Evolution I: Historical Perspective

Course Details: Evolution I: Historical Perspective, Dr. Buchheim, Office Hours: 2:00-4:00, Room 04300.
Course Structure: 4 exams, no cumulative final, no quizzes.
Study Recommendations: Review PowerPoint presentations and avoid reliance solely on Quizlets. Importance of reorganizing notes emphasized.

Paradigm Shift: The evolution of biology as a scientific discipline.
Youngest Science: Evolution is noted as one of the latest fields of scientific inquiry.
Historical Context of Science:
- Early interpretations of natural phenomena (e.g., solar eclipses) attributed to supernatural causes.
- Human ailments were viewed as spiritual afflictions; shamans were the primary healthcare providers before the advent of medical doctors.

Definition: A scientific approach that limits itself to natural causes and excludes supernatural explanations.
Implication: Science should not evaluate supernatural claims, leading to debates on whether science disproves the supernatural.
Philosophical Naturalism: The stance that posits the non-existence of the supernatural.

Biology: The study of life; characterized by its methods and approaches.
Methodological Naturalism: A method focused on investigating natural phenomena through observable evidence.
Philosophical Naturalism: The belief that only natural laws and forces operate in the world, denying supernatural influences.

Darwin's Theory of Evolution: Key concepts include:
- The Struggle for Existence: A principle where organisms compete for limited resources.
- Descent with Modification: Species evolve over time through mutations and adaptations leading to changes in traits beneficial for survival.
- Survival of the Fittest: The concept that those best adapted to their environment are most likely to survive and reproduce.

Adaptation: Traits that enhance an organism's fitness—increasing their chances of survival.
Definition of Fitness: The ability of an organism to pass on its genes to the next generation.
Example: Giraffes stretching their necks, a hypothesis that can be tested.
- Both giraffes and humans share similarities in cervical vertebrae (C1-C7).
- Notable differences in traits between species (e.g., Okapia vs. Giraffe).

Characteristics of sexual dimorphism in giraffes, where males exhibit larger shoulder heights due to combat for mates.
Implications of Sexual Selection: Explains why certain traits evolve, influencing mating decisions.

Aristotle: Believed in a fixed hierarchy among species (Scale of Nature).
Thomas Aquinas: Developed Natural Theology, arguing for God's glory seen in the complexity of living beings.
- Argument from Design: Complexity indicates a designer; counterpoints include Hume's critique emphasizing lack of empirical evidence for divine design.

Charles Lyell: Introduced the concept of deep time, suggesting Earth's age is significantly greater than previously thought, through uniformitarianism.
Criticism of earlier evolutionary ideas like Lamarck's ladder of life.
- Common Ancestry: Viewed as foundational in understanding evolutionary development.

Charles Darwin: Notable for his voyage on HMS Beagle (1831-1836) where he observed various species, particularly in the Galapagos Islands.
- Inspired the formulation of Natural Selection amidst concerns over overpopulation (Malthus's principles).
- Published "On the Origin of Species" (1859) outlining his views on descent with modification and natural selection.

Homology: Similar structures indicating common ancestry.
Analogous Structures: Similar functions arising independently (example: wings in birds and insects).
Biogeography: Distribution patterns of species support evolutionary theory (Law of Succession).
Transitional Fossils: Fossils showing traits linking different species, supporting the gradual change through evolution.

Mendel's Work: Essential foundation for understanding heredity and variation although Darwin was largely unaware of Mendel's findings at his time of writing.
Hardy-Weinberg Equilibrium: A principle stating allele frequencies remain constant in a population under certain conditions (no evolution occurring if: large population size, random mating, no natural selection, no migration, no mutation).
- The equation: p^2 + 2pq + q^2 = 1 where p and q are allele frequencies.

Genetic Drift: Random changes in allele frequencies, especially in small populations, leading to loss of genetic diversity.
- Bottleneck Effect: A sharp reduction in the size of a population due to environmental events.
- Founder Effect: Establishment of a new population by a small number of individuals.
Natural Selection: Selection of alleles based on fitness advantages.
Non-Random Mating: Influences genotype frequencies leading to certain traits becoming more or less common in a population.

Stabilizing Selection: Favors intermediate variants over extremes.
Directional Selection: Favors individuals at one end of the phenotype spectrum.
Disruptive Selection: Extremes are favored over intermediate phenotypes.
Sexual Selection: A form of natural selection based on the success of individuals to attract mates.

Definition: Changes in DNA that may result in new traits.
Types of Mutations:
- Point mutations affecting a single base.
- Chromosomal mutations affecting larger segments.
Polyploidy: A condition in which an organism has more than two complete sets of chromosomes, significant in plant evolution.

Biological Species Concept: Populations that can interbreed and produce viable offspring. Challenges include asexual reproduction.
Reproductive Isolation Mechanisms:
- Pre-zygotic barriers (habitat, temporal, behavioral, mechanical) prevent mating or fertilization.
- Post-zygotic barriers (reduced viability, infertility) occur after fertilization.

Relative Dating: Using the Law of Superposition to determine age. Older strata are typically found deeper.
Radiometric Dating: Uses isotopes and their half-lives to determine the absolute age of fossils, aiding in understanding extinction events (e.g., Permian extinction).

Heterochrony: Changes in the timing of development leading to new forms.
Developmental Genetics: Homeobox genes and regulation crucial for anatomical development.

Phylogeny: The evolutionary history and relationship among species, visualized through phylogenetic trees.
Key Taxonomic Ranks:
- Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Monophyly: Groups containing a common ancestor and all its descendants.
Non-monophyletic Groups: Do not contain all descendants of the most recent common ancestor, indicating a more complex evolutionary history.

A comprehensive understanding of evolution integrates ideas from genetics, fossil records, biogeography, and observed natural phenomena to explain the complexity of life on Earth, emphasizing adaptability and change over time.