IV. The History of Life

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IV. The History of Life

• The Fossil Record
• 1. Provides evidence about the history of
  life on Earth and how organisms have changed
  over time
• 2. More than 99 of all species that
  have ever lived on Earth have become extinct

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• 3. Fossil Formation
• a. Most form in sedimentary rock
• b. Layers of sediment build up, dead
  organisms sink to bottom and become
  buried, more sediment falls on top
• c. Record is incomplete conditions
  must be perfect for fossils to form, most
  things dont fossilize

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• 4. Interpreting Fossil Evidence
• a. Relative Dating age of fossil is
  determined by comparing placement with
  fossils in other layers
• - index fossils easily recognized

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• b. Radioactive Dating age calculated based on
  amount of remaining radioactive isotope found
• - half-life length of time required for ½
  of the radioactive atoms in a sample to decay

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• 5. Geologic Time Scale
• a. After Precambrian Time, the basic
  divisions (from larger to smaller) are eras
  and periods
• b. Eras (from oldest to most recent)
• Paleozoic, Mesozoic, Cenozoic

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• Earths History
• 1. Early Earth
• a. Atmosphere probably composed of
  hydrogen cyanide, carbon dioxide, carbon
  monoxide, nitrogen, hydrogen sulfide, and
  water (NO OXYGEN!)
• b. Volcanic activity, bombardment by
  comets and asteroids, no oceans because
  surface was extremely hot

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• 2. First Organic Molecules
• a. Miller and Urey experiment
  suggested how mixtures of the organic
  compounds necessary for life could have arisen
• b. Organic molecules do not form on their
  own today because of the presence of oxygen

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Mixture of gases simulating atmospheres of early
Earth
Spark simulating lightning storms
Cold water cools chamber, causing droplets to form
Condensation chamber
Water vapor
Liquid containing amino acids and other organic
compounds
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• 3. Beginnings of Life
• a. Once liquid water was present, life on
  Earth could form
• b. Proteinoid microspheres have
  selectively permeable membranes, store and
  release energy
• c. Evolution of DNA and RNA

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• 4. Endosymbiotic Theory
• a. Proposes that eukaryotic cells arose
  from communities of prokaryotic organisms
• b. DNA in mitochondria and chloroplasts
  is similar to bacterial RNA
• c. Mitochondria and chloroplasts have
  ribosomes similar to bacteria
• d. Mitochondria and chloroplasts
  reproduce through mitosis like bacteria

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• Evolution of Multicellular Life
• 1. Precambrian time
• a. 90 of Earths history
• b. Prokaryotes formed eukaryotes, some
  formed multicellular organisms

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• 2. Paleozoic Era
• a. Cambrian Period diversification of
  life
• b. Ordovician and Silurian Periods
  first vertebrates
• c. Devonian Period Age of Fishes
• d. Carboniferous and Permian
  Periods mass extinction

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• 3. Mesozoic Era Age of Reptiles
• a. Triassic Period First dinosaurs
• b. Jurassic Period Dinosaurs dominant
  land animals
• c. Cretaceous Period Dinosaurs
  dominant, trees and flowering plants

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• 4. Cenozoic Era Age of Mammals
• a. Tertiary Period large mammals and
  birds
• b. Quaternary Period climate cooled,
  ice ages, Homo sapiens

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• Patterns of Evolution
• 1. Mass Extinctions large number of species
  disappear, leaves new habitats open,
  encourages rapid evolution of surviving
  species
• 2. Adaptive Radiation small group of
  species has evolved into several different
  forms that live in different ways

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• 3. Convergent Evolution unrelated organisms
  evolve similarities when adapting to similar
  environments
• 4. Coevolution two species evolve in response
  to changes in each other
• 5. Punctuated Equilibrium long, stable
  periods interrupted by brief periods of rapid
  evolutionary change

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Chapter 18

• Classification

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Taxonomy the science of classifying and naming
organisms

• Importance of scientific names
• 1. Eliminates confusion
• 2. Gives ease of communication
• 3. Allows precision

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• Carolus Linnaeus
• 1. Established a system for classifying and
  naming called binomial nomenclature (2
  word naming)

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• 2. Seven levels of organization, or taxonomic
  categories (from largest to smallest)
• Kingdom
• Phylum (division)
• Class
• Order
• Family
• Genus
• Species
• the more categories organisms have in
  common, the more similar they are

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• How to write a scientific name
• 1. Genus name (noun)
• a. First
• b. Capitalized
• c. Underline or italics
• 2. Species name (adj. describes noun)
• a. Second
• b. Not capitalized
• c. Underline or italics

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• Examples
• 1. Canis lupis wolf dog
• 2. Canis familiaris familiar dog
• 3. Felis domesticus domestic cat
• 4. Mus domesticus domestic mouse
• 5. Homo sapien wise man
• 1 2 are related, 3 4 are not. Why?

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Modern Classification

• Problems with traditional classification
• 1. Taxonomists relied on body structure
  comparisons to classify
• 2. Due to convergent evolution, organisms
  that are different from each other evolve
  similar body structures

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• Evolutionary Classification
• 1. Biologists had to classify organisms based
  on evolutionary descent, not just physical
  similarities

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• 2. Classification using Cladograms
• a. Derived characters characteristics
  that appear in recent parts of a lineage
  but not in its older members
• b. Derived characters can be used to
  construct a cladogram an
  evolutionary tree that shows the
  evolutionary relationships among a group of
  organisms

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• Similarities in DNA and RNA
• 1. all organisms use DNA and RNA to pass on
  information
• 2. similarities in genes can be used as
  criteria to help determine common ancestry
• Molecular Clocks
• - use DNA comparisons to estimate the length
  of time that two species have been evolving
  independently

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III. The Six Kingdoms

• Complete the table in your notes using
  page 459 in your text
• Eubacteria and Archaebacteria were previously
  grouped together in a kingdom called Monera
• It is thought that the three domains of living
  things diverged from a common ancestor before the
  evolution of the main groups of eukaryotes

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Making a Dichotomous Classification Key

1. Pick distinguishing characteristics
2. Write a and b statementsone of which must
   always be true for any specimen
3. Statements must either identify the specimen or
   give a go to instruction

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D. Write a key for the flowers
A
D
C
B
E