Geol 1003 Test 2

What are the 4 types of natural selection?

Sexual Selection, Artifical selection, coevolution, survival of the fittest

Sexual Selection

A. Choosing mates based on beauty/physical prowess. B. Morefavorable mates have higher chance of reproducing -> these traits have become more prevalent. C. Not always positive -> black widow/mantids -> sexual cannibalism

Artifical Selection

Choosing traits you like and breeding for those traits. Variation, Inheritance, Selection, Time

Coevolution

When 2 species affect evolutionary trajectory. Can be a mutally benefical relationship or a parasitic relationship

Survival of the fittest

Organisms with better traits will leave behind more offspring

List Darwin’s evidence for Natural Selection

1. Embrology

2. Homologous & Analogous structures

3. Vestigial structures

4. Breeding experiments

5. Fossil record

6. Adaptation (survival of the fittest)

Embrology

Study of unborn/unhacted offspring. Ex: Vertebrates are indistinguishable from one another in earliest stages of life

Homologous Structures

Organs, skeletal parts, or other features that have a similar position and evolutionary organ, but no necessarily have the same function or not identical in structure. Can be traced to a single ancestral species

Analogous Structures

Same function different evolutionary origin

Vestigial Structures

Those that are disappearing from a species or lineage of species. Reduced in size or function so as to become useless

What are the two hypotheses for speciation rate?

Phyletic gradualism and Punctured speciation

Phyletic gradualism

Slow changes in organisms – millions of years

Punctured Speciation

Rapid changes in organisms followed by long interval of no changes

Ancestor descendent relationships

Tree showing what organism evolved from which other organism

Cladogram

Clusters taxa according to their degree of relatedness

Dollo’s Law

Once a species has experienced genetic change, this change cannot be reversed. Once a species has gone extinct, it cannot come back into existence

Extinction

annihilation of all individuals of a species

Mass extinction

Many species go extinct in a short amount of time (10’s of thousands to a few million)

How many major mass extinctions have occured?

5 (but there have been other minor mass extinctions)

List the causes of extinction

1. Overhunting

2. Infectious diseases

3. Loss of habitat

4. Loss of major food source

List the causes of mass extinction

1. Rapid climate change

2. High levels of volcanic acitvity

3. Meteorite impacts

4. Rapid spread of infectious diseases

5. Decrease of sea level, exposure of continental shelves

6. Deforestation of land

Facies

Sedimentary units that has a set of characteristics particular to a local environment

Lithofacies

Sediment of depositional environment

Biofacies

Distinctive set of fossils

Aqueous or subaerial

under water or land

Oxic or anoxic

O2 avaliable or no O2 present

High or low energy

Water moves fast, turbulent or water moves slow or not at all

What are two factors that affect grain size?

Distance from source and current energy

Sorting

Measure of range of grain sizes (How different is the largest grain from the smallest grain)

What is the difference between well sorted rock and poorly sorted rock

In a well sorted rock grains are similar sizes, in a poorly sorted rock grains are different sizes

What is a factor that affects roundess?

The energy in an environment

What are the two types of sedimentary rocks?

1. Detrital (Clastic) -> need a source and a method of transport 

2. Carbonates -> limestone (biochemical)

Detrital (clastic) Rocks

Made of particles (clasts); Classified by grain size (tells us info about environment); Breccia, Conglomerate, Sandstone & Shale are examples

Biochemical rocks

Found in warm shallow water/ shells & skeletons/ piling up on sea floor; made of CaCO3, can also be made of SiO2: Chert -> marine (SiO2) - ooze of SiO2 plankton

What are sedimentary structures?

Features of sediment reflecting physical, chemical, or biological controls on their accumulation. (Structures that form at the same time the sediment is deposited)

List some examples of sedimentary structures

Bedding, Bioturbation, Ripples, Cross bedding, Graded beds, Mudcracks, Stromatolites

Bedding

Layering in sedimentary rocks, reflects change over time

Bioturbation

Reworking of sediment by organisms (burrowing)

Ripples

Forms from moving air or water in a current (Symmetrical or Asymmetrical ripples)

Cross bedding

Strata inclined at different angles formed by the rippling of sediment

Graded Beds

A single event sdeimentary bed in which there is a progessive vertial change in grain size (Ex. Turbidites and Alluvial Fans)

Mudcracks

Form from dying and shrinking of mud (Tells geologist which way is up)

Stromatolites (sedimentary structure definition)

Indication of warm, shallow water

Walther’s law

Vertical stacking of rock layers were once laterally adjacent to on another at the time of deposition. Sea level shift causes movement of facies from the transgression/regression cycle

What are non-marine depositional envrionments best identified by?

The presence of terrestrial or freshwater fossils, and sometimes by reddish colors in the sediments

List some examples of non-marine depositional environments

Channels, floodplains, swamps, freshwater lakes, varves, eolian environments (sand dunes)

Swamps/Freshwater lakes

Low energy, deposition of clays and silts

Varves

Layers can be separated by color (lighter layers and darker layers) Lighter layers indicate summer and darker layers indicate winter

Eolian enviornments

Erosion by wind, sand sized grains, large cross beds (dunes)

List the marginal marine depositional environments

Beaches, Deltas, and Continetal shelves

Beaches

Deposition of sand, some marine fossils

Deltas

Walther’s law is demonstrated here; high velocity water at beginning of delta, low velocity water at the end; Coarse to fine grained sediments

Continental Shelves

Source of most macroscopic body/trace fossils; cross-beds, ripples, flute casts

List the marine depositional environments

Continental slope and deep ocean

Continental slope

clay/silt and turbidites

Deep ocean

Fine muds; plankton pile up - chert and limestone

How can we use oxygen isotopic ratios through time?

To provide information of ancient temperatures and glacial ice volumes

How can we use carbon isotopic ratio through time

To provide information of ancient plant volume and glacial ice volumes

How did the moon form?

At ~4.5 Ga a mars sized rock (Theia) collided w/ Earth. The debris from the impact would start to orbit around Earth and eventually form the moon

What is one hypotheses about how the water got ot Earth?

From meteors that hit the Earth ~3.9 Ga, it is believed that these meteors contained salt & water

When did plate tectonics begin?

During the archean era; however the rocks were fromed from processes not similar to modern plate tectonics. Small blocks of continetal crust were compressed between protocontinents & oceanic crust was trapped and deformed instead being subducted (so plate tectonics did occur but different)

What is greenstone?

Old oceanic crust and a common archan rock type. Chlorite-rich greenstone is unqiue to the precambrian and more mafic than modern rocks. Greenstone belts are remnants of ocean basins

Are there any greenstones younger than the archean?

No

Were there blueschist and parallel mm belts in the Archean?

No

When did continental crust form?

During the “mobile crust phase”, these were faster, smaller blocks

Where were many ancient subduction zones adjacent to?

Protocontinents

What were some other typical archean rocks?

Chert, BIFs, and Stromatoltes

Chert (archean rock)

Comes from weathering of volcanic material (Not SiO2 plankton yet)

BIFs (archean rocks)

Interlayered chert and iron rich materials, unqiue to the precambrian, occured during anoxic enviroments (most prior to ~1.8 Ga, but some periods of anoxia later in precrambrian)

Stromatolites (archean rocks)

Limestones + cyanobacteria (photosynthesizers)

Was there continent above sea level during the archean?

Yes, but very little. Archean rocks are mostly classified as marine rocks

Summary of proterozoic eon events

1. Atmosphere and oceanic changes

2. Typical plate tectonic begin (formation of 1st supercontinent)

3. Snowball Earth

4. Changes to life

How did Earth’s atmosphere form

From the gasses spewe by volcanoes (way more hydrogen sulfide, methane, and carbon dioxide than today)

How many years during the proterozoic eon did it take for the Earth’s surface to cool enough for water to collect on it?

½ Billion years

What did the Miller and Urey experiment show?

That early molecules and elements, when introduced to an electrical spark, lead to the formation of organic molecules

How did the salt get into the oceans?

From the chemical weathering of rocks

When did Earth’s ocean reach current salinity?

By the end of the archean by ~2.5 Ga

When did BIFs stop forming?

During the proterozoic eon, this switch is due to the introduction of red beds (more O2 in atmosphere than ocean)

How long into the proterozoic Eon were BIFs forming?

3.0-2.0 Ga

At what time did red beds begin to become extinsive

1.9 Ga, because O2 was building up in the atmosphere instead of the ocean

At what point did our atmosphere become like today’s?

Not until the end of the precambrian

Did the proterozic eon have more modern plate tectonic processes?

Yes

Examples of proterozoic plate tectonics

Arcuate belts of tectonic activity, parallel belts of mm rocks, and orogenic zones

What are orogenic zones and what do they lead to?

Zones of mountain building lead to cont-cont collision

Laurentia

Proto North America

Avalonia

Great Britain/ Maine

How were continents formed during the protoerozoic eon?

Colliding cratons

Rodinia

1st well studied supercontinet (form 1.6 Ga broke up 1 Ga)

Grenville Orogenic Belt

An arcuate orogenic region, 1.3-1.0 Ga, extensive area of present-day North America and adjacent regions

What is the supercontinet cycles?

Build a supercontinet, break down, build up again (Open ocean, closed ocean, open ocean - Wilson cycle)

What did the paleozoic continents form from?

The neoproterozoic supercontinents

Gondwana

Huge continent, persists from late precambrian until breakup of Pangea. Consisted of Africa, Antarctica, Australia, South America, India

What was the late paleozoic sea level related to?

Plate tectonics, high sea levels lasted until the end of the precambrian

In terms of plate tectonics what was going on at the end of the proterozoic?

The breakup of a supercontinent, high rifting rates (large volume of warm, relatively expanded oceanic lithosphere), ocean basins are smaller (less deep)

What happened in snowball Earth?

Entire Earth froze, glaciers/snow covered the Earth from the poles to the equator

How many snowball Earth events were there?

3, ~720-660 Ma, ~645-640 Ma, ~580 Ma

What is some geologic evidence for snowball Earth?

Glacial striations, tillites & diamicities, dropstones, reappearance of BIFs (oxygen was trapped in ocean due to ice)

What is the process of Snowball Earth? (start to finish)

1. Rodinia began to split up causing increasing rifting and volcanism

2. Global heating increased which lead to increased limestone formations

3. Increased limestone formation leads to decreased CO2, causing global cooling

4. More snow begins to fall, reflecting the sun leading to even more cooling

5. limestone eventually stops forming leading to an increase in CO2

6. Volcanoes erupt causing even more CO2 in the atmosphere and Earth returns to normal

What appears after snowball Earth?

1st animals (belived to be because of the mass extinctions which left room for animals to take over as well as the increase on O2 after the cooling period)

Important dates in Precambrian

~3.8 Ga: C12 enrichment in sedimentary rocks, 3.5 Ga: stromatolites and 1st fossil, 2.2 Ga: 1st eukaryote, ~560 Ma: 1st animals