Animal Kingdom Test 9

The vertebral column is a series of approximately 33 bones called vertebrae, which are separated by intervertebral discs. The column can be divided into five different regions, with each region characterised by a different vertebral structure.

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. 

Lateral line system, also called lateralis system, a system of tactile sense organs, unique to aquatic vertebrates from cyclostome fishes (lampreys and hagfish) to amphibians, that serves to detect movements and pressure changes in the surrounding water.

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.

 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.

Metamorphosis is the phenomena in which there are changes which transform the organism form 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 (Urochordata or Tunicata). The progressive, active and alert larva metamorphoses into a retrograde and sedentary bag-like creatures. The adult remains attached to a rocky substratum all their lives and use a current of water passing through their large and perforated pharynx to collect microorganisms on which they feeds.
Thus, the correct answer is option B.

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.

Pyrosoma are tunicates. These are the free-floating colonial tunicates. These organisms live on the upper layers of the oceans. They are cylindrical or conical shaped colonies. The colonies are made up of many number of individuals which are called as zooids. They are brightly bioluminescent. They have the ability to flash a pale blue-green light. This light is bright enough to be seen from a very far distance.
Thus, the correct answer is option A.

Urochordata is also called as Tunicata or tunicates. The term tunicates has been derived from the unique outer covering or tunic. The tunic is formed from proteins and carbohydrates. The tunic acts as an exoskeleton. The tunic is also referred as test. 
Thus, the correct answer is option D.

The notochord is also known as chorda dorsalis. It is a rod-shaped cord of cells on the dorsal aspect of an embryo, defining the primitive axis of the body and serving as the center of development of the axial skeleton. It is the common factor of all chordates.
So, the correct answer is option A.

Balfour (1880) established the phylum Chordata which included the vertebrates, Amphioxus and tunicates.The Phylum Chordata unites the diverse forms having a notochord, hollow dorsal nerve cord and pharyngeal gill-slits.

Urochordata is also called as Tunicata or tunicates. The term tunicates has been derived from the unique outer covering or tunic. The tunic is formed from proteins and carbohydrates. The tunic acts as an exoskeleton. The tunic is also referred as test. All urochordates are marine organisms. Most of them are sedentary and some are pelagic. The body is covered by a test. It is formed by tunicine which is rallied to cellulose. 
Thus, the correct answer is option B.

Urochordate animals show all three characters, like neoteny, retrogressive metamorphosis and paedogenesis. Neoteny is the phenomenon whereby an organism retains larval characteristics, when sexually mature and most likely occurs by mutation, in the course of evolution. They only reproduce sexually and produce tadpole-like larvae that are free-swimming and metamorphose into the adult in the water column. The larvae possesses advanced features like the notocord. The features are lost while the development of the larvae to form an adult. This type of metamorphosis in which there is retrograde loss in the features of the larvae is called as retrogressive metamorphosis. Paedogenesis is the act of reproduction by an organism that has not achieved physical maturity. 
Thus, the correct answer is option D.

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.

A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata, which is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals.Because of the high concentration of vanadium in the blood, it has been assumed that vanabins are used for oxygen transport like iron-based hemoglobin or copper-based hemocyanin. Unfortunately no scientific evidence can be found to back this hypothesis.

Protochordates are closely related to vertebrates. These lack some of the peculiar characteristics of chordates like the true skull, brain, skeleton. These are invertebrates. 
So, the correct answer is option A.

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.

The wheel organ is found in amphioxus, which is a specialized epithelium in the roof and sides of the adult lancelet oral cavity. It borders the oral epithelium proper. The wheel organ cells are tall and strongly ciliated and have dark, heterochromatin-rich nuclei. It draws food through the use of its cilia for digestion. 
So, the correct answer is option B.

The epithelial lining of oral hood forms 6 to 8 pairs of finger -like folds each formed by a ciliated groove bounded by a ciliated ridge and collectively called as 'wheel organs' or 'Muller's organs'. In rotifers, the cilia of wheel organ set up a vortex so that food can sweep into the mouth from water current. Hence, option B is correct.

The unpaired 'Hatscheck's nephridium' is the largest and most anterior of the nephridia in the body of the Branchiostoma. It is a single tubule which lies on the left side of the notochord running parallel to the left anterior aorta. It stretches from the anterior vestibule to a point immediately posterior to the velum where it opens into the endodermal pharynx. 
So, the correct answer is option B.

Herdmania is commonly known as sea squirt. It is an exclusively marine organism. They are found in shallow water. These are solitary and sedentary organisms which are attached to a rocky sea bottom. They are imbedded in a sandy flour. It is a cilliatory feeder and a microphagus animal. It is hermaphrodite and fertilization is external and development is indirect. 
Thus, the correct answer is option B.

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.

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.

Cephalochordates are the animals which belong to the chordates. The cephalochordates like Amphioxus and lancelets are known as filter feeders. These are the organisms that use cilia to generate a current of water. This current helps the movement of phytoplankton particles into the mouth. The fluid or water is entered through the ciliary current into the mouth of the organisms. 
Thus, the correct answer is option A.