Order out of Chaosclassification and naming

in biology. Part 1

Sandy KnappDepartment of Life SciencesThe Natural History Museum

London

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CLASSES - Numbers of males (stamens) – Monandria to Polyandria

•Public marriages (flowers visible)

•In one bed (male and female together)

•Equal rank (males all the same size)

ORDERS - Numbers of females (pistils) – Monadelphia to Polydelphia

Monoecia (husbands and wives in the same house, but different beds); Dioecia (husbands and wives in different houses); Polygamia (husbands live with wives and concubines)

•In two beds (male and female in separate flowers)

Solanum sinuatirecurvum – “Pentandria Monogynia”

Paeonia officinalis – “Polyandria Digynia”

Thomas Pennant to Joseph Banks (1767)

• “I have no very high opinion of Linnaeus’s zoological merits…… he is too superficial to be thought of…”

• “My vanity will not suffer me to rank Mankind with Apes, Monkies, Maucaucos and Bats.”

Biological Classification

• Hierarchical• Nested sets of smaller and smaller

groups• (Kingdom (Order (Family (Genus

(species)))))• Eukaryota (Animalia (Hominidae (Pan

(trogolodytes)+ (Homo (sapiens))))

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Darwin (1859) - Species

• “From these remarks it will be seen that I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms.”

On the origin of species Chapter II: 52

Pierre Belon (1555) L'Histoire de la nature des oyseaux

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Homology and analogy - Owen• Homology – “same organ in different

animals under every variety of form and function”

• Analogy – “part or organ in one animal which has the same function as another part or organ in another animal”

Richard Owen (1849) On the Nature of Limbs

Homology after Darwin

• Homology - similarity in structure due to descent from a common ancestor; homologous structures are derived from a structure in a shared common ancestor of two organisms

• Unique homologies define groups

Characters

Apomorphy – derived characterSynapomorphy – shared, derived characterAutoapomorphy – derived character unique to a particular taxonPlesiomorphy – “primitive” character

FLY

BAT

COW

COW

BAT

FLY

BAT

FLY

COW

Let’s take three organisms:

•Fly

•Bat

•Cow

Kinds of groups - cladistics

Monophyletic = ALL and ONLY descendents of a common ancestor

Kinds of groups - cladistics

Paraphyletic = some descendents of a common ancestor, but not all