BIO 151 – Chapter 22: Evolution Theory and Natural Selection

What did Plato's typological view say about species?

Species are fixed; variation is deviation from a perfect type.

What was Aristotle's Scala Naturae?

A fixed hierarchy of organisms arranged by complexity.

What two ideas defined Lamarck's evolution theory?

Use/disuse and inheritance of acquired traits.

What did Weismann's mouse-tail experiment test?

Whether acquired traits could be inherited.

What is biogeography?

Study of how organisms differ across geographic locations.

How did Buffon's observations of similar body structures among quadrupeds challenge the idea that species were completely separate and fixed?

That these modern quadrupeds may have arise from a smaller amount of ancestral forms, anticipating the idea of common ancestry.

What evidence did Cuvier provide?

Fossils showed that species can become extinct.

What is uniformitarianism?

Small geological changes accumulate over long periods.

How did Lyell influence Darwin?

He showed that gradual change over vast time can create major effects.

What is Smith's Principle of Faunal Succession?

Characteristic fossils occur in predictable rock layers.

What did Darwin notice about fossils and living species?

Extinct forms often resembled living species from the same region.

What is a transitional species?

A form with features intermediate between ancestral and later groups.

What is a vestigial trait?

A reduced trait resembling a functional trait in related species.

What are homologous traits evidence for?

Common ancestry.

What three levels of homology are in the slides?

Genetic, developmental, and structural.

What is Darwin's "descent with modification"?

Populations change over time and species share common ancestors.

What replaced typological thinking in evolutionary theory?

Population-level thinking.

What are Darwin's four postulates for evolution by natural selection to occur?

Variation of traits, heritability of said traits, variable success resulting from said traits, and nonrandom survival/reproduction.

What does biological fitness mean?

Relative reproductive success compared with other phenotypes.

Is the longest-living organism automatically the most fit?

No. Fitness depends on reproductive success in its environment.

What does natural selection require to cause evolution?

Heritable variation plus differential reproductive success.

Does selection act on individuals or populations?

Individuals.

Does evolution occur in individuals or populations?

Populations.

Why is natural selection not Lamarckian?

Individuals don't change alleles because they need a trait.

Acclimatization vs. adaptation?

Acclimatization is individual change; adaptation is heritable population change.

Is evolution goal-directed?

No. Mutations arise without regard to what organisms need. Natural selection is nonrandom, but it can only act on heritable variation that already arises; it does not anticipate future needs or work toward a predetermined goal.

Is evolution always progressive toward complexity?

No. Traits and complexity can be gained or lost.

What caused antibiotic resistance in the TB case?

An rpoB point mutation altered RNA polymerase and conferred resistance.

How did antibiotics drive evolution in the TB population?

Susceptible cells died; resistant mutants survived and reproduced.

What happened to Daphne Major finches during the 1977 drought?

84% died, and survivors had greater average beak depth.

Did individual finches grow larger beaks during the drought?

No. Birds with certain beaks survived more; population averages changed.

What can constrain evolution?

1. Genetic Constraints: evolution can only act on genetic variation that exists/arises

2. Historical Constraints: organisms inherit an existing body plan from their ancestors; evolution must modify that.

3. Fitness trade-offs: improving one trait can come at a cost to another.

Why can lack of genetic variation limit adaptation?

Selection can only act on available heritable variation.

What did Belyaev select for in the farm-fox experiment?

Tameness toward humans.

What happened as tame foxes were bred repeatedly?

Tameness increased and dog-like traits appeared within generations.

Why swap tame and aggressive fox kits between mothers?

To separate genetic effects on tameness from rearing environment.