EvolutionThe 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

Ocean

Rain

Atmosphere

Lightning

Volcanoes

Miller and Urey

– Discovered that organic molecules could be made from inorganic

– Organic molecules were produced in the closed system

Endosymbiosis TheoryPossible 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

http://taggart.glg.msu.edu/isb200/HOMOL.GIF

http://www.citruscollege.edu/pic/46/0345l.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• 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

http://www.blog.speculist.com/archives/gem-dna.jpg

Mimio Revie

w

Cladogram

Shows evolutionary relationships based on similarities:•In characteristics•DNA or amino acids

More in common = closer COMMON ANCESTOR

Copy into lab Notebook:

Biochemical Evidence of Evolution

Results

Number of Differences in Amino Acid Sequences

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

• Has offspring with no tail

Actual• Cut off mouse’s 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 selection1. Stabilizing selection2. Directional selection3. 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 LabPurpose: 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.

Length in mmPeanut 1 2 3 4 5 6 7 8 9 10

Length(mm)

Group Data

Length(mm)

16 - 20 21 - 25 26 - 30 31 – 35 36 – 40 41 – 45 46 – 50 51 – 55 56 - 60

Class Data

Variation Lab AnalysisDue 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 environmentwww.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://lpmpjogja.diknas.go.id/kc/a/animal/animal-camouflage-1.jpg

http://3quarksdaily.blogs.com/3quarksdaily/images/wolfe_seal_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?

Make a data table for your group and for the class data.

Macaroni Rubber Bands Paper Clips Toothpicks

Spoon

Scissors

Tweezers

Clip

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 occur1.Geographic isolation2.Reproductive isolation3.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 ways1. populations become different in reproductive

(courtship) behavior and stop reproducing2. 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 finchesHawaiian 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://cactiguide.com/graphics/x_noncacti_euphorbia_600.jpg

http://www.milosh.net/photo/usa99/organ1.jpg

How fast does speciation occur?

• 2 timeframes for speciation

1. Gradualism2. 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?

p + q = 1

Color # before selection

Frequency before selection

# after 1st selection

Frequency after 1st selection

# after 2nd selection

Frequency after 2nd selection

Blue (p)

Clear (q)

Total

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?