Geol 107 Midterm

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Stano's 3 Principles

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1. Superposition

2. Law of Original Horizontality

3. Law of Original Continuity

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Superposition

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Oldest rocks are at the bottom (deposited first) youngest rocks are on top

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Law of Original Horizontality

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Strata are deposited in horizontal layers that are parallel with each other

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Law of Original Continuity

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Deposited continuously over lateral distances

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3 Types of Age Boundaries

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1. Conformity: when the boundary is distinct

2. Disconformity: when you are missing time

3. Angular Unconformity: mountain building

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Absolute Age

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Best way to determine is through radioactive decay

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Reasons for Continental Drift

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1. Continents fit together

2. Distribution of fossils

3. Distribution of glacial deposits

4. Mountain belts

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Fossils found on Gondwana

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1. Mesosaurus

2. Glossopetris

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Geophysical Evidence of Plate Tectonics

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1. Mid-Ocean Ridge

2. No ocean crust older than 200 Ma

3. Paleomagnetics

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3 Supercontinents

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Pangea 300-200 Ma (Carboniferous - Triassic)

- most recent w Gondwana

Rodinia 1200-800 Ma

Nuna (ca. 2000 Ma)

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Continental Breakup

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1. Rift Valley

2. Spreading produces linear sea

3. Continues spreading to produce a full ocean

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Wilson Cycle

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Oceans = transitory features that are created as mega/super continents break up and disperse and then are destroyed when continents come back together

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Fossil

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Remains of ancient organisms (anything left behind)

- shells, bones or features made by them (footprints, burrows)

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5 Main Categories of Fossils

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1. Bones

2. Shells

3. Cellulose

4. Trace Fossils

5. Soft Tissues

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Bones

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- made of phosphate which is more resistant to weathering than soft tissues

- most bones not found in the same place

- conditions of fossilization (taphonomy) important in determining whether they will be preserved

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Shells

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-made of carbonate which is not as resistant

-typically found as molds of the inside

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Cellulose

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- can be preserved as is if the plants are dried out or oxygen is excluded

- wood can be petrified (filled w silica)

-origin of all the coal in the world

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Trace Fossils

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- includes tracks, burrows, and borings of animals

- record behaviour of the animal that made them

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Soft Tissues

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- normally decomposes so not preserved as fossil

- known as fossil Lagerstatten

- important in recreating the history of life

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Faint Young Sun

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- sun only 80-85% as bright

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Early Archean Characteristics (Warrawoona)

3.5 Billion Years Ago

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1. volcanic islands no true continents

2. sun only 80-85% as bright

3. volcanic atmosphere with NO oxygen

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3 Steps in Synthesis of Life

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1. formation of simple organic molecules

2. combination simple organic molecules into complex organic molecules

3. replication

1+3 have been explained and occur naturally unable to solve 2

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Miller-Urey Experiment

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-volcanic gases+ spark = all amino acids essential to life

-energy source is unimportant the reaction NEVER works if oxygen is present

-

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RNA - World

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- accepted DNA could not have been first complex organic molecule since its formation requires proteins

- RNA can replicate itself and act as catalyst in reactions (like proteins) so favoured model

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Speigelman Monster

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- shows that self-replicating living systems can consist of little more than short strand RNA

- QB Virus, could not live out of test tube shows simplest life form possible

- got rid of excess functions

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Where did life occur

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- probably evolved in hot spots

- mid ocean ridges

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Evidence that Life Existed

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1. Stromatolites

2. Organic Microfossils

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Stromatolites

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- layers of sediments reflect presence of mats of unicellular organisms build up

- occur in extreme environments (Shark Bay)

- oldest occur in rocks 3.5 Ga from Warrawoona

- Baberton SA

-continents started to grow which created shallow seas where stromatolites formed

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Organic Microfossil

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-filaments and spheres of carbon that reflect the walls of unicellular organisms

- formed in submarine hot springs rather than shallow seas

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Age of Stromatolites

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Proterozoic

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Banded Iron Formation

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- indicate iron reduced state in ocean

- ocean and atmosphere prior to 2.4 Ga contained no free oxygen

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Faint Young Sun

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- sun on Early Earth = only 75% as bright

- required higher CO2 levels

- as suns energy increased the CO2 decreased

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Photosynthesis

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- all cyanobacteria use photosynthesis for metabolism

- fixes CO2 and liberates oxygen and atmosphere

-evidence of increasing oxygen after 2.7 Ga

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3 Main Stages of Oxygenation of Earth

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1. Iron Ocean (prior to 1.8 Ga)

2. Canfield Ocean (1.8 - 0.6 Ga)

3. Modern Ocean (after 0.6 Ga)

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Iron Ocean (prior to 1.8 Ga)

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- dissappearance of BIF at 1.8 Ga

- oxygen oases formed in immediate vicinity of cyanobacteria

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Canfield Ocean (1.8-0.6 Ga)

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- atmosphere and shallow oceans contain some free oxygen

- brief appearance of iron ocean in conjunction with "snowball" glaciation

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Modern Ocean (after 0.6 Ga)

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- atmosphere, shallow ocean and deep ocean all oxygenated

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The Great Oxidation Event (1.8-2.4 Ga)

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- the transition from an oxygen-free world to one with limited oxygen in the atmosphere and shallow seas

- most profound organism-induced global change in Earth history

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3 Aspects of Evolution

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1. Speciation

2. Convergence

3. Co-Evolution

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Speciation

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- different responses within a species to different environments (divergence)

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Convergence

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- similar life habits in similar environments lead to evolution of similar morphology among organisms that are unrelated

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Gene Pool

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all genetic information in a population

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Anagenesis

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- continual evolution of a species until it becomes a new species

- single lineage slowly progressing

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Cladogenesis (Divergence)

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- splitting of one species into 2 as different populations of the species respond to changing circumstances

- ancestral population splits -> splits -> splits

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Convergence

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- how two organisms that are not related find the same solution to the same problem

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Sabre Tooth

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- designed for cutting chunks of flesh out of prey and then leaving them to bleed out

- evolved independently at least 5 times

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Co-Evolution

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- how organisms adapt to each other and as a response to their environment

(1) Arms Race

- between predator and prey

(2) Mutualism

- relationship that is beneficial to both species

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Van Valen (1973)

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The Red Queen Effect

- always competing and improving

- evolution in a species forces the evolution of all species it interacts with

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Court Jester Effect (Baranosky 2001)

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- states that abiotic factors, which are not under organisms control also shape their evolution

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Phylogeny

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- biological classification of organisms must reflect evolutionary history

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2 Fundamental Divisions

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(1) Prokaryotes

- unicellular, lack a cell nucleus or organelles

- binary fission

(2) Eurkaryotes

- unicellular or multicellular, DNA in nucleus

- sexual reproduction

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Linnean Classification

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- based on hierarchy proposed by Carl von Linne (1735-38)

- higher you are the better you are

- no concept of evolution

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Three Domains (Super Kingdoms)

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1. Bacteria

2. Archaea

3. Eukarya

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Eukarya 4 Kingdoms

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1. Protoctista

2. Fungi

3. Plantae

4. Animalia

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Classifying Organisms

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1. Cladistics

2. Molecular Phylogeny

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Cladistics

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- proposed by Willi Hennig (1966)

- offers hypothesis re: evolutionary history or relationships between organisms

- uniting organisms that share unique features into clades

- good for inferring patterns of relationships but cannot identify evolutionary mode

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Strengths of Cladistics

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- testable and rigorous

- can be used at almost any level of taxonomy

- includes fossils and living species in the same cladogram

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Monophyletic Group

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- all decendents form a common ancestors

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Paraphyletic

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- common ancestor but does not include all descendants

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Polyphyletic

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- more than one ancestor

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Three Sets Morphological Characteristics

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1. Primitive

- shared derived characteristic relates to ancestor

2. Derived

- only one lineage has it

3. Convergent/Analogous

- similar feature in unrelated organisms

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Cladogram

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- shows the order of evolutionary appearances of derived characteristics

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Molecular Phylogeny

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-Francis Crick

-measures degree of substitution in DNA, RNA or proteins

- directly measures genetic differences

- as you go farther from modern organisms it gets less accurate

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Strengths of Molecular Phylogeny

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- rigorous and testable

- can be used at any level of taxonomy

- directly measures genetic differences

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Suspension feeding

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- take microorganisms out of water

- no mouths during Ediacaran

- no predators

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Rangeomorphs

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- extinct clade

- had no mouths so were suspension feeders

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Snowball Earth Period (730-580 Ma)

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- Sturtian 715 Ma

- Marinoan 635 Ma

- Gaskiers 580 Ma

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Mistaken Point

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- oldest Ediacaran fossils (580 Ma) found

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Stem Group

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- on the line of arthropod but doesn't have all characteristics

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Ediacaran Biota

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- went extinct rapidly w appearance of first shells of Cambrian biota = when life exploded

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Garden of Ediacara

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- almost entirely autotrophic

- no one had mouths and all just layed there so there were no predators

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Early Cambrian

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- most profound and rapid diversification event in history of life

- rise in diversity

- reflects emergence of skeletons and brains

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Archaeocyathan

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- first skeletal reef builders

-extinct end of Early Cambrian

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Burgess Shale

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- exceptional preservation of hard and soft-bodied marine animals

- one of most important Lagerstatten fossils of all time

- key info on stem-group arthropods

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Causes of Cambrian Explosion

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1. Rise in Oxygen

2. Ecological Feedback

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1. Rise in Ocean

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- formation of collagen required >10% present Atmospheric level by Ediacaran

- exoskeleton requires even oxygen levels

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2. Ecological Feedback

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- Cambrian Arms Race

- evolutionary development of increasingly sophisticated armour and weapons = brains

- Agronomic Revolution