Chordata Digestive System

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Members of the Phylum Chordata are among the most advanced in the animal kingdom - these include fish, amphibians, reptiles, birds, and mammals. Read this lesson to learn about similarities and differences among the digestive systems found in this phylum.

The Phylum Chordata

Did you ever think that you could have the same digestive system as a globular looking sea squirt at the bottom of the ocean? As different as you both are, you belong to the same group and have some similarities in how you process food.

The Phylum Chordata (also known as chordates) is a diverse classification of animals that probably includes most of the critters you're familiar with! And these animals are fascinating! Despite being so diverse, they actually share many characteristics. Let's take a look.

We can break this phylum up into 3 sub-groups:

  1. Urochordata, also known as the tunicates (sea squirts)
  2. Cephalochordata, also known as the lancelets (fish-like creatures)
  3. Vertebrata, also known as the vertebrates (fish, amphibians, reptiles, birds, and mammals).

Vertebrates are the largest group, a lot of animals - over 40,000 species - so the group is very diverse.


The digestive system of any organism has three main functions.

  1. to digest the food by breaking it down into smaller, usable pieces.
  2. to assimilate nutrients from the food
  3. to eliminate waste material from the body.

These functions are completed by a group of organs and structures that are collectively called the digestive system.

Digestive Systems of Chordates

We know that the chordates are a diverse group of organisms, but there are a number of similarities in how they function. 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. The tube starts at the mouth and ends at the anus.

Salivary glands help begin the digestive process before ingested food moves on to the stomach by way of the esophagus. From the stomach, food moves to the intestines where nutrients are absorbed and assimilated before waste is eliminated from the body. Organs like the liver, pancreas, and kidneys help at various parts of the process. Though the details may differ, these major components are present in all members of Chordata.

All chordates (including this human) use a mouth, stomach, and intestines for digestion.
human digestive system


To fully understand how Chordata digestion works, let's take a look at a few examples.

Tunicates are commonly known as sea squirts! These organisms live on the ocean floor. Food enters the body from the inhalant siphon, which basically functions as a mouth. It then passes through a structure called a pharynx where food particles are filtered out of the surrounding water that was also ingested.

Captured food moves to the stomach, where it is digested, and then on to the intestines, where nutrients are absorbed. Waste material leaves the intestines and goes into the atrium until it is expelled via the exhalant siphon. Though some of the structures are different, the general pathway food takes is the same as other chordates.

A tunicate, or sea squirt, on the ocean floor.

Birds may eat plants and/or other animals. Food is ingested through the mouth and the beak or bill and the tongue are adapted to the bird's diet. Food enters the esophagus on its way to the stomach and is sometimes stored in the crop, where it softens more before entering the stomach.

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