Extinction my CCSD

					Chapter 17, 18 and 19
    Evolution Unit
Earth: The Just-Right, Adaptable Planet

                  • During the 3.7
                    billion years since life
                    arose on Earth, the
                    average surface
                    temperature of the
                    earth has remained
                    within the range of
                    10-20oC
                                     Figure 4-1
   The consistent
 temperature range
 has allowed life to
Evolve, Flourish and
create the Diversify
   on Planet Earth

    Our Home
  Evolution of Life On Earth
             Chemical Evolution                                 Biological Evolution
             (1 billion years)                                  (3.7 billion years)


 Formation                    Large                                                   Variety of
                                             First      Single-cell   Single-cell
   of the       Small        organic                                                 multicellular
                                          protocells   prokaryotes    eukaryotes
   earth’s     organic     molecules                                                 organisms
                                         form in the      form in       form in
    early    molecules   (biopolymers)                                                form, first
                                            seas         the seas      the seas
 crust and     form in       form in                                                 in the seas
atmosphere    the seas      the seas                                                   and later
                                                                                        on land




                                                                                    Fig. 4-2, p. 84
    Stanley Miller’s Experiment
  Or- How we figured our how life
evolved from non-living components
                 http://highered.mcgraw-
hill.com/sites/9834092339/student_view0/chapter26/an
         imation_-_miller-urey_experiment.html
    Stanley Miller’s Experiment
Vial of Material from Original Experiments Found
  (youtube) 1.5 mins

Bill Nye Explains Stanley Miller’s Experiments
Creating the Potential for Life (united streaming) 8
  mins

Time Line -1953 Miller’s Experiments
           1977 Undersea vent discovery
 Time Frame of Human Evolution
• Time Scales Demonstration-string
                                  Modern humans (Homo
                                  sapiens sapiens) appear
                                  about 2 seconds before
                                  midnight
                      Age of      Recorded human history
                      mammals     begins about 1/4 second
               Age of
               reptiles           before midnight
    Insects and
    amphibians
    invade the                           Origin of life
    land
                                         (3.6-3.8 billion
                                         years ago)


First fossil
record of
animals

     Plants
     begin
     invading
     land     Evolution and
              expansion of life



                                                 Fig. 4-3, p. 84
• If the diagram of
  Evolution were a
  clock, at what time
  would Fish have
  evolved?

• What time are
  flowering plants
  present?

• What time do humans
  evolve?
 Evolution and Geological Time
• Over the last billion years, the
  location of the continents has
  changed. This has led to the
  evolution of similar species on
  different continents…
225 million years ago   135 million years ago




65 million years ago          Present

                                            Fig. 4-5, p. 88
http://contintental drift theory pangae
Changes in climate throughout the earth’s
 history have shifted where plants and
 animals can live




                                        Figure 4-6
Asteroids and meteorites hitting the
 earth have wiped out large numbers
 of species and created evolutionary
 opportunities for Natural Selection of
 new species
Ex: KT Meteorite killed off dinosaurs
 and gave rise to the “age of
 mammals”
Our knowledge about past life comes from
 fossils, chemical analysis, cores drilled out
 of buried ice, and DNA analysis
       NATURAL SELECTION
• Evolution by natural selection involves
  the change in a population’s genetic
  makeup through successive generations
• Through either:
   –genetic variability
   –Mutations: random changes in DNA
    that can be inherited by offspring
 Natural Selection and Adaptation:

3 conditions are necessary for
   evolution:
  1. Genetic variability
  2. Traits must be heritable
  3. Trait must lead to differential
    reproduction
         Types of Natural Selection
• Stabilizing: occurs when the most common
  phenotype is selected for.
• Disruptive: occurs when changes favor
  individuals at both extremes of the distribution,
  individuals at the extremes contribute more
  offspring than those in the center, producing two
  peaks.
• Directional: occurs when natural selection favors
  a single phenotype and therefore allele frequency
  continuously shifts in one direction.
http://wps.pearsoncustom.com/wps/media/obje
  cts/3014/3087289/Web_Tutorials/17_A02.swf
Directional Selection
Microevolution occurs when allele frequencies
   change from one generation to the next
          Ex. Industrial melanism
Moth Populations: Directional
         Selection




             PLAY
           ANIMATION
Wrap Up of Natural Selection Types
      Adaptive Trait Game




                PLAY
              ANIMATION
  Limits on Adaptation through
        Natural Selection
• A population’s ability to adapt to
 new environmental conditions
 through natural selection is limited
 by its gene pool and how fast it can
 reproduce.
          Coevolution
• Interacting species can engage
  in a back and forth genetic
  contest in which each gains a
  temporary genetic advantage
  over the other. This often
  happens between predators and
  prey species
 Example: Toxic Newts
Every species in an ecosystem has a specific
 role or Niche

 1. Fundamental niche: the potential
 range conditions and resources a species
 could theoretically use
 2. Realized niche: to survive and avoid
 competition, a species usually occupies
 only part of its fundamental niche
2 Species of Barnacles- 2 niche
In the previous diagram the two species of
  barnacles grow on different parts of the rocks.
  When the lighter coloured (Balanus sp.) were
  removed from the rocks the darker coloured
  (Chthamatus sp.) was able to move down onto the
  unoccupied surface. But when the Chthamatus
  sp. was removed from the upper areas of the rock
  Balanus sp. was not able to move up and occupy
  these upper areas, because Balanus sp. can't
  stand to be exposed to the air for a long time,
  which is the case with rocks close to the high tide
  mark. Balanus can only occupy the lower niche.
            Generalist and Specialist
                                        Generalist
                                        species
Specialist
                                        tolerate a
  species can
                                        wide range
  only
                                        of
  tolerate a
                                        conditions.
  narrow
  range of
  conditions.




                                            Figure 4-7
Cockroaches: Nature’s Ultimate
          Survivors
            • 350 million years old

            • 3,500 different species

            • Ultimate generalist
              – Can eat almost anything.
              – Can live and breed
                almost anywhere.
              – Can tolerate radiation. 4-A
                                     Figure
   Specialized Feeding Niches




• Resource partitioning reduces competition
  and allows sharing of limited resources.



                                              Figure 4-8
                                     Avocet sweeps bill through
                                     mud and surface water in
                                     search of small crustaceans,
                                                                                                      Ruddy
                                     insects, and seeds
                                                                            Herring gull is a     turnstone
                                                                            tireless scavenger     searches
                             Brown pelican                                                      under shells
                             dives for fish,                                                    and pebbles
                             which it locates              Dowitcher probes deeply                 for small
Black skimmer
                             from the air                  into mud in search of               invertebrates
seizes small fish
at water surface                                           snails, marine worms,
                                                           and small crustaceans




                         Louisiana heron wades into
                         water to seize small fish
                                                                                          Piping plover feeds
Flamingo        Scaup and other                 Oystercatcher feeds on
                                                                                          on insects and tiny
feeds on        diving ducks feed               clams, mussels, and
                                                                                          crustaceans on
minute          on mollusks,                    other shellfish into which
                                                                                          sandy beaches
organisms       crustaceans,and                 it pries its narrow beak
in mud          aquatic vegetation                                       Knot (a sandpiper)
                                                                         picks up worms and
                                                                         small crustaceans left
                                                                         by receding tide

(Birds not drawn to scale)                                                                  Fig. 4-8, pp. 90-91
         SPECIATION
• Speciation: A new species can
  arise when member of a
  population become isolated for
  a long period of time
              Pre-zygotic Barriers

Mechanical isolation:
     Structural differences prevent gamete
     exchange.
Gametic isolation:
     Gametes die before uniting with gametes   of
 other species, or gametes fail to unite.
         Post-zygotic Barriers

Hybrid inviability:
     Hybrid zygotes fail to develop or fail to
     reach sexual maturity.
Hybrid sterility:
     Hybrid fails to produce functional gametes.
Hybrid breakdown:
     Offspring of hybrids are weak or infertile.
          Allopatric Speciation
• Induced when the ancestral population becomes
  separated by a geographical barrier.

• Example:
     Grand Canyon and ground squirrels
           Adaptive Radiation
• Emergence of numerous species from a common
  ancestor introduced to new and diverse environments.

• Example:
     Darwin’s Finches
          Sympatric Speciation
• Result of a radical change in the genome that produces
  a reproductively isolated sub-population within the
  parent population (rare).

• Example: Plant evolution - polyploid
     A species doubles it’s chromosome # to
     become tetraploid.

                                       Parent population
                 reproductive sub-
                 population
Evolutionary Divergence
                • Each of the
                  finches
                  evolved into a
                  new species,
                  from a
                  common
                  ancestor, to fill
                  a niche


                             Figure 4-9
Animation: Evolutionary Tree
         Diagrams




             PLAY
           ANIMATION
         Geographic Isolation




• …can lead to reproductive isolation, divergence
  of gene pools and speciation.
                                            Figure 4-10
                Extinction:
                         • Extinction occurs
                           when the
                           population cannot
                           adapt to changing
                           environmental
                           conditions.

The golden toad of Costa Rica’s
Monteverde cloud forest became extinct
because of climate change.
                                         Figure 4-11
                                          Bar width represents relative     Species and families
Era            Period       Millions of                                          experiencing
                            years ago     number of living species
Cenozoic                                                                       mass extinction
             Quaternary      Today                           Extinction Current extinction crisis caused
                                                                        by human activities.
               Tertiary
                                                             Extinction
                               65
                                                                          Cretaceous: up to 80% of
             Cretaceous                                                   reptiles (dinosaurs)
Mesozoic




              Jurassic                                     Extinction     Triassic: 35% of animal families
                              180
              Triassic

                              250                          Extinction     Permian: 90% of animal families
              Permian

            Carboniferous
                              345                          Extinction
                                                                          Devonian: 30% of animal
Paleozoic




                                                                          families
              Devonian

               Silurian

             Ordovician                                    Extinction
                              500                                         Ordovician: 50% of animal
              Cambrian                                                    families

                                                                                                    Fig. 4-12, p. 93
II. Mass Extinctions
   A. Paleozoic Era between Ordovician/ Silurian 438 mya
   (million years ago): First Ice Age=75% of all species
   extinct
Paleozoic Era between Devonian/ Carboniferous 360 mya:
   Sea levels rising=70% of all species extinct
Paleozoic Era between Permian/Triassic 245 mya: all land
   masses colliding together to form Pangaea and single
   world ocean=90% of all species extinct
Mesozoic Era between Triassic/ Jurassic 214 mya: comets
   hitting the Earth (theory)
    60% of all species extinct-first extinction of some
      dinosaurs
Mesozoic/Cenozoic Era: Cretaceous/Tertiary 65 mya:
   Volcanic lava, maybe an asteroid hitting the earth.
    2nd and final extinction of most dinosaurs
                     GREATEST EXTINCTIONS THROUGHOUT HISTORY




                                                                                                                     Current Day
                                                                                                    Cretaceous
                              Ordovician




                                             Devonian




                                                        Permian

                                                                  Jurassic
                                                                             Dinosaurs go extinct
                                                                                                                         Terrestrial
Number of families




                                                                                                                                   Marine




                     Millions of years ago



                                                                                                                 Fig. 4-13, p. 94
   Effects of Humans on
        Biodiversity
• The scientific consensus is
  that human activities are
  decreasing the earth’s
  biodiversity.

                            Figure 4-13
    GENETIC ENGINEERING
 • We have used artificial selection to change the
   genetic characteristics of populations with
   similar genes through selective breeding.
 (Cows are an example of this)

• We have used
 genetic
 engineering to
 transfer genes from     The mouse on the right has been
 one species to          engineered to be obese.
 another.
                                                   Figure 4-15
       Genetic Engineering:
Genetically Modified Organisms (GMO)
                          recombinant
                            DNA: genes
                           from
                           different
                           organisms
                           are
                           combined.



                               Figure 4-14
How Did We Become Such a Powerful
       Species so Quickly?
• We lack:
  – strength, speed, agility.
  – weapons (claws, fangs), protection (shell).
  – poor hearing and vision.
• We have thrived as a species because of
  our:
  -opposable thumbs, ability to walk upright, and
    complex brains (problem solving).

				
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