Organizing Life On Earth Summary

Summary

Scientists continually gain new information that helps understand the evolutionary history of life on Earth. Each group of organisms went through its own evolutionary journey, called its phylogeny. Each organism shares relatedness with others, and based on morphologic and genetic evidence, scientists attempt to map the evolutionary pathways of all life on Earth. Historically, organisms were organized into a taxonomic classification system. However, today many scientists build phylogenetic trees to illustrate evolutionary relationships.

Glossary

basal taxon

branch on a phylogenetic tree that has not diverged significantly from the root ancestor

binomial nomenclature

system of two-part scientific names for an organism, which includes genus and species names

branch point

node on a phylogenetic tree where a single lineage splits into distinct new ones

class

division of phylum in the taxonomic classification system

family

division of order in the taxonomic classification system

genus

division of family in the taxonomic classification system; the first part of the binomial scientific name

kingdom

division of domain in the taxonomic classification system

order

division of class in the taxonomic classification system

phylogenetic tree

diagram used to reflect the evolutionary relationships among organisms or groups of organisms

phylogeny

evolutionary history and relationship of an organism or group of organisms

phylum

(plural: phyla) division of kingdom in the taxonomic classification system

polytomy

branch on a phylogenetic tree with more than two groups or taxa

rooted

single ancestral lineage on a phylogenetic tree to which all organisms represented in the diagram relate

sister taxa

two lineages that diverged from the same branch point

systematics

field of organizing and classifying organisms based on evolutionary relationships

taxon

(plural: taxa) single level in the taxonomic classification system

taxonomy

science of classifying organisms