Evolutionary Mechanisms

• Natural Selection: Organisms with advantageous traits thrive and reproduce more successfully.
• HWE (Hardy-Weinberg Equilibrium): Absence of evolution in a population due to no gene flow, random mating, lack of natural selection, and a large population size.
• Mutation: Alterations in DNA introduce new traits.
• Genetic Drift: Random shifts in allele frequencies within a population.
• Homologous Structure: Similarity in body parts among different animals due to shared ancestry.
• Convergent Evolution: Development of similar traits in unrelated animals, often from different geographical locations or evolutionary lineages.
• Balanced Polymorphism: Maintenance of two or more phenotypes in a population through natural selection.
• Macroevolution: Large-scale evolutionary changes in species over extended periods.
• Bottleneck Effect: Significant reduction in population size.
• Founder Effect: Establishment of a new population by a small number of individuals.

Sexual Selection

• Traits that increase an animal's likelihood of finding a mate.

Speciation

• Allopatric Speciation: Formation of new species due to geographic isolation.
• Sympatric Speciation: Species formation without geographic isolation.
• Parapatric Speciation: Speciation in partially isolated populations experiencing distinct selective pressures.
• Reproductive Isolation: Mechanisms preventing interbreeding between different species.
• Prezygotic Isolation: Mechanisms preventing fertilization.
• Postzygotic Isolation: Mechanisms occurring after fertilization.
• Hox Genes: Genes regulating body plan and development in animals.
• Cladogram: Diagram illustrating evolutionary relationships among species.
• Heterochrony: Evolutionary changes in the timing or rate of development.
• Gene Flow: Transfer of genetic material between populations of the same species, increasing genetic variation.
• Allele Frequency: The proportion of different alleles (e.g., BB, Bb, bb) in a population.
• Genotype: The specific combination of alleles an individual carries.
• Phenotype: Observable traits influenced by genotype and environment.
• Directional Selection: Natural selection favoring a single phenotype.
• Stabilizing Selection: Natural selection maintaining constant allele frequencies.
• Frequency Dependent Selection: Fitness of a phenotype depends on its prevalence in the population.
• Positive Frequency Dependent: Common traits have higher survival rates.
• Negative Frequency Dependent: Rarer traits have higher survival rates.
• Linnaean Taxonomy: A hierarchical system for classifying organisms (kingdom, phylum, class, order, family, genus, species).
• Transitional Fossils: Fossils showing traits of both ancestral and descendant groups.
• Speciation: Process by which new species evolve from a common ancestor.
• Artificial Selection: Selective breeding of organisms for desired traits.
• Gene Duplication: Process where genes are copied, resulting in multiple copies of the same gene.
• Autopolyploidy: Multiple sets of chromosomes from the same species.
• Allopolyploidy: Multiple sets of chromosomes from different species, often through hybridization.
• Behavioral isolation: Differences in mating behaviors prevent interbreeding.
• Reduced hybrid viability: Hybrid offspring fail to survive or develop properly.
• Reduced hybrid fertility: Hybrid offspring are sterile.
• Mechanical isolation: Physical incompatibility prevents mating.
• Habitat isolation: Species live in different environments.
• Temporal isolation: Species breed at different times.
• Mechanical isolation: Incompatible reproductive organs prevent mating.
• Gametic isolation: Sperm and egg cannot fuse.
• Gene regulation: Mechanism controlling which genes are expressed in cells.
• Balancing Selection: Maintains multiple alleles at a gene locus within a population.
• Coevolution: Two species evolve in response to each other (e.g., predator and prey).
• Adaptation: A trait improving a species' survival in its environment (e.g., camouflage).
• Neutral Evolution: Evolution driven by chance events with no impact on survival.
• Punctuated Equilibrium: Rapid evolutionary bursts followed by long periods of stasis.
• Genetic Recombination: Gene mixing during reproduction creates new combinations in offspring.
• Exaptation: A trait evolves for one purpose and is later co-opted for another (e.g., feathers for temperature regulation evolving into flight).
• Gene Pool: Total collection of genes and alleles in a population.
• Molecular Evolution: DNA changes over time driving genetic-level evolution.
• Speciation Genes: Genes facilitating new species formation by preventing interbreeding.
• Monophyletic: Includes an ancestor and all its descendants.
• Paraphyletic: Includes an ancestor but not all its descendants.
• Polyphyletic: Includes unrelated species without their common ancestor.
• Orthologous Gene: Same gene in different species due to speciation.
• Paralogous Genes: Duplicated gene within the same species.
• Outgroup: A closely related species not part of the group being studied.
• Molecular Clocks: Using DNA to estimate when species diverged.