Download Evidence, Speciation, Macroevolution

Evidence, Speciation,
Macroevolution
Evidence supporting evolution
Fossil record
shows
change over time
Anatomical record
comparing
body structures
homology
& vestigial structures
embryology & development
Molecular record
comparing
protein & DNA sequences
Artificial selection
human
caused evolution
Homologous structures (Divergent Evolution)
Structures that come from the same origin
homo- = same
-logous = information
Forelimbs of human, cats, whales, & bats
same structure
same development in embryo
different functions
on the inside
on the outside
evidence of common ancestor
But don’t be fooled by these…
Analogous structures
look similar
on the outside
same function
different structure &
development
on the inside
different origin
no evolutionary
relationship
Analagous or Homologous?
Dolphins: aquatic mammal
Fish: aquatic vertebrate
both adapted to
life in the sea
not closely related
Convergent evolution (Analagous structures)
evolving similar solutions to similar problems
3 groups with wings
Does this mean they have a
recent common ancestor?
What data from the
Genome Project can tell us
about evolution of humans
Chromosome Numbers
in the great apes:
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
46
48
48
48
Change in chromosome number?
If these organisms share a
common ancestor, then is there
evidence in the genome for this
change in chromosome number
Ancestral
Chromosomes
Chromosome Numbers
in the great apes
(Hominidae):
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
46
48
48
48
Fusion
Homo sapiens
Inactivated
centromere
Telomere
sequences
Centromere
Telomere
Testable prediction:
If common ancestor had 48 chromosomes (24 pairs)
then humans carry a fused chromosome; or
If common ancestor had 46 chromosomes (23 pairs)
then apes carry a split chromosome.
Human Chromosome #2 shows the exact
point at which this fusion took place
Homo sapiens
Inactivated
centromere
Telomere
sequences
“Chromosome 2 is unique to the human lineage of
evolution, having emerged as a result of head-tohead fusion of two acrocentric chromosomes that
remained separate in other primates. The precise
fusion site has been located in 2q13–2q14.1 (ref. 2;
hg 16:114455823 – 114455838), where our analysis
confirmed the presence of multiple subtelomeric
duplications to chromosomes 1, 5, 8, 9, 10, 12, 19,
21 and 22 (Fig. 3; Supplementary Fig. 3a, region
A). During the formation of human chromosome
2, one of the two centromeres became inactivated
(2q21, which corresponds to the centromere from
chimp chromosome 13) and the centromeric
structure quickly deterioriated (42).”
Chr 2
Hillier et al (2005) “Generation and Annotation of the DNA
sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.
Discuss with a Partner
WHAT ARE THE MAIN EVIDENCES
FOR EVOLUTION?
WHICH DO YOU FEEL IS THE
STRONGEST SUPPORT OF NATURAL
SELECTION?
WHY?
Speciation
A theory that species can
change over time to become
different groups because of
isolation, mutation, and evolution
Species
Groups of organisms that can successfully
reproduce, having viable offspring
(A species can indefinitely perpetuate).
Speciation requires…
Isolation
Mutation
Evolution
How does one group become separated and isolated?
Reproductive Isolation
Speciation requires reproductive isolation
(If they cannot mate, they’re considered different
species)
Western Meadowlark
Eastern Meadowlark
Reproductive Isolation may be:
A. PRE-ZYGOTIC Isolation
o
(mating or fertilization
prevented)
B. POST-ZYGOTIC Isolation
o
(hybrid zygote forms, but
may die early, be weak, or
be sterile)
Prezygotic Isolation
A. Geographical
o
o
separated by habitat
Ex: land & water, mountain & valley, tree &
grass
Prezygotic Isolation
B. Temporal
o
o
Separated by time
Ex: nocturnal v. diurnal, 17-year cicadas
Prezygotic Isolation
C. Behavioral
o
Ex: mating song or dance
Prezygotic Isolation
D. Mechanical
o
physically do not fit, cannot
mechanically mate
MULE
Are horses and donkeys the same species?
ZEBROID or ZORSE
ZONKEY?
Are horses and zebras the same species?
How about a donkey and zebra?
WHOLPHIN?
Are dolphins and orcas the same species?
TIGON
Are lions and tigers the same
species? Evolution Video
Macroevolution
How then do we get from the mechanism of speciation to
evolution on a grand scale; i.e., macroevolution?
Two models:
- Gradualism model
-
change is gradual with the accumulation of unique
morphological adaptation.
- Punctuated Equilibrium model
-
rapid change occurs, with a new species “erupting” from
the ancestral lineage and then staying the same
thereafter.
Discuss with your Partner
What defines a species?
Come up with 2 examples of reproductive isolation.
What are the two models of Speciation?
Selection
Directional
Selection
Shift in one
direction
One extreme or the
other is selected
Stabilizing
Selection
Disruptive
Selection
• Intermediate
• Two extreme
forms of a trait are forms of a trait
selected
are selected
• Most of the
population is
“average”—
extremes are
selected against
• Most are one
extreme or the
other—middle is
selected against
DRAW THESE!
This is
Directional
__________
Selection
This is
Stabilizing
__________
Selection
This is
Disruptive
__________
Selection
This is
Directional
__________
Selection
Discus with your Partner…
Using the fish in the lake below come up with an
example of selection.
What could cause Directional Selection?
What could cause Stabilizing Selection?
What could cause Disruptive Selection?
Hint: Look at body
size, color, patterns
(stripes or spots).
Think about food
sources and other
resources. Consider
Predators!
Adaptive Radiation
When one species increases in number without
competition and evolves into new species in a new
environment.
Extinction
Irrevocable loss of a species
(Usually followed by adaptive radiation
of other species)
Artificial Selection
occurs when humans
select traits that
survive and proliferate
(Selective breeding)
What Does This Picture Have To
Do With Artificial Selection?
What Kind
Of Dog Do
YOU Like?
Speciation Charades!
Each group will pick a random vocabulary term
Spend 3 minutes planning how you will act out your
concept.
No talking
Props are encouraged!
Each group will present until the class can
correctly identify the concept on their white
boards or paper.
Possible Terms
Reproductive
Isolation
Divergent
Evolution
Adaptive
Radiation
Homologous
structures
Speciation
Punctuated
Equilibrium
Geographic
Isolation
Analogous
Structures
Convergent
Evolution
Gradualism
Artificial
Selection
Vestigial
Structures