Animal Kingdom Test 8

Tunicin is also called as animal cellulose. It is a substance present in the mantle, or tunic of the tunicates, which resembles or is identical with the cellulose of the plant kingdom. these are structural cellulose which is mainly present in the shell of several animals like tunicates.

Metamorphosis is the phenomena in which there are changes which transform the organism from its juvenile stage to adult stage. In the case of retrogressive metamorphosis, the larva possesses the advanced features which get lost during the development. The adult is sedentary or degenerated with the primitive characters. Retrogressive metamorphosis is a characteristic of ascidians. They are from the group of Urochordates or Tunicates. The active and alert larva metamorphoses into a retrograde and sedentary bag-like creature. The adult remains attached to a rocky substratum. 
Thus, the correct answer is option B.

Pronephros is the most basic of the three excretory organs that develop in vertebrates, corresponding to the first stage of kidney development. It is succeeded by the mesonephros, which in fish and amphibians remains as the adult kidney.The excretory organs of Amphioxus occur as segmentally arranged structures throughout the pharyngeal region and may be divided into three components: the solenocytes, the renal tubule, and the renal glomerulus.The solenocytes possess foot processes that rest upon the coelomic surface of the ligamentum denticulatum.

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.

Amphioxi are small marine animals found widely in the coastal waters of the warmer parts of the world and less commonly in temperate waters. Both morphological and molecular evidence show them to be close relatives of the vertebrates. A brief treatment of amphioxi follows. For full treatment, see cephalochordate.

Herdmania is called as degenerated Chordata because its excretory system contains protonephridia. The absence of heart and kidney, paired limbs or paired fins, a distinct head, distinct paired sense organs, gonads are without gonoducts.
So, the correct answer is option D.

A neural gland (supra neural gland) is present in the brain in Herdmania. It is brown in colour. It is present in the mantle. It is 4 mm in diameter. It shows branching tubules. So, the correct answer is option B.

The fertilized eggs of urochordates undergo holoblastic and unequal cleavage. The egg develops to form the blastula. The blastula shows upper micromeres and lower macromeres. When the invagination of the macromeres occurs, gastrulation takes place and the structure of gastrula is formed. This gastrula develops into a tailed larva. This larvae is called as tadpole larva.The larva is free-swimming and exhibits all chordate characteristics. It has a notochord, a dorsal nerve cord, pharyngeal slits and a post-anal tail.
Thus, the correct answer is option B.

Chordates are animals possessing a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle and a post-anal tail for at least some period of their life cycles. So, the nerve cord is hollow and is placed dorsal to the gut.
So, the correct answer is option B.

Chordates are animals possessing a notochord. The notochord, later on, gives rise to a bony vertebral column, which surrounds and protects the spinal cord.
So, the correct answer is option D.

Retrogressive metamorphosis means degenerative changes wherein an active larva metamorphoses into a sedentary adult. 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.

Chordates have central dorsal hollow nerve cord, which is absent in non-chordates. Chordates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail for at least some period of their life cycles.
So, the correct answer is option B.

The solitary ascidian Herdmania momus is one of the most commonly encountered species of ascidians. While commonly referred to simply as sea squirts, this name is ambiguous, as it can refer to any member of the sub-phylum Tunicata.This solitary ascidian is sometimes referred to as the red-throated ascidian, as its two siphons are a vivid red in colour. However, most solitary ascidians that are encountered are so covered in algae that the coloration is often not visible. When found at depth the red colourations may also not be visible, as lower frequencies of light are absorbed by the layers of water above.

The solitary ascidian Herdmania momus is one of the most commonly encountered species of ascidians. While commonly referred to simply as sea squirts, this name is ambiguous, as it can refer to any member of the sub-phylum Tunicata.

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.

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.

Branchiostoma is one of the few living genera of lancelets. It is the type genus of family Branchiostomidae. These small vaguely eel- or snake-like animals are close relatives of vertebrates.

Adult tunicates, such as the ones shown in Figure below, do not bear much resemblance to other chordates. As adults, most tunicates are sessile (they do not move around) filter feeders that lack a notochord and a post-anal tail. They also lack the body segmentation that is found in other chordates characters.

Herdmania is a marine animal. They belongs to phylum Chordata. They are included in the sub phylum Urochordata. They are sedentary type of animals. They are fixed to the substratum or rock with the help of the flat base like structure. Whenever the organisms are disturbed, they suddenly contracts their body and emits inner contents with force through its apertures. So, they are commonly called as sea squirt. The larvae show retrogressive metamorphosis in which there is loss of advanced features while development to adult. 
Thus, the correct answer is option A.

Chordates are basically segmented (metameric) animals, although this repeating pattern often can be seen strongly only as embryos develop. One can see a hint of segmentation in the construction of the backbone, it's attached muscles, and our peripheral nervous systems. 

Therefore, the correct answer is option C.