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Chapter 6 The Fossil Record
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Fossils

• the remains or traces of ancient life which have
  been preserved by natural causes in the Earth's
  crust.
• remains of organisms - bones or shells
• traces of organisms - tracks, trails, and burrows
  (trace fossils).
• It has to be AT LEAST 10,000 years old

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• Fossil preservation
• The vast multitude of organisms that lived in the
  past have left no indication that they were here
• Fossil preservation is actually a very rare
  occurrence
• Requirements needed to make a fossil

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• Have preservable parts. Hard parts (bones,
  shells, teeth, wood) rather than soft parts
  (muscle, skin, internal organs).
• Be buried by sediment. Protection from decay or
  being eaten.
• Escape physical, chemical, and biological
  destruction after burial. Remains could be
  destroyed by decay, burrowing (bioturbation),
  dissolution, metamorphism, or erosion.

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• Organisms do not all have an equal chance of
  being preserved.
• must live in a suitable environment
• Marine and transitional (shoreline) environments
  more favorable for preservation than continental
  environments
• rate of sediment deposition tends to be higher
• swamps, river floodplains may be OK
• Take an African safari
• Lots of animals..they die
• Where are their bones? (some elephants have
  been known to take the bones and hide them)

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• How are critters preserved?
• Unaltered hard parts (original material)
• Chemical alteration of hard parts
• Imprints
• Preservation of unaltered soft parts
• Traces

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• Unaltered hard parts
• shells of invertebrates and single-celled
  organisms, or vertebrate bones and teeth. May
  have the following compositions (biology starts
  in here)
• Calcite echinoderms, foraminifera.
• Aragonite - clams, snails, scleractinian corals.
  Aragonite is metastable (in time recrystallizes
  to calcite).
• Phosphate - bones and teeth of vertebrates,
  conodonts (a strange fossil), and the outer
  covering of trilobites. The shiny scales of
  fossil fish are phosphatic.
• Silica - diatoms and radiolarians, some sponges.
• Organic hard parts - chitin, cellulose, keratin,
  sporopollenin, or collagen.

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• Hard parts of many fossil organisms are
  chemically altered by the addition, removal, or
  rearrangement of chemical constituents.
• Permineralization - filling of pores (tiny holes)
  in bone or shell by deposition of minerals from
  solution. Added mineral matter makes the
  permineralized fossil denser than the original
  material. Often, bone.
• Replacement - molecule-by-molecule substitution
  of the original material by another mineral of
  different composition. Fine details of shell
  structures and wood are generally preserved.
  Minerals which commonly replace hard parts are
  silica and pyrite.

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Original bone
Fossil bone permineralized ( replaced?)
(cavities filled, bone likely replaced)
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Replacement wood replaced by silica, Petrified
Forest, Arizona
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• Recrystallization
• Many modern shells are made of aragonite
  (metastable calcium carbonate).
• With time, the aragonite alters or recrystallizes
  to calcite (stable form of CaCO3).

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• Carbonization
• soft tissues of plants or animals preserved as a
  thin carbon film, usually in fine-grained
  sediments (shales, volcanic ash). Fine details of
  the organisms may be preserved.
• Plants, soft-bodied animals such as jellyfish or
  worms

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This wasp got caught by a volcanic eruption
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Fern in shale - carbonized
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• Molds casts (or, imprints)
• no shell or other material present at all. Hard
  parts are commonly destroyed by decay or
  dissolution after burial, but may leave a record
  of their former presence in the surrounding
  sediment
• organism (or part of an organism) in the
  sediment. A shell buried in sandstone may be
  leached or dissolved by groundwater, leaving a
  mold of the shell in the surrounding sediment.

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• External molds - imprints of the outside of a
  shell in the rock. If the original shell was
  convex, the external mold will be concave. If
  the mold is later filled in, yields a cast.
• Internal molds - imprints of the inside of the
  shell in the rock. Produced when shell is filled
  with sediment which becomes cemented, and then
  the shell is dissolved away. Sometimes called
  steinkerns.

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Internal mold of a gastropod (steinkern).
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Cast (top) and mold (bottom) of a trilobite
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• Unaltered soft parts
• RARE
• Soft parts of organisms such as insects, small
  frogs, or lizards may be preserved if the
  organism becomes trapped in pine resin (which
  later alters to amber).
• freezing (Example Pleistocene wooly mammoths
  frozen in Siberia and Alaska. Appr. 44,000 yrs
  old) and desiccation (natural drying or
  mummification).
• Larger animals may become trapped in oily,
  tar-like asphalt (example mammals preserved in
  the LaBrea tar pits in Los Angeles, California),
  or in peat bogs.

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Insect in amberand, we cant clone a dinosaur
from any DNA from such a critter (or can we?)
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Baby mammoth from the permafrost in
Siberia.preserved with body hair (44,000 yrs old)
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• Trace fossils (ichnofossils)
• markings in the sediment made by the activities
  of organisms.
• movement of organisms across the sediment
  surface, tunneling of organisms into the
  sediment, or ingestion and excretion of
  sedimentary materials.
• Provides information about ancient water depths,
  paleocurrents, availability of food, and sediment
  deposition rates.
• In many cases, tracks of animals are the only
  record of their existence.
• For example, dinosaur tracks are much more
  abundant than dinosaur bones. During its
  lifetime, a single dinosaur makes millions (a
  bunch) of tracks, but leaves only one skeleton,
  which may or may not be preserved.

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Some dino tracks (drawing from a real
site).which one went first (two-legs or
four-legs), and, how can you tell?
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A man
dinosaur tracks, Glenrose, Texas (the small
tracks have been attributed, by some, to be those
of man)
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What yall think happened here?
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Worm burrows
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Trace fossils a crawling traces b- resting
traces c dwelling traces d grazing
traces e feeding traces
Often arent easy to observe or decipher
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The organization of life

• Carl von Linne (in Latin Carolus Linnaeus)
• Came up with a way of naming living things
• The binomial nomenclature (two names)

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• The first of the two names is the genus and the
  second name is the species.
• The genus and species names are underlined or
  italicized. The name of the genus is capitalized,
  but the name of the species is not.
• Examples
• Felis domesticus, the house catFelis leo, the
  African lionFelis onca, the jaguarCanis
  familiaris, the dogHomo sapiens, the human

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• Genus
• a group of organisms that appear to be related
  because of their general similarity

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• Species
• the fundamental unit of biological
  classification.
• Definition A group of organisms that have
  structural, functional, and developmental
  similarities able to interbreed and produce
  fertile offspring.
• Different species do not interbreed under natural
  conditions. Reproductive barriers between species
  prevent interbreeding. Closely related (but
  different) species, CAN interbreed, but do not
  produce FERTILE offspring (horse and donkey
  breed, producing a mule).

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• Some variation exists within a species, such as
  the differences between the sexes (sexual
  dimorphism), differences between different
  developmental stages (tadpole vs. frog), and
  individual variation.
• Individuals are generally similar, but not
  identical

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• Biologic taxonomy
• the ultimate naming scheme
• eight classification units

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• The categories (taxonomic groups taxa)
• Domain highest level. Three have been
  identified (on this planet) (ex. Eukarya)
• Kingdom a large group of related critters
  (phyla), of which there are six (ew. Animalia)
• Phylum a group of related classes (ex.
  Chordata)
• Class group of related orders (ex. Mammalia)
• Order group of related families (ex.
  Primates)
• Family group of related genera (ex.
  Hominidae)
• Genus (pl. genera) group of species having
  close ancestral relationships (ex. Homo)
• Species group of organisms having structural,
  functional, developmental similarities, are
  able to interbreed produce fertile offspring
  (ex. sapiens)

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Domains (or, superkingdoms) Based on
evolutionary relationships determined through the
study of molecular structures and sequences. Most
recent scheme has three Bacteria - Kingdom
Monera - including cyanobacteria (blue-green
algae) Archaea - sometimes called archaebacteria
(perhaps incorrectly) - as different from the
bacteria as the eukaryotes are from the
prokaryotes (say what?....to be explained
LATER..) Eucarya - animals, plants, fungi, and
protists
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• Traditional system has 6 kingdoms
• Animalia (animals)
• Plantae (plants)
• Fungi (mushrooms, fungus)
• Protista (single-celled organisms)
• Archaebacteria (live under extreme conditions
  extremophiles)
• Eubacteria (in water or soil, or within larger
  organisms)

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• All organisms composed of cells.
• Fundamental difference between organisms based on
  the type of cells
• Prokaryotes - cells without a nucleus and without
  organelles prokaryotic cells.
• Eukaryotes - cells with a nucleus (or nuclei) and
  organelles eukaryotic cells.
• A bit more on them later

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Evolution

• Simply put, evolution change
• For example, through time, automobiles and
  computers have evolved (OK, they had help)
• Organic evolution - changes in populations
• Darwin was not the first, nor the only one to
  come up with ideas of evolution
• Several had noted the changes in fossils through
  time

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• Jean Baptiste de Lamarck
• French naturalist, late 1700s early 1800s
• Viewing fossil evidence, concluded all species
  were descended from other species
• However, concluded new structures appear in an
  organism because of a need or inner want of the
  organism
• Similarly, structures/features that arent
  wanted eventually disappear
• Has its problems
• White people like to get suntans however, their
  children are not born with a suntan
• Mouse tail experiments

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• Charles Darwin/Alfred Wallace
• Concept of natural selection
• Published at about the same time
• Darwin - after years of data collection
  analysis
• Wallace more by a sudden insight
• Basically, " the survival of the fittest ".
• Competition for food, shelter, living space, and
  sexual partners among species with individual
  variations and surplus reproductive capacity will
  inevitably result in the elimination of the less
  well-fitted and the survival of those which are
  better fitted (adapted) to the environment.
• Darwin published On the Origin of Species by
  Means of Natural Selection(the short title) in
  1859 (the underlined bit is whats important)

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• Natural selection was a reasonable explanation,
  but lacked the reason for its occurrence
• Cause actually was discovered about the same time
  by J. Gregor Mendel
• Experiments on garden peas
• Published in 1865, but in an obscure journal
• Article rediscovered in 1900 (later than Darwin)
• Led to the science of genetics (the study of
  heredity or inheritance)

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• chromosomes
• Structures within the nucleus of cells.
• Consist of long DNA molecules, highly folded and
  coiled and combined with a variety of protein
  molecules.
• Gene - part of the DNA molecule active in the
  transmission of heriditary traitslinked together
  to form chromosomes.
• DNA - deoxyribonucleic acid.
• The general form of the DNA molecule is described
  as a " double helix", which resembles a twisted
  ladder. Parallel strands of phosphate sugar
  compounds, linked with cross-members of specific
  nitrogenous bases (some biochemistry thrown at
  ya).

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A piece of a DNA molecule
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• Mutations
• chemical changes to the DNA molecule.
• caused by chemical substances (including certain
  drugs), or by exposure to radiation (including
  cosmic radiation, ultraviolet light, and gamma
  rays).
• may occur in any cell, but only those in sex
  cells will be passed on to succeeding
  generations.
• produce much of the variability on which natural
  selection operates.

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• Population - a group of interbreeding organisms.
• Free exchange of genes within the population
• Gene pool - the sum of all of the genetic
  components in a population.
• Speciation the origin of new species.

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• Barriers between species
• Reproductive interbreeding becomes impossible
• Geographic - e.g., the Isthmus of Panama as a
  barrier preventing the marine animals of the
  Atlantic and Pacific from coming into contact
  with one another populations of land animals
  that have become isolated on different islands
• Genetic differences may accumulate to the point
  that the different populations are no longer able
  to interbreed. At this point, they would be
  considered separate species.

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• Adaptive radiation
• Branching of a population to produce descendants
  adapted to particular environments or living
  strategies
• Often occur around the fringes of the major
  habitat

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Hawaiian honeycreepers adapted to various niches
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• Adaptation
• The acquisition of beneficial characteristics
• Inheritable

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Spines provides support anchorage in seabed
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Eyestalks allows critter to tunnel thru
sediment while watching above it
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• How fast is evolution?
• 2 models
• Punctuated equilibrium
• sudden changes " punctuating" (interrupting) long
  periods of little change, termed stasis. Most
  change occurs over a short period of time.
• Phyletic gradualism
• Gradual, progressive change by means of an almost
  infinite number of small, subtle steps
• Fossil evidence can be interpreted to support
  both models

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Evolution prove it

• Can we do experiments to see if evolution is
  fact?
• Not really (unless we look at viruses harmful
  bacteria)
• Several have become resistant to our modern
  methods of treatment
• We have to rely on various evidence
• This can always be interpreted in several ways
• Geologists rely on the idea of, the present is
  the key to the past
• Again, this all didnt happen at one time

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• Paleontological evidence
• Example horses
• Started as small browsing animals that had four
  toes on their front feet, three toes on their
  rear feet
• Through time, the toes change to become hooves,
  and the animals become larger
• Changed from browsing to grazing
• Their teeth
• Grass contains silica, which is harder than
  teeth
• Teeth became longer, more suitable to grinding
  grasses

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Evolution of the lower foreleg in horses from the
Eocene (left) to the modern horse (right)
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Changes in horse teeth thru time
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• As the horses evolved, others probably did too
• Predators that pursued them
• Grasses became more resistant to damage from
  grazing

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• Biological evidence
• Homology study of body parts with similar
  origin, history and structure, without reference
  to function.
• Homologous organs and bone configurations have a
  common origin and ancestry (toes of land-dwelling
  mammals vs. bat wings). Evidence of this abounds
  in animal and plant kingdoms
• Vestigal organs remains of body parts from
  earlier ancestral forms
• Our appendix, ear muscles (unless you can wiggle
  yours?), coccyx (tail bone)
• Whales
• Embryos

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Homologous bones of the right forelimb of several
vertebrates
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Vestigal - The pelvis upper leg bone of a whale
(whales started on land, went back to the seas)
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Embryos of vertebrates gills (red), tails (blue)
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• DNA sequencing
• All life (as we know it) based on DNA
• Comparing the sequence of the nucleotide base
  pairs between different groups indicates the
  degree to which they are related
• Chimpanzee gorilla sequences are 97.9
  identical
• Chimpanzee human sequences are about 95
  identical
• Monkeys are on a different lineage

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Fossils stratigraphy

• Principle of Biologic (Fossil) Succession
• Fossils occur in a consistent vertical order in
  sedimentary rocks all over the world
• Thus, certain rock units could be identified by
  the assemblages of fossils they contained

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• Other uses of fossils
• Fossil species appear and disappear throughout
  the stratigraphic record.
• Basis of the Geologic Time Scale
• Each Era ends with a mass extinction.
• Period boundaries have smaller extinction events,
  followed by appearances of new species.
• Fossils can be used to recognize the approximate
  age of a unit and its place in the stratigraphic
  column.
• They can also be used to correlate strata from
  place to place

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• Geologic range
• Interval between the first and last occurrence of
  a fossil species in the geologic record.
• Determined by recording the occurrence of the
  fossils in numerous stratigraphic sequences from
  hundreds of locations.
• Ranges are well known for some species, and
  poorly known for others

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• Correlating with fossils
• Fossils help correlate time-rock units,
  especially when the lithology changes

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• Cosmopolitan species
• found almost everywhere they are not restricted
  to a single geographic location in the
  environment
• useful to establish the contemporaneity (same
  time) of strata
• Endemic species
• confined to a restricted area in the environment
  in which they live
• good indicators of the environment where the
  strata were deposited

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• Example lets come back in 2 million years
• We find, in various spots, some fossils
• Opossum (N. America)
• Wallaby (Australia)
• Aardvark (Africa)
• Did they all live at about the same time?
• Hard to tell
• At each site, we also find fossils of Homo
  sapiens
• Strongly suggests they all lived at the same time

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• The appearance or disappearance of species may
  indicate
• evolution
• extinction
• changing environmental conditions that cause
  organisms to migrate into or out of an area

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• Reworked fossils
• Some fossils are resistant to erosion chemical
  decay
• May be eroded out of older rocks, and redeposited
  in younger rocks
• The younger rocks may then be assigned an older
  age

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• Index (guide) fossils
• Abundant
• Widely dispersed
• Lived during a relatively short interval of
  geologic time (the shorter the better)
• Used to identify time-rock units correlating
  them from area to area

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• Biozone
• a body of rock identified only on the basis of
  the fossils it contains.
• the basic unit for biostratigraphic
  classification and correlation (much as the
  formation is the fundamental unit for
  lithostratigraphy)
• Range zone the rock body containing the total
  geologic range of a species
• Assemblage zone based on several species or
  genera that coexisted, therefore occur together
• Concurrent range zone overlapping ranges of two
  or more species or genera

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Concurrent range zone of the 3
Range zone of Assilina
Ranges
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Fossils indicate past environments

• Ecology the relationship between organisms
  their environment(s)
• Ecosystem any part of the environment, along
  with the plants animals in it
• Habitat the environment in which the organism
  lives
• Niche the way in which the organism lives - its
  role or lifestyle.
• Community the association of several species of
  organisms in a particular habitat (the living
  part of the ecosystem)

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• Paleoecology
• Study of how ancient organisms interacted with
  one another their environments
• Comparisons of ancient organisms with living
  organisms. Modern analogs help us interpret
  something about the way in which the fossils
  lived and related to their environment

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Foraminifera by studying living species,
paleontologists can deduce the water depth,
temperature, salinity of the ocean in which
fossil species were deposited
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Fossils paleogeography

• Environmental limitations control the
  distribution of modern plants and animals, by
  inference, past ones
• Note locations of fossil species of same age on a
  map, interpret the paleoenvironment, and produce
  a paleogeographic map for that time interval
• Example Modern coral reefs occur in the
  tropics, within 30º north and south of the
  equator. Ancient coral reefs likely had similar
  distributions (assuming climate patterns were
  always the same!)
• Plot locations of non-marine (terrestrial)
  deposits using locations of land-dwelling
  organisms such as dinosaurs or mastodons,
  fossilized tracks of land animals, and fossils of
  land plants

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• Mixtures of marine and non-marine fossils may
  indicate a stream entering the sea, or a delta.
• The migration and dispersal patterns of land
  animals can indicate the existence of " land
  bridges" or former connections between
  now-separated areas
• Camels (where did they come from?)

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Migration of camels
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Fossils past climates

• Or, is global warming real?
• We can make guesses as to the climate in the
  geologic past
• The accuracy (VERY likely) decreases the further
  back we go
• Still, the evidence is based on what we observe
  today, and what we measure from past sources

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• Fossil spore and pollen grains
• can tell about the types of plants that lived -
  an indication of the paleoclimate.
• Corals
• indicate tropical climates
• Plant fossils
• aerial roots, lack of yearly rings, and large
  wood cell structure indicate tropical climates
• Marine molluscs (clams, snails, etc.) with spines
  and thick shells
• inhabit warm seas

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• Planktonic organisms
• vary in size and coiling direction according to
  temperature for example the foraminifer
  Globorotalia
• Compositions of the skeletons
• shells in warmer waters have higher magnesium
  contents
• Oxygen isotope ratios in shells.
• Oxygen-16 evaporates easier than oxygen-18
  because it is lighter. O-16 falls as
  precipitation and gets locked up in glaciers,
  leaving sea water enriched in O-18 during
  glaciations. Shells that are enriched in O-18
  indicate times of glaciation (colder times)

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• Ice cores
• Air bubbles contain past atmospheric data
• Still gotta watch for cross-contamination
• Global temperatures
• Often taken at major airports
• ..think about it

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Late Carboniferous to Early Permian time (315 mya
-- 270 mya) is the only time period in the last
600 million years when both atmospheric CO2 and
temperatures were as low as they are today
(Quaternary Period ). Temperature after C.R.
ScoteseCO2 after R.A. Berner, 2001 (GEOCARB III)
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A brief overview of the history of life
Major milestones of life

• Oldest evidence of life
• remains of cyanobacteria (formerly called
  blue-green algae) more than 3.5 billion years
  old. Found in algal mats and stromatolites.

Modern stromatolites
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• Trace fossils of first multicellular organisms
• about 1 billion years ago.
• First body fossils of multicellular organisms
• (such as worms, jellyfish, and arthropods) about
  0.7 billion years ago.
• Principle invertebrate phyla with hard parts
  appeared in late Proterozoic/early Paleozoic

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• Plants
• Seem to be the first organisms that evolved
• In the sea first, then the land

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• Animals
• More fossil evidence, due to preserved hard parts

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• Extinctions
• The history of life has been marked by
  extinctions.
• The five largest extinction events are termed
  mass extinctions - sudden, global in extent, and
  very devastating.
• Mass extinctions occurred at the ends of the
  following periods
• Ordovician
• Devonian (roughly 70 of the ocean's
  invertebrates disappeared)
• Permian (the greatest extinction. More than 90
  of all species at that time disappeared or nearly
  went extinct)
• Triassic
• Cretaceous (affecting the dinosaurs and other
  animals on land as well as organisms in the sea
  about one fourth of all known families of animals
  became extinct)

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Life elsewhere

• Does life exist only on Earth?
• We dont know
• So far, it seems so
• Again, what exactly is life?
• Suggestive evidence from Mars, yet.
• Some are searching
• SETI, tabloids, etc.
• New telescopes, looking for spectral signs
• Will we find results in our lifetime?......