Taxonomy and phylogenetic trees help us understand life's diversity. They give us tools to classify organisms based on shared traits and evolutionary relationships. This system lets scientists organize and study the vast array of living things on Earth.

These concepts are crucial for grasping how life forms are connected. By using names, categories, and visual diagrams, we can see how species relate to each other and trace their evolutionary history. It's like a family tree for all living things!

Taxonomy and Classification

Taxonomy and binomial nomenclature

• Taxonomy involves naming and classifying organisms into groups based on shared characteristics
• Linnaeus developed the modern system of classification in the 1700s which uses a two-part naming system called binomial nomenclature
• Binomial nomenclature assigns each species a two-part scientific name consisting of the genus and specific epithet (Homo sapiens)
• The first part of the name identifies the genus and the second part identifies the species within the genus
• Scientific names are always italicized with the genus capitalized and the species lowercase (Canis lupus)

Hierarchical classification system

• Hierarchical classification system groups organisms into increasingly broad categories
• Species is the most specific category and includes organisms that can interbreed and produce fertile offspring (Canis lupus)
• Genus is the next level up and includes closely related species (Canis)
• Family includes genera that share similar characteristics (Canidae includes wolves, dogs, and foxes)
• Order includes related families (Carnivora includes canines, felines, bears, and seals)
• Class includes related orders (Mammalia includes all mammals)
• Phylum contains animals within a kingdom with a similar body plan (Chordata includes all vertebrates)
• Kingdom is a high-level classification that includes animals, plants, fungi, protists, and bacteria
• Domain is the broadest category and includes archaea, bacteria, and eukarya

Evolutionary Relationships

Phylogenetic trees and cladograms

• Phylogenetic tree is a branching diagram that shows the evolutionary relationships among various biological species believed to have a common ancestor
• Cladogram is a diagram used in cladistics which shows relations among organisms
• Phylogenetic trees and cladograms are hypotheses about evolutionary relationships and history
• Both diagrams have a common ancestor at the base of the tree from which different lineages descend
• As lineages evolve independently, they diverge from their common ancestor and form new branches on the tree (birds and mammals diverged from a common reptilian ancestor)

Clades and taxa

• Clade is a group of organisms that includes an ancestor and all of its descendants
• Clades are nested within each other and form a nested hierarchy (birds are a clade within the clade of reptiles)
• Taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit
• Taxa are given a taxonomic rank and can be placed at various levels in a phylogenetic tree (genus Panthera is a taxon that includes species like lions, tigers, and leopards)