Question

The cephalochordates
A. Are exclusively marine in habitat
B. Retain the three primary chordate characters throughout the life
C. Are ciliary feeders
D. All of the above

Answer 1

Cephalochordates have notochord and nerve cord present throughout life along the entire length of the body.

Step by step answer:
Cephalochordata is the subphylum of Protochordata. They are lower vertebrates, do not have a cranium, vertebral column, and skull. They are marine animals.
They have the three primary chordate characters- Notochord, dorsal hollow nerve cord, and paired gill slits. They are ciliary feeders which means that they use cilia for filter-feeding. Water is drawn into the mouth along with the phytoplankton present in the marine water with the help of the beating action of cilia. The motion of cilia resembles a moving wheel.

So, the answer is D, All of the above

Additional information:
The body is basically cylindrical and is divided into head and tail regions. Notochord extends from the rostrum to the tail. The buccal cavity has a wheel organ called Muller’s organ/rotary organ. The circulation is of closed type as they lack heart. The contraction is done by the ventral aorta. They have cells of Joseph which are sensory cells over the oral hood. They have olfactory receptors that are chemoreceptors in Kolliker’s pit. The excretion is done by protonephridia.
The sexes of cephalochordate are separate and development is indirect. Free swimming larvae show progressive metamorphosis. The sperm of Cephalochordata are the smallest among chordates.

Note: Protochordata is also known as acrania. Some examples of Cephalochordata are – Lancelet, Amphioxus, Branchiostoma.