A4.1 Speciation (HL)

Vocabulary flashcards covering the key terms and definitions related to biodiversity and speciation presented in the lecture.

Speciation

The formation of a new species from a pre-existing one when populations become reproductively isolated and genetically diverge.

Biological Species Concept

Defines a species as a group of organisms that can interbreed and produce fertile, viable offspring, sharing a common chromosome number.

Reproductive Isolation

Any mechanism that prevents gene flow between populations, ultimately leading to speciation.

Pre-zygotic Isolation Barriers

Mechanisms that act before fertilisation, preventing the formation of a zygote (e.g., spatial, temporal, behavioural barriers).

Post-zygotic Isolation Barriers

Mechanisms that act after fertilisation, reducing the viability or fertility of hybrid offspring.

Geographic Isolation

A pre-zygotic barrier in which populations occupy different environments or niches, preventing interbreeding.

Behavioural Isolation

A pre-zygotic barrier caused by differences in mating or courtship rituals that prevent interbreeding.

Temporal Isolation

A pre-zygotic barrier in which populations reproduce or are active at different times or seasons.

Hybrid Inviability

A post-zygotic condition where hybrid offspring die early or fail to develop to reproductive maturity.

Hybrid Infertility

A post-zygotic condition where hybrid offspring survive but are sterile, e.g., mules.

Adaptive Radiation

Rapid diversification of a single ancestral lineage into multiple species adapted to different ecological niches.

Allopatric Speciation

Speciation that occurs when populations are geographically separated and exposed to different selection pressures.

Sympatric Speciation

Speciation that occurs within the same geographic area, often via temporal or behavioural isolation or polyploidy.

Polyploidy

The condition of possessing more than two complete sets of chromosomes; can cause instant speciation, especially in plants.

Autopolyploidy

Polyploidy arising within a single species when meiotic errors produce unreduced gametes that double chromosome number.

Allopolyploidy

Polyploidy resulting from hybridisation between two species, with both parents contributing unreduced gametes.

Hybrid Vigour (Heterosis)

Enhanced growth or robustness often observed in hybrid or polyploid offspring due to additional alleles.

Dichotomous Key

A systematic tool that identifies organisms through a series of paired, alternative statements about their traits.

DNA Barcoding

Species identification method using short (~500 bp) DNA sequences flanked by conserved regions for universal PCR primers.

Environmental DNA (eDNA)

Genetic material released by organisms into their surroundings, enabling non-invasive monitoring of species presence.

Chromosome Number (Species Trait)

Characteristic chromosome count shared by members of a species; incompatible counts hinder gamete compatibility.

Hybridisation

Interbreeding between different species; often produces infertile hybrids unless compatible chromosome sets exist.