Chapter 26 Bio

Taxon

A named group of organisms.

Taxonomy

The science of classifying and naming organisms.

Systematics

The science of classification of organisms and evolutionary relationships between organisms.

Phylogeny

The evolutionary history of a species or related groups.

Phylogenetic Tree

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.

Phylogenetics

The study of the reconstruction of evolutionary relationships among organisms.

Family

A group of related genera.

Order

A group of related families.

Class

A group of related orders.

Phylum

A group of related classes.

Kingdom

Related phyla.

Domain

The highest level of classification.

Sister Taxa

Two taxa that share a more recent common ancestor with each other than with any other taxon.

Monophyletic (clade)

Includes most recent common ancestor and all descendants.

Paraphyletic

Includes most recent common ancestor but not all descendants.

Polyphyletic

Does not include most recent common ancestor.

Cladistics

An approach to systematics that uses common ancestry to classify organisms.

Homology

Similar traits due to shared ancestry.

Analogy

Phenotypic and genetic similarities without shared ancestry.

Convergent Evolution

Occurs when similar environmental pressures and natural selection produce similar adaptations in organisms found in different evolutionary lineages.

Shared Ancestral Character

A shared trait that originated in the ancestor of the taxa.

Shared Derived Character

A trait shared by all members of the taxa but not the ancestor of the taxa.

Synapomorphy

A trait shared by all members of the taxa but not the ancestor of the taxa.

Maximum Parsimony

Assumes that the most likely tree is the one that requires the fewest evolutionary events.

Outgroup

A group of organisms that is outside of the monophyletic group under consideration but closely related to that group.

Maximum Likelihood

Identifies tree most likely to have produced a given set of DNA based on probability rules about how DNA changes over time.

Phylogenetic Bracketing

Predicts that features shared by two closely related groups will be present in their ancestor and all its descendants.

Gene Duplications

Increase the number of genes in the genome and provide opportunities for evolutionary change.

Gene Families

Groups of related genes within an organism’s genome.

Orthologous Genes

Homology is the result of speciation; same gene, different species.

Paralogous Genes

Homology is the result of gene duplication; same species, different gene.

Molecular Clock

Used to estimate the absolute time of evolutionary change, allowing us to date phylogenetic trees built with genetic data.

Eukaryotes

Organisms from the Domain Eukarya, including plants, fungi, and animals.

Prokaryotes

Organisms from the Domains Archaea and Bacteria.