AS91605 Speciation Vocabulary

A comprehensive collection of vocabulary terms and definitions related to AS91605 Speciation, covering patterns of evolution, selective mechanisms, and reproductive isolation.

Adaptations

Phenotypes that allow an organism to better survive in its environment.

Adaptive radiation

The process of a single ancestral species evolving into a diverse array of descendant species, each adapted to a specific ecological niche (also known as divergent evolution).

Allele frequency

The proportion of an allele for a specific gene in a gene pool.

Alleles

Alternative form of a gene; for example, black or chestnut coat colour in horses.

Allopatric speciation

A type of speciation where geographic isolation disrupts gene flow between two populations of a species resulting in evolution into different species.

Allopatric species

Where similar species are reproductively isolated due to geographic separation.

Allopolyploid

An organism that contains $2$ or more sets of chromosomes from $2$ or more different species.

Amphiploid (sterile hybrid)

Formed by crossing $2$ different species and is sterile. It undergoes nondisjunction in meiosis to become fertile, having $2$ sets of homologous chromosomes, becoming an allopolyploid.

Analogous structures

Traits in different and unrelated species that have similar functions but have evolved independently due to similar selection pressures, such as wings in birds and insects.

Asexual reproduction

A single parent copies itself to form a genetically identical offspring.

Autopolyploid

Having more than $2$ sets of chromosomes from a single species.

Biogeography

The study of the geographical distribution of extinct and modern species.

Bottleneck effect

The phenomenon in which a population is dramatically reduced in size, but then rebounds again, typically resulting in the loss of alleles and reduced genetic diversity.

Behavioural adaptation

A way of responding to the environment that is specific to a species of organisms that allows the organism to better survive in its environment.

Characteristics

A feature of an organism (trait/phenotype).

Clade

A grouping or branch of a taxonomic tree that includes a common ancestor and all the descendants (living and extinct) of that ancestor.

Cline

A gradual change in the frequency of an allele or the average value of a phenotype across a geographical area.

Co-evolution

Where $2$ or more species affect each other’s evolution by acting as selection pressures on each other, such as tūī beak shape and harakeke flower shape.

Convergent evolution

The evolution of similar phenotypes by species of different ancestral origins due to similar selection pressures, such as torpedo shapes in penguins and fish.

Deme

A sub-population within a larger one that is partly isolated from interbreeding with other sub-populations present.

Directional selection

A type of natural selection where individuals at one extreme of a phenotype distribution in a population have higher survival and reproduction rates than the rest of the population.

Disruptive selection

A type of natural selection where extreme phenotypes are favoured over average phenotypes, potentially leading to a population splitting into distinct groups.

Divergent evolution

The process where $2$ or more populations of a species are exposed to different selection pressures and evolve distinct phenotypes over time, becoming increasingly different.

Ecological equivalents

Species that inhabit the same niche but in different geographical areas, which will compete if put in the same environment.

Endemic

Species found naturally occurring in only a particular location, such as the kiwi in New Zealand.

Evolution

Gradual change in the genetic code of populations over a long period, which may result in the formation of new species.

Extant

Species with members still living.

Extinct

Species with no living members.

Fitness

The ability of an individual to successfully reproduce and pass on their genetics.

Fitness Cost

The loss of non-target alleles from a gene pool during the process of natural selection.

Founder effect

A new colony started by a few members of an original population where allele frequencies are not representative and rare alleles may become fixed or lost.

Gametes

Sex cells containing half the chromosomes of the parent.

Gause’s Competitive Exclusion Principle

No $2$ species can occupy the same ecological niche; one will either die or change niches.

Gene flow

Occurs when individuals migrate between different populations and cause changes in the genetic composition of the resulting populations.

Gene pool

The complete set of genes and their various alleles in a breeding population.

Genome

The complete genetic composition of an individual or species.

Genotype

An individual’s allele combination for a particular phenotype.

Genetic drift

The random change in a small population’s allele frequency from one generation to the next due to chance.

Genetic variation/diversity

The variation of alleles/heritable traits in a population of organisms.

Geographical isolation

Where any physical feature of the Earth, such as mountains or rivers, prevents gene flow.

Gradualism

The evolution of new species by gradual accumulation of small genetic changes over long periods of time.

Homologous structures

Features of similar ancestral origin that have different functions due to differing selection pressures, such as the arm of a human and wing of a bat.

Hybrid

Individual formed through crossing $2$ different species where the offspring may be sterile or show hybrid vigour.

Hybrid breakdown

A reproductive isolating mechanism where there is a decline in fitness or viability of hybrid offspring in later generations ($F_2$ and beyond) compared to $F_1$ hybrids.

Hybrid inviability

A reproductive isolating mechanism where hybrids fail to develop into healthy, mature adults, either in utero or after birth.

Hybrid sterility

A reproductive isolating mechanism where the hybrid reaches maturity but cannot produce viable offspring, such as a mule.

Introduced species

A species moved by humans from a native ecosystem to another ecosystem.

Mitochondrial DNA

Circular DNA found in the mitochondria passed through the maternal line; it has a constant mutation rate, no proofreading, and no crossing-over.

Mutation

A permanent change in DNA or genetic material; only important to evolution if heritable.

Natural selection

The process by which selection pressures act on populations, allowing individuals with advantageous heritable traits to survive and reproduce more successfully.

Niche

The habitat and ecological role of an organism.

Non-Random Mating

Occurs when individuals with specific phenotypes are mated preferentially.

Phenotype

How a gene is expressed as a protein, characteristic, or trait.

Phylogenetic tree

A diagram that describes the evolutionary relationships among various species.

Polyploidy

Where an organism has $3$ or more sets of homologous chromosomes.

Population

Number of organisms of the same species living in a defined area.

Prezygotic isolating mechanism

A reproductive isolating mechanism that keeps species separate by acting before fertilisation occurs, such as courtship differences.

Post-zygotic mechanism

A reproductive isolating mechanism that keeps species separated by acting after fertilisation, such as an infertile hybrid.

Punctuated equilibrium

Long periods of little change in a species evolution followed by short bursts of speciation due to rapid change in the environment or selection pressures.

Reproductive Isolating Mechanism

An evolutionary mechanism that prevents different species from interbreeding and producing viable, fertile offspring; may be temporal, behavioural, mechanical, or gametic.

Ring species

A series of geographically distributed populations where neighbors can interbreed, but extreme ends of the series exhibit a gradual change that prevents interbreeding.

Selection pressures

Environmental factors such as resource scarcity or predation that affect the fitness and survival of individuals and change allele frequencies.

Sexual selection

A process where some individuals are more successful at attracting mates and therefore produce more offspring, such as peacocks with larger tails.

Speciation

The process by which one species gives rise to $2$ or more new species.

Species

A group of organisms that can breed with each other and produce fertile offspring.

Stabilising selection

A type of natural selection where individuals with average phenotypes are more fit than those with extremes, narrowing phenotypic variation.

Morphological isolating barrier

When reproductive structures between related species are incompatible.

Sympatric speciation

The process by which new species evolve from a single ancestral species whilst both still inhabit the same geographical region.

Sympatric species

Similar species living in the same geographical area but which are reproductively isolated.

Temporal isolating mechanism

When groups are reproductively isolated due to being active at different times of the day or seasons.

Vestigial structure

An anatomical feature that has no apparent function but resembles a structure of a presumed ancestor, such as a kiwi wing.

Y-chromosome

A nuclear chromosome passed down through the male line that does not undergo crossing-over; used to compare relatedness of extant and extinct species.

Zygote

The fertilised egg or ovum.