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Lecture 11

GLGY 307 Lecture Notes - Lecture 11: Monomer, Paleoarchean, Hydrogen CyanidePremium

4 pages68 viewsFall 2017

Course Code
GLGY 307
M.Dan Georgescu

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Lecture 11: Biological & Paleontological Species
Species are considered today the fundamental units in the classification of the
life forms on Earth; this means that practically each living or fossil organism on
our planet belongs to a certain species
Carl Linnaeus (1701-1778) introduced the term ‘species’ in the current scientific
classification practice, and the term was used ever since
The term of Linnaean species was coined to recognized the species concept
defined according to general morphological resemblance. The Linnaean species
were considered originally unchangeable entities of divine origin
The concept of morphospecies, which is widely used by paleontologists today is
derived from that of Linnaean species
Modern and fossil species morphological features are included and can be
plotted within the morphospace
The significant advances in understanding the evolutionary process resulted in a
major re-evaluation of the Theory of Evolution, which begun in the first half of the
20th century, and is known as the Modern Sythesis of Evolutionary Theory
The Modern Synthesis represents a major split between: biology, genetics,
Probably the best known concept of biological species was given by Ernst Mayr
(1904-2005) in the book Principles of Zoological Classification, published in
o “Species are groups of interbreeding natural populations that are
reproductively isolated from other such groups”
The original concept of genetical species was provided by Theodosius
Dobzhansky (1900-1975) in his book Genetics and the Origin of Species,
published in 1937.
o Today we consider a genetic species an array of natural populations that
are genetically compatible, and are genetically isolated from other units of
similar rank
The concept of paleontological species was given by George Simpson (1902-
1984) in Principles of Animal Taxonomy, a book published in 1963:
o “a lineage (an ancestral-descendant sequence of populations) evolving
separately from others, and with its own unitary evolutionary role and
A composite paleontological species is the basic unit with taxonomic significance
in the fossil record, and has the following characteristics
1. It is monophyletic
2. It has a distinct range of morphological variability, showing relative stability
over a definable period of time & presentinfcrg relatively discrete
evolutionary changes
3. It is a morphologically heterogeneous and discontinuous entity, consisting
of one or (mostly) more morphological and/or paleoecological varieties.
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