For example, all chordates (with a few bizarre exceptions) eat by ingesting food, rather than by absorption. This means that food is consumed through the mouth, rather than by photosynthesis or absorption through the skin. To over-simplify, all chordates have a tube that food travels through.

What do chordates feed on?

They feed by taking water in through the mouth, using the gill slits as a kind of filter. The feeding apparatus in cephalochordates is similar. They have a well-developed musculature and can swim rapidly by undulating the body.

How do chordates digest?

The lower digestive tract of the primitive chordate is a simple tube with a saclike stomach. There are only indications of the specialized areas and of glandlike structures, such as the liver and pancreas, that occur in vertebrates.