1. River Dell High School Biology
ORIGIN OF LIFE Theories Past and Present Nature of Early Cells Evolution of Cells
River Dell High School Biology

2. Main QUESTIONS
What is evolution and how do we determine evolutionary relationships?
Where does variation come from and what role does it play in evolution?
Is there one best way to be?
Which wolf activity…
Describe your wolf (physically and behaviorally)
What is good about it?
What are its disadvantages?

3. EVOLUTION
The idea that over time things change in response to the environment.
Variation is at the heart of evolution because there is no one best way to be all the time.
Where does this variation come from?
Meiosis
Sexual reproduction
Crossing over and independent assortment
mutations

4. EVIDENCE
The evidence we gather to determine these evolutionary relationships come from observing the similarities and differences of and today’s living organisms and those that used to be living.

5. I. Evidence of Evolution A. Fossils
1. Definition - trace or remains of
organisms that are preserved
2. types
a. mold (rock imprint)
b. cast (mold that is filled)
c. petrified (converted into stone/mineral)
d. preserved in amber or tar pits

6. Mold Fossil Cast Fossil
Fossil in Amber Petrified Wood

7. Dinosaur Fossils Toe of a Dinosaur

8. I. Evidence of Evolution A. Fossils
3. location
a. sedimentary rock
b. amber or tar pits
4. distribution
a.Law of Superposition(Steno )
1) relative age
2) absolute age
b. Biogeography (study of location of organisms around the world)

9. Fossils Are Found in Tar Pits

10. Sedimentary Rock Showing Layers
Law of Superposition – younger fossils are closer to the surface – older fossils are deeper
Sedimentary Rock Showing Layers

11. IV. Radioactive Decay and Dating
A. Isotope – atoms of the same element that differ in the number of neutrons
B. Radioactive decay – process in which unstable nuclei release particles and/or energy until they are stable
C. Half-life – the length of time it takes for ½ any amount of a radioactive isotope to decay

12. Half-lives 256 14C atoms at time 0 ---------------------------
128 14C and
128 14N atoms
after 5,600 years or
1 half-life
64 14C and
192 14N atoms
after 11,200 years or
2 half-lives

13. Half-lives 32 14C and 224 14N atoms after 16,800 years or 3 half-lives
16 14C and
240 14N atoms
after 22,400 years or
4 half-lives
8 14C and
248 14N atoms
after 28,000 years or
5 half-lives

14. Half-lives 4 14C and 252 14N atoms after 33,600 years or 6 half-lives
2 14C and
254 14N atoms
after 39,200 years or
7 half-lives

15. 500 C-14 atoms will remain (1/2 original amount)
The half-life of C-14 is 5,600 years and a sample today has 1,000 C-14 atoms, after 5,600 years 
500 C-14 atoms will remain (1/2 original amount)
After two half lives (11,200 years) 
250 C-14 atoms will remain (1/4 original amount)
Proportion of isotope left
1/4
1/8
1/16 1
1/2 3 4 5 2
Half-lives 1

16. I. Evidence of Evolution B. Comparative Anatomy
1. homologous structures
a. similar structure, evolution,
development
b. wing, arm, flipper
2. analogous structures
a. similar function
b. wing of a bird and an insect

18. Homologous vs Analogous Structures

19. I. Evidence of Evolution B. Comparative Anatomy
3. vestigial structures
a. useful in past organisms but not
now
b. appendix, tail vertebrae,
ear muscles

20. Vestigial Structures Appendix in Humans Leg Bones in a Whale

21. I. Evidence of Evolution C. Embryology Similarities
1. Haeckel( ) [German]
a. “ontogeny recapitulate phylogeny”
1) embryo undergoes changes
that repeat evolutionary
development

22. Diagram Showing Similarities in Early Stages of Embryo Development

23. I. Evidence of Evolution D. Biochemistry
1. similarity in amino acids in specific
proteins
2. similarity in RNA and DNA base
sequences

24. Comparing Amino Acid Differences of Several Organisms to Humans

25. II. Theories of Evolution A. Lamark (1744-1829)
1. Acquired traits – traits that
develop during one generation
can be passed to the next
generation
2. Law of Use and Disuse – if a trait
is not used it will be lost
“use it or lose it” mentality….

26. Lamarck and Law of Use and Disuse
According to Lamarck the giraffes pictured grew longer necks in order to reach the leaves in taller trees
The longer necks were then passed to the next generation

27. II. Theories of Evolution B. Charles Darwin(1809-1882)
1. Biography
a. Darwin attended medical school
b. studied to be a clergyman
c. 22 years old - signed on
HMS Beagle
1) collect specimens as a naturalist
2) refined data for 21 years

28. Charles Darwin Darwin’s Home

29. HMS Beagle in Sydney Australia Harbor

30. Darwin’s Voyage

31. Darwin’s Finches

32. II. Theories of Evolution B. Charles Darwin(1809-1882)
2. The Origin of Species (1859)
a. Descent with modification
1) all species descend from a
small number of original types
2) there is variation among
organisms

33. II. Theories of Evolution B. Charles Darwin(1809-1882)
b. Modification by Selection
1) environment limits growth of populations
-competition for life’s necessities
-specific traits are selected
2) adaptive advantage
- trait favorable for a given environment
- adaptations make some organisms
more likely to survive than others

34. II. Theories of Evolution B. Darwin’s terms
3) fitness - ability of an organism to
make a genetic contribution to the
next generation
4) natural selection allows individuals
with survival adaptations to pass
traits to offspring

35. II. Theories of Evolution
5) speciation - formation of new species as favorable adaptations accumulate (butterfly- white/black)
6) “survival of the fittest” - those organisms with favorable traits reproduce and pass their traits to future generations

36. Darwin’s theory in a nutshell
Overproduction of Organisms
Variation in organisms
Competition to survive
Some characteristics increase chances for survival and reproduction
These characteristics allow organisms with them (Fit organisms) to reproduce better than others (which will die out and not pass on genes)
Good characteristics will get passed on as organisms “evolve” to have the trait.
Maybe forms new species? (speciation)

37. III. Patterns of Evolution A. Coevolution
1. changes in two or more species
closely associated
2. examples
a. predator and prey
b. parasite and host
c. plants and plant pollinators

38. III. Patterns of Evolution B. Convergent Evolution
1. similar phenotypes are selected (b/c of environment) but ancestors are very different
a. natural selection of analogous
structures because of envir. demands.
2. examples
a. wings in insects and birds
b. fins & shape of sharks, fish, porpoise

39. Examples of Convergent Evolution

40. III. Patterns of Evolution C. Divergent Evolution
1. two or more related populations or
species become more dissimilar
a. speciation - new species may form
2. example geographic isolation
a. brown bear  polar bear

41. III. Patterns of Evolution C. Divergent Evolution
3. adaptive radiation
a. many species evolve from same
ancestor
1) ancestor migrates to different
environments (example) -
Galapagos finches

42. Adaptive Radiation – Darwin’s Finches

43. Beak shape Depends Upon Food Source

44. Adaptive Radiation – Hawaiian Honeycreepers

45. IV. Variation in Populations
A. Distribution of variations
1. graph is a bell curve
B. Natural Selection and Changes in
Populations
1. Stabilizing Selection – favors average
form
2. Directional Selection – average shifts
to one extreme or the other
3. Disruptive Selection – extreme forms
are favored- number of individuals
with the average form is reduced

46. Stabilizing Selection

47. Directional Selection

48. Disruptive Selection

49. V. Speciation and Rate of Evolution
A. Species - organisms that are
morphologically similar and can interbreed to produce fertile offspring
Speciation - process of forming
species

50. V. Speciation and Rate of Evolution A. Species and Speciation
2. Isolating mechanisms that result in
speciation
a) geographic barriers separate populations
1) gene flow stops and natural selection
and genetic drift result in divergence
b) reproductive barriers - prevent breeding
of organisms in the same geographic area

51. V. Speciation and Rate of Evolution B. Rate of Evolution
2. Gradualism (Darwin) - new species arise slowly and continuously through small, gradual changes
3. Punctuated Equilibrium (Steven Gould and Niles Eldredge) - there are long periods (up to millions of years) with little or no change - then there is a short period of rapid change

52. SO WHERE THE VARIATION EVOLUTION ACTS UPON COME FROM
SO WHERE THE VARIATION EVOLUTION ACTS UPON COME FROM??? AND WHAT CAUSES CHANGES IN POPULATIONS OVER TIME??

53. Variation in Populations C. Genetic Sources of Variation
1. Mutations
a) a specific gene mutates in
1/10,0000 gametes
b) thousands of genes in each gamete
c) some mutations in every zygote
d) most mutations are recessive
2. Recombination
a) random meeting of sperm and egg
b) crossing over during meiosis