The Origin of Species and Speciation Processes

Macroevolution

Origin of new taxonomic groups over time.

Microevolution

Genetic variation within a species across generations.

Biological species concept

Species defined by potential interbreeding and viable offspring.

Speciation

Process of forming a new species from existing ones.

Anagenesis

Accumulation of traits transforming a population into a new species.

Cladogenesis

Branching evolution creating new species from an ancestral species.

Isolation

Separation of populations preventing interbreeding.

Prezygotic barriers

Prevent mating or fertilization between different species.

Habitat isolation

Species occupy different habitats, limiting encounters.

Behavioral isolation

Unique mating signals prevent interbreeding between species.

Temporal isolation

Species breed at different times, preventing mating.

Mechanical isolation

Anatomical incompatibility prevents successful mating.

Gametic isolation

Sperm and egg must recognize each other for fertilization.

Postzygotic barriers

Prevent hybrid offspring from developing or reproducing.

Reduced hybrid viability

Hybrids fail to develop properly, aborting early.

Reduced hybrid fertility

Hybrids are sterile, unable to produce viable gametes.

Hybrid breakdown

First-generation hybrids are fertile, but next generation is not.

Ecological species concept

Species defined by ecological niche and resource use.

Pluralistic species concept

Species maintenance factors vary, including reproductive isolation.

Morphological species concept

Species defined by unique structural features.

Genealogical species concept

Species defined by unique genetic histories and DNA.

Allopatric speciation

Speciation occurring in geographically isolated populations.

Sympatric speciation

Speciation occurring in overlapping geographic populations.

Polyploidy

Condition of having more than two sets of chromosomes.

Adaptive radiation

Rapid evolution of diverse species from a common ancestor.

Gradualism model

Evolutionary change occurs gradually over time.

Punctuated equilibrium

Rapid evolutionary changes followed by long stability periods.

Exaptations

Structures evolving for one purpose but serving another.

Differential reproduction

Variation in reproductive success based on environmental factors.