Macroevolution, Development, and Molecular Biology Lecture Review

Comprehensive vocabulary flashcards covering macroevolution, speciation models, phylogenetic trees, embryonic development, evolutionary forces, and the molecular mechanisms of transcription and translation.

Speciation

The evolutionary process wherein a lineage or clade splits into two or more distinct groups that are no longer classified as the same, requiring both isolation (reduction in gene flow) and divergence.

Biological Species Concept

A species concept that defines a species as groups of actually or potentially interbreeding natural populations that can successfully reproduce to create fertile offspring.

Morphospecies Concept

A species concept that delineates and classifies distinct species based on observable morphological or phenotypic trait similarities and differences.

Ecological Species Concept

A species concept that defines and delineates a species based on the specific ecological niche and role it occupies in the environment.

Phylogenetic Species Concept

A species concept that defines a species based on common ancestry and relatedness on a phylogenetic tree constructed from molecular and genetic data.

Pre-zygotic Isolation

Barriers to reproduction that prevent mating or fertilization from occurring prior to the formation of a zygote, such as behavioral isolation, temporal differences, or incompatible genitalia.

Post-zygotic Isolation

Barriers to reproduction that take effect after fertilization and zygote formation, including hybrid inviability, reduced hybrid fitness, epistasis inhibiting essential proteins, or hybrid sterility.

Allopatric Speciation

Speciation that takes place when populations become geographically separated from one another in physical space.

Dispersal

A mechanism of allopatric speciation occurring when individuals from one population colonize a distant, isolated location, potentially resulting in peripatric speciation.

Vicariance

A mechanism of allopatric speciation that occurs when a physical or geographic barrier arises within an existing contiguous population, dividing it into isolated groups.

Parapatric Speciation

Speciation occurring when populations are largely separated in physical space but maintain a narrow zone of overlap where they come into contact.

Hybrid Zone

A geographic region where two distinct species overlap and interbreed to produce hybrid offspring.

Sympatric Speciation

Speciation that occurs within populations inhabiting the exact same physical space and spatiotemporal environment, often driven by disruptive selection, mating preferences, or habitat specialization.

Adaptive Radiation

The rapid speciation and divergence of a focal lineage to fill open ecological niches following the relaxation of stabilizing selection, often precipitated by the removal of competitors or colonization of a new habitat.

Co-evolution (Co-speciation)

The reciprocal evolutionary process in which speciation in one closely-interacting organism (such as a host or plant) triggers speciation in its counterpart (such as a parasite or pollinator), producing matching phylogenetic trees.

Phylogenetic Tree

A branching diagrammatic hypothesis describing the evolutionary relationships, common ancestry, and patterns of lineage divergence among taxa.

Node

A branching point on a phylogenetic tree representing the most recent common ancestor of descendant taxa, which can be rotated without changing evolutionary relationships.

Synapomorphy

A shared, derived character state or evolutionary novelty that arose in an ancestor and is shared exclusively among closely related descendant taxa.

Principle of Parsimony

The phylogenetic criterion stating that the tree hypothesis accounting for the data through the fewest evolutionary transitions, gains, or losses is most likely to be accurate.

Homologous Traits

Morphological, anatomical, or genetic traits in different taxa that are similar because they were inherited from a shared common ancestor.

Analogous Traits

Traits that exhibit similar structures or functions across taxa due to convergent evolution rather than common descent.

Totipotent

The developmental potential of an embryonic cell (such as a zygote) to differentiate into any cell type in the body to form an entire organism.

Pluripotent

The developmental potential of an embryonic stem cell to differentiate into any specialized cell type within a given embryonic germ layer.

Multipotent

The developmental capacity of an adult or progenitor stem cell to differentiate into several specific, related cell types.

Master Regulators

Highly conserved regulatory genes that orchestrate the development and differentiation of complex bodily structures by controlling the expression of numerous downstream genes.

Hox Genes

A conserved group of master homeotic genes that encode transcription factors and dictate the specification and development of body segment identities along the anterior-posterior axis.

Life History Traits

Organismal characteristics regarding how resources and energy are invested over a lifespan, encompassing the timing and patterns of growth, survival, and reproduction.

Character Displacement

The evolutionary divergence in the mean value of a morphological or physiological trait within a population in response to natural selection.

Directional Selection

A mode of natural selection that favors individuals displaying one extreme phenotypic value, causing the mean trait value of the population to shift toward that extreme over time.

Stabilizing Selection

A mode of natural selection that favors intermediate phenotypes while selecting against extreme variants, maintaining the trait average and reducing phenotypic variance.

Disruptive Selection

A mode of natural selection that favors individuals at both phenotypic extremes while disfavoring intermediate phenotypes, potentially lowering hybrid fitness and spurring speciation.

Adaptive Landscape

A theoretical multidimensional model that maps population mean fitness against genotypic or phenotypic trait dimensions, illustrating fitness peaks and fitness valleys.

Genetic Drift

Stochastic fluctuations in allele frequencies from generation to generation occurring strictly by chance in finite populations, independent of natural selection.

Genetic Bottleneck

A dramatic reduction in population size and genetic diversity caused by an environmental or anthropogenic event, leaving a surviving gene pool whose allele frequencies differ randomly from the ancestral population.

Gene Flow

The transfer and incorporation of alleles into or out of a population resulting from the physical migration and interbreeding of individuals or their gametes.

Founder Effect

A loss of genetic variation and alteration of allele frequencies occurring when a small number of colonizing individuals establish a new, isolated population away from the original gene pool.

Central Dogma

The foundational principle of molecular biology stating that genetic information flows sequentially from DNA to RNA via transcription, and from RNA to functional protein via translation.

RNA Polymerase

The multi-protein enzyme complex responsible for unwinding DNA and synthesizing a complementary, antiparallel RNA transcript from a DNA template strand in the $5'$ to $3'$ direction.

Promoter

A non-coding regulatory DNA sequence situated upstream of a gene where general transcription factors and RNA polymerase assemble to initiate transcription.

Enhancer

A regulatory DNA sequence bound by transcriptional activator proteins that loops DNA to interact with the mediator complex and promoter, facilitating transcription initiation.

Combinatorial Control

The regulation of eukaryotic gene transcription via specific combinations of multiple activator and repressor proteins binding to enhancer and silencer elements.

Allosteric Interaction

A regulatory mechanism where the binding of a small effector molecule to an allosteric site induces a conformational shape change in a protein, altering its active site and activity.

Epigenetics

Heritable changes in gene expression and transcriptional accessibility caused by modifications to chromatin packaging, histone acetylation, or DNA methylation without altering the underlying nucleotide sequence.

Alternative Splicing

A post-transcriptional eukaryotic process in which the spliceosome arranges exons in variable configurations while excising introns, allowing one primary transcript to produce multiple distinct protein products.

Peptide Bond

The covalent chemical bond formed through a condensation reaction linking the carboxyl carbon of one amino acid to the amino nitrogen of the adjacent amino acid in a polypeptide chain.

Functional Domain

A discrete, evolutionarily conserved structural region within a protein's tertiary structure that folds independently and performs a specialized functional or binding role.

Transfer RNA (tRNA)

An adaptor RNA molecule with an anticodon loop that base-pairs with a specific mRNA codon, delivering its covalently attached amino acid from its $3'$ CCA terminus to the growing peptide chain.

Translation

The ribosome-catalyzed biological process in which mRNA codons are read in a $5'$ to $3'$ direction to sequentially assemble amino acids into a polypeptide chain.