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					Environmental Sciences: Towards
a Sustainable Future Chapter 4 Part 2

   Ecosystems and Evolutionary
This Lesson Discusses Those Factors
That Contribute to Ecosystem Change
   Change is inevitable.
   Adaptations, natural selection and
    sexual reproduction are the tools of
   Differential vulnerability of each
    species to environmental change.
   Change on a geological time scale.
Selection of Traits and Genes:
   DNA: molecule that carries the
    genetic code of an organism
   Chromosome: structure on which
    DNA of an organism is arranged
Selection of Traits and Genes:
   Gene: segment of DNA that codes for
    a particular protein
   Allele: form of a gene. Each person
    carries 2 alleles for each gene
   Trait: certain characteristic of an
    organism; e.g., hair color, disease
    resistance, intelligence
The Link Between DNA and Traits
Selection by the Environment
   Genetic variation: genetic differences
    that exist among individuals
   Gene pool: sum total of all the genes
    that exist among individuals of a
Selection by the Environment
is “Natural Selection”
   Differential reproductive success (or
    “fitness” in Darwinian terms): some
    individuals in the population survive
    to reproduce more than others
    Change Through Selected Breeding
    is “Artificial Selection”
   Selected breeding:
    artificial selection
      e.g., selection for
         dogs with shorter
      Corn for higher
         yeilds even with
   Process is repeated
    in subsequent
Change Through Natural Selection
   Factors of environmental resistance act as
    selective pressures
   Natural selection: the process by which
    evolution occurs
    Individuals which possess certain traits
    can produce more viable offspring than
    individuals lacking those traits and
    continue their gene line, while others who
    are less adapted die off
Recipe for Change

       For? or Against?
Selective Pressure
Genetic Variation
   Generated by sexual reproduction
   Each gamete (sperm and egg) carries
    one set of alleles
   Fertilization or the union of sperm and
    egg results in the combination of both
    sets of alleles = unique individual
Genetic Variation in Eye Color
Genetic Variation in Eye Color
Genetic Variation
   Mutation: any inheritable change in
    the DNA molecule.
   Lethal mutation: results in death of
Genetic Variation
   Neutral mutation: neither harms nor
    benefits organism.
   Mutations are rare and random events.
       Spontaneous
       Induced
Speciation (Evolution)
   Process by which separate populations
    of a single species develop into
    distinct species.
   Must have geographic separation (to
    prevent interbreeding) and have
    different selective pressures in the new
   Populations of a given species become
    isolated from each other.
   No interbreeding between populations
Speciation: Foxes
Speciation: Galapagos Finches
Developing Ecosystems
   All ecosystems have the same
    functional “parts”. Only the “actors”
    who play these parts are different
    across ecosystems.

      Example: Buffalo vs. Kangaroo
Developing Ecosystems
   Why have species evolved so
    differently across ecosystems with
    similar environmental conditions?
    (Hint: remember the recipe for
The Limits of Change
   New selective pressures require
    species to:
   adapt
   migrate
   or go extinct.
The Limits of Change
   Factors affecting species’ adaptation
    to environmental change:
       Geographical distribution.
       Habitat specialization.
       Genetic variation.
       Size of individual.
       Reproductive rate.
Will The Panda Survive In A
Changing Environment?
 Natural selection occurs slowly vs.
Punctuated equilibrium theory: model of
  evolution in which there is little
  change in a balanced ecosystem. A
  shift in the environmental conditions
  will alter selective pressures, thereby
  causing rapid changes in the species
  until balance is restored.
Geological Time Scale
Drifting Continents

                     250 million
                      years ago

                     Today
Plate Tectonics
Plate Tectonics
   Tectonic plates: slabs of rock that
    make up the earth’s surface; 14 major
   Tectonic plates move approximately
    6cm per year
   4 basic tectonic plate interactions
Divergent Boundaries
   Rising convection currents of hot less
    dense magma force apart plates
   Result: mid-ocean ridges, rift valleys
Transform Boundaries
   Two plates slide
    past each other
   Result: fault lines
    marking major
    activity; San
    Andreas fault in
Convergent Boundaries Ocean-Continental
    Plates moving toward each other
    Result: dense oceanic plate moves under a
     continental plate creating subduction zone,
     oceanic trench and volcanic activity; like Cascade
     mountains of California
   Convergent Boundaries
   Continental-Continental Collision
      Formation of mountain ranges like
       Himilayas, Alps etc.
  What happened when Mount St.Helens
Convergent Boundaries
Ocean-Ocean Collision
   Create subduction zones, oceanic trenches and
    underwater volcanoes, often resulting is island
    chains (island arcs)
Tectonic Movement has dramatic
Climatic Effects
   Changing position on earth’s surface
    isolates or connect new communities
   Movements alter ocean currents
   Mountain formation alters air currents
   Geological Activity along boundary
    lines like volcanoes and earthquakes
Evidence Of Evolution
   Fossil record
   Species evolution
   DNA nucleotide similarities and
    Fifth Principle of Ecosystem

   Ecosystems
    depend on
Stewardship of Life: A Question
   Why is the fifth principle of
    sustainability (biodiversity) important
    in understanding the following issues?
       Endangered species
       Agriculture
       Biotechnology
       Medicine

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