The document discusses the concept of species and how it affects paleontology. It notes that there is no single agreed upon definition of a species, and that paleontologists often have to rely on morphological characteristics to define fossil species since they cannot observe behaviors like interbreeding. The document also discusses two models of speciation - phyletic gradualism where species change gradually over time, and punctuated equilibrium where species remain stable with occasional rapid speciation. It argues that punctuated equilibrium better fits the fossil record, which generally shows stasis with occasional new species appearing.
This is my attempt to explain punctuated equilibrium vs. phyletic gradualism and how both ideas contribute to the controversy of what constitutes a species.
This is my attempt to explain punctuated equilibrium vs. phyletic gradualism and how both ideas contribute to the controversy of what constitutes a species.
Cause of Diversity
Evolution
Lamarck’s Theory of Evolution
Darwin’s Theory of Evolution
Natural Selection
Evidence of Evolution
Misconceptions
References
The evolutionary development or history of a species or of a taxonomic group of organisms (The phylogeny of a group of taxa (singular: taxon) (species, etc.) is its evolutionary history)
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Thespeciesproblem 120415203649-phpapp02
1. The Species Problem
How it Affects Paleontology
“
“The boundaries of the species, whereby
men sort them, are made by men.”- John
Locke
2. What is a Species?
• A species is “the fundamental
taxonomic unit in nature” (39.)
• Species “recognize each other.”
• Proof of this “recognition” is
displayed in reproductive
habits, or the potential for
interbreeding.
4. Variation in a Single Butterfly Species
Species
Agrias
Kingdom - Animalia
Phylum - Arthropoda
Class - Insecta
Order – Lepidoptera
Family- Nymphalidae
Genus-Agrias
5. What is phylogeny?
Loosely (according to the dictionary)
phylogeny is the evolutionary history of a
group of organisms as depicted in their family
tree or “cladogram.”
7. Two Concepts of Species (p 39)
• Morphological
Species
Diagnosible cluster
Pattern of ancestry
Self contained group
“beyond which there
is not” (Eldredge and
Cracraft)
• Biological Species
Population array
Actual
interbreeding
OR
Potential
interbreeding
Reproductive
isolation
8. These opposing ideas break into
two camps:
Phyletic Gradualism
•Often favored by
biologists and life
scientists
•Speciation is slow,
uniform and
gradual
Punctuated Equilibrium
•Makes more sense in
the context of
paleontological studies
•Most species exhibit
little net evolutionary
change
10. Scientists Today…
-Tend to adhere to a biological
concept of species.
-This can pose a problem for
Paelontologists.
11.
12. There are at least 24 different
species concepts and none of
them can be applied to all
organisms that have ever lived.
(Hey, J. 2001 qtd in Techne)
13.
14. How do Paleontologists Know?
•Fossils cannot demonstrate
interbreeding or the lack
thereof.
•Therefore, typological
(morphological) species
divisions make the most sense.
22. Determining a “Cut Off”
GAPS IN RECORD VS
• Artificial
• Convenient
CONTINUOUS SERIES
First Specimen?
Halfway through?
New Problem: Pseudoextinction
23.
24. What is “Pseudoextinction?”
• Parent species go extinct as new
species evolve in succession
• Not the same as extinction.
• Part of the evolutionary species
concept.
26. Take your Pick!
• Biostratigraphers
make use of many
fine species divisions
to date layers of
stratigraphy.
• General
paleontologists will
find the evolutionary
species concept (a
lineage that evolves
separately with
separate lineages and
tendencies) more
practical
27. A Solution to the Mayhem
Punctuated Equilibrium to the Rescue!
•Phyletic gradualism(gradual
transformation among species) is actually
not that common in the fossil record.
•Actually, fossil records appear to remain
static and relatively unchanged
throughout paleo reconstructions for the
most part.
28.
29. Punctuated Equilibrium
• Most large species populations do
not evolve in any direction.
• Fossil populations remain in stable
equilibrium for long periods,
• Punctuated by the introduction of
a new species formed in an isolated
area (and then migrated back to
main group.)
30.
31. Eldredge and Gould
Stephen J. Gould Niles Eldredge
There is very little proof of
anagenetic transformations taking
place.
33. Exception:
George Simpson of Columbia
University says,
“The state ofrest is the
exception and it seems that
some restraint or force must be
required to maintain it."
34. Main Idea
Anagenetic continua are rare, and thus
species division is not as complicated as
it seems.
Nietzche says, “Out of chaos comes order.”
Punctuated Equilibrium simplified the
species problem significantly.
35.
36. Sources:
"Biostratigraphy." Harvard University Museum of Comparative Zoology. Harvard
University, 2004. Web. 7 Sep 2011.
<http://www.mcz.harvard.edu/Departments/InvertPaleo/Tren
ton/Intro/GeologyPage/Sedimentary%20Geology/biostrat.htm
Crampton, , James. Gale, A. "A plastic boomerang: speciation and
intraspecific evolution in the Cretaceous bivalve Actinoceramus."
Paleobiology 31.4 (2005): 559-577. BioOne. Web. 7 Sep 2011.
<http://www.bioone.org/doi/abs/10.1666/04003.1>.
Phylogeny. (2012, April 14). Retrieved from www.dictonary.com
Prothero, Donald. Bringing Fossils to Life. 2nd ed. NY: McGraw-Hill, 2004.
39-45. Print.
Punctuated Equilibrium." Wikipedia. Online. 2011. Print.
<www.wikipedia.com>.
Unknown. (Image Creator). (2012). Phylogenetic tree of life. [Print Photo].
Retrieved from http://en.wikipedia.org/wiki/Phylogenetic_tree
