Classification Systems

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Classification Systems

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3-30 million kinds of animals in the world

• As wildlife biologists, its our job to study and
  compile information on them all
• How to begin such a big task?
• A logical place to start is to organize them into
  manageable groupsbut how?

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Carolus Linnaeus (a.k.a. Carl von Linné)

• Father of Taxonomy
• 1707-1778

Only 20,000 or so animals known in his day, so
he thought he could come up with a good system
to arrange them
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Linnaeus step 1 Name the animals

• People were already naming animals (of course)
• Common names too confusing

What do you call this animal?
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Early scientific names

• Latin language used for scientific names
  because unchanging and considered scholarly
• No standard methodology
• Some species had up to 10 words in their name!
• Example Abronia maritima millefolium
  fasciculatum praecox

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Linnaeus had the idea to use just 2 words to name
an animal. He called these genus and species.
What a good idea!
Canis is the genus for dog-like animals each
specific kind of dog has its own species name
gray wolf Canis lupus
coyote Canis latrans
golden jackal Canis aureus
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Accipiter is the genus for forest-dwelling
hawks there are 3 species of Accipiter in North
America
coopers hawk Accipiter cooperi
sharp-shinned hawk Accipiter striatus
northern goshawk Accipiter gentilis
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Why are genus and species names always
italicized?

• Because they are in Latin!
• Have you ever noticed that all foreign words in
  books are italicized?
• Ghezunteit!
• R.S.V.P.
• Yo quiero Taco Bell
• By the way how do you italicize a word when you
  are writing by hand?

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Linnaeus step 2Organize the species into
groups

• Used a hierarchical system, so that lower groups
  fit into larger groups
• All similar genera (genera is plural of genus)
  belong to the next highest group family
• All similar families belong to next highest group
  and so on

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Family Canidae
gray wolf Canis lupus
swift fox Vulpes velox
coyote Canis latrans
red fox Vulpes vulpes
golden jackal Canis aureus
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Order Carnivora
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Kingdom Phylum Class Order Family G
enus Species
Kings Play Chess On Fine Green Sand King Phillip
Came Over For Grandmas Soup
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gray wolf

• Kingdom Animalia
• Phylum Chordata
• Class Mammalia
• Order Carnivora
• Family Canidae
• Genus Canis
• Species lupus

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• Orders usually end in -formes
• Families usually end in -dae (pronounced dee)
• Everything is Capitalized except species
• Only genus and species are italicized
• Common names are not capitalized, because they
  are not part of the scientific name

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One problem with Linnaeus system how do the
bigger groups relate to each other?

• Kingdom Animalia
• Phylum Chordata
• Class Mammalia
• Order Carnivora
• Family Canidae
• Genus Canis
• Species lupus

• Kingdom Animalia
• Phylum Chordata
• Class Aves
• Order Falconiformes
• Family Accipitridae
• Genus Accipiter
• Species striatus

How are these 2 animals related ?
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Two approaches to classifying groups of animals
in relation to each other

• MorphologicalHow things look
• Historical/AncestralHow things are related to
  each other (which evolved first)

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Example How do we classify these 3 animals in
relation to each other?
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MORPHOLOGICAL
ANCESTRAL
(methods agree)
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MORPHOLOGICAL
ANCESTRAL
(methods disagree)
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3 schools of thought on classification of animals

• Phenetic (morphological)
• Cladistic (ancestral)
• Evolutionary (combines the first 2)

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Phenetic method

• From Greek word phainein, to appear
• Groups kinds of animals together by similarities
  in body traits.
• Before computers, a few significant traits were
  chosen
• Now, multivariate statistics are used to classify
  according to 100s of traits

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Modern phenetic classification method of 5 furry
animals using multivariate statistics
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5
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Length of leg bone
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Length of arm bone
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Where does animal number 3 go?
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1
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3
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4
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Nearest Neighbor Analysis
Average Neighbor Analysis
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Problems with phenetic method

• No method for determining which traits to use
• Biased, because even with sophisticated new
  methods, the researcher must decide in which
  group to put some animals

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Cladistic method

• From Greek clados, branch
• Started by Willi Hennig, a German entomologist
  (studied insects)
• Animals grouped according to most recent common
  ancestor
• The Truth is Out There?

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How to determine evolutionary relationships

• Based solely on new inventions that species
  have in common these are called shared, derived
  traits
• Fossil record often consulted
• Examples
• Feathers in birds
• Sonar in bats
• Certain shape of skull
• Relationships determined with computer software

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Oldest fishes had no jaws
Later fishes had jaws
Mouth of shark, a newer fish
Mouth of lamprey, an early fish
derived character jaws
ancestral character no jaws
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Cladogram
fish with ancestral character (no jaws)
fishes with shared, derived character (jaws)
NODE FOR JAWS
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(skeleton not bony)
(skeleton bony)
NODE FOR JAWS
NODE FOR BONY SKELETON
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Problem with cladistic methodhow to tell if 2
species with a shared derived character are
really related?

• Homologous traita physical characteristic that 2
  species share as a result of common ancestry
• Analogous traita physical characteristic 2
  species share that is not a result of common
  ancestry, but rather of evolving in similar
  habitats or under similar conditions

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Homologous traits
Forelimbs of human, dog and horse are derived
from same structures
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Analogous traits
Wing of bat
Wing of bird
Bird wings and bat wings are analogous traits,
because an analysis of which bones the wings go
on tells us that birds and bats did not inherit
their wings from a common ancestor. Rather, both
evolved separately.
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Example Adaptations of these diving birds were
once thought to be homologous traits, now known
to be analogous
least grebe Tachybaptus dominicus
yellow-billed loon Gavia adamsii
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Another problem with cladistic methodcounter-intu
itive groups are formed
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P.C. Phylogentically Correct(for cladists
only!)

• Under a strict cladistic classification, there is
  no such thing as a birdbirds are called avian
  dinosaurs
• Dinosaurs are non-avian dinosaurs
• The group most people call reptiles does not
  exist!

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Evolutionary Systematics

• Combines phenetic and cladistic methods
• Classifies animals primarily by evolutionary
  relationships, but allows for traditional groups
  too
• Method we will use in this class

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Problems with evolutionary systematics

• Biased
• No way to know if groups are based on morphology
  or ancestry

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Under all methods, the classification of
vertebrates is constantly changing

• New fossils are discovered
• DNA evidence is found
• People change their minds!
• There is no one universally excepted
  classification scheme for all animals.

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Why should I care how animals are classified?

• You cant get away from the classification of
  animals in wildlife biology
• Knowing how a group of animals is classified is
  the first step in learning about that group

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Vocabulary

• Taxonomy
• Analogous trait
• Homologous trait
• Morphology
• Cladistics
• Phenetic
• Evolutionary Systematics
• Subjective
• Objective
• Cladogram

• Derived character
• Ancestral character
• Biased
• Genera