Chordates

What do fish, birds, mammals, and even simple sea creatures like sea squirts have in common? They all belong to a group called chordates.

Even though chordates look different, they all have four key traits.

First, they have a post-anal tail, which extends beyond the anus and helps with movement. Some chordates, like fish and reptiles, keep their tails for life, while others, like humans, lose them before birth.

Second, chordates have a dorsal hollow nerve cord, a tube-like structure along the back. This develops into the brain and spinal cord in many chordates, controlling movement and sensation.

Third, they have a notochord that supports and allows muscles to attach for movement. In most vertebrates, it is replaced by the spinal column.

Lastly, chordates have openings in the throat region called the pharyngeal slits. In fish, these turn into gills for breathing underwater. In land animals like us, they become parts of our throat and ears, helping us swallow and hear.