Evolution

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Evolution
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Evolution A summary

• Evolution - The process of change
• Evolution applies to the universe also. Matter
  and the nature of matter has changed over time
• Evolution applies to life, implies that life is
  not static, but responds to the environment.
• Previous western thought held the universe, earth
  animals, and man were created by a greater
  being/entity.
• Held the earth and life were created in the
  thousands of years in the past..
• Life and the earth were thought to be static and
  unchanging.
• Modern evolution holds that the universe is
  billions of years old (between 9-12b years)
• Earth was created approx 4.5b years ago.
• Human existence is only a small fraction of time
  since the beginnings of the universe.

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The Cosmic Calendar

• If the 12 billion year history of the universe
  was fit into a calendar year, it would look like
  this..

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Cosmic Calendar (From The Dragons of Eden - Carl
Sagan) Pre-December Dates
Big Bang January 1
Origin of Milky Way Galaxy May 1
Origin of the solar system September 9
Formation of the Earth September 14
Origin of life on Earth September 25
Formation of the oldest rocks known on Earth October 2
Date of oldest fossils (bacteria and blue-green algae) October 9
Invention of sex (by microorganisms) November 1
Oldest fossil photosynthetic plants November 12
Eukaryotes (first cells with nuclei) flourish November 15

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December
DECEMBER
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
1 Significant oxygen atmosphere begins to develop on Earth. 2 3 4 5 Extensive vulcanism and channel formation on Mars. 6
7 8 9 10 11 12 13
14 15 16 First Worms. 17 Precambrian ends. Paleozoic Era and Cambrian Period begin. Invertebrates flourish. 18 First oceanic plankton. Trilobites flourish. 19 Ordovician Period. First fish, first vertebrates. 20 Silurian Period. First vascular plants. Plants begin colonization of land.
21 Devonian Period begins. First insects. Animals begin colonization of land. 22 First amphibians. First winged insects. 23 Carboniferous Period. First trees. First reptiles. 24 Permian Period begins. First dinosaurs. 25 Paleozoic Era ends. Mesozoic Era Begins. 26 Triassic Period. First mammals. 27 Jurassic Period. First birds.
28 Cretaceous Period. First flowers. Dinosaurs become extinct. 29 Mesozoic Era ends. Cenozoic Era and Tertiary Period begin. First cetaceans. First primates. 30 First evolution of frontal lobes in the brains of primates. First hominids. Giant mammals flourish. 31 End of Pliocene Period. Quaternary (Pleistocene and Holocene) Period. First humans.
December 31
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December 31
Origin of Proconsul and Ramapithecus, probable ancestors of apes and men 130 p.m.
First hominids A. afarensis 1030 p.m.
Widespread use of stone tools by Homo habilis 1100 p.m.
Domestication of fire by Homo erectus 1146 p.m.
Beginning of most recent glacial period. Homo Neanderthalis Homo sapiens evolve 1156 p.m.
Seafarers settle Australia 1158 p.m.
Extensive cave painting in Europe 1159 p.m.
Invention of agriculture 115920 p.m.
Neolithic civilization first cities. Colonization of North and South America across Bering straits 115935 p.m.
First dynasties in Sumer, Ebla and Egypt development of astronomy 115950 p.m.
Invention of the alphabet Akkadian Empire 115951 p.m.
Hammurabic legal codes in Babylon Middle Kingdom in Egypt 115952 p.m.
Bronze metallurgy Mycenaean culture Trojan War Olmec culture invention of the compass 115953 p.m.
Iron metallurgy First Assyrian Empire Kingdom of Israel founding of Carthage by Phoenicia 115954 p.m.
Asokan India Ch'in Dynasty China Periclean Athens birth of Buddha 115955 p.m.
Euclidean geometry Archimedean physics Ptolemaic astronomy Roman Empire birth of Christ 115956 p.m.
Zero and decimals invented in Indian arithmetic Rome falls Moslem conquests 115957 p.m.
Mayan civilization Sung Dynasty China Byzantine empire Mongol invasion Crusades 115958 p.m.
Renaissance in Europe voyages of discovery from Europe and from Ming Dynasty China emergence of the experimental method in science 115959 p.m.
Widespread development of science and technology emergence of global culture acquisition of the means of self-destruction of the human species first steps in spacecraft planetary exploration and the search of extraterrestrial intelligence Now The first second of New Year's Day
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Darwin Natural Selection

• Modern evolutionary thought arose through the
  inquiries of Charles Darwin.
• Darwin was a Naturalist aboard an exploration
  ship called the HMS Beagle.
• Collected and catalogued biological specimens for
  return to England.

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The Voyage of the Beagle
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The Galapagos Finches
Was fascinated by the species of Finches he
observed in the Galopagos Islands. Found that
these birds were quite similar to a species found
on mainland South America. However they differed
significantly in the shapes of their
beaks. Darwin reasoned that these species of
finches arose from a common ancestor, and
gradually changed over to accommodate their
particular diets. Led him to develop his theory
of evolution through Natural Selection
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Darwin Evolution

• The notion of evolution was dominated by 2
  theories.
• Lamarckian Theory of Inheretance of acquired
  characteristics
• Held that traits acquired throughout life of an
  organism would be passed on to offspring.
• "Use it, or lose it principle"
• Eg. If you lifted weights during your life, your
  children would be stronger or, if you did'nt
  exercise your children would be weaker
• Theory has been replaced by Darwin's theory of
  natural selection.
• Natural selection
• Based on following premises
• There are not enough resources for all organisms
  to survive.
• Some organisms are more "fit" to survive.
• Fitness refers to
• The ability of an organism to survive in its
  environment.
• The ability of an organism to survive long enough
  to reproduce.
• Natural pressures "weed-out" those individuals
  "less fit" to survive. Thus changing a species
  over time.
• New genes/traits arise from random mutations.
• Most are either Neutral (no effect), or
  disadvantageous (decrease an organism's chance
  for survival).

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Natural Selection The Peppered Moth

• The peppered moth is a species of moth which uses
  camouflage against tree bark to avoid being eaten
  by birds. It is normally a light grey color.
• During England's industrial revolution, pollution
  caused a darkening of the bark of the trees.
• There was a natural variation in moth coloration
  with some being darker than others.
• Those moths of a lighter color, were easier to
  spot and eat by birds. And were eaten at a faster
  rate.
• The survivors tended to be darker, and when they
  mated, their offspring tended thus to be darker
  also.
• Over time, this resulted in the species becoming
  darker in color.

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Lamarck vs. Darwin
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Effects of Natural Selection

• Natural selection can have many different effects
  on species phenotypes.
• These types of natural selection have been named
  as
• Directional selection
• Stabilizing selection
• Disruptive selection

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Directional Selection

• Eliminates one extreme variation from an array of
  possible phenotypes. Results in a shift towards
  the other extreme.

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Stabilizing Selection

• Selection acts to eliminate both extremes of an
  array of phenotypes. Results in an increase in
  individuals exhibiting an intermediate phenotype.

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Disruptive Selection

• Selection acts to remove the intermediate
  phenotypes favoring the extreme phenotypes

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Convergence

• Convergence occurs when species evolve into a
  common phentoypic form due to a common need. For
  example the diagram below portrays a shark,
  ichthyosaurus, a penguin and a dolphin. These are
  fish, reptile. bird and mammal respectively (very
  different families of animals). Yet they all have
  a torpedo body shape, pectoral, caudal and dorsal
  fins. This is based on their common need to swim
  rapidly in an aquatic environment.

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Divergence / Adaptive Radiation

• Divergence occurs when species evolve in several
  directions away from a common ancestor. This
  happens usually to fill a vacant ecological
  niche. Also known as adaptive radiation.

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Convergence and Divergence Together

• By contrasting North American placental mammals
  with Australian marsupials. One can see how
  convergence and divergence works together.
• In each case an ancestor mammal evolved into
  several ecological niches.
• Since each niche required a specific phenotype,
  what results are 2 groups of mammals which have
  NEVER made contact, evolving into similar shapes.

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Rates of Speciation

• Two models exist to describe the rates of
  speciation.
• Gradualism
• Refers to the model which holds that evolutionary
  change occurs in a gradual linear fashion. A
  species will change its morphology over time.
• Punctuated equilibrium
• Describes the process in which a species remains
  relatively unchanged for relatively long periods
  of time. Following which, a period of stress
  causes rapid change, followed by another period
  of relative stability.

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Rates of Speciation
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Evidences of Evolution

• Fossils
• Formed when animal remains are trapped in
  sedimentary layers.
• Organic material replaced by minerals over
  millions of years.
• Result is a "mineral cast" of the dead organism.
• Where a fossil is located in the sedimentary
  strata can indicate it's age.
• Successive changes in fossil forms of an organism
  can help in developing a fossil record of an
  organism's evolution.
• Some rare fossils can show "soft tissues" which
  give invaluable information on an organism's
  physiology
• Example paleontologists recently discovered a
  dinosaur with a fossilized heart. This indicates
  that this species was most likely warm blooded.

Fossilized Trilobite
Fossilized Dinosaur Heart
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Radiometric Dating

• Based on the fact that radioactive materials
  decay at a fixed rate.
• Rate is known as a half-life The amount of time
  in which only 1/2 of a radioactive sample remains
• By measuring the amount of radioactive material
  in a fossil, one can determine how old it is.
• Example is 14C dating.
• 14C is an isotope of 12C which radioactively
  decays to 14N.
• It occurs naturally in the environment, and is
  ingested by organisms while alive.
• Once an organism dies, 14C intake stops, and the
  14C begins to decay
• One can then measure the amount of 14C remaining
  in a sample, and determine its age.

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Similarities in Embryological Development

• In early embryological development, it appears
  that embryos "play out" their evolutionary
  history.
• Known as Ontonogy recapitulating Phylogeny.
• Implies that genetically, we have not "forgotten"
  our evolutionary history, only built upon it.

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Homologous Structures

• Refers to the fact that organisms' structures are
  formed from similar anatomy.
• Example the wing of a bird, arm of a man, wing of
  a bat, and flipper of a whale, all appear to be
  formed from a common set of bones.
• Implies that these organisms evolved from some
  common ancestor.

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Vestigal Structures

• Refers to the fact that organisms have structures
  which are disused
• These structures, however, a remnants of
  structures the organisms used earlier in their
  evolutionary history.
• Examples
• Hip bones in whales
• Tail in humans
• Appendix in humans
• Legs/hips in snakes