Evolution Slideshow

Evolution: Chapter 7

• Adaptation:
• A structural, behavioral, or physiological trait that enhances survival and reproduction (e.g., hibernation).
• Mimicry: Directional selection can favor individuals resembling something harmful or non-threatening.
• Variation:
• Differences among individuals (structural, functional, or physiological).
• The environment determines if a variation is positive, negative, or neutral.
• Example: Peppered moths adapting to environmental changes.
• Artificial Selection:
• Humans apply selective pressure to modify traits (e.g., purebred dogs, crop varieties).
• Mutations:
• Permanent, random changes in DNA during replication.
• The only source of new genetic variation.
• Selective Advantage:
• A genetic trait improving survival in a changing environment.
• Example: Antibiotic-resistant bacteria reproduce quickly, passing on resistance genes.
• Selective Pressure:
• Environmental conditions that favor certain traits while disadvantaging others.
• Natural Selection:
• Populations change as individuals with advantageous traits survive and reproduce.
• Two steps:
• i. Variation in the population.
• ii. Non-random survival and reproduction.

Evolution: Chapter 8

• Charles Darwin:
• Natural selection theory: traits suited to the environment are passed on.
• Georges-Louis Leclerc:
• Proposed species can change over time and Earth is older than 6,000 years.
• Thomas Malthus:
• Overpopulation leads to competition for limited resources.
• Charles Lyell:
• Advocated for uniformitarianism (gradual processes shape Earth).
• Jean-Baptiste Lamarck:
• Inheritance of acquired traits (discredited).
• Georges Cuvier:
• Developed paleontology; proposed catastrophism (extinctions due to events like floods).
• Darwin and Wallace:
• Co-proposed the theory of natural selection.

Evolution: Chapter 8

• Evidence for Evolution
• Fossil Records:
• Show evolutionary history and extinct species.
• Anatomy:
• Homologous structures: Similar origin, different functions.
• Analogous structures: Different origin, similar function.
• Embryology:
• Early developmental similarities among species suggest common ancestry.
• Biogeography:
• Study of species distribution over time and space.
• DNA Evidence:
• Genetic analysis reveals relationships between species.

Evolution: Chapter 9

• Mutation:
• Increases variation within a population.
• Gene Flow:
• Movement of alleles between populations via migration and interbreeding.
• Non-random Mating:
• Mating based on traits or genetic relatedness (e.g., inbreeding).
• Genetic Drift:
• Random changes in allele frequency, especially in small populations.
• Founder Effect: New population formed by few individuals.
• Bottleneck Effect: Reduced genetic diversity after a population crash.
• Natural Selection Types:
• Stabilizing: Favors the average trait.
• Directional: Favors one extreme trait.
• Disruptive: Favors both extremes over intermediates.
• Sexual Selection:
• Traits evolve to enhance mating success.

Evolution: Chapter 9

• Reproductive Isolation:
• Prevents gene flow, leading to new species.
• Pre-Zygotic Barriers: Prevent mating or fertilization. Examples:
• Behavioral (different courtship).
• Temporal (different mating times).
• Mechanical (incompatible anatomy).
• Post-Zygotic Barriers: Fertilization occurs, but offspring are inviable or sterile.
• Sympatric Speciation:
• New species arise within the same geographic area due to genetic differences.
• Allopatric Speciation:
• Geographical isolation leads to speciation through independent evolution.
• Adaptive Radiation: Diversification of one species into multiple adapted forms.
• Evolutionary Patterns
• Divergent Evolution:
• Species from a common ancestor become increasingly distinct.
• Convergent Evolution:
• Unrelated species develop similar traits due to similar environments.
• Gradualism:
• Evolution occurs slowly and steadily.
• Punctuated Equilibrium:
• Long periods of stasis interrupted by bursts of evolutionary change.