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Evolution by linxiaoqin

VIEWS: 8 PAGES: 92

									Evolution
Evolution
  The Universe formed
13.7 GYA as a product of
     the “Big Bang”.
 • The Solar
system formed
    4.6 GYA
            Our Sun is a Star


 • Its life span is
  approximately 10
billion years…. Our
  star has 5 billion
      years left.
     Jean Baptiste Lamarck
   • Published his
 Theory of Evolution
       in 1809.
• Proposed that Life
     changed from
  simple to complex
       over time.
  According to Lamarck
Fossils were the remains of past life
               forms.
   Lamarck’s Mechanisms
           1. Use and Disuse
Body parts used to survive become larger
               and stronger.

Body parts not used to survive deteriorate.
   Lamarck’s Mechanisms
      2. Acquired Characteristics
Modifications acquired by use/disuse were
           passed on to offspring.
  Lamarck’s Mechanisms

3. Natural Transformation of Species
….species change with every generation.
Problems with Lamarck’s Theory
        • No knowledge of genetics.
• Acquired traits are not transmitted offspring.
      To Lamarck’s Credits
• Did suggest correctly the role of fossils in
                 evolution.
   • Did suggest that adaptation to the
     environment is a primary product of
                 evolution.
 James Hutton (geologist)
           Gradualism - 1795



• Gradualism is the idea that changes to
   the Earth’s surface is the cumulative
     product of a slow, but continuous
                processes.
               Result
• Changes on the earth were gradual, not
              catastrophic.
        Charles Lyell
      Uniformitarianism
 • Incorporated
     Hutton’s
gradualism into a
   theory called
Uniformitarianism.
       Uniformitarianism
• Geological processes have operated at
  the same rate over the Earth’s history.
             Result
• The Earth must be VERY old. (much
    older than 6000 years of the fixed
            species concept).
• Idea that slow and subtle processes,
    such as volcanoes, erosions and
   earthquakes can cause substantial
      change to the Earth’s surface.
       Thomas Malthus
            1798 and 1826

• Malthus's idea of man's "struggle for
     existence" had an influence on
  Darwin's theory of evolution….. This
  struggle for existence of all creatures
      provides the catalyst by which
       Natural Selection produces
       the "survival of the fittest“.
  Origin Theories Before Darwin




• The prevailing worldview, before Darwin’s ideas took
  hold, was that the earth was very young, species did
   not change, and the intricate features we now call
     adaptations were designed by a Creator. This
   worldview had held for about 2,000 years, since the
                    time of Aristotle.
Charles Darwin
       (1809–1882) was the most
       influential contributor to our
      current ideas about evolution.
        His book, On The Origin of
         Species, written in 1859,
          described evidence for
      changes in species over time
      and presented a mechanism,
         natural selection, for how
         these changes occurred.
          Darwin - 1859

• Publication of
  "The Origin of
    Species”
     “The Origin of Species”
• Documented the occurrence of evolution.
   • Suggested that the mechanism for
      evolution was Natural Selection.
          Comment
• Darwin is best remembered for the
 theory because of his overwhelming
              evidence.
         Voyage of the Beagle




 In 1831, Charles Darwin began a 5-year voyage around the world
as a naturalist on the HMS Beagle. What he saw on that trip had a
  tremendous influence on his ideas about the natural world. In
  particular, he saw the organisms on the Galapagos Islands as
examples of descent with modification, which was Darwin’s term
                           for evolution.
   Darwin's had two evolutionary
ideas...........they were "descent with
 modification" and "modification by
         natural selection".....
   explain both and give an example
                   both.
Descent with Modification
Evolution is defined as descent with
modification from a common ancestor.
Evolution only occurs when there is a
  change in gene frequency within a
 population over time. These genetic
 differences are heritable and can be
  passed on to the next generation.
The central ideas of evolution are that life
    has a history—it has changed over
  time—and that different species share
          common ancestors.
• On the next slide, you can explore
      how evolutionary change and
      evolutionary relationships are
  represented in “family trees,” and
how these trees are constructed. You
        will also find a timeline of
 evolutionary history and information
on some specific events in the history
of life: human evolution and the origin
                   of life.
    Natural Selection
Natural selection is one of the basic
     mechanisms of evolution.

  Darwin’s idea of evolution by natural
  selection is relatively simple but often
  misunderstood…. It is composed of 4
ideas: 1.) variation in traits, 2.) differential
reproduction, 3.) heredity, and 4.) the end
                   result.
      To find out how
    “Natural Selection”
works, imagine a population
         of beetles:
  1. There is variation in traits.
For example, some beetles are green and
            some are brown.
2. There is differential reproduction.
   Since the environment
  can’t support unlimited
population growth, not all
      individuals get to
   reproduce to their full
potential. In this example,
 green beetles tend to get
eaten by birds and survive
  to reproduce less often
  than brown beetles do.
       3. There is heredity.
The surviving brown beetles have brown
  baby beetles because this trait has a
              genetic basis.
               4. End result
The more advantageous
  trait, brown coloration,
 which allows the beetle
 to have more offspring,
 becomes more common
 in the population. If this
    process continues,
        eventually, all
     individuals in the
     population will be
            brown.
If you have variation, differential
 reproduction, and heredity, you
  will have evolution by natural
            selection.
 Evidences of Evolution
                 1. Fossils
             2. Biogeography
3. Homologous and Analogous Structures
          4. Vestigial Structures
       5. Biochemical Similarities
                          Fossils
   are the remains or traces of once living organisms.




Molds are fossils which formed     Casts are fossils which are
from an impression of the shape    formed when sediments fill
   or tracks of an organism.           in the cavity left by
                                    decomposing organisms.
    Fossils can be used to
  1. Show the course of natural selection…
      how organisms change overtime.
   2. Fossils can tell us a great deal about
     an organism’s surroundings and the
        conditions under which it lived.
3. Certain parts of certain fossils can tell us
     about growth, injury, disease, form,
       function, activities, and instincts.
            Preserved Bones




Bones can tell us a great deal about the area where the muscle
attaches to the bone and leaves marks that indicate size, shape,
              and functions of these varied organs.
  An example of this kind of
fossilization is petrified wood.
Amber is fossilized resin of a coniferous tree.




 Fossils that are preserved in amber give us information about
  the anatomy of that organism; since the organisms that are
preserved in amber, mostly insects, are usually preserved intact
  without any disintegration of organs, muscles, and coloring.
• The cavities and the channels in skulls give
 us an idea of intelligence, behavior, and their
               principle features.
        Dating of Fossils
• The two methods of Dating fossils are:

          • 1. “Relative” Dating

                  And

         • 2. “Absolute” Dating
                    Relative Dating
       Using the Law of
  Superposition (successive
layers of rock were deposited
     one on top the other)
  scientists can estimate the
   “Relative” age of a fossil.
Fossils are approximately the
same age as the layer they are
           found in.
The younger fossils are found
   closer to the surface, the
 older fossils are found in the
         deeper layers.
Grand Canyon

        250 million years old



            255 million years old



                 260 million years old




                        265 million years old




                                           285 million years old
Absolute, or Numerical Dating
using Radioactive Isotopes to determine the age of a sample.
 To Determine the Age of the
      Earth Scientists use
       Radiochronometry
    (The use of radioactive
isotopes to determine the age
           of rocks)
 Radioactive isotopes:
are atoms with too many, or, not
enough neutrons to stabilize their
nucleus…. As a result the nucleus
           “decays”.
        Atomic Structure
• Atoms have Atomic numbers and Atomic masses
                     (amu)

• Atoms can be identified by their atomic numbers

  • If you change the number of protons in the
           nucleus, you change the atom.

        • Atomic number of Hydrogen : 1
          • Atomic number of Helium: 2
          • Atomic number of Gold : 79
           • Atomic number of Lead: 82
        • Atomic number of Uranium: 92
       • Atomic number of Plutonium: 94
Types of Radioactive Decay

    Alpha Radiation, Alpha
    Particles are composed
      of 2 protons and 2
    neutrons…. a He nuclei



•       Beta Radiation, Beta
         particles are high
         energy electrons




    •    Gamma Radiation,
        Gamma rays are high
          energy photons
Parent Element   Daughter Element    Half-life
•   238 U          206 Pb:            4.51 Gyr
•   235 U          207 Pb:           710 Myr
•   87 Rb          87 Sr:            50 Gyr
•   40 K           40 Ar:           1.30 Gyr
Earth’s oldest rock
Rock solidified 4.3
 billion years ago
             How Carbon-14 Dating Works
• Carbon-14 dating is a way of determining the age of certain
 fossils up to about 50,000 years old. It is used in dating things
 such as bone, cloth, wood and plant fibers. Carbon-14 dating
    can only be used to date fossils which were once alive.
          How Carbon-14 is Made
 Cosmic rays enter the earth's
 atmosphere in large numbers
 every day. For example, every
   person is hit by about half a
million cosmic rays every hour.
     It is not uncommon for a
  cosmic ray to collide with an
     atom in the atmosphere,
  creating a secondary cosmic
 ray in the form of an energetic
neutron, and for these energetic
      neutrons to collide with
    nitrogen atoms. When the
 neutron collides, a nitrogen-14
       (seven protons, seven
   neutrons) atom turns into a
  carbon-14 atom (six protons,
eight neutrons) and a hydrogen
      atom (one proton, zero
      neutrons). Carbon-14 is
  radioactive, with a half-life of
          about 5,730 years.
Carbon-14 in Living Things
  • The carbon-14 atoms that cosmic rays create
combine with oxygen to form carbon dioxide, which
  plants absorb naturally and incorporate into plant
  fibers by photosynthesis. Animals and people eat
   plants and take in carbon-14 as well. The ratio of
  normal carbon (carbon-12) to carbon-14 in the air
   and in all living things at any given time is nearly
 constant. Maybe one in a trillion carbon atoms are
      carbon-14. The carbon-14 atoms are always
     decaying, but they are being replaced by new
carbon-14 atoms at a constant rate. At this moment,
   your body has a certain percentage of carbon-14
atoms in it, and all living plants and animals have the
                     same percentage.
              Dating a Fossil
• As soon as a living organism dies, it stops taking in
   new carbon. The ratio of carbon-12 to carbon-14 at
       the moment of death is the same as every other
      living thing, but the carbon-14 decays and is not
    replaced. The carbon-14 decays with its half-life of
   5,730 years, while the amount of carbon-12 remains
      constant in the sample. By looking at the ratio of
  carbon-12 to carbon-14 in the sample and comparing
     it to the ratio in a living organism, it is possible to
      determine the age of a formerly living thing fairly
                             precisely.
• Because the half-life of carbon-14 is 5,730
 years, it is only reliable for dating objects up
    to about 60,000 years old. However, the
 principle of carbon-14 dating applies to other
   isotopes as well. Potassium-40 is another
  radioactive element naturally found in your
  body and has a half-life of 1.3 billion years.
   Other useful radioisotopes for radioactive
  dating include Uranium -235 (half-life = 704
   million years), Uranium -238 (half-life = 4.5
    billion years), Thorium-232 (half-life = 14
 billion years) and Rubidium-87 (half-life = 49
                   billion years).
                 Biogeography


   Biogeography is the
study of the distribution
   of fossils and living
     organisms. The
  distribution of fossils
 indicate the continents
   were once part of a
 single super-continent
    known as Pangea
•
     Changes to the
    Crust of the Earth
Edge-on View of Crust




   Continent
                     Sea Floor       6 miles
25 miles




               Convection Currents
              Plate Tectonics
Theory that the Earth’s Crust is Broken into moving Plates.
Some of the Major Plates
Convection currents
 in the Mantle are
  responsible for
moving the various
       plates.
The Edges of the Plates are areas of Intense Geologic
Activity, such as Earthquakes, Volcanoes an Mountain
                       Building.
Transform Zone: one Plate slips by an adjacent Plate
                San Andreas Fault

                                  North American
                                        Plate




    Pacific Plate
       San Andreas Fault
Approximately 1
  million years
  from now the
 “Bay-Bridge”
series (baseball)
 will be between
 San Francisco
and Los Angeles.
“Homologous” Structures
          and
 "Analogous" Structures
Homologous Structures in Animals




  Homologous Structures are body parts which resemble one another in
  different species because they have evolved form a common ancestor.
Homologous structures may look different because the anatomy is modified
                     to live in different environments.
    Analogous Structures in Animals



                BAT                               BIRD




                    Analogy of bat & bird wings
•   Analogous structures are body parts that resemble one another in different
      species, not because they have evolved form a common ancestor, but
    because they evolved as adaptations to their environment. Wings of bat and
    wings of a bird are analogous because they are both adaptations for flying.
    The fins of a whale and the fins of a shark are also analogous because they
                         are both adaptations for swimming.
                 “Vestigial Structures”
are functionless structures that were once functional in ancestral species.

    This is a skeletal
      view of what
      would be the
   pelvic region of a
       boa - a large
     snake. Snakes
    obviously do not
      have legs, yet
    these boas have
       the vestigial
   remnants of both
   pelvic girdles and
    limbs, complete
          with a
   rudimentary claw.
•   In the illustration above, the coccyx or "tail-bone" of a human is shown. It is a
     much-shortened version of the tail present in most mammals. The tail is also
      equipped with vestigial muscles and nerves, yet it is short, rigid, contained
      completely within the body in most people, and completely non-functional!
     Other examples of such structures in humans include the appendix, wisdom
    teeth, and the muscles to used move the ears. In the case of the appendix and
      wisdom teeth, the structures are not only non-functional, but they have the
                       potential for serious infection or even death.
Biochemical (macromolecule) Similarities
                 and
         Molecular Evolution

• For evolutionists the revolution in DNA technology has been a
    major advance. The reason is scientists can determine the
  nucleotide and amino acid sequences of DNA and proteins form
     different species. Closely related species share a higher
      percentage of sequences than species distantly related.

    • More than 98% of the DNA sequences in humans and
         chimpanzees are identical…..did we evolve from
  chimpanzees?...of course not….if we did there would no longer
  be chimpanzees…….however, there is strong evidence that we
                   share a common ancestor.
           What is a Species?
A species is often defined as a group of individuals that actually
                 or potentially interbreed in nature.




For example, these happy face spiders look different, but since
   they can interbreed, they are considered the same species:
                       Theridion grallator.
                        Speciation
   Speciation is a lineage-splitting event that produces two or more
separate species. Imagine that you are looking at a tip of the tree of life
  that constitutes a species of fruit fly. Move down the phylogeny to
   where your fruit fly twig is connected to the rest of the tree. That
  branching point, and every other branching point on the tree, is a
    speciation event. At that point genetic changes resulted in two
 separate fruit fly lineages, where previously there had just been one
                                 lineage.




         The branching points on
          this partial Drosophila
         phylogeny represent long
          past speciation events.
    Adaptive Radiation
• An adaptive radiation generally means
    an event in which a lineage rapidly
     diversifies, with the newly formed
 lineages evolving different adaptations.
   Different factors may trigger adaptive
 radiations, but each is a response to an
        opportunity. These include:
The evolution of a key adaptation
  A key adaptation usually
   means an adaptation that
     allows the organism to
     evolve to exploit a new
   niche or resource. A key
    adaptation may open up
     many new niches to an
   organism and provide the
  opportunity for an adaptive
     radiation. For example,
  beetle radiations may have
        been triggered by
  adaptations for feeding on
         flowering plants.
   Release from competition/vacated niches:
    Lineages that invade islands may give rise to adaptive radiations
 because the invaders are free from competition with other species. On
 the mainland, other species may fill all the possible ecological niches,
 making it impossible for a lineage to split into new forms and diversify.
On an island, however, these niches may be empty. Extinctions can also
 empty ecological niches and make an adaptive radiation possible. For
example, open niches vacated by dinosaur extinctions may have allowed
   mammals to radiate into these positions in the terrestrial food web.
     Specialization:
 Specialization may subdivide
 a single niche into many new
  niches. For example, cichlid
fishes have diversified in East
  African lakes into more than
         600 species. This
diversification may have been
   possible because different
  fish lineages evolved to take
  advantage of different foods
    (including insects, algae,
    mollusks, small fish, large
 fish, other fishes’ scales, and
    even other fishes’ eyes!).
         Genetic Drift
• Changes in the gene pool of a small
       population by chance.
By Chance
            Convergent Evolution
     Even though fish are not at all
     closely related to whales and
dolphins, they look very similar. Both
   groups have pairs of fins, a tailfin
 and a streamlined form. Since these
     characteristics are extremely
  successful for animals living in the
  water, these groups evolved along
  the similar lines. This is known as
   convergent evolution - i.e. similar
characteristics evolving as the result
   of living in similar environmental
  circumstances. Wings are another
   example of convergent evolution;
 they can be found in birds, bats and
insects, and these animals are not at
           all closely related!
          Divergent Evolution


Divergent Evolution occurs
when one species evolves
into two (or more) species,
 which continue to change
over time and become less
       and less alike.
     Coevolution
Coevolution is the evolution of one
   species in response to new
adaptations that appear in another
             species.
    • Pollination of many of flowers occurs as a result of the
     coevolution of finely-tuned traits between flowers and their
                              pollinators.




Yucca tree flowers have coevolved with moths who roll the pollen into balls
        and carry it to another Yucca tree deposit it on the stigma.
  Pollination of many of flowers occurs as a result of the
coevolution of finely-tuned traits between flowers and their
                         pollinators.




 Red, tubular flowers have coevolved with hummingbirds who have long beaks
                            and are attracted to red.
By studying inherited species' characteristics and other historical
  evidence, we can reconstruct evolutionary relationships and
      represent them on a "family tree," called a phylogeny.

								
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