Option B.Pharyngeal gill slits are present in hemichordates as well as in chordates. Notochord is present in chordates only. Ventral tubular nerve cord is characteristic feature of non-chordates

Hemichordates and Chordates: Similarities in Pharynx with Gill Slits

Hemichordates and Chordates are two phyla of animals that share several similarities, one of which is the presence of a pharynx with gill slits. This characteristic is crucial for their respiratory and feeding functions.

1. Hemichordates
Hemichordates are a group of marine organisms that are considered to be the closest living relatives of the Chordates. They are characterized by their unique body plan, which consists of three main parts: proboscis, collar, and trunk.

The pharynx in hemichordates is a muscular structure located in the anterior part of the body. It serves as both a respiratory organ and a filter-feeding apparatus. The pharynx is lined with gill slits, which are openings that allow water to flow in and out. These gill slits are similar to the ones found in Chordates.

2. Chordates
Chordates are a diverse group of animals that includes vertebrates (animals with backbones) and some invertebrate relatives. They are characterized by several key features, including a notochord, a dorsal hollow nerve cord, and pharyngeal gill slits.

The pharynx in chordates is an important structure involved in respiration and feeding. It is located in the throat region and connects the mouth to the esophagus. Like in hemichordates, the pharynx in chordates also possesses gill slits. These slits are openings on the sides of the pharynx that allow water to pass through. In aquatic chordates, such as fish, the gill slits are essential for respiration, while in terrestrial chordates, such as humans, they are present during embryonic development but later develop into other structures, such as the eustachian tube.

3. Similarity: Pharynx with Gill Slits
The presence of a pharynx with gill slits is a significant similarity between hemichordates and chordates. Both groups utilize these gill slits for respiration and feeding purposes. The gill slits allow water to enter the pharynx, where oxygen exchange can occur in aquatic species, and in both groups, the gill slits are lined with specialized structures that aid in filter-feeding.

Conclusion
In conclusion, the important characteristic shared by hemichordates and chordates is the presence of a pharynx with gill slits. This similarity reflects their common ancestry and the evolutionary significance of this structure in their respiratory and feeding functions.