What are Chordates?
Organisms which have a proper notochord and other related features all throughout their life are called Chordates. Chordates are further divided into three major subphyla:
(i) Urochordata
- They are also called Tunicata. They have sac-like bodies which are usually found to be sessile.
- They have a notochord, a dorsal nerve cord, pharyngeal gill slits, and other characteristics that chordates
- The larval forms have post anal tails which help them swim. The larvae usually swim and settle on a solid and reliable substrate where they can adhere and then
- The sac-like structure helps in the movement of water in and out of the organism’s
For example, Ascidians, Thaliacea, etc.
Urochordata
Larva of Urochordata
Urochordates
- Cephalochordata
- They are small animals found buried in the sand for most of the They are also called
Amphioxus or Lancelets.
- They form an important link between the invertebrates and
- They have a dorsal nerve cord supported by the
- The other features of vertebrates are not developed
- They lack a proper digestive system. The digestive system consists of a simple, slender pouch with associated glands that aid by giving out digestive
- The mouth contains a unique feature called the Wheel organ which is a set of ridges that surrounds the oral cavity. It helps in the trapping of food particles as they enter the mouth along with water.
- The nervous system and other senses are also poorly
- Sexes are separate in the cephalochordates and fertilisation takes place externally. The initial life stages are spent as larvae which seem to be fish-like free-living
Cephalochordata
Wheel organ of Cephalochordata
- Vertebrata
- It includes highly evolved and well-developed
- It shows many subphyla under