Chapter 13 Determining the Releatedness of Species (copy)

Analogous

A feature (e.g organ or structure) that has a similar structure and function in unrelated species and has evolved independently due to similar environmental selection pressures

Branch

A line on a phylogenetic tree that represents the evolutionary path from a common ancestor

Clade

A group of organisms that includes an ancestor and all descendants of that ancestor

Cladogram

A branching diagram representing the evolutionary relationships between taxa. The branches of a cladogram are scaled (the length of the branches do not represent evolutionary distance)

Common ancestor

An organism from which two or more species diverged. Also known as a shared ancestor

Convergent evolution

The evolution of similar features in unrelated groups of organisms

Divergent evolution

The evolution of two or more different species from a common ancestral species

Homologous features

Features that have a common evolutionary origin, which is evident in the underlying fundamental similarities in their structure. Homologous features are found in different organisms and may have evolved different functions (e.g a human hand and a bat wing) as a result of divergent evolution from a common ancestor. DNA sequences or proteins can also be homologous

Leaf

The branch tip on a phylogenetic tree where the scientific name of the taxon is

Lineage

All the species that are descendents of a common ancestor

Molecular homology

A DNA or protein molecule (or their precise sequence) shared by two species or other taxa because of common ancestry

Monophyletic group

A taxonomic group containing a common ancestor and all its descendants

Mutation rate

The rate at which genetic mutations occur over time

Node

The point at which two branches in a phylogenetic tree diverge (also known as branch point). The node represents the last common ancestor that the two diverging taxa shared

Outgroup

A taxonomic group that is closely related to the other groups (ingroups) but less closely related than any single one of the ingroups that is older than the common ancestor of the ingroups. It is included in phylogenetic trees for common comparison to the group of interest

Phylogenetic tree

A diagram that represents the evolutionary relationships between different species, but does not show evolutionary distance. It may be rooted or unrooted

Phylogeny

The evolutionary relationships of organisms, usually represented by a branching tree diagram (phylogenetic tree)

Phylogram

A branching diagram representing the evolutionary relationships between taxa. The ranches of a phylogram are scaled (i.e the length of the branches represent evolutionary distances)

Point mutation

A type of gene mutation that typically only affects a single nucleotide. Types include substitution and frameshift

Root

The part of a phylogenetic tree that represents the common ancestor of all the taxa in the tree

Sister taxa

A pair of taxa group together in a phylogenetic tree (the closest relative of any given taxon)

Structural morphology

The study of form and structure of organisms

Taxon (plural taxa)

A biological group classified on the basis of their shared characteristics and evolutionary relationships

Taxonomy

The science of the classification of organisms into hierarchical groupings based on their shared characteristics and evolutionary relationships

Vestigial structure

A remnant structure that has lost almost of its original function in an organism in the course of evolution