information concerning ancestors,
duration of lineages, and amount of evolutionary change must be included (compared to cladogram)
Taxonomic Characters and Phylogenetic Reconstruction
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A cladogram
Amphioxus is the “outgroup” because it doesn’t share any of the defining
characteristic with the other taxa. What characteristic separates Bass from
Horses?
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Sources of Phylogenetic Information (What do we use to identify animals??)
Comparative Morphology Examines shapes, sizes and development of
organisms
Skull bones, limb bones, scales, hair and feathers
Living specimens and fossils are used
Taxonomic Characters and Phylogenetic Reconstruction
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Comparative Biochemistry Analyzes sequences of amino acids in proteins
and nucleotides sequences in nucleic acids
Recent studies show comparative biochemistry can be applied to fossils
Comparative Cytology Examines variation in number, shape and size
of chromosomes
Used almost exclusively on living specimens
Taxonomic Characters and Phylogenetic Reconstruction
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Phylogenetic Tree based
On Cytology:
Comparing base
substitutions on
Cyctochrome C
(a respiratory protein).
#’ s represent number of
Mutations that occurred.
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Animal Kingdom Patterns of Organization
Symmetry
Asymmetrical (no central
body point/axis) ex.
sponge
Bilateral (if divided
right/left sides are mirror
image) ex. vertebrates
Radial (any plane cut
through organism makes
mirror image) ex. Sea
anemone
Embryonic Tissue Layers: Diploblastic - 2 tissues
(ectoderm and endoderm)
Triploblastic - 3 tissue layers (also mesoderm)
Zygote Cleavage Protostome - blastopore
becomes mouth
Deuterostome -blastopore becomes anus
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