Evolution occurs through natural selection, where organisms better adapted to their environment are more likely to survive and pass on their traits. The evidence for evolution includes fossils showing gradual changes over time, similarities in anatomy across species, and molecular comparisons showing closer genetic relatedness between more closely related organisms. Disruptions to genetic equilibrium such as mutations, genetic drift, and natural selection can drive evolutionary changes within populations over many generations.

1. Evolution
An Introduction

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

3. The Origin of Life
What the heck happened?

4. BANG!!!!!!!!!

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

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

13. Prokaryote → Eukaryote

14. First Eukaryotes

15. Theories and Evidence

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

21. A Phylogenetic Tree

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

28. Human Vestigial Structures

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

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

33. Patterns of Evolution

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

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

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