GLG Exam 1

What are some key differences between Catastrophism and Uniformitarianism?

catastrophism theorizes earth was shaped by catastrophes (i.e. Noah’s flood); young earth

* idea that natural laws of the past were not the same as the current natural laws

uniformitarianism theorizes earth was formed through slow processes (i.e. erosion)

* idea that the same patterns and processes of the past are occurring today; ancient earth

What were some of the main ideas of the version of Catastrophism known as Neptunism?

Named after Neptune, Roman God of the Sea because believers theorized that each type of rock came from a specific time, and that they originated in the primeval ocean

* primary rocks (granite)→ precipitation
* transitional rocks (nonfossiliferous sed)
* tertiary rocks (alluvial poorly consolidated sed) seen as modern rock
* volcanic (minor importance) → crystallized from water

What were some of the main ideas behind of Hutton’s version of Uniformitarianism and how did Lyell’s ideas differ?

Hutton’s Uniformitarianism

* continuous upcycle of uplift, erosion, deposition, burial, re-uplift
* same processes ; unchanging laws
* ancient earth + deep time

Lyell’s Ultra-Uniformitarianism

* same laws AND rates
* all geologic processes are gradual (no catastrophe)
* no process witnessed by humans had geologic importance
* all rocks and organisms were unchanging
* extinct organisms would reappear

Why is Actualism an obvious improvement over Uniformitarianism?

Actualism is a reformed version of uniformitarianism by allowing space for catastrophic events

* natural laws are constant but processes vary
* earth’s systems have evolved over history and continue to do so

What were the basic contributions of Wegener, du Toit, Hess, Vine and Matthews, and Wilson to the development of plate tectonic theory? Who was Marie Tharp?

(ALL for PT)

Wegener: proposed theory of continental drift

du Toit: established fossil evidence

Hess: sub-marine surveys figured mechanism was from convection cells at Mid Ocean Ridges

* Hess proposed Seafloor Spreading

Vine & Matthews: seafloor paleomagnetic data as evidence for SFS -- magnetic polarity reversals matched ocean floor basalts at Juan de Fuca Ridge

Wilson: put together final touches (Earth’s surface has lithospheric plates (C or O) divergent and transform boundaries, O lithosphere recycled into mantle at subduction zones)

* Marie Tharp: used sound waves to create ocean map that backed up continental drift by showing V shape running along mid-atlantic ridge

Describe the different lines of evidence Wegener had for continental drift.

* “fit” of continents
* location of glacial deposits
* similarities of rock types and structures (folds, faults)
* paleoclimate evidence
* distributions of certain fossils

Why wasn’t continental drift accepted when Wegener proposed it?

Wegener didn’t have a mechanism to explain why the tectonic plates moved

What observations were important to Hess’s proposal of sea floor spreading?

* Guyots: isolated underwater peaks with flat tops
* Depths of guyots (and sea floor) increased along linear trends
* only 1/16th of expected sediment and volcanic islands

What type of data first showed that sea floor spreading was occurring?

Hess saw long chains of underwater mountains with rift valleys in the center , now called Mid-Ocean Ridges

What type of data ultimately confirmed sea floor spreading beyond a doubt in the late 1960’s?

‘60s Deep Sea Drilling Program dated seafloor rocks + sediments, confirming sea floor age data and validating both sea floor spreading and plate tectonics

How does plate tectonics operate and why is water so important to its occurrence?

young ocean basin rock is generated when hot convections cells cause ocean basin rock at MOR to move away from ridges. rock cools and settles as it moves away from the heat to form guyots. old ocean crust sinks back into mantle at deep-sea trenches.

water is crucial because:

* it lubricates subducting slabs
* flux melting
* descending slabs become denser when they lose water

Why do we care where the continents were previously?

we care about Pangaea because putting the continents together makes glacial deposits, rock types, paleoclimate and paleontological evidence, and paleomagnetic evidence to all line up for continental drift.

What are the principles of relative dating developed by Steno and Hutton, and how do they work?

Steno:

* superposition: in any succession of sedimentary rock layers lying in their original horizontal position, the rocks at the bottom of the sequence are older than those lying above
* lateral continuity: sediments are deposited in layers that extend laterally in all directions until either reaching the edge of basin or thin out and terminate
* original horizontality : sediments are deposited in layers that are horizontal or nearly so

Hutton:

* inclusions: any inclusion in a rock is older than the rock containing it
* cross-cutting relationships: faults, fractures, igneous intrusions, and erosional surfaces that cut across a given stratum or series of strata are younger than the rocks containing it
* recognized and understood unconformities

What is the difference between relative and numerical dating? How can they be used to complement each other?

Relative dating - based on rock layer + other found items

Numerical dating - uses number of half-lives experienced by a rock

Can be used together to see order of events in age order as well as actual age

What are isotopes and why can radioactive isotopes be used to date certain rocks?

isotopes are elements with a different amount of neutrons

Radioactive isotopes with slow decay rate can be used to find the half-life and age of rocks in their chemically closed system.

Who was Arthur Holmes and what did he accomplish?

British geologist who came up with the first reliable radiometric ages for rocks.

Author of The Age of the Earth

Estimated age of earth as 4.5 billion years old

What data are necessary to calculate numerical ages? Why does the half-life of a parent isotope determine the age-range over which a given parent-daughter system is useful?

To calculate numerical ages, there must be parent isotope material in original rock with no decay having begun.

There must be no loss or gain of P or D except through radioactive decay (closed)

Half-life must be appropriate to event

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(ASK)

Why is it best to confirm the age of a rock with multiple isotopic systems (P-D pairs)?

There is inherent error within every growing daughter / decaying parent so using multiple systems to double check is useful for accuracy

What two processes combine to lithify sediments?

Lithification transforms loose sediment particles into solid rock

* compaction: Pressure from overlying material places grains closer to each other
* Cementation: Precipitation of quartz, calcite, or iron oxide around grain perimeters (binds grain together)

What are the main textural and compositional properties of siliciclastic sedimentary rocks and how are they used in the classification of these rocks?

Siliciclastic (clastic) rocks are formed from weathered bits of pre-existing rocks

Textural:

Grain size:

Conglomerate or breccia, sandstone, siltstone, claystone, mudstone

Sorting: Well to poorly sorted

Degree of rounding reflects transport distance (farther= rounder)

Grading: Due to current strength variations (e.g. Coarsening upward)

Composition:

* Dominance of quartz implies longer transport from source area
* Dominance of feldspars and/or rock fragments implies shorter transport from source area
* Quartz, feldspar, rock fragments, percent Matrox (finer grains)

What are sedimentary structures?

The larger, generally 3-D physical features of sedimentary rocks; best found in large outcrop instead of through microscope

Lamination, beds, cross-bedding, graded bedding, trace fossils, mud cracks, ripple marks

What are the common components of biochemical carbonate rocks and where do these components come from?

Limestone: Minerology dominated by calcite or aragonite

Dolostone: Minerology dominated by dolomite

Formed from the shells and bodies of underwater organisms

What is meant by the statement that sedimentary rock layers are time-transgressive?

this means rocks units are not time units. Sedimentary rock layers differ in age from place to place.

What is meant by correlation, and what are unconformities?

correlation: establishing the relationships between the order of events in two or more locations

* lithostratigraphic correlation matches rock units w/o regard for time
* time-stratigraphic correlation uses fossils to demonstrate time-equivalence of rock units

unconformities represent gaps in the rock record.

How does lithostratigraphy differ from biostratigraphy?

lithostratigraphy involves the classification of any rock where biostratigraphy deals only with fossiliferous rocks

Who is credited with developing the Principle of Faunal Succession? What biological and geological facts form the basis for this principle? How did the addition of this correlation “tool” revolutionize stratigraphy?

William Smith

Principle states that the biological history on earth is captured within rocks based on their fossils. All rocks with the same types of fossils were deposited during the duration of that species existence on Earth.

The Principle of Faunal Succession in application created Biostratigraphy

* only practical dating method for geologic history as well as correlating strata in search of oil and gas

What are key properties that make a good index fossil, and why?

* easy to recognize
* short stratigraphic range: precise dating
* large geographic range: abundance
* found in many environments: abundance
* easily preserved

What are the different types of biostratigraphic zones and what two main factors determine a fossil’s range? What are “facies fossils” and why are they not good to use for biostratigraphy?

Types of Zones:


1. taxon range zone
2. concurrent range zone (2 or more taxa)
3. lineage zona: based on successive first occurrences within a single evolving lineage
4. interval zone: 2 successive first or last occurrences of unrelated taxa
5. abundance zone: sudden increase n number of certain taxon

Determined by evolution and paleoecology

Facies Fossils are appear and disappear; controlled by changes in sedimentary faces.

* many biostratigraphy zonation’s fail b/c key taxa were facies controlled

What are FADs, LADs, Lazarus taxa, Elvis taxa, and Zombie taxa?

First Appearance Datum (FADs): abundance

Last Appearance Datum (LADs): extinction

Lazarus taxa: facies fossils

Elvis taxa: extinction confusion when taxa look alike

Zombie taxa: when durable fossils are eroded and redeposited, giving impression that taxa survived longer than they did

Why is a concurrent range zone probably the most robust type of biozone?

Concurrent range zone is the most robust because there are 2 or more taxa’s range zones overlapping.

What are the basic ideas behind magnetic stratigraphy, chemostratigraphy, cyclostratigraphy, and event stratigraphy? What are marker beds? Why is it best to use all of the stratigraphic tools available to you when studying a stratigraphic section?

magnetic: dating based on magnetic reversals

chemo: dating based on isotopic ratios

cyclo: how astronomically forced cycles affect dating

event: dating of strata, fossil assemblage intervals, and interfaces

* marker beds (like ash between sediments) show distinctly that an event occurred within strata

What are Global Stratotype Section and Points (aka Boundary Stratotypes) and why are they important to stratigraphy?

the GSSP defines the base of each stratigraphic unit by name and rank.

These reference points of stratigraphic sections of rock define the lower boundaries of stages on the International Chronostratigraphic Chart.

What is the difference between body fossils and trace fossils?

body fossils require hard parts: carbonates, silica, calcium phosphates, complex organics (cellulose, chitin, spongin)

* unaltered remains (amber), permineralization, recrystallization, dissolution & replacement, carbonization, compressions/impressions

trace fossils (ichnofossils) are biologically generated sedimentary structures

* tracks, burrows, fecal pellets, etc

What are some important factors affecting preservation?

(rapid burial, anoxic burial environment)

organism makeup:

* hard (inorganic) vs soft (organic) parts
* number of skeletal elements
* mineral composition of hard parts

ecology:

* numerical abundance
* size of organism
* habitat
* terrestrial: subjected to net erosion
* subaqueous: subjected to net deposition
* infaunal (living in sediment) OR epifaunal (living on or above sediment)

Be able to define and distinguish taphonomy, biostratinomy, and diagenesis.

taphonomy: study of death, decay, burial, fossilization (‘grave’ → found)

* biostratinomy: processes occurring between death and final burial (stratification laws- biological & mechanical agents, chemical degradation)
* diagenesis: processes occurring after final burial (compaction, dissolution, replacement)

What are the three main types of biostratinomic processes affect the preservation of organic remains?

mechanical: transport, breakage, exhumation

chemical: oxidation & early changes in minerology

biological: decay, scavenging, bioturbation, encrustation, boring

What is meant by bioturbation?

bioturbation: the disturbance of sedimentary deposits by living organisms

* performed by infaunal organisms (live/burrow into sediment)
* causes disarticulation

Lagerstätte – definition, significance, and depositional conditions that could produce a lagerstätte.

“storage place” in English

significance: extraordinary fossil deposit that preserves soft tissues and sometimes even skin texture and color patterns

depositional conditions: rapid burial + anoxic burial environment

What is evolution (include natural selection in your definition)?

evolution: descent with modification

all life has common ancestor

natural selection: variability in traits → traits enhancing survivability → heredity of desirable traits

What were the main ideas/contributions of Lamarck, Darwin, Wallace, and Mendel?

Jean Baptiste de Lamarck: ‘inheritance of acquired characteristics’ traits arise from need and are heritable

Charles Darwin: species change, natural and artificial selection

Alfred Russell Wallace: same conclusions as Darwin; encouraged publication of ‘On the Origin of Species’

Gregor Mendel: pea plant experiments;

* traits controlled by genes which occur in multiple forms (alleles). alleles may be dominate or recessive and the offspring received one allele from each parent
* particulate inheritance→ F2 experience 1/4 recessive expression

What are the sources of genetic variation?

Mutations (failed DNA copy OR external influences)

Migration (gene mixing)

Sex recombination (new gene combinations)

Genetic drift (lucky/unlucky gene survival)

Natural selection (desirable traits survive)

What are allopatric speciation, phyletic gradualism, and punctuated equilibrium?

allopatric speciation: new species from mixed homelands

* phyletic gradualism: continuous and gradual minor change over time
* punctuated equilibrium: long periods of no change interrupted by rapid change (bottleneck effect)

What are divergent and convergent evolution?

divergent evolution: different environmental pressures bring about accumulated differences in closely related population within species → speciation

convergent evolution: independent evolution of similar features in species of different lineages (bat wing / bird wing / insect wing)

What is the difference between microevolution and macroevolution?

microevolution: gene frequency changes in population over a generation

macroevolution: major feature changes in species; wings, legs, etc)

What are HOX genes and why are they important to evolution?

homeotic genes are regulatory genes (“master switch”) which cause replacement of organ systems in organisms

* the DNA code itself is a homology that links all life on Earth to a common ancestor

What evidence do we have for evolution? What is a transition fossil?

homology: similar characteristics due to relatedness

the fossil record: biostratigraphy showing evolution of common ancestor over time

cellular & molecular evidence: likeness in cell structure & DNA

vestigial features: anatomical remnants of ancestors

transitional fossils (transitional forms) show intermediate states between ancestral form and that of its descendants

developmental biology: study of embryological development; comparative embryology reveals fundamental development similarities

ecology: environment affects the evolution of living things

Know the three domains of life. Of the three domains, which two are more closely related to each other? What is LUCA?

3 domains: Bacteria, Archaea, Eukarya

Archaea and Eukarya are more closely related

LUCA: Last Universal Common Ancestor; microbe

How does a biologist define a species? What about a paleontologist? What difficulties do paleontologists have in defining species?

(biologists) Biological species concept: a group of populations that are actually or potentially inter-breeding and are reproductively isolated from other such groups under natural conditions

(paleontologists) Morphological species concept: Organisms classified in the same species if they appear ‘identical’ by morphological (shape) criteria

* original difficulty for paleontologists to use the biological species concept because, for fossils, naturally occurring interbreeding populations cannot be tested

What is the study of phylogeny and what are some of the difficulties associated with its main goal of reconstructing the Tree of Life?

Phylogeny: Evolutionary history of a genetically related group of organisms

Difficulties in reconstructing tree of life:


1. Don't know the total diversity of living organisms
2. Know even less of the diversity of fossil organisms
3. How to tell if fossil is direct ancestor to another fossil and not a close relative of that direct ancestor?

Why was cladistics developed, i.e., why is it useful – what does it facilitate?

Cladistics is a taxonomical technique developed as an approach to making phylogenic trees

* needs both phylogenetically informative characters and uninformative (misleading) characters to avoiding using them

What is the difference between homologies and homoplasies?

Homologies (homologous traits) \* useful

* Similar traits due to common ancestry
* Traits evolve and can be modified
* useful for recognizing / defining closely related groups of organisms
* Hair, skeletal elements, feathers

Homoplasies (convergent traits) \*not useful

* analogous traits evolved independently in separate lineages due to similar ecological pressures
* False similarity, not due to common ancestor
* Wings, eyes, flippers

What is molecular phylogeny and why is it thought to be more robust than anatomical phylogeny?

molecular phylogeny is an approach to making phylogenic trees using DNA, RNA, etc.

the analysis of molecular similarities and differences between proteins, amino acids, antigens, chromosomes + DNA to evaluate their evolutionary relationships.

More robust than anatomical phylogeny because there are less homoplasies and the data is readily quantifiable