The change in a population’s genetics over time

• 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

• Redi- tested the spontaneous generation hypothesis-1668
– Discovered that rotting meat does NOT produce maggots
– Thought this only applied to large organisms, not microbes

• Pasteur- demonstrated that microorganisms are not spontaneously generated
The Control:
The Experiment:

• 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

• 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

• Tested Oparin’s hypothesis
Lightning
Atmosphere
Rain
Volcanoes
Ocean

– Discovered that organic molecules could be made from inorganic
– Organic molecules were produced in the closed system

Possible evolution of mitochondria (aerobic organisms) and chloroplasts (plants) http://faculty.ircc.edu/faculty/tfischer/images/endosymbiosis.jpg

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

• Anatomy:
– Homologous Structures
• Same structure, different function
• Ex. Bones of human, whale, crocodile
– Analogous Structures
• Same function, different structures
• Ex. Bird wings, butterfly wings
– Vestigial Structures http://taggart.glg.msu.edu/isb200/HOMOL.GIF
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

• 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

• Biochemistry
– Compare DNA and proteins
– More common points = close relationship
Mimio
Review http://www.blog.speculist.com/archives/gem-dna.jpg

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 Chimpanzee Gorilla Other
0 Human
Chimpanzee
Gorilla
Other
0
0
0

• 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.

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…

Expected
• Cut off mouse’s tail
• Has offspring with no tail
Actual
• Cut off mouse’s tail
• All offspring have tails!!!

• “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

• Variation already exists
• Favorable adaptations = survival
• Avg neck length increases with time

• 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

• Populations evolve through natural selection
• 3 main types of natural selection
1. Stabilizing selection
2. Directional selection
3. Disruptive selection

• Natural selection that favors the average individual

• Favors one extreme variation of a trait
– Ex. the giraffe with the longest neck maybe able to reach more food

• Both extreme variations are favorable
– Ex. light and dark shells blend in, medium are seen and eaten

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
Length
(mm)
7 8 9 10
Length in mm
Class Data
Length
(mm)
16 - 20 21 - 25 26 - 30 31 – 35 36 – 40 41 – 45 46 – 50 51 – 55 56 - 60

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?

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

• 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

• 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

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

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 –

• 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

• 2 populations separated by geography (river, mountain, etc.)
• Cannot cross barrier
• Stop reproducing  become 2 different species
• Ex. mice separated by mountains
Rocky Mountains

• 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

• A common ancestor leads to many variations
• Species fill many niches, cause divergent evolution
• Ex. Galapagos finches
Hawaiian birds
Common Ancestor

• 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 )
600.jpg
rbia_ ho up ti_e cac on /x_n ics aph om/gr e.c
id gu acti p://c htt http://www.milosh.net/photo/usa99/organ1.jpg

• 2 timeframes for speciation
1. Gradualism
2. Punctuated equilibrium
• Both result in new species http://stowa.de/shop/pix/a/z/antea365/b1.jpg

• Species originate gradually through a number of adaptations

• Quick rapid bursts of change (adaptations) followed by periods of stability

Purpose: Will gene frequencies change over time?
Color # before selection
Frequency before selection
# after 1 st selection
Frequency after 1 st selection
# after 2 nd selection
Frequency after 2 nd selection
Blue (p)
Clear (q)
Total p + q = 1

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?