Transcript Lec3

Evidence for Evolution II: contemporary
Lecture
Contemporary evidence for
evolution
Natural selection, theoretical
problems, and new evidence
Goal
Summarize how molecular
and developmental biology
support evolution; what new
discoveries convinced
scientists of natural selection
Problem for Darwin I: Lord Kelvin
and the age of the earth
Estimating the age of the earth
Problem for Darwin II: absence of
transitional fossils
Archaeopteryx:
Ancestors of whales
Ambulocetus natans – 50 mya.
Problem for Darwin III: plausibility
of Natural Selection
Contemporary evidence for
evolution: Molecular genetics
Arbitrary nature of genetic code
Developmental Biology
see figure 3.15
Pax6 controls eye development in
all triploblasts!
Embryological experiments: the
same gene can function in multiple
organisms
Evidence for evolution: historical
constraints
Evolution in Natural Populations
Human Immunodeficiency Virus (HIV)
Sequence Evolution in six children
Human Immunodeficiency Virus (HIV) – Ganeshan et al. 1997
Why areHuman
branches
longer
in
children
D-F?
Immunodeficiency Virus (HIV) – Ganeshan et al. 1997
Evolution in Natural Populations
Human Immunodeficiency Virus (HIV) – Ganeshan et al. 1997
•A brief interlude for some genetics review
•Mutations within a gene can be classified as:
– Synonymous (silent)
– Non-synonymous
Distinguishing selection from mutation
Effect of mutation
Not selected
(neutral)
Selected against
(deleterious)
Selected for
(favorable)
Relative probability of mutation
remaining in population
Evolution in Natural Populations
Dispersal in island plant populations – Cody & Overton 1996
•
•
•
Studied weedy, wind-dispersed plants
located on the islands off the west coast
of Vancouver Island
Censused the plant populations of 200
islands and a region of the mainland over
a 10-year period
Extinction and recolonization events
occurred frequently on the islands.
Evolution in Natural Populations
Dispersal in island plant populations – Cody & Overton 1996
•Studied two species:
– Hypochaeris radicata
– Lactuca muralis.
William S. Justice @
USDA-NRCS PLANTS Database
© Markku Savela
Evolution in Natural Populations
Dispersal in island plant populations – Cody & Overton 1996
•Both are Asteraceae
(composites).
•Both produce achenes
consisting of a feathery pappus
and a seed.
Evidence of selection on dispersal
Speciation and selection?
Provisional definition:
Species – An interbreeding group of organisms
that is reproductively isolated from (does not
interbreed with) other groups of organisms
Selection and speciation?
Habitat selection in Drosophila – Rice & Salt 1988, 1990
•
Flies choose
– lightness or darkness (left vs.
right) – selection for
phototaxis
– up or down – selection for
geotaxis
– acetaldehyde (white vial) or
ethanol (black vial) –
selection for chemotaxis
•
Experimenters choose time period:
early (E), middle (M), and late (L) –
selection for development time
Selection and speciation?
Habitat selection in Drosophila – Rice & Salt 1988, 1990
•
Flies mated within the maze
•
Control lines: 120 females chosen
randomly
•
Selected lines – 60 females each from:
• dark, up, acetaldehde, early (5E)
• light, down, ethanol, late (4L)
Evolution and Artificial Selection
Habitat selection in Drosophila – Rice & Salt 1988, 1990
• Experimental larvae were
mixed and placed together in
the maze to start the next
generation.
• Controls were run through
the maze separately.
•
Offspring of mothers collected from
5E and half of the controls were
raised on a chemical that turned
their eyes brown.
Selection and speciation - outcome
Habitat selection in Drosophila – Rice & Salt 1988, 1990
Dotted line: 5E
Solid line: 4L
5E
4L
5E
Selection and speciation: summary
Habitat selection in Drosophila – Rice & Salt 1988, 1990
Contemporary evidence: new
species
Hedylepta
New species:
Tragopogon mirus
More creationist / ID arguments
Letter to the editor, Nature, December 2006.
I believe that, as a result of media bias, there seems
to be total ignorance of new scientific evidence
against the theory of evolution. Such evidence
includes (1) race formation (microevolution), which is
not a small step in macroevolution because it is a
step towards a reduction of genetic information and
not towards its increase. It also includes formation of
(2) geological strata sideways rather than vertically,
(3) archaeological and palaeontological evidence that
dinosaurs coexisted with humans, (4) a major
worldwide catastrophe in historical times, and so on.
Dr. Maciej Giertych, Polish member of European parliament
PhD in tree physiology, U Toronto.
Readings and study questions
• Chapter 2 in Freeman and Herron (3rd or 4th edition)
• Questions 2 and 4 at end of chapter 2
Sources
Cody and Overton. 1996. Short-term evolution of reduced dispersal in
island plant populations. J. of Ecology 84:53-61.
Ganeshan et al. 1997 Human immunodeficiency virus type 1 genetic
evolution in children with different rates of development of disease.
J. of Virology 71:663-677
Giertych, M. 2006. Letter to editor. Nature 444:265.
Ownbey, M. 1950. Natural hybridization and amphiploidy in the genus
Tragopogon. American Journal of Botany 37:487-499.
Rice, WR and Salt, GW. 1988. Speciation via disruptive selection on
habitat preference – experimental evidence. American Naturalist
131:911-917.
Rice, WR and Salt, GW. 1990. The evolution of reproductive isoation
of a correlated character under sympatric conditions – experimental
evidence. Evolution 44:1140-1152.