Transcript Chapter 17 The History of Life

Chapter 17
The History of Life
The Fossil Record (pp. 417-422)
Earth’s Early History (pp. 423-428)
Evolution of Multicellular Life (pp.429-434)
Patterns of Evolution (pp. 435-440
Updated July 2005
Created by C. Ippolito
July 2005
Chapter 17 Section 1
The Fossil Record
Objectives:
Describe the fossil record.
State the information that relative dating and radioactive dating
provide about fossils
Identify the divisions of the geological time scale.
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Fossils and Ancient Life
Paleontologists
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Scientists who collect and study
fossils
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Structure of organisms
What organisms ate
Who ate them
Environment lived in
Fossil Record
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All information inferred by study
of fossils
Evidence of the history of life on
Earth
How groups of organisms
changed over time
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How Fossils Form
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Fossils form in sedimentary rock
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Rock exposed to rain, heat, wind, and cold breaks into
small particles
Particles settle to the bottom in layers
Fossils form when:
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Particles cover remains of dead organism
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imprint left in rock after decay (imprint)
hard parts replaced by minerals (petrifaction)
complete cover before decay by fine particles (mold)
Body caught in plant resin (amber)
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Types of Fossils
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Mold Fossils
Imprint Fossil
Petrified Fossil
Fossil in Amber
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Interpreting Fossil Evidence
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Two ways to determine age of fossil:
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Relative Dating – age compared to other fossils
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Sedimentary rock forms in layers
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Index Fossils
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2.
Oldest in lower layers
More recent in upper layers
Short lived
Found in specific layers
Radioactive Dating – age calculated based on
amount radioisotopes found in sample
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Half-life – time for half of radioisotope to decay
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Carbon-14 ---- 5730 years
Potassium-40 ---- 1.25 billion years
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Geological Time Scale
Developed to represent
evolutionary time
Precambrian Time – Big
Bang to first
multicellular life forms
(88% of time)
Eras
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Paleozoic – vertebrates &
invertebrate life
Mesozoic – age of
dinosaurs
Cenozoic – age of
mammals
Periods
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Smaller subdivisions of
the eras
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Geological Time Scale
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If we consider time scale as 24 hours:
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Homework
Section Assessment 17-1 on page
422 (1 thru 4) and Checkpoints on
pages 418 and 420
Updated July 2005
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July 2005
Chapter 17 Section 2
Earth’s Early History
Objectives:
Describe how conditions on early Earth were different from conditions
today.
Explain what Miller and Urey’s experiments showed.
State the hypotheses that have been proposed for how life first arose on
Earth.
Identify some of the main evolutionary steps in the early evolution of life.
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Formation of Earth
Post Big Bang cosmic debris attracted together over 100 million
years
As surface cooled molten material  crust; then oceans
Surface broken by many volcanoes
Early Atmosphere – very different gases
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hydrogen cyanide (HCN)
carbon dioxide (CO2)
carbon monoxide (CO)
nitrogen (N2)
hydrogen sulfide (H2S)
water (H2O)
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First Organic Molecules
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Urey Miller Experiment
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Lab simulation of early
atmosphere
Gases
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Energy
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methane (CH4)
ammonia (NH3)
water (H2O)
Spark (lightning)
Heat (Bunsen burner)
Radiation (sun lamps)
Result
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Water contained amino acids
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and simple sugarsCreatedJulyby2005
How Did Life Begin?
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Formation of Microspheres
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Sidney Fox Experiment
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Clusters of proteins form cell-like
structures (a.k.a coacervates or
proteinoids)
Some may contain “enzymes”
Evolution of DNA and RNA
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Origin unknown some hypothesis
include various ways of self
replication
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Free Oxygen
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Microfossils – prokaryotic cells
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Appear to be similar to modern bacteria
Anaerobic Respiration Life
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Lack of free oxygen in atmosphere
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Photosynthetic Life
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Primitive photosynthetic bacteria
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Used nutrients in oceans and add carbon dioxide
Make own food and add free oxygen
Aerobic Respiration Life
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Free oxygen allows more frugal use of
nutrients
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Origin of Eukaryotic Cells
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Endosymbiotic Theory
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Proposed by Lynn Margulis
Eukaryotic cells with organelles formed from
communities of prokaryotic cells
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DNA in mitochondria and chloroplasts
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Homework
Section Assessment 17-2 on page
428 (1 thru 5) and Checkpoints on
page 424 and 426
Updated July 2005
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Chapter 17 Section 3
Evolution of Multicellular Life
Objectives:
Describe the key forms of life in the Paleozoic,
Mesozoic, and Cenozoic Eras.
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Precambrian Time
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Longest period of Earth’s history
Prokaryotic cells
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Anaerobic
Photosynthetic
Aerobic
Eukaryotic Cells
Soft Bodied Multicellular Organisms
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Paleozoic Era
Rapid evolution of marine life
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Cambrian Period
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Ordovician and Silurian Periods
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Ferns
Fish – sharks, bony fish with scales
Land Animals - amphibians
Carboniferous and Permian Periods
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Invertebrates – octopi, squid, insects
Land Plants
Vertebrates – jawless fish
Devonian Period
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Invertebrates – jellyfish, worms, sponges
Shelled – clam and mussel ancestors
Exoskeleton – Trilobites
Land Animals – reptiles and winged insects
FIRST MASS EXTINCTION occurs – most marine organisms
die out
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Mesozoic Era
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Age of Dinosaurs
Flowering Plants appear
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Triassic Period
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Jurassic Period
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Dinosaurs dominant
Archaeopteryx – first bird
Cretaceous
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First dinosaurs
Small mammals
T. Rex dominant
Flowering plants
SECOND MASS EXTINCTION occurs – 50%
of organisms die out – all of dinosaurs
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Cenozoic Era
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Age of Mammals
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Tertiary Period
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Grasses evolve
Large grazing mammals and birds
Quaternary Period
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Multiple Ice Ages and Glacial Movements
Man appears at end
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Homework
Section Assessment 17-3 on page
434 (1 thru 4) and Checkpoints
on pages 430 and 432
Updated July 2005
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Chapter 16 Section 4
Patterns of Evolution
Objectives:
Identify important patterns of macroevolution.
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Macroevolution
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Large scale evolutionary changes that
occurred over long periods of time
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Mass Extinction
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Permian – volcanic activity and shifting
continents
Cretaceous – asteroid collision in Caribbean
Ocean
Adaptive Radiation
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One ancestral form changes in to many different
form to take advantage of adaptations (finches)
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Convergent Evolution
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Natural selection
causes unrelated
species to resemble
one another.
Analogous structures
are produced by
convergent evolution.
bandicoot
rat
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Coevolution
 Two
or more
species evolve
in response to
each other
through
cooperative or
competitive
adaptations
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Rate of Evolution
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Gradualism - species
arise slowly and
continuously as
changes accumulate
over millions of years
Punctuated Equilibrium
- species stay same for
long periods and
change abruptly by
spurts of rapid evolution
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Homework
Section Assessment 16-4 on page
440 (1 thru 5) and Checkpoints
on pages 437 and 438
Updated July 2005
Created by C. Ippolito
July 2005