Give any two distinctive characteristics of chordates.

Two defining characteristics of phylum Chordata (present at least during embryonic development):

1. Notochord: A flexible, rod-like supporting structure running along the back (dorsal side) of the organism. In primitive chordates and embryos, it provides skeletal support. In vertebrates, it's largely replaced by the vertebral column (backbone) during development, though remnants persist as intervertebral discs.
2. Dorsal hollow nerve cord: A tubular nerve cord positioned dorsally (along the back), above the notochord. Unlike invertebrates with solid, ventral nerve cords, this hollow structure develops into the brain and spinal cord in vertebrates, forming the central nervous system.

Other chordate features (for context): pharyngeal slits/pouches (gill slits), post-anal tail, and a closed circulatory system with ventral heart.

Examples: All vertebrates (fish, amphibians, reptiles, birds, mammals) plus primitive chordates like lancelets (Branchiostoma) and tunicates.