Modern Evolutionary Classification

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Phylogeny Noun

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[fy-lahj-uh-nee]

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Phylogeny

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The study of the evolutionary history and relationships among lineages of organisms, showing how they have developed over time.

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Example: This diagram shows how scientists group organisms based on shared evolutionary history, with branches representing common ancestors and new traits appearing over time.

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Clade Noun

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[klayd]

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Clade

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A group of species that includes a single common ancestor and all of its descendants, both living and extinct.

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Example: This evolutionary tree shows groups of related organisms. A clade includes a common ancestor (numbered circle) and all its descendants (letters). Each colored box highlights a complete clade.

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Cladogram Noun

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[klad-uh-gram]

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Cladogram

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A diagram that links groups of organisms by showing hypotheses about how evolutionary lines branched off from common ancestors.

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Example: This cladogram shows how animals are grouped by shared evolutionary traits. Branch points indicate a common ancestor, and labels show new traits like 'four limbs'.

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Derived character Noun

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[di-rahyvd kar-ik-ter]

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Derived character

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A trait that arose in the most recent common ancestor of a particular lineage and was passed to its descendants.

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Example: This cladogram shows that a derived character, like a 'fuzzy tail,' is a new trait that appears in a group and is passed to its descendants.

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Cladistic analysis Noun

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[kluh-dis-tik uh-nal-uh-sis]

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Cladistic analysis

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A method of classification that groups organisms based on shared, unique characteristics inherited from a common ancestor.

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Example: This cladogram shows how cladistic analysis groups organisms based on shared evolutionary traits. For example, the amniotic egg is a shared trait uniting reptiles, birds, and mammals.

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Taxon Noun

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[tak-son]

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Taxon

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A group or level of organization into which organisms are classified, such as a kingdom, phylum, or clade.

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Example: This diagram shows that a taxon is any level in the classification of life, such as the Domain Eukarya or the Kingdoms within it (Fungi, Plantae, Animalia).

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Peptidoglycan Noun

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[pep-tih-doh-gly-kun]

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Peptidoglycan

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A substance made of sugars and peptides that forms the rigid cell walls of many bacteria, providing structural support.

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Example: This diagram shows that peptidoglycan is the material that makes up the strong, outer cell wall of a bacterium, located just outside the cell membrane.

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Chitin Noun

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[kahy-tin]

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Chitin

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A fibrous polysaccharide that is the primary component of the cell walls of fungi and the exoskeletons of arthropods.

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Example: This image shows that animals like insects, spiders, and crustaceans have an exoskeleton made of chitin, a key trait used in evolutionary classification.