Test: Phylum Hemichordata and Chordata - NEET MCQ

Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. These can be traced in cartilaginous fish, such as sharks and rays. Early embryos of different vertebrates resemble each other in possessing certain similar structures, like gill slits. Therefore gill slits of chordates occur in the pharynx of all chordates embryos and pharynx of some aquatic adult chordates. Hence, option C is correct.

The dorsal hollow nerve cord is part of the chordate central nervous system. In vertebrate fishes, the pharyngeal slits become the gills. Humans are not chordates because humans do not have a tail. Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column.

Amphioxus are fish-like marine chordates. The notochord is a flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In case of Amphioxus, it is retained in the adults.
So, the correct answer is option C.

• Lobe-finned fishes were ancestors of tetrapods.
• Tetrapoda are classified into 4 sub-classes i.e. Amphibia, Reptilia, Aves and Mammalia.
• The word tetrapoda means those that have four limbs.
• Most of them are terrestrial.

Protochordates are an informal category of animals (i.e., not a proper taxonomic group). This group has the animals that possess some but not all characteristics of chordates. They have pharyngeal gill slits and a dorsal nerve cord, however, they lack vertebral column and paired appendages.
So, the correct answer is option D.

To determine how many of the statements are correct, let's analyze each one:

A. Mouth is located ventrally: This is typically true for certain aquatic animals like fishes.

B. Notochord is persistent throughout life: This is true for some chordates like members of the subphylum Cephalochordata.

C. Gill slits are separate and with operculum: This is true for bony fishes (class Osteichthyes) where the gill slits are covered by an operculum.

D. Air bladder is absent: This is true for cartilaginous fishes (class Chondrichthyes) where the air bladder (swim bladder) is absent.

Since we don't have the actual figure, I'll provide possible interpretations:

• If the figure represents a bony fish (Osteichthyes), statements A, C, and D would be correct, but B would be incorrect (as the notochord is not persistent in bony fishes).

• If the figure represents a cartilaginous fish (Chondrichthyes), statements A, B, and D would be correct, but C would be incorrect (as they do not have an operculum).

Assuming the figure represents a fish with characteristics closest to either class, three statements are most likely correct.

The correct answer is:

3. Three.

 A method of feeding used by lancelets and many other aquatic invertebrates. The movement of cilia causes a current of water to be drawn towards and through the animal, and microorganisms in the water are filtered out by the cilia. "ciliary feeding.

Protochordates are an informal category of animals. Protochordates are also known as Acrania. They are characterized by the absence of vertebral column. They do not have the skull or cranium. They do not possess jaws. This group is composed of the phylum Hemichordata and the subphyla Urochordata and Cephalochordata. 
Thus, the correct answer is option B.

In chordates, four common features appear at some point during development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

The Urochordata , also known as Tunicates and Ascidians , are more commonly known as "sea squirts." They belong to the same phylum as the vertebrates although adults do not have a backbone. The name sea squirt comes from the way water is pushed out through the exhalant siphon.

Solution:
Both statements are correct. Hemichordates were previously considered a sub-phylum under Phylum Chordata but are now classified separately. The stomochord is homologous to the notochord, explaining their reclassification.

 In Urochordata or tunicates, the notochord is present only in the larval tail. Tail and nervous system are reduced in adult because the adult is sedentary. Common examples of Urochordata are Ascidia, Salpa, Doliolum. Salpa is a barrel-shaped, planktonic tunicate. Doliolum is a genus of tunicates.
Thus, the correct answer is option C.

• In amphibians, blood passes the heart twice i.e. they have double circulation.
• Left auricle deals with oxygenated blood whereas right auricle deals with deoxygenated blood.
• Ventricle deals with both oxygenated and deoxygenated blood.
• Tympanum represents ears in amphibians.

Cephalochordates are Urochordates are marine organisms. In the members of the cephalochordates, the notochord is persistent. The notochord is present throughout the body. In case of the members of the Urochordates, the notochord is present in posterior half of the body of the organism. Thus, the organisms in the two groups are divided on the basis of the length of notochord. 
Thus, the correct answer is option A.

Cephalochordata are small, segmented marine animals that possess elongated bodies with a notochord that extends the length of the body, extending from head to tail, persisting throughout the animal's life. Cephalochordates are represented in modern oceans by the Amphioxiformes. 

Hemichordata closely relates the Chordates. It contains marine deuterostome animals. They have a tubular structure known as stomochords. Stomochords arise in embryonic development as an out-pocketing from the roof of the embryonic gut anterior to the pharynx. In adults, they extend dorsally from the pharynx into the proboscis and serve to communicate with the oral cavity. Their walls are composed primarily of epithelial cells, but ciliated and glandular cells are also present.Balanoglossus belongs to the Hemichordata phylum. So, it has buccal diverticulum.
So, the correct answer is option C.

• Urochordata is classified under Protochordates.
• They have post anal tail only till their larval stage.
• Most of these are marine and almost extinct.
• They contain pharyngeal gill slits in the form of gill clefts.

 In hemichordates, Circulatory system is of open type. Respiration takes place through gills. Excretory organ is proboscis gland. Sexes are separate. Fertilisation is external. Development is indirect.