IB Biology Topic A4.1: Evolution and Speciation Key Definitions

Adaptive radiation is the evolutionary process by which a single ancestral species rapidly diversifies into many species, each specialized to exploit a different ecological niche.

Allopatric speciation occurs when populations are physically separated by a geographical barrier, such as a river, mountain range, or ocean.

Analogous structures are anatomical features in different species that serve similar functions but do not share a common evolutionary origin.

Cladistics is a method of classifying organisms into groups (clades) based on common ancestry, determined by analysis of base sequences of DNA or amino acids.

Convergent evolution is when distantly related organisms independently evolve similar traits or behaviors to adapt to similar environments

Evolution is defined as a change in the heritable characteristics of a population over time.

The movement of genes from one population to another

The total collection of all alleles present in a population.

Genotype refers to the genetic makeup of an organism, specifically the combination of alleles it inherits for a particular trait.

Homologous structures are anatomical features that share a similar structure and position across different species but serve different functions.

Hybridization occurs when two distinct species interbreed, producing offspring with genetic contributions from both parents.

Meiosis is a type of cell division that reduces the chromosome number by half, producing four genetically distinct haploid cells. This process occurs in gamete-producing cells and is essential for sexual reproduction.

Natural selection is the process where individuals with traits better suited to their environment have higher reproductive success, passing these traits to the next generation.

Polyploidy is the duplication of an organism’s entire chromosome set.

Postzygotic barriers occur after fertilization, ensuring that hybrid offspring are inviable or sterile.

Prezygotic barriers act before fertilization, stopping different species from mating or ensuring that fertilization is unsuccessful.

Reproductive isolation occurs when populations are prevented from interbreeding, creating separate gene pools. This isolation ensures that evolutionary changes in one population do not affect the other.

Selective breeding, or artificial selection, is the process by which humans intentionally breed animals or plants to enhance specific traits.

Speciation is the evolutionary process through which one species splits into two or more distinct species.

Sympatric speciation occurs when populations in the same geographical area become reproductively isolated.

A vestigial structure is a reduced anatomical feature that has lost its original function but is retained as an evolutionary remnant of a common ancestor.