Idea of Evolution

• Species of living things change over time

• Under the right circumstances this change can produce new species of living organisms from existing ones

Before Darwin

Theology played a major role in thought. Christian Bible accepted as literal truth and was used for knowledge of the natural world.

All life, and existence itself, were a simultaneous creation of a supernatural being (God).

Emergence of Evolutionary Thought

• Sequence of Fossil Types

• Existence of Rudimentary Organs

• Evidence of Common Underlying Plan

• Facts of Animal & Plant Breeding

• Struggle for Existence

• Evidence of New Explorations

Sequence of Fossil Types

By 18th century fossils recognized as remains of critters that had become extinct or still existed but in different forms. In other words, living things changed.

Rudimentary Organs

Non-functional eye bulbsIn cave-dwelling salamanders

Pelvis & femur in whalesCheck out the article on whale evolution at:

http://www.edwardtbabinski.us/whales/evolution_of_whales/

If organisms were created "de novo,"

why do they retain these vestiges?

Common Underlying PlanAll mammals’ forelimbs are constructed on a similar anatomical plan due to a SHARED ANCESTRY.

Animal & Plant Breeding

Starting with the ancestral rock pigeon (middle), Darwin produced a wide variety of morphologically distinct types in a few generations by selective breeding.

Struggle for ExistenceThe elephant, one of the slowest breeders in the animal kingdom, could take over the planet if it reproduced unhindered for long enough. Even if after only 500 years, one pair would leave 15 MILLION descendants. So why aren’t there at least 15 million elephants?

Evidence of New Explorations

Ideas That Shaped Darwin’s Thinking

• Georges-Louis de Buffon (1707-1788): Uniformitarianism

• James Hutton (1726-1797): Founder of modern geology; geological forces worked very slowly, thus earth very, very old

• Charles Lyell (1797-1875): Principles of Geology; Formalized uniformitarianism; Stimulated Darwin: if earth changed over time, what about life?

Uniformitarianism

Mt VesuviusC.E. 79; last time 1944

Mt. St. Helens15 eruptions in last 4000

years

SF QuakeC.E. 1906

PinnaclesBegan as a volcano that first erupted about 195 miles south of its present location. It has traveled northward along the San Andreas Fault, and currently moves at a rate of about 2 - 3 cm/year.

Oxbow Lakes

Geological Forces Work Slowly

Marine terraces north of Santa Cruz.

Coastal uplift: 5 mm/yr

Mt. EverestUplift: 10mm/yr

Pre-Darwin Explanation of Evolution

• Jean-Baptiste de Lamarck (1744-1829)– Plants / animals adapted to their

environments

– When environment changes (as the geological record shows), organisms must change if they are to continue to exist

– Organisms change because they WANT or FEEL A NEED to change

– Inheritance of Acquired Characteristics

Acquired Characteristics

Darwin’s Explanation for Evolution

• We’re not created equal (variations in phenotypes & genotypes)

• Limited stuff (finite resources)

• Produce more offspring than finite resources can support

• Struggle for existence

• Favorable vs. unfavorable traits (relative to the environment)

• Inheritance

Not Created EqualOver the past 200,000 years or so, natural selection favored subtle variants allowing different human populations to adapt to their different environments.

Limited Stuff

Too Many BabiesToo Few Resources

Struggle For Survival

Favorable vs. Unfavorable Traits

Variants best adapted to conditions of life are most likely

to survive & reproduce

Over time, favorable traits increase, less favorable traits

decrease

Darwin’s Conclusions

• Nature an open-ended process of becoming: life continually evolves

• Emergence of new species: result of Descent with Modification

• Evolution NOT a single line of ascent but an irregularly branching tree (adaptive radiation)

Darwin vs. Lamarck

Descent With Modification

The Genetic Code

•Life has the same underlying genetic code

•DNA sequences of organisms are similar

Evolution

A change in the relative frequencies of alleles in a

population from one generation to the next

HOW DOES EVOLUTION WORK?

• Natural Selection

• Mutation

• Genetic Drift

• Gene Flow