Evolution, Population Genetics, Speciation, and Phylogeny: Study Guide

Study Guide - Smart Notes

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Evolution is the process by which populations of organisms change over generations. It includes both microevolution (small-scale changes within a species) and macroevolution (large-scale changes that can result in new species).
Microevolution: Changes in allele frequencies within a population over time.
Macroevolution: Broad patterns of evolutionary change above the species level.

Cuvier: Advocated catastrophism, explaining fossil record changes by sudden events.
Lyell: Proposed uniformitarianism, suggesting geological processes are consistent over time.
Lamarck: Suggested inheritance of acquired traits, which was later disproven.
Malthus: Argued that populations grow faster than resources, influencing Darwin’s ideas on competition and survival.
Darwin: Synthesized these ideas into the theory of natural selection.

Natural selection is the process where organisms better adapted to their environment tend to survive and produce more offspring.
Evidence for evolution includes fossil records, comparative anatomy, embryology, and molecular biology.
Examples: Darwin’s finches show adaptive radiation; antibiotic resistance in bacteria demonstrates ongoing evolution.

Comparative embryology: Studies similarities in embryonic development across species.
Molecular biology: Examines genetic similarities and differences.

Hardy-Weinberg equilibrium describes a population that is not evolving. The allele and genotype frequencies remain constant from generation to generation.
Conditions: No mutation, random mating, no natural selection, extremely large population size, no gene flow.
Equation: (where p and q are allele frequencies)

Genetic drift: Random changes in allele frequencies, especially in small populations.
Gene flow: Movement of alleles between populations.
Bottleneck effect: Sharp reduction in population size affects allele frequencies.
Founder effect: New population started by a small group, leading to different allele frequencies.

Biological species concept: Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.
Strengths: Focuses on reproductive isolation. Weaknesses: Not applicable to asexual organisms or fossils.

Prezygotic barriers: Prevent mating or fertilization (e.g., habitat, temporal, behavioral isolation).
Postzygotic barriers: Prevent hybrid offspring from developing into viable, fertile adults (e.g., hybrid inviability, hybrid sterility).
"Nesting doll" hierarchy: Organize barriers from broadest (prezygotic) to most specific (postzygotic).

Allopatric speciation: Occurs when populations are geographically separated.
Sympatric speciation: Occurs without geographic separation, often via polyploidy or habitat differentiation.

Gradualism: Species evolve slowly and steadily.
Punctuated equilibrium: Species remain unchanged for long periods, interrupted by brief, rapid changes.

Fossils provide evidence for the history of life and evolutionary transitions.
Stratigraphy: Study of rock layers to date fossils and reconstruct evolutionary history.

Steps for abiogenesis: Formation of simple molecules, polymerization, formation of protocells, origin of self-replicating molecules.
RNA world hypothesis: RNA was likely the first genetic material due to its ability to store information and catalyze reactions.

Phylogenetic tree: Diagram showing evolutionary relationships among species.
Systematics: Study of biological diversity in an evolutionary context.
Monophyletic group: Includes ancestor and all descendants.
Paraphyletic group: Includes ancestor and some descendants.
Polyphyletic group: Includes unrelated organisms from different ancestors.

Homologous characters: Traits inherited from a common ancestor.
Analogous characters: Traits that evolved independently due to similar selective pressures.

Group Type	Definition	Example
Monophyletic	Ancestor and all descendants	Mammals
Paraphyletic	Ancestor and some descendants	Reptiles (excluding birds)
Polyphyletic	Unrelated organisms	Marine mammals and fish