Biology 1A    Sept 22, 1998
Lecture 7 - Evolution

Page Contents :

• Reading Assignment
• Overview of Lecture
• Overview of Lab
• Lecture Outline
• Vocabulary
• Study Questions
• Related Websites

Stern: Chapter 15

Overview of Lecture:

The diversity of life is the result of evolution.
Evolution is descent with modification through time.
Charles Darwin proposed natural selection as the mechanism of evolution.
Evolution since Darwin.

Overview of Lab:

(A bullet indicates a handout.)
• Patterns in Evolution.

A. Life has been, and is, very diverse
1. Reprise: Five Kingdoms
2. Species
a. What are species?
b. How many species are there?
B. This diversity is the result of evolution
1. Evolution is "change through time".
2. Evolution has occurred over a vast span of time
3. Species can change over time
4. Composition of species can change over time.
5. Species can go extinct.
C. Evidence for evolution
1. Fossils provide evidence of evolution
a. A fossil is any evidence of life preserved in the geologic record.
b. Fossil evidence indicates that life has changed over time.
c. Transitional fossils possess a mix of traits from two currently separate groups.
2. Other lines of evidence
a. embryonic development
b. shared morphological features
c. DNA sequences
d. distributions of organisms on Earth

A. Evolution - some common misconceptions
1. Darwin never used this word
a. wasn't in "Origin of Species"
b. meant "progress" in Darwin's time, so he purposely avoided it, since evolution is NOT "progress"
c. Great Chain of Being - idea of levels of perfection; a philosophical and religious idea, NOT a scientific idea.
2. Darwin never referred to "survival of the fittest"
a. social idea published by Herbert Spenser
b. hotly debated in Darwin's time
c. probably influenced capitalism, imperialism, communism, and totaliarianism, but is NOT a scientific idea.
B. is - constantly happening and still going on
1. Evolution is not an existential concept, but can be observed.
2. Is evolution "only a theory"?
a. theory versus hypothesis in science.
b. Evolution is a theory, repeatedly tested and supported by the evidence.
c. some supporting observations
3. Even before Darwin, scientists appreciated that change had occurred.
C. descent - offspring tend to look like parents
D. with modification
1. Children aren't exact copies of their parents
a. There is natural variation in populations
b. This variation results from mutation
c. Variation is the raw material of evolution
d. Populations evolve, individuals cannot.
2. Interaction with the environment removes some of the variation
a. Example: Peppered moths and industrial melanism
b. This is selection
c. Note: Selection acts on phenotypes, NOT genotypes
3. The result of modification is adaptation.
E. through time
1. Most evolution happens over spans of time that are hard to comprehend.
2. geologic time
F. Summary:
1. Genetically determined characteristics of organisms change with time.
2. This change is directed by natural selection.

A. Charles Darwin, England (1809-1882)
1. Studied theology, but loved biology and natural history
2. 1831-1836 Voyage of HMS Beagle
3. 1859 "On the Origin of Species"
B. Observations and ideas that contributed to Darwin's Theory
1. Biological richness of tropical forests
2. Fossils
3. Oceanic islands
4. Biogeography
5. Charles Lyell's "Principles of Geology"
a. Rocks have changed over time.
b. These changes occur according to observable laws.
6. Thomas Malthus -- "prodigality of nature"
7. artificial selection
C. Why is Darwin's work so important?

A. We now know a LOT more than Darwin did; his theory has been expanded accordingly.
B. 1920s-1930s : Modern Synthesis incorporated understanding of genetics into evolutionary theory
C. Scales of evolution
1. microevolution - change at or below the level of a species; results from a change in allele frequency in a population
2. macroevolution - evolution above the level of species
D. Rates of Evolution
1. punctuated equilibrium
2. gradualism
3. Both concepts probably valid; rate may change over time

• What are species? What is the number of species estimated to exist today?
• What is diversity and where does it come from?
• What is evolution?
• What is microevolution? What are some examples of observed microevolution?
• What is macroevolution? What are some examples of macroevolution?
• Can extinct species have living descendants? Do they have to?
• Do species that exist today have to have evolved from other species that exist today?
• What is extinction? How is this different from a mass extinction?
• What is a fossil? Are petrified eggs fossils? preserved trackways? preserved burrows? preserved fungal spores? preserved riverbeds?
• Why is Archaeopteryx such an important disovery?
• Besides fossils, what other lines of evidence support the idea of biological evolution?
• Has evolution ever been observed? Has the theory of evolution been tested? How?
• What is the Great Chain of Being, and why is it not part of evolutionary theory?
• Who published the idea of "survival of the fittest"? Is this concept part of evolutionary theory? Why or why not? Do you think it has influenced evolutionary ideas? How?
• Who published the idea of the "prodigality of nature"? Is this concept part of evolutionary theory? Why or why not? Do you think it has influenced evolutionary ideas? How?
• Who published the idea that the Earth itself has changed over time according to observable laws? Is this concept part of evolutionary theory? Why or why not? Do you think it has influenced evolutionary ideas? How?
• Can an individual evolve to better suit its environment? Why or why not?
• What must exist in a population before evolution can occur?
• What is an adaptation? What is a "preadaptation"?
• Explain what happened to the peppered moths in England at the time of the Industrial Revolution? Is this an example of evolution?
• What is geologic time, and why is it important?
• How did the distribution of living organisms on Earth influence Darwin's concept of evolution?
• Why is Darwin's work so important?
• What additions have been made to evolutionary theory since Darwin published "On the Origin of Species"?
• What is creationism? Is creationism science? Why or why not?

• The talk.origins Archive, especially the FAQ file
• UCMP - Enter Evolution: The History of an Idea (Biographies of people who contributed to evolutionary ideas)
• UCMP - Tours Through Time