Question

An important characteristic that Hemichordates share with Chordates is-

• A. Absence of notochord
• B. Ventral tubular nerve cord
• C. Pharynx with gill slits
• D. Pharynx without gill slits

Answer 1

The correct option is C

Pharynx with gill slits

The correct option is C

Explanation of correct option

1. Hemichordate refers to marine worm-like invertebrates that serve as a connecting link between echinoderms and chordates.
2. Examples include Balanoglossus, Graptolithina, Pterobranchia, etc.
3. Chordate refers to organisms that exhibit the presence of notochord during their developmental stage.
4. Examples include mammals, birds, reptiles, fishes, and amphibians.
5. Hemichordates and chordates consist of pharyngeal gill slits. These openings are situated between the outside and pharynx.
6. In hemichordates they help to filter feed on food particles whereas, in amphibians and fishes, they are used for gaseous exchange.

Explanation of incorrect option

Option A

1. The notochord is a rodlike flexible structure made of mesodermal cells.
2. It helps in distinguishing Hemichordates from Chordates, as Chordates have a tubular, dorsal notochord.
3. In Hemichordates, it is absent and the nervous system is present in the collar region.

Option B

1. The nerve cord refers to the nervous tissue present above the notochord. In the vertebrates, the fate of the embryonic nerve cord is the brain and the spinal cord.
2. Nerve cord present in Chordates is dorsal and hollow.
3. Nerve cord present in Hemichordates is dorsal and restricted to the collar region.

Option D

1. Hemichordates and Chordates show the presence of pharyngeal gill slits.
2. They are absent in Non-chordates.

Final answer

An important characteristic that Hemichordates share with Chordates is pharynx with gill slits.