Evolution… day 2

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Evolution day 2
Barbara McClintock
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Misconceptions (continued)

• THEORY
• Evolution is just a theory
• The theory of evolution is flawed
• The theory of evolution is incomplete

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Misconceptions

• THEORY
• Evolution is just a theory
• Theory a scientifically accepted general
  principle to describe or explain a particular
  natural phenomenon

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Misconceptions

• THEORY
• The theory of evolution is flawed
• Wellnot on philosophical or scientific grounds.
• When flaws are found, they are used to correct
  the theory!

Scientists in the field dont debate whether
evolution has occurred, but they may disagree on
how it happens.
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Misconceptions

• THEORY
• The theory of evolution is incomplete
• Maybe ?
• Science works by self-correcting over time.
• We may not understand all the mechanisms, at this
  time.
• Does NOT equal that we dont understand most of
  them!
• Newest UPDATE happening NOW
• The 2nd Modern Synthesis of Evolution
  (TaaaDaaa)

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Misconceptions

• POLITICS
• Evolution Religion
• Opposite arguments OR apples oranges?
• Creation Science Intelligent Design
• Are these two different?
• Which creation do you mean?
• What is science and what isnt??
• Science seeks explanation in natural phenomena
  Supernatural explanations of any type are not
  options

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Dover Decision2005 Kitzmiller v. Dover Area
School District

• Issue started in rural community of Dover,
  Pennsylvania, and progressed to become a federal
  court test case for science education.
• Dover School Board wanted to require science
  teachers to offer intelligent design (ID) as an
  alternative to evolution.
• Parents initiated the lawsuit and sought to show
  that the School Board had religious motivations
  for teaching ID, who denied the motivation.
• Required textbook for ID, Of Pandas and People,
  had originally been a creationist text.
• Judge's decision Members of the school board
  had religious motivations for introducing
  intelligent design into the classroom and that ID
  was not a scientific theory.
• http//www.pbs.org/wgbh/nova/teachers/programs/341
  6_id.html

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• back to science

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Modern Synthesis

• Natural Selection
• Genetics
• Mutations
• Chromosomal changes
• Duplication of a gene or genes
• Incomplete reproductive isolation (hybrids)
• Population size or composition
• Immigration or loss of portions of original
  group
• Emigration from outside sources
• Nonrandom mating
• Historic Contingency
• Random events (e.g., huge meteors! disease!
  Fast climate change!, etc.)

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1st Modern Synthesis

• Natural Selection
• Genetic mechanisms
• Population size or composition
• Nonrandom mating (mate selection)
• Historic contingencies
• 2nd Modern Synthesis
• adds DEVELOPMENTAL MECHANISMS
• (TaaaDaaa !!)

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The population genetics approach to understanding
evolution emphasizes variations within a species
that allow certain individuals to reproduce more.
The developmental approach looks at variation
between groups and emphasizes actions of
regulatory genes responsible for formation of
shape, tissues, organs, and body parts. This
approach is more apt to explain evolutionary
novelty and constraint. Think of evolution as
evolving embryos NOT just adults! Together,
population genetics and development make a more
complete approach to understanding how evolution
happens ( mechanisms).
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Phenomenon Retention of juvenile
characteristics
PAEDOMORPHOSIS
Chimpanzee Skull Growth
Human Skull Growth
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Bottom line

• Organic EVOLUTION
• DESCENT WITH MODIFICATION

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Phylogenetics

• IN CLASS
• Consider the following groups
• MAMMALS
• FISH
• AMPHIBIANS
• BIRDS
• REPTILES
• Draw a TREE OF LIFE showing the relationships
  among these groups
• You have 5 minutes!

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Implications A fish evolved into an amphibian An
amphibian evolved into a reptile All Reptiles
existed before birds and mammals
etc.
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Trees inherently represent species (or
populations) and thus, each bifurcation
represents hypothesized speciation events.
Although we can replace species with groups of
species, the assumption of sharing a
most-recent common ancestor must be met (we
call this monophyly or one origin). If a
species splits (diverges from its past genetic
profile), we distinguish descendant
species from the original ancestor.
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Thus, each species or group of species is
hypothesized to share a most-recent common
ancestor.
B and C sister taxa, since they share a
most recent common ancestor. A and the
ancestor to BC are sister taxa i.e., A
BC And so on
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We dont know enough about the group reptiles
to place specifically on the tree. We need more
information and we ADMIT IT!
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What is needed?

• Actuallymore data!
• CHARACTERISTICS!
• Shared because primitive
• Plesiomorphy
• Shared because descendant
• derived or Synapomorphy
• (NOT advanced)
• Shared because convergent
• Homoplasy

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Convergence?
BEWARE! Convergence depends on how well the
character is defined! Bat wings ? bird wings ?
insect wings
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What is needed?

• Actuallymore data!
• CHARACTERISTICS!
• More distinctive groups
• Outgroup(s)
• Monophyletic in groups

Monophyletic clade any group with a shared
common ancestor
GROUP doesnt include all descendants
GROUP doesnt include a common ancestor
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MAMMALS Egg-layers, Marsupials, Placentals
CROCODILES
BIRDS
LIZARDS SNAKES
feathers
Other Dinosaurs
Mammary glands, 3 ear bones
TURTLES
AMPHIBIANS Frogs, Toads, Salamanders, Caecilians
DINOSAURS
shell
LOBEFINNED FISHES
horny scales
BONY RAY-FINNED FISHES
Amniotic Egg
LUNGFISHES
CARTILAGE FISHES Chondrichthyes
Limbs, 1 Ear Bone Stirrup Larynx (from gill
bar)
PLACODERMS f
Lobed Fins
JAWLESS FISHES Ostracoderms f, Lampreys,
Hagfishes
simple lung
Bone, Jaws (from gill bar)
Cranium, Brain, Vertebrae
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Your homework problem
CHARACTERISTICS A--R
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Step 1 2 using A, B, D and R, you produce
this tree
Sally
Amber
Ronnie
Who
R1
Carla
OUT
Harry
Gary
Angela
Paul
D1
A1
Step 3 resolve the groups still clustered
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• Remember
• You also must turn in the topic you have selected
  for your major paper.