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Evolution
The change in a population’s genetics over
time
The history of Evolution
• People first thought that life originated by
spontaneous generation
– Nonliving material gives rise to living material
– i.e. that maggots and flies
spontaneously appear in
rotted food
web.utk.edu/.../5rubrics/graphics/04_01.gif
History continued
• Redi- tested the spontaneous generation
hypothesis-1668
– Discovered that rotting meat does NOT produce maggots
– Thought this only applied to large organisms, not microbes
History continued- mid 1800s
• Pasteur- demonstrated that microorganisms
are not spontaneously generated
The Control:
The Experiment:
Biogenesis
• Living organisms can only come from other
living organisms
http://www.historyoftheuniverse.com/images/cell_division.gif
http://www.kingsstilecottage.co.uk/images/lion-with-cubs.jpg
So… Where did life begin?
• Oparin- hypothesized that life began in the ocean from
organic molecules
– Inorganic molecules from volcanoes and evaporation were in
atmosphere
– Lightning storms caused inorganic molecules to fuse – became organic
– (C, H, O)
– Rain washed organic molecules into ocean
– Life began there
http://southdakotapolitics.blogs.com/south_dakota_politics/images/2008/04/20/fertilization2.jpg
Miller and Urey
• Tested Oparin’s hypothesis
Lightning
Atmosphere
Rain
Volcanoes
Ocean
Miller and Urey
– Discovered that organic molecules could be made
from inorganic
– Organic molecules were produced
in the closed system
Endosymbiosis Theory
Possible evolution of mitochondria (aerobic organisms)
and chloroplasts (plants)
http://faculty.ircc.edu/faculty/tfischer/images/endosymbiosis.jpg
Evolution Video
How do we know evolution
happens?
Evidence for evolution
It took Charles Darwin 2 decades to develop his
theory of evolution
What evidences did he look for?
• Fossils-earliest record of life
– Deep are simple, oldest
– Shallow are complex, newest
(in undisturbed rock layers)
http://www.sculpturegallery.com/three/fossil_fish.jpg
Evidence for evolution
• Anatomy:
– Homologous Structures
• Same structure, different function
• Ex. Bones of human, whale, crocodile
– Analogous Structures
http://taggart.glg.msu.edu/isb200/HOMOL.GIF
• Same function, different structures
• Ex. Bird wings, butterfly wings
– Vestigial Structures
http://www.citruscollege.edu/pic/46/0345l.jpg
• Organ with no function today, but worked in the past
• Ex. Pelvic bones in snake, hip bones in whale
http://www.answersingenesis.org/assets/images/articles/ee/v2/whale-vestigial-structure.jpg
Evidence for Evolution
• Embryology
– Study of developing
fetus/baby
– All vertebrates have some
common characteristics
– Ex. Tail bones, gill slits
– Show common origins
apps.carleton.edu/.../photostock/193602.jpg
Evidence for Evolution
• Biochemistry
– Compare DNA and proteins
– More common points = close relationship
Mimio
Review
Cladogram
Shows evolutionary relationships based on similarities:
•In characteristics
•DNA or amino acids
More in common = closer COMMON ANCESTOR
Results
Copy into lab Notebook:
Biochemical Evidence of Evolution
Number of Differences in Amino Acid Sequences
Human
Human
Chimpanzee
Gorilla
Other
Chimpanzee
Gorilla
Other
0
0
0
0
Lab Questions/Analysis
• Sketch a cladogram to show the evolutionary
relationships
• Which organism is most closely related to
humans?
• Explain how you determined this?
• Briefly describe the process of using amino
acid sequences or DNA to determine
evolutionary relationships among organisms.
The Mechanism
How Does Evolution Happen?
Lamarck- Inheritance of acquired
characteristics
• Organisms acquire
adaptations during
lifetime
• Adapt because they
have to
• Use and disuse
– Variation gained during
lifetime
– Giraffe’s neck got longer
through use
– Trait passed on to
offspring
Does variation exist in a population
or is it acquired through a lifetime?
Let’s find out…
Problems with Lamarck
Expected
• Cut off mouse’s tail
Actual
• Cut off mouse’s tail
• Has offspring with no tail
• All offspring have tails!!!
Charles Darwin ~ 1831
• “Father of Evolution”
• Studied in Galapagos Islands
• Developed theory of evolution by natural
selection
– First to propose logical mechanism
– Organisms with favorable traits will survive to
reproduce and pass on traits to offspring
Darwin’s Giraffes
• Variation already
exists
• Favorable
adaptations =
survival
• Avg neck length
increases with time
4 aspects of Natural Selection
• Overproduction – more offspring are born than can survive,
not all survive
• Variation – individuals in a population vary in characteristics
• Competition – organisms with favorable variations survive
and reproduce
• Populations change – over time
favorable traits (inherited traits)
increase in a population
Natural selection
• Populations evolve through natural selection
• 3 main types of natural selection
1. Stabilizing selection
2. Directional selection
3. Disruptive selection
Stabilizing selection
• Natural selection that favors the average
individual
Directional selection
• Favors one extreme variation of a trait
– Ex. the giraffe with the longest neck maybe able to
reach more food
Disruptive Selection
• Both extreme variations are favorable
– Ex. light and dark shells blend in, medium are seen
and eaten
Variation Lab
Purpose: Does variation exist in a population?
You will be given 10 peanuts. Open the shells and measure each shell.
Record the length (in millimeters) of each shell in the data table.
We will make a tally sheet from each group for the class data table.
Group Data
Peanut
1
2
3
4
5
6
7
8
9
Length
in mm
10
Length
(mm)
Class Data
Length
(mm)
16 - 20
21 - 25
26 - 30
31 – 35
36 – 40
41 – 45
46 – 50
51 – 55
56 - 60
Variation Lab Analysis
Due to variation, we need a large sample size (class data).
Analysis:
1. What is the largest peanut shell in the sample?
2. What is the smallest shell in the sample?
3. What is the mean value of shell lengths?
4. What is the mode of shell lengths?
5. Draw a bar graph of the results. Dependent variable
is # of pods, Independent variable is pod size.
6. What is the shape of the curve over the bars of the
graph?
7. What type of selection does this represent?
Adaptations
the process or structure that enables organisms
to become better suited to their environment
www.doe.virginia.gov/VDOE/LFB/glossary/index.html
http://www.lapshin.org/nikita/cacti/Echinocactus-grusonii2.jpg
Adaptations
• Camouflage – ability to blend into surrounding
environment
http://3quarksdaily.blogs.com/3quarksdaily/images/wolfe_seal_1.jpg
http://lpmpjogja.diknas.go.id/kc/a/animal/animal-camouflage-1.jpg
Adaptations
• Mimicry - resembling
another species or
object to hide, for
protection from
predators
http://abc-rags.tripod.com/Peru/StickInsect.JPG
http://mrgrassosclass.com/images/mimicry.gif
Competition Activity
Purpose: Does variation allow for success in
competition for resources?
Macaroni
Rubber Bands
Paper Clips
Toothpicks
Spoon
Scissors
Tweezers
Clip
Make a data table for your group and for the
class data.
Enter Data
Here
Competition Activity Analysis
1. What strategy was used to get the most
food?
2. What variation was best for each type of
food? Use data to support your answer.
3. How does this relate to natural selection?
a) Competition b) Variation c) Overproduction –
How do new species form?
• Speciation- the evolution of new species
– Species can only reproduce with the same species
to produce fertile offspring
• 3 ways for speciation to occur
1. Geographic isolation
2. Reproductive isolation
3. Adaptive radiation
www.bio.indiana.edu/.../broodxmovies/index.htm
Geographic Isolation
• 2 populations separated by geography (river,
mountain, etc.)
• Cannot cross barrier
• Stop reproducing  become 2 different species
• Ex. mice separated by mountains
Rocky Mountains
Reproductive Isolation
• Can occur 2 different ways
1. populations become different in reproductive
(courtship) behavior and stop reproducing
2. Incompatible DNA
• Ex. songbirds with different or incomplete
songs
Adaptive radiation
• A common ancestor leads to many variations
• Species fill many niches, cause divergent
evolution
• Ex. Galapagos finches
Hawaiian birds
Common Ancestor
Convergent Evolution
• unrelated species have similar adaptations
while living in different locations
– Ex. Euphorbia and Organ Pipe cactus: cactus like
plants share fleshy body types and no leaves
(one in deserts of Africa, other in deserts of N. and S.
America)
http://www.milosh.net/photo/usa99/organ1.jpg
http://cactiguide.com/graphics/x_noncacti_euphorbia_600.jpg
How fast does speciation occur?
• 2 timeframes for speciation
1. Gradualism
2. Punctuated equilibrium
• Both result in new species
http://stowa.de/shop/pix/a/z/antea365/b1.jpg
Gradualism
• Species originate gradually through a number
of adaptations
Punctuated Equilibrium
• Quick rapid bursts of change (adaptations)
followed by periods of stability
Fishy Frequency Lab
Purpose: Will gene frequencies change over
time?
Color
# before
selection
Frequency
before
selection
# after 1st
selection
Frequency
after 1st
selection
Blue (p)
Clear (q)
Total
p+q=1
# after 2nd
selection
Frequency
after 2nd
selection
Fishy Frequency Lab Analysis
1. What happened to the frequency of the blue
colored fish? Why?
2. What happened to the frequency of the clear
colored fish? Why?
3. Which colored fish had the advantage
(selected for)? Why?
4. How would Darwin have explained these
results?