Chapter 18: Evolution and the Origin of Species Flashcards
Define natural selection and provide an example of directional selection.
Natural selection is the process where organisms better adapted to their environment tend to survive and reproduce.
Example: Peppered moths in industrial areas (dark moths became dominant due to pollution).
How does genetic drift differ from gene flow?
Genetic drift: Random changes in allele frequencies (e.g., founder effect in isolated populations). Gene flow: Transfer of alleles between populations via migration (e.g., pollen dispersal between plant populations).
What role do mutations play in evolution?
Mutations introduce new genetic variation, providing raw material for natural selection.
Example: antibiotic resistance in bacteria.
Compare allopatric and sympatric speciation.
Allopatric: Geographic isolation splits a population (e.g., Darwin’s finches on different Galápagos islands). Sympatric: Speciation without geographic barriers (e.g., polyploidy in plants like wheat).
What are prezygotic and postzygotic reproductive barriers? Give examples.
Prezygotic: Prevent mating/fertilization (e.g., temporal isolation in mating seasons of cicadas). Postzygotic: Reduce hybrid fitness (e.g., mule sterility).
How do fossil records support evolutionary theory?
Fossils show transitional forms and chronological changes in species.
Example: Tiktaalik linking fish to tetrapods.
Explain homologous vs. analogous structures.
Homologous: Shared ancestry, different functions (e.g., human arm vs. whale flipper). Analogous: Similar functions, different origins (e.g., bird wings vs. insect wings).
How does molecular biology provide evidence for evolution?
DNA/protein sequence comparisons reveal evolutionary relationships.
Example: cytochrome c in humans/chimpanzees.
Contrast Lamarck’s inheritance of acquired traits with Darwinian natural selection.
Lamarck: Traits acquired during life are inherited (e.g., giraffes stretching necks). Darwin: Heritable traits favoring survival/reproduction become common over generations.
What is the modern synthesis of evolution?
Integrates Darwinian selection with Mendelian genetics and population genetics.
Example: Hardy-Weinberg equilibrium.
What is a cladogram, and how is it constructed?
A cladogram diagrams evolutionary relationships using shared derived traits.
Example: presence of feathers grouping birds.
Define convergent evolution and give an example.
Unrelated species evolve similar traits due to similar environments.
Example: sharks and dolphins developing streamlined bodies.
Describe key milestones in hominin evolution.
Sahelanthropus tchadensis (6–7 mya, bipedalism). Homo habilis (2.4 mya, tool use). Homo sapiens (300,000 ya, complex culture).
How do genetic studies support the ‘Out of Africa’ hypothesis?
Mitochondrial DNA and Y-chromosome data trace modern humans to a common ancestor in Africa ~200,000 years ago.
How does evolution explain antibiotic resistance?
Overuse of antibiotics selects for resistant bacterial strains.
Example: MRSA via mecA gene mutations.
What is evolutionary medicine?
Applies evolutionary principles to understand diseases.
Example: mismatch between modern diets and ancestral adaptations causing obesity.
Why is the teaching of evolution controversial in some regions?
Conflicts with religious/cultural beliefs.
Example: creationism vs. natural selection in U.S. schools.
How can evolutionary biology aid conservation efforts?
Identifying evolutionary significant units (ESUs) helps prioritize genetically unique populations for protection.
How did the evolution of lactose tolerance in humans occur?
Natural selection favored lactase persistence in populations with dairy farming.
Example: high frequency in Northern Europeans.
How is molecular clock analysis used in evolutionary studies?
Estimates divergence times between species based on mutation rates.
Example: dating human-chimp split to ~6–7 mya.
