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Phylogeny

the study of the evolutionary history and relationships among individuals, groups, or species, often represented by branching diagrams known as phylogenetic trees.

Cladogram

A cladogram is a branching tree diagram that shows ancestral relationships among organisms

Character

any observable, recognizable feature or heritable trait of an organism, such as morphology, behavior, or molecular markers, used to determine evolutionary relationships.

Shared character

a biological trait unique to a specific clade, inherited from a common ancestor, and used to determine evolutionary relationships

Derived character

a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants.

Outgroup

a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup, the set of organisms under study

Biological species concept (BSC)

defines a species as a group of organisms that can interbreed in nature and are reproductively isolated from other such groups.

Niche

the specific functional role, position, and "job" a species plays within its ecosystem, encompassing all its interactions with biotic (living) and abiotic (non-living) factors.

Prezygotic

biological mechanisms that prevent different species from interbreeding and forming a zygote, occurring before fertilization.

Postzygotic

reproductive isolating mechanisms that occur after fertilization, where hybrid offspring between two species are unable to develop, survive, or reproduce.

Speciation

the evolutionary process by which populations evolve to become distinct species, defined as groups that are reproductively isolated from one another

Divergent evolution

a biological process where related species evolve distinct, unique traits over time, often driven by different environmental pressures or geographical isolation, leading them to become less similar than their common ancestor

Allopatric

the study of species or populations that are geographically isolated from one another by physical barriers (mountains, rivers, oceans), preventing interbreeding.

Sympatric

species or populations that inhabit the same, overlapping geographic area, frequently encountering each other.

Adaptive radiation

an evolutionary process where a single ancestral species rapidly diversifies into numerous new forms to exploit vacant ecological niches.

Gradualism

the theory that evolution proceeds chiefly through the accumulation of slow, steady, and consistent small genetic or morphological changes over long periods, rather than via sudden, massive leaps

Punctuated equilibrium

an evolutionary theory proposing that species experience long periods of stability (stasis) with little change, "punctuated" by brief, rapid bursts of significant evolutionary change and speciation

RNA world hypothesis

a scientific proposal that early life on Earth relied solely on RNA (ribonucleic acid) for both storing genetic information and catalyzing chemical reactions, predating the evolution of DNA and proteins