Duke Primate Skeleton First Lecture

TAXONOMY Aristotele: Aristotele “Historia Animalium” (384-322 BC)

Carolus Linnaeus: Linnaeus “Systema Naturae” (1707-1778) assumptions

Nature classified by means of comparative methods and based on morphology

Binomial nomenclature: Homo sapiens Genus name

Species name

Morphological characteristics; species and genera unchangeable. Typological classification, no questions about relatedness Species definition: a class of objects, members of which shared certain defining properties. Such a class is constant, it does not change in time, all deviations from the definition of the class are merely “accidents”

Charles Darwin: Darwin “Origin of species” (1861)

Living organisms descended from a common ancestor They are connected each other by genealogical relationships

HIERARCHICAL CLASSIFICATION Every group resemble each other and is related to each other by evolution through time

Classification categories

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Primates

Family

Pongidae

Genus

Pan

Species

Pan troglodytes

CLASSIFICATION Inclusion of dynamic biological facts about relatedness Mayr definition of biological species: a group of interbreeding natural populations that is reproductivily isolated from other such groups Today classification Morphological, structural, behavioral, biomechanical similarities ANALOGIES vs. HOMOLOGIES

METHODS OF CLASSIFICATION Evolutionary classification Based on assessment of homologies, especially of morphological characteristics. Also ontogeny, cell biology, behavior can be considered Use of phylogenetic trees

Illustrate ancestordescendant relationships and time passed, but do not represent classification

Strength: a weighting system is used that favors some derived characters over others. Major critique to this method: relies too much on individual experience

Numerical or Phenetic Classification Relies on equal weighting of all visible characters. All characters are evaluated of equal importance. Does not require knowledge of the taxon classified Cladistics 1. Phylogeny occurs only by means of dichotomies: a parent taxon splits in two sister taxa and ceases to exist after the split 2. Dichotomy based on common possession of uniquely derived characters (Sinapomorphies) 3. Variables (morphological, behavioral, or molecular) recorded as character states (0,1,2) 4. Computer generation of many treelike diagrams 5. The most parsimonious tree (requires the fewest steps for all characters) is chosen

CLADISTICS Cladograms can be constructed for any group of organisms They all share a common origin; their current forms are all derived from branching events somewhere in the phylogenetic past. When did these branches occur?

Derived Characters segmented

jaws

hair

placenta

multicellular

limbs

kangaroo

+

+

+

-

+

+

earthworm

+

-

-

-

+

-

amoeba

-

-

-

-

-

-

lizard

+

+

-

-

+

+

cat

+

+

+

+

+

+

sponge

-

-

-

-

+

-

salmon

+

+

-

-

+

-

Strength Cladograms emphasize the sequence or order in which derived characters arise from a central phylogenetic tree

Cladogram

Critique Nothing in a cladogram indicates how strong the derived character is, and its evolutionary importance

CLADOGRAM vs. PHYLOGENETIC TREE

THE FAMILY HOMINIDAE Evolutionary classification Hominoidea Hylobatidae Hylobates Symphalangus Pongidae Pongo Pan Gorilla Hominidae Homo

Cladistic classification Hominoidea Hylobatidae Hylobatinae Hylobates Symphalangus Pongidae Ponginae Pongo Paninae Gorilla Pan

Human classified in another family because of differences in adaptive features

Homo Human classified in the same family and tribe of Pan and Gorilla based on molecular evidences (phylogeny based)