2. Evolution vs. Creationism
Here are a few websites you can look at to
inquire further into the arguments for both
creationism and evolution.
Creationism
http://www.talkorigins.org/faqs/wic.html
http://www.creationism.org/
Evolution (and creationism)
http://www.talkorigins.org/origins/faqs-mustread.html
http://www.bcholmes.org/wicca/evolution.html
6. The Universe
Big Bang Theory
15 bya
Things cooled
Atoms formed
Planets, stars and solar systems formed
More on the Big Bang Theory
http://www.umich.edu/~gs265/bigbang.htm
7. The Earth
About 4.5 bya
Formed from collecting dust, gases, etc.
Atmosphere of CO2, H2O, N2, CO and NH3
Earth cools
Liquid water – needed for life
3.8 bya
More information
http://mediatheek.thinkquest.nl/~ll125/en/bigbang.h
8. First Organic Compounds
H2 + CH4 + NH3 + heat + lightening = simple organic
compounds
Amino acids
Monosaccharides
Miller and Urey (1950’s)
Tested Oparin’s
hypothesis
Meteorites?
More information
http://www.chem.duke.edu/~jds/cruise_chem/Exobiolo
gy/miller.html
9. First Cell-like Structures
Protobionts
Microspheres
Proteins organized as a membrane
Coacervates
Droplets of organic compounds
So what?
Life-like
Grow in size
Take in substances from surroundings
Bud in two (reproduce)
Catalyze reactions
Maintain membrane potential
Spontaneous
Could lead to first cells
10. First “Cells”
RNA considered key
Many forms
Simpler than DNA
Ribozymes
RNA can act as an enzyme!!!!
Mechanism for self-replication
Maybe . . .
Self-replicating RNA ended up inside a
coacervate or microsphere creating first cell-
like structure
11.
12. First Prokaryotes
3.5 bya
Very simple single-celled organisms
Similar to some of today’s prokaryotes
Chemoautotrophs first
Break down inorganic compounds for energy
Archaebacteria
Photoautotrophs evolve
Create oxygen
Changed everything
16. Definition of Evolution
The processes that have transformed life on Earth
from its earliest forms to the vast diversity that
characterizes it today
Mechanism for Evolution
Natural Selection
Two types of evolution
Intraspecies
Single species evolves
Interspecies
New species evolves
17. Historical Context
Aristotle
For 2000 years -- species are perfect, they don’t
evolve
Religion
Creationism – same idea, God created all life
Most Scientists (1700’s)
Natural Theology dominated – again, same idea
Lamarck (1809)
Organisms evolve from ancestors-(1 st to say)
Use and disuse
Acquired characteristics
Darwin (1859)
“The Origin of Species”
Few people held similar beliefs at that time
18. The Voyage of the Beagle
Darwin’s observations
One – Species fertility = exponential growth
Two – Populations generally stable
Three – Resources limited
Leads to competition
Four – Individuals vary
Five – Much of this variation is heritable
If variation is beneficial, variation will flourish
(lots)
19. Darwin’s Conclusion
Evolution through adaptation due to natural
selection
i.e. Some individuals (because of variation) in
a population will have better success at
surviving and reproducing; therefore, the
heritable traits of those organisms will be
passed on while the heritable characteristics
of less successful individuals will not.
20. Darwin’s Overall View
Unity in life – all organisms relate back to an
unknown original ancestor
New species arise through evolution
Depicted by a phylogenetic tree
Shows evolutionary history
22. “The Origin of Species"
Two main points
States the occurrence of evolution (descent
with modification)
Natural selection is the mechanism for
evolution
23. Things to Note
A population is the smallest unit that can
evolve (a population is a group of
interbreeding individuals belonging to a
particular species in a given geographical
area).
Only heritable characteristics can be
amplified or diminished through natural
selection
Generally, natural selection leads to evolution
slowly over a long period of time.
24. EVIDENCE OF EVOLUTION
One – BIOGEOGRAPHY
Geographical distribution of species
Example
Kangaroo
Armadillo
Question: Why are tropical animals of South
America more closely related to species of
South American deserts than to species of the
African tropics?
25. EVIDENCE OF EVOLUTION
Two – FOSSIL EVIDENCE
Fossil age can be determined through
radioactive dating
Similarities in anatomy/morphology can be
compared between fossils and similar extant
organisms
Often supports and is supported by other
evidence.
26. EVIDENCE OF EVOLUTION
Three – COMPARATIVE ANATOMY
Homologous Structures
Vertebrate forelimbs
Vestigial Structures
Tailbone in humans
Pelvic bones, hind legs of whales
29. EVIDENCE OF EVOLUTION
Four – COMPARATIVE EMBRYOLOGY
A study of embryos and how they develop.
Closely related organisms go through similar
stages of embryonic development.
Example
All vertebrates (birds, snakes, mammals, fish,
frogs) go through an embryonic stage where they
have gill pouches on the sides of their throats
Figure 15-9, page 291
30.
31. EVIDENCE OF EVOLUTION
Five – MOLECULAR BIOLOGY
compare amino acid sequences of proteins
compare DNA/RNA
Mitochondrial, ribosomal
All organisms have nucleic acids made up of the same
kinds of molecules, universal!!!
Humans and even the simplest prokaryotes share
some genes/proteins in common.
Example – Cytochrome C, a protein involved in
aerobic respiration.
NOTE: very similar DNA = very closely related
32. Direct Evidence of Intraspecies
Evolution
Selective breeding in animals
Selective breeding in plants, especially crops
Guppies (Poecilia reticulata) of South
America and Trinidad
http://www.pbs.org/wgbh/evolution/sex/guppy/low_bandwidth.html
34. COEVOLUTION
Species closely associated with each other
evolve together
Example
Long-nosed fruit bat and the flowers on which
they feed
35. CONVERGENT EVOLUTION
Distantly related species evolve in similar
ways due to similar environment.
Example – Sharks and Porpoises
Morphologies are adapted to life in the water
and are very similar.
Analogous structures are associated w/
convergent evolution
36. DIVERGENT EVOLUTION
Closely related species become more and
more dissimilar
Can result in a new species
ADAPTIVE RADIATION
Many related species evolve from a single
ancestor
Galapagos Finches – likely related to food
ARTIFICIAL SELECTION (selective breeding)
Domesticated dogs
37. Genetic Equilibrium
Population Genetics
Study of evolution from a genetic point of view,
i.e. traits
POPULATION-smallest unit which may evolve
Bell curves
When graphed, many traits within a species
take on the shape
Indicates high # of individuals in the middle
(average) with fewer #’s at either extreme
(high or low) for a given trait.
Many polygenic, quantitative traits show this
type of distribution
38.
39. Genetic Equilibrium
Punnett’s square’s allow genotype and
phenotype predictions for a new generation of
offspring from a parent gene pool
Recall that from one generation to the next
genotype and phenotype (gene pool) vary
greatly.
In nature, gene pools tend to remain stable
more than in the finite example we have
looked at.
40. Genetic Equilibrium
Hardy-Weinberg Genetic Equilibrium
Allele frequencies in a population tend to
remain the same from generation to
generation unless acted on by outside
influences
Based on an “ideal” population (hypothetical)
41. Hardy-Weinberg Equilibrium
1. No net mutations occur (no change due to
mutation)
2. Individuals do not enter or leave population
3. Large population (infinitely)
4. Random mating required
5. Selection does not occur
More than anything, allows us to consider
forces which may disrupt equilibrium and as
a result, drive evolution
42. Disruption of Genetic Equilibrium
Mutations
Caused by outside factors
Migration
No immigration or emigration from population
Genetic Drift
Random chance affects allele frequency (more
likely in small populations)
Nonrandom Mating
Humans violate with assortative mating
Animals violate by mating by geographic
proximity
43. Disruption of Genetic Equilibrium
Natural Selection
Stabilizing selection – individuals with
average form of trait have highest overall
fitness for environment
Directional selection – individuals with an
extreme form of a trait have better fitness for
environment
Disruptive selection – individuals with either
extreme of a trait have better fitness than
individuals with average form
Sexual selection – mating based on certain
traits , only genes of reproducers are
important in evolution
44.
45. Speciation
The process of species formation
Species – single type of organism capable of
producing fertile offspring in nature
Occurs with a disruption in genetic
equilibrium, often a form of isolation
Geographic isolation
Physical separation
Reproductive isolation
Prezygotic isolation
Postzygotic isolation