Week 2.1 Life as we define and name it
Readings: 2: 30, 46-47, 12: 313-338
1. Identify differences among domains and kingdoms.
2. Identify organisms using a dichotomous key
What characteristics would you look for to determine if something is living?
An attribute unique to living organisms:
Homeostasis – maintain constant internal environment regardless of the changing external
environment. Chemical balance
Classifying (grouping) and naming organisms
Start with morphology
Binomial Nomenclature: put organisms into broad groups then organize them further, into more specific
People have the innate tendency to put things into groups to organize information in their heads.
Aristotle (384 – 322 B.C.) viewed living organisms as unchanged (fixed), and arranged organisms, based
on their complexity, on a ladder (scale) with human beings on top.
Carolus Linnaeus (Carl von Linné), a Swedish botanist (1707 –1778), was the founding father of
taxonomy – the branch of biology devoted to describing, naming species and classifying species (putting
them into groups). Linnaeus viewed species as being created independently and separately from one
another; he was not thinking about the relationships among different species of organisms.
Example: Helianthus annuus, the sunflowerSystem of Nature) in
which he presented his idea of naming living organisms
(Latin taken originally from Greek helios =sun; anthos = flower; Latin annuus =
according to a Latin binomial (two-part Latin name).
Rules for the Latin Binomial:
1. underline or italicize, each part of the scientific name separately,
2. capitalize the genus, The genus (first part of the name) is always capitalized, the
specific epithet (second part of the name) is always written in small letters
For a given specimen, if we know the genus, but not the species, we use the
abbreviation sp. (e.g. Helianthus sp.)
Linnaeus created a hierarchical filing system that groups species into a hierarchy of successively more
general, broader categories (Species to Kingdoms). Similar species were grouped together.
Ex. Panthera pardus
Linnaeus initially proposed that species be divided into two Kingdoms: animal and plants. In late 1960s,
biologists proposed a system of five Kingdoms.
Carl Woese (1980s) created a new taxonomic level Domain to distinguish organisms based on their
cellular structures and functioning. Three major groups occur: (1) the Bacteria; (2) another group of