Charles Darwin & The Theory of Evolution.

1) Consider This…

• “Individual organisms live, reproduce and die. Individuals, however, do not evolve; populations do. Evolution is the change in gene frequency that occurs in a population over time.”

– Audesirk, T. & Audesirk G. Biology – Life on Earth. 4th edition. © 1996

– Population: all the individual members of a particular

species living in a given area.

2) Charles Darwin

• 1831• At only 22 years old, this

British nature lover went for a 5-year cruise onboard her majesty’s Beagle ship.

• He sailed around the world to look at stuff. The most famous stop being the Galapagos islands off the coast of South America.

Biodiversity

VARIATION!

Beaks differ

Abundant babies!!!!!

OVERPRODUCTION!

Blue feet?

ADAPTATIONS ?

3) Darwin’s Notes

• Observation 1:Overproduction – Organisms make more offspring than can survive.

• Observation 2: Resources are Limited.• Conclusion 1: Competition for survival and reproduction among

species.

• Observation 3: Individuals Differ from one another within a species’ population.

• Conclusion 2: Fitness – the most well-adapted individuals from one generation will usually leave the most offspring.

4) Twenty Years Later

• Darwin finally publishes his book On the Origin of Species, sharing his theory of Evolution by Natural Selection (1859).

5) Darwinian Terms

• Natural Selection- Nature selects who stays!!– This is what drives evolution.

• Evolution- change in population genotypes from one generation to the next.– a.k.a. change over time.

• Adaptation- A trait that helps an organism to survive & reproduce (born with it).

• Adaptations are favorable variations.

• Variation- Differences between individuals of the same species.

• Examples: color, shape, size, behavior, chemistry.– Variations come from:

» Mutations. » Meiosis Cross Over (challenge topic)

Populations will have a pool of genes.

• A gene pool is all the genes that occur in a population.

Evolution, part IIEvolution, part II

Oh yea, PROVE IT!Oh yea, PROVE IT!

Introduction:Introduction:

Recall that a scientific theory is Recall that a scientific theory is testabletestable; ; and and explains many observationsexplains many observations..

A A claimclaim must have must have evidenceevidence.. In other words, show sound reason, or be In other words, show sound reason, or be

logical.logical.

So…Show me the So…Show me the proofproof that biological that biological evolution accounts for the evolution accounts for the origin of origin of speciesspecies..

1) Fossils1) Fossils Fossils are the Fossils are the remains of past liferemains of past life

dug up from the earth’s crust. dug up from the earth’s crust. Fossil formation is Fossil formation is rarerare.. Most fossils form in Most fossils form in sedimentary sedimentary

rockrock.. Examples of Fossils:Examples of Fossils:

Bones, teeth, molds, casts, impressionsBones, teeth, molds, casts, impressions.. Because the Earth’s crust is layered Because the Earth’s crust is layered

over time, over time, younger fossilsyounger fossils are are found closer to the top.found closer to the top.

1a) Fossil Record1a) Fossil Record

If you piece together If you piece together all the millionsall the millions of fossils that scientists have dug up of fossils that scientists have dug up and and sequence them by time (sequence them by time (ageage),), you have the Fossil Record.you have the Fossil Record.

How do you know a fossils age?How do you know a fossils age? Relative datingRelative dating

Top vs. Bottom layersTop vs. Bottom layers.. Radioactive datingRadioactive dating

Unstable element decay of nearby rocksUnstable element decay of nearby rocks..

2) Embryology2) Embryology

Looking at the Looking at the early developmentearly development of of one organism and comparing it to one organism and comparing it to another allows scientists to make another allows scientists to make inferencesinferences about their evolutionary about their evolutionary relationship.relationship.

Embryo:Embryo: Not yet born, developing Not yet born, developing multicellular organism.multicellular organism.

Inference:Inference: using clues to make a using clues to make a conclusion.conclusion.

3) Homologous Structures3) Homologous Structures

Definition: Definition: similar structuressimilar structures that that related species have inherited from a related species have inherited from a common ancestor.common ancestor.

Example: Example: dolphin’s flipper, bird’s wing, dog’s legdolphin’s flipper, bird’s wing, dog’s leg..

4) Biochemistry4) Biochemistry

Results from Results from DNA & proteinDNA & protein analysis further support the theory of analysis further support the theory of evolution by natural selection.evolution by natural selection.

5) Class Discussion5) Class Discussion

Which is more likely to form a fossilWhich is more likely to form a fossil Jellyfish or crab?Jellyfish or crab?

Why are there gaps in the fossil Why are there gaps in the fossil record?record?

How do you interpret an evolutionary How do you interpret an evolutionary tree diagram?tree diagram?

6) Summary6) Summary

Evolution by means of natural selection Evolution by means of natural selection explains explains the history of life on earththe history of life on earth. . This claim is supported by an abundance of This claim is supported by an abundance of evidence. evidence.

Key Concepts are:Key Concepts are: Species share Species share common ancestorscommon ancestors.. Descent with modification: (Descent with modification: (perpetual changeperpetual change)) Nature chooses which species stay (Nature chooses which species stay (extantextant) and ) and

which go (which go (extinctextinct).).

7) 7) High SchoolHigh School Challenge Challenge

Describe the role that Describe the role that geographic isolation can play in geographic isolation can play in speciationspeciation..

Speciation = new species formationSpeciation = new species formation.. Research:Research:

Allopatric speciationAllopatric speciation Vicariant vs. founder effect.Vicariant vs. founder effect.

Sympatric speciationSympatric speciation

Darwin’s Work

• 1. Variation: There is Variation in Every Population.2. Competition: Organisms Compete for limited resources.3. Offspring: Organisms produce more Offspring than can survive.4. Genetics: Organisms pass Genetic traits on to their offspring.5. Natural Selection: Those organisms with the Most Beneficial Traitsare more likely to Survive and Reproduce.

The History of Evolutionary Thought

• Plato (Greek philosopher 427-347 B.C.E.)-

• Aristotle (Plato’s student 384-322 BCE)-

Evidence

• Proof– Fossils– Comparative Anatomy– Comparative Embryology– Vestigial Structures– Comparative Biochemistry

High School Challenge

• Lamarck v. Darwin– Who is Jean-Baptiste Lamarck & how did his

take on evolution differ from Darwin’s?

• Hardy-Weinberg equation

• p2+2pq+q2=1; p+q=1