Glossary

- taken & adapted from Hillis et al (1996), Majerus et al (1996) and Walker (1989)

Adaptive radiation: The evolutionary diversification of a monophyletic lineage, leading to a variety of forms each adapted to particular environmental conditions.

Alignment: The juxtaposition of amino acids or nucleotides in homologous molecules to maximise similarity or minimise the number of inferred changes among the sequences.

Analogy: see Homoplasy.

Antibody: A large protein made in response to a foreign antigen (generally a protein).

Antigen: Any molecule that elicits an antibody response.

Bifurcation: A node in a tree that connects exactly three branches. If the tree is directed (rooted), then one of the branches represents an ancestral lineage and the other two branches represent descendant lineages.

Bootstrapping; A statistical method for placing some form of confidence limits on a set of observations without making too many assumptions. It is therefore well-suited to the analysis of phylogenetic trees.

Character state: The specific value taken by a character in a specific taxon or sequence (e.g., possessing green eyes, or glycine at position 12 of a particular protein).

Cladistics: Method of classifying organisms into groups (taxa) based on 'recency of common descent ' as judged by the possession of shared derived (i.e., not primitive) characters.

Cladogenesis: The formation of independently evolving lineages from a single ancestral line through speciation.

Cladogram: A tree that depicts inferred historical branching relationships among entities. Unless otherwise stated, the depicted branch lengths in a cladogram are arbitrary; only the branching order is significant.

Complementary DNA: DNA reverse transcribed from an RNA template. Congruence: Agreement among data or data sets.

Deoxyribonucleic acid: The principle heritable material of all cells. Chemically it is a polymer of nucleotides, each nucleotide subunit consisting of the pentose sugar 2-deoxy-D-ribose, phosphoric acid and one of the four nitrogenous bases adenine, cytosine, guanine or thymine.

DNA polymerase: An enzyme that catalyses synthesis of a DNA under direction of single-stranded DNA template.

Evolutionary distance: An idealised measure of the evolutionary separation of sequences or taxa, such as the total number of substitutional events. They are defined so that the values are additive and hence will precisely fit an additive evolutionary tree.