Speciation and the Origin of Species

These flashcards cover the definition of species, various species concepts, reproductive isolation mechanisms, allopatric and sympatric speciation, and evolutionary patterns like punctuated equilibrium and heterochrony.

Speciation

The process describing the origin of new species.

Biological Species Concept

Defines a species as a population or group of populations whose members can interbreed and produce fertile offspring.

Reproductive Isolation

The condition of different species that prevents gene flow between them.

Morphological Species Concept

A classification of organisms based on observable phenotypic traits.

Ecological Species Concept

Defines a species by its specific ecological role.

Phylogenetic Species Concept

Defines a species as a set of organisms with a unique genetic history.

Prezygotic Isolation

A category of reproductive isolation that happens before a zygote is formed, including habitat, temporal, ethological, and mechanical factors.

Habitat Isolation

A prezygotic barrier where species prefer different environments, such as $Gryllus\,pennsylvanicus$ preferring sandy soil and $Gryllus\,firmus$ preferring loamy soil.

Temporal Isolation

Isolation based on time-related factors, such as different life cycle timings in species like Arctic Grayling and various Salmon.

Behavioral Isolation

Also known as ethological isolation, it involves specific rituals like courting dances or pointing displays that prevent interbreeding.

Mechanical Isolation

A prezygotic barrier where structural differences, such as different insects pollinating black sage versus white sage, prevent mating.

Gametic Isolation

A barrier where sperm and egg are incompatible and do not fuse to form a zygote.

Postzygotic Isolation

Barriers that occur after fertilization, including zygotic mortality, hybrid inviability, and hybrid sterility.

Hybrid Inviability

A postzygotic barrier where hybrid offspring do not survive.

Hybrid Sterility

A postzygotic barrier where hybrid offspring are unable to reproduce.

Hybrid Breakdown

A postzygotic barrier where the first generation of hybrids is fertile, but succeeding generations are not.

Allopatric Speciation

A mechanism of speciation that occurs through geographic isolation, such as the separation of Chimpanzees and Bonobos.

Sympatric Speciation

A mechanism of speciation that occurs within the same geographical area, often through meiotic errors or polyploidy.

Polyploidy

The condition of having extra sets of chromosomes; it is common in plants and accounts for $30\text{-}80\%$ of all plant species.

Triticum aestivum

Commonly known as Bread wheat, it is a polyploid with $42$ chromosomes that evolved approximately $8,000$ years ago.

Adaptive Radiation

The rapid evolution of diversely adapted species from a common ancestor.

Punctuated Equilibrium

An evolutionary model suggesting that long periods of stasis are interrupted by sudden, rapid change.

Irreducible Complexity

The concept mentioned by Darwin regarding complex organs, like the eye, that may not have formed through numerous successive slight modifications.

Heterochrony

Changes in the timing and duration of developmental events, often compared between humans and chimpanzees from fetus to adult stages.