Speciation, Taxonomy, and Systematics

Vocabulary practice flashcards covering the key terms of macroevolution, speciation, taxonomy, and cladistics based on Brooker Chapters 24 and 25.

Macroevolution

Evolutionary changes that create new species and groups of species; it concerns the diversity of organisms established over long periods of time through the evolution and extinction of many species.

Species

A group of related organisms that share a distinctive set of attributes in nature.

Speciation

The process by which new species are formed.

Subspecies

Slightly different groups within a species that display some unique traits but are not distinct enough to be separate species.

Ecotype

A genetically distinct geographic variety or population within a species adapted to specific environmental conditions.

Reproductive Isolation

The existence of biological factors (barriers) that prevent members of two different species from interbreeding and producing viable, fertile offspring.

Morphological Species Concept

A definition of species based on physical characteristics or body shape.

Biological Species Concept

Defines a species as a group of individuals whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but cannot successfully interbreed with members of other species.

Evolutionary Lineage Concept

Defines species based on the separate evolution of lineages over time.

Ecological Species Concept

Defines a species in terms of its ecological niche—the set of resources it uses and its role in the biological community.

General Lineage Concept

An integrated concept that views a species as a population of an independently evolving lineage.

Prezygotic Isolation

Reproductive isolating mechanisms that prevent the formation of a zygote.

Postzygotic Isolation

Reproductive isolating mechanisms that prevent a hybrid zygote from developing into a viable, fertile adult.

Allopatric Speciation (Allopatry)

Speciation that occurs when a population becomes geographically isolated from other populations of the same species.

Adaptive Radiation

The process in which a single ancestral species evolves into a wide array of descendant species that differ greatly in their habitat, form, or function.

Sympatric Speciation (Sympatry)

Speciation that occurs when members of a species that occupy the same habitat diverge into two or more different species.

Polyploidy

A condition in which an organism has more than two complete sets of chromosomes ($e.g., 3n, 4n$).

Alloploidy

A type of polyploidy resulting from the contribution of chromosomes from two or more different species.

Gradualism

The hypothesis that new species evolve continuously over long spans of time.

Punctuated Equilibrium

The hypothesis that evolution is sporadic, with long periods of equilibrium (stasis) followed by short periods of rapid change.

Taxonomy

The science of describing, naming, and classifying extant (living) and extinct organisms.

Systematics

The study of biological diversity and the evolutionary relationships among organisms.

Taxon

A group of organisms at any level of a hierarchical classification system ($plural: taxa$).

Binomial Nomenclature

The standard method for naming species using a two-part scientific name consisting of the genus name and a specific epithet.

Phylogeny

The evolutionary history of a species or group of species.

Anagenesis

A process of evolutionary change in which a single species is transformed into a different species over many generations.

Cladogenesis

A pattern of evolution in which a species diverges into two or more species.

Node

The branch points in a phylogenetic tree, representing distances in time where cladogenesis occurred and common ancestors were present.

Clade

A group of species consisting of a common ancestral species and all of its descendant species.

Monophyletic Group

A taxon that is a clade, signifying it contains a common ancestor and all of its descendants.

Paraphyletic Group

A group that contains a common ancestor and some, but not all, of its descendants.

Polyphyletic Group

A group that consists of members of several evolutionary lines and does not include the most recent common ancestor of the included lineages.

Homology

Similarity that occurs because structures or traits were derived from a common ancestor.

Cladistics

An approach to systematics where organisms are classified based on the order in time that branches arise along a phylogenetic tree.

Shared Ancestral Character (Symplesiomorphy)

A character that is shared by two or more different taxa and inherited from ancestors older than their last common ancestor.

Shared Derived Character (Synapomorphy)

A character that is shared by two or more species or groups and has originated in their most recent common ancestor.

Ingroup vs. Outgroup

The ingroup is the set of taxa being studied, while the outgroup is a species or group that is related to the ingroup but diverged before them.

Parsimony

The principle that the preferred phylogenetic tree is the one that is the simplest for all characters and their states, requiring the fewest evolutionary changes.

Molecular Clock

A method for estimating the time of divergence between species based on the constant rate of neutral mutations over time.

Horizontal Gene Transfer

The process in which an organism incorporates genetic material from another organism without being its offspring.