Key Concepts in Species Classification and Speciation

A set of vocabulary flashcards covering key concepts related to species classification, speciation mechanisms, and associated terminology.

Systematics

A branch of biology involved with the investigation of the diversity of living organisms in relation to their evolutionary history.

Phylogeny

The evolutionary history of a species or related species.

Taxonomy

The component of biology dealing with classification.

Taxonomic hierarchy

The classification of organisms from broad to specific: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

Biological Species Concept (BSC)

All members of a species can interbreed under natural conditions and produce viable, fertile offspring.

Viable

Able to survive.

Fertile

Capable of reproducing.

Natural conditions

Conditions without human manipulation.

Limitations of BSC

Difficult to apply; does not apply to asexual organisms; cannot be applied to fossils.

Morphological Species Concept

Based on similarity of physical traits; applicable to extinct or asexual species.

Phylogenetic Species Concept

Smallest set of organisms sharing an ancestor, distinguishable from other such sets.

Genetic Cluster Species Concept

Groups of individuals that form distinct genetic clusters with few or no intermediates, based on absence of gene flow.

Allopatric Speciation

Speciation that occurs when populations are divided by a physical barrier, leading to different evolutionary paths.

Sympatric Speciation

Speciation that occurs in the same geographic area without physical barriers.

Prezygotic barriers

Factors that prevent the formation of a zygote between different species.

Habitat Isolation

Prezygotic barrier where species live in different habitats or rarely encounter each other.

Temporal Isolation

Prezygotic barrier where species breed during different times of day, different seasons, or different years.

Behavioral Isolation

Prezygotic barrier where unique courtship rituals or other behaviors prevent mate recognition between species.

Mechanical Isolation

Prezygotic barrier where morphological differences prevent successful mating.

Gametic Isolation

Prezygotic barrier where the sperm of one species cannot fertilize the eggs of another species.

Postzygotic barriers

Factors that prevent development of viable or fertile offspring after a zygote has formed.

Reinforcement

The process where the frequency of hybrids declines over time until no more hybrids form.

Fusion

The merging of two species back into one due to extensive hybridization.

Zygote

A diploid cell resulting from the fusion of two haploid gametes (sperm and egg) during sexual reproduction.

Reduced Hybrid Viability

Postzygotic barrier where the genes of different parent species interact in ways that impair the hybrid's development or survival in its environment.

Reduced Hybrid Fertility

Postzygotic barrier where hybrids may be vigorous but sterile, often due to an inability to produce normal gametes.

Hybrid Breakdown

Postzygotic barrier where some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, the next generation is feeble or sterile.

Polyploidy

A mechanism of sympatric speciation where an organism has more than two sets of chromosomes, often due to errors during cell division. This can lead to reproductive isolation from diploid parents.

Sexual Selection

A mechanism of sympatric speciation where preferences for certain traits in mates can lead to reproductive isolation between populations within the same geographic area.