Mechanisms of Speciation and Genetic Evolution

This set of vocabulary flashcards covers the mechanisms of allopatric and sympatric speciation, including genetic variations like polyploidy and aneuploidy, and ecological principles like resource partitioning based on university-level biology lecture notes.

Allopatric Speciation

Speciation occurring when populations are in two different geographical areas due to a physical barrier that separates them.

Sympatric Speciation

Speciation occurring within the same geographical distribution where no physical barrier exists.

Vicariance

A process where a continuous population is separated by a physical catastrophe or phenomena, such as a river changing course or tectonic plate movements.

Dispersal

A mechanism of allopatric speciation where a small group of individuals moves to a different geographical area, such as ancestors of iguanas moving from Ecuador to Galapagos.

Biogeography

The study of the distribution of species and ecosystems; in this context, the movement of floating plates on the molten core over the last $715$ million years acting as a vicariance event.

Competitive Exclusion Principle

An ecological principle stating that when two species or members of the same species compete for the same resource, one will either go extinct or they will partition the resource.

Resource Partitioning

When members of a population exploit slightly different resources in the same area to avoid competition, such as the weevil beetles adapting to different seed sizes in apple trees.

Ploidy

The number of complete sets of chromosomes in a cell.

Haploid

A cell containing one complete set of genetic traits, represented as $n=1$.

Diploid

A cell containing two sets of chromosomes, represented as $2n$.

Polyploidy

A condition where an organism has more than two multiples of chromosome sets; it is severe in animals but common and tolerated in plants.

Aneuploidy

A condition where a cell has an abnormal number of chromosomes, specifically $2n + 1$ (trisomy) or $2n - 1$ (monosomy).

Down Syndrome

A form of aneuploidy known as trisomy $21$, where an individual has three copies of chromosome $21$ instead of two.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate during meiosis I, meiosis II, or mitosis.

Turner Syndrome

A condition also known as monosomy X, where a female is born with only one copy of the X chromosome.

Octaploid

Having eight copies of the genome, a characteristic found in commercial strawberries which makes them reproductively isolated from wild varieties.

Autopolyploidy

A type of polyploidy resulting from nondisjunction within a single species, leading to a duplication of its own genome.

Allopolyploidy

A type of polyploidy occurring when two different but closely related species interbreed and create a hybrid with multiple sets of chromosomes.

Parenchyma

Simple plant cells that are totipotent, allowing plants to reproduce asexually even with unbalanced chromosome numbers.

Totipotent

The potential of a single cell, like parenchyma, to produce every single part of an organism.