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Lecture 10

GLGY 307 Lecture Notes - Lecture 10: Paleontology, Essentialism, Nominalism

Course Code
GLGY 307
M.Dan Georgescu

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Module 4: Principles of Evolution
Species distribution in space & time having as main purpose sediment & rock
Assemblages zones, interval zones, acme zones
A biostratigraphical zone or biozone is defined as the fundamental unit in
biostratigraphy. It represents a layer or group of layers with a fossil content
distinct from those of the adjacent layers or groups of layers.
Assemblage Zones
General fossil content of a zone
Oppel Zones: accent is put on the boundaries, which are defined by more than one
Interval Zones: fewer species are necessary to define a biozone
Acme Zones: the abundance of one taxon or group of taxa is taken in consideration. It
has limited applicability in the correlation at regional or intercontinental scale
Species Variability
Ontogentic: growth stages
Genetic: genetic structure
Nongenetic: environmental causes
Ontogenetic Morphologic Variability
Ontogenetic variability in the result of the organism growth during its lifetime
There are three stages during the lifetime of an organism
o Juvenile
o Adult
o Genontic
Ontogenetic trajectory: organism growth can be plotted to define the so-called
ontogenetic trajectory (illustrated in the case of two planktic foraminifers)
Types of Growth
Isometric: organism shape remains the same during the ontogeny
Anisometric: organism shape changes
Growth Strategies
Accretion: continuity in the development of the various skeletal parts
o Eg: mollusks, solitary corals, etc.
Addition: new skeletal parts are added throughout the ontogeny
o Eg: echinids, radiolarians
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