IB Environmental systems and societies 2.1L Classification Methods Key Definitions

Body structures that look or work alike in different species but evolved independently under similar pressures, not from a common ancestor. They are not evidence of close relationship.

A clade is a group of organisms that includes a common ancestor and all its descendants.

Cladistics is the branch of biology that classifies organisms according to their evolutionary relationships, not just physical similarities.

Body structures shared by different species because they were inherited from a common ancestor, even if they now look different or do different jobs. They are evidence of shared ancestry.

A branching diagram that shows the evolutionary relationships between organisms, tracing how lineages descend and diverge from common ancestors over time.

Synapomorphies are traits shared by members of a clade that evolved from a common ancestor, distinguishing them from other groups.

A taxon (plural taxa) is any group of organisms that shares common characteristics and has been given a rank in the taxonomic hierarchy.