GER week 5+6

Differentia Specifica & Classification Systems

Aristotle introduced the concept of definition. According to Aristotle, the definition of a species

consists of genus proximus (e.g. animal, i.e. “a living organism that feeds on organic matter, typically

having specialized sense organs and nervous system and able to respond rapidly to stimuli”,

according to the OED) and differentia specifica (e.g. having reason). The differentia specifica is that part

of the definition not provided by the genus.

The genus expresses an is–a relationship, while the differentia specifica expresses a has–a relationship.

Two species (e.g. humans and elephants) with the same genus (animal) are said to be members of

that genus (animal). The differentia is the attribute by which one species is distinguished from all

others of the same genus, i.e. what differentiates humans from elephants?

Differentiation

(a) An animal is a human if it has the capacity for reason.

(b) An animal is an elephant if it has a trunk.

Example (a) defines, per genus proximus and differentia specifica, the species human by presenting

the genus (animal) and the differentia specifica (capacity for reason). Example (b) defines another

member of the same genus (animal) by differentiation (has a trunk).

(Adapted from: http://pennance.us/home/downloads/definition.pdf )

What are other differentia specifica of humans, i.e. what makes human different from other

animals or zombies or plants? Think of a few differentiations other than ‘having reason’ that

hold up across various comparisons.

Take a look at the following classification systems/taxonomies. How does each of them

divide up living beings? Are there any differences?

1) Aristotle's Scala Naturae or Ladder of Life (from Charles Singer, A Short History of Biology):

2) The Great Chain of Being (sometimes called Divine

Order): http://www.jasonbengtson.com/earlymodern/index.html# (explore the tiers by

clicking on them)

3) Linnaeus' Systema Naturae (1735), here animal kingdom (identify the names of categories I-VI

if you can): https://en.wikipedia.org/wiki/File:Linnaeus_-_Regnum_Animale_(1735).png

4) Tree of Life:

a. Darwin's only illustration in On the Origin of Species By Natural

Selection (1859): http://darwin-online.org.uk/graphics/Origin_Illustrations.html

b. Haeckel's tree of life in The Evolution of

Man (1879): https://en.wikipedia.org/wiki/File:Tree_of_life_by_Haeckel.jpg

c. The Tree of Life project explains

phylogeny: http://tolweb.org/tree/learn/concepts/whatisphylogeny.html

d. The Hillis Plot (tree of life based on completely sequenced genomes):

http://www.zo.utexas.edu/faculty/antisense/tree.pdf (zoom in!)

e. The “New Tree of Life”: http://www.nytimes.com/2016/04/12/science/scientists-

unveil-new-tree-of-life.html (read explanation and click on picture to see details)