Begin by understanding what chordates are. Chordates are a diverse group of animals that share certain key anatomical features during at least some stage of their development.
Identify the four key features that characterize all chordates. These features are: notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.
The notochord is a flexible, rod-shaped body found in the embryonic stage of all chordates, providing skeletal support.
The dorsal hollow nerve cord is a tube-like structure located dorsally (on the back) of the notochord, which develops into the central nervous system: the brain and spinal cord.
Pharyngeal slits are openings in the pharynx (throat area) that can develop into gills in aquatic organisms or other structures in terrestrial organisms. The post-anal tail is an extension of the body past the anal opening, providing locomotion in aquatic species.