Transcript Evolution…day 1

Alfred R. Wallace
Charles Darwin
Evolution… day 2
Thomas
Huxley
Gregor Mendel
R.A. Fisher
Theo. Dobzhansky
Barbara McClintock
J.B.S.
Haldane
Stephen J. Gould
Misconceptions (continued)
“THEORY”
• Evolution is “just” a theory…
• The theory of evolution is flawed…
• The theory of evolution is incomplete
Misconceptions
“THEORY”
• Evolution is “just” a theory…

Theory = a scientifically accepted general principle to
describe or explain a particular natural phenomenon
Misconceptions
“THEORY”
• The theory of evolution is flawed…


Well…not on philosophical or scientific grounds.
When flaws are found, they are used to correct the theory!
Scientists in the field don’t debate
whether evolution has occurred,
but they may disagree on how it
happens.
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 don’t understand most of them!

Newest UPDATE: happening NOW
The 2nd Modern Synthesis of Evolution (Taaa…Daaa)
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 isn’t…??

Science seeks explanation in natural phenomena:
Supernatural explanations of any type are not options
“Dover Decision”
2005 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/3416_id.html
back to science …
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.)
“1st” Modern Synthesis
Natural Selection
Genetic mechanisms
Population size or composition
Nonrandom mating (mate selection)
Historic contingencies
“2nd” Modern Synthesis
adds DEVELOPMENTAL MECHANISMS
(Taaa…Daaa !!)
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).
Phenomenon =
Retention of juvenile characteristics
= PAEDOMORPHOSIS
Chimpanzee Skull Growth
Human Skull Growth
“Bottom line”
Organic EVOLUTION
= DESCENT WITH MODIFICATION
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!
Mammals
Birds
Reptiles
Implications:
A fish evolved into an amphibian
An amphibian evolved into a reptile
Amphibians
All Reptiles existed before birds
and mammals
etc.
Fish
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.
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 B+C are
“sister” taxa i.e., A + [B+C]
And so on…
Mammals
Reptiles ?
Birds
Reptiles ?
Amphibians
Fish
We don’t know enough about the group “reptiles” to
place specifically on the tree. We need more information
and we ADMIT IT!
What is needed…?
• Actually…more data!

CHARACTERISTICS!
Shared because primitive
= Plesiomorphy
Shared because descendant
= derived or Synapomorphy
(NOT “advanced”)
Shared because convergent
= Homoplasy
Convergence?
BEWARE! Convergence depends on
how well the character is defined!
Bat wings ≠ bird wings ≠ insect wings
What is needed…?
• Actually…more data!


CHARACTERISTICS!
More distinctive groups
 Outgroup(s)
 Monophyletic “in” groups
Monophyletic clade = any group
with a shared common ancestor
GROUP doesn’t include all descendants
GROUP doesn’t include a common ancestor
MAMMALS
Egg-layers, Marsupials, Placentals
CROCODILES
LIZARDS +
SNAKES
Mammary glands, 3 ear bones
DINOSAURS
f
shell
f
LOBEFINNED
FISHES
CARTILAGE FISHES
Chondrichthyes
PLACODERMS f
Amniotic Egg
f
Limbs, 1 Ear Bone “Stirrup”
Larynx (from gill bar)
f
Lobed Fins
JAWLESS FISHES:
Ostracoderms f,
Lampreys, Hagfishes
simple lung
Bone, Jaws (from gill bar)
Cranium, Brain, Vertebrae
horny scales
f
LUNGFISHES
Other
Dinosaurs
TURTLES
AMPHIBIANS
Frogs, Toads, Salamanders,
Caecilians
BONY RAY-FINNED
FISHES
f
feathers
f
f
BIRDS
Your homework problem:
CHARACTERISTICS A--R
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
OUT
1
1
1
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
Angela
1
1
1
1
1
0
0
0
0
0
0
2
0
0
0
0
0
0
Gary
1
1
1
1
1
1
1
0
0
0
0
2
0
0
0
0
0
0
Carla
1
1
1
1
1
1
1
1
0
0
0
?
0
0
0
0
0
0
Amber
1
1
0/1
1
1
1
1
0/1
1
0
0
3
0
0
0
0
0
0
Ronnie
1
1
1
1
1
1
1
0/1
1
1
1
3.5
0
0
0
0
0
0
Sally
1
1
1
1
1
1
1
1
1
1
1
?
0/1
1
1
0
0
0
Paul
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
1
1
0
Harry
1
1
0
1
1
1
1
1
1
1
1
4
1
1
1
1
1
0
Who
1
1
0
1
1
1
1
1
1
1
1
4
1
1
1
1
1
1
GROUP
Step 1 + 2 = using A, B, D and R, you produce this tree:
Sally
Amber
Ronnie
Who
Carla
R=1
OUT
Harry
Gary
Angela
Paul
B=1
A=1
D=1
Step 3 = resolve the groups still clustered
Remember…
You also must turn in the topic you have selected
for your major paper.