Download Classification of Animals

Classification of Animals
How many species?
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described
8-10 million total estimate, some estimates as high as
Standardized system : International Code of Zoological Nomenclature
Disciplines of classification
 Taxonomy  Systematics  First taxonomist: Karl von Linne, aka
1778)
(1707-
Original Linnaean system
 Imperium ("Empire") - the phenomenal world
 Regnum ("Kingdom") - the three great divisions of nature at the time animal, vegetable, and mineral
 Classis ("Class") - subdivisions of the above, in the animal kingdom six
were recognized (mammals, birds, amphibians, fish, insects, and
worms)
 Ordo ("Order") - further subdivision of the above - the class Mammalia
has eight
 Genus - further subdivisions of the order - in the mammalian order
Primates there are four. e.g. Homo
 Species - subdivisions of genus, e.g. Homo sapiens.
 Varietas ("Variety") - species variant, e.g. Homo sapiens europaeus.
Hierarchical classification
Traditional mandatory taxa:
 Kingdom
 Phylum (phyla, pl)
 Class
 Order
 Family (-idae)
 Genus (genera, pl)
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 Species
Current classification schemes
 taxonomy is a dynamic science
1st – 2-kingdom system – plants and animals (botany & zoology)
2nd – 3 kingdom – plants, animals & protists
3rd – Whittaker 5 kingdom system in 1970’s
4th – Woese-Fox 3 domain system
Five kingdom system
1)
2)
3)
4)
5)
Three domain system
1)
2)
3)
Nomenclature
 system of naming objects
 Binomial system of nomenclature adopted for species for several
reasons:
1) Common names - too many for some sp.
2) Some common names are used for diff. sp.
3) Scientific names - universal
4) two-part system indicates relationship with other similar organism
Scientific name
 Genus name - first letter capitalized, either italicized or underlined
 Specific epithet - all lower case, underlined or italicized
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

– Common Tern named by Linnaeus

– Least Tern scientific name revised
since first description
Systematics
 has to accomplish to two tasks:
1)
2)
 Attempt is made to classify organisms according to phylogenetic
relationships
Problems when classifying
1) convergent evolution –
2) traits used to determine phylogenies don’t always agree
3) different definitions of species
Species definition
 Typological species –
 doesn’t address variations w/in species
 Biological species - Dobzhansky & Mayr – 1930s
 expanded in 1980s to include that species “occupies a specific niche in
nature”
 not useful for fossils or asexual organisms
 Simpson 1940s
 “a single lineage of ancestor-descendant populations that maintains its
identity from other such lineages and that has its own evolutionary
tendencies and historical fate”
 uses mostly morphological features
 allows defining species in fossils & asexually reproducing species
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Phylogenetic species concept
 Joel Cracraft 1989
 “irreducible (basal) grouping of organisms diagnosably distinct from
other such groupings and within which there is a parental pattern of
ancestry and descent”
 tends to separate subspecies into species
 increases the number of species
 doesn’t involve evolutionary process
Origin of taxa
 monophyletic  paraphyletic –
 polyphyletic –
Different evolutionary trees
 Evolutionary taxonomy version
1) life begins with:
2) from bacteria, evolved into nucleated organisms –
3) from protistans, multicellularity evolves into three major groups:
Evolutionary tree according to cladistics
 cladistics – method of statistically looking at groups & classifying only
by monophyletic groups
 the following tree used ribosomal RNA
1)
2)
3)
Evolutionary trends in body plans
 symmetry - how parts of animal are arranged around a point, axis, or
plane.
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1) asymmetry 2) radial 3) bilateral –
Cephalization
 formation of a head
 animals w/bilateral symmetry tend to always move in one direction
(forward).
 accompanying bilateral symmetry was development of:
Terms assoc. w/bilateral symmetry
Planes:
 sagittal  transverse  frontal Orientation terms:
 anterior  posterior  dorsal  ventral Layers of tissue in embryonic stages
 protoplasmic or unicellular - .
 cell specialization - multicellular w/no tissue differentiation
 diploblastic  triploblastic 5
Body cavity
 in triploblastic animals
 acoelomate  pseudocoelomate –
Eucoelomate
 true coelom Deuterstomes vs. Protostomes
Different developmental pathways
Segmentation or metamerism
 repeating of similar body parts (segments)
 segments maybe very similar, e.g. annelids
 or start to specialize e.g., arthropods, & chordates
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