Test: Classification of Chordates

Leech possesses a ventral central nervous System, Scorpion has a dorsal heart. Pharyngeal gill S|its and post- anal tail are characteristic features of chordates  Chameleon is a chordate, so it possesses pharyngeal gill-slits in embryonic stage. Octopus is a non-chordate.

Prawn, which is an arthropod, has colourless blood (haemolymph). Haemocyanin is a blue respiratory pigness present in the blood of molluscs.

Complete metamorphosis is a phenomenon by which a larva after moulting several times changes into an adult form. The life cycle of Musca includes four stages egg larva, pupa and adult.

Mollusca is normally oviparous and its development may be direct or indirect. If development is indirect then a occurs  through trochophore or veliger larva. Echinoder show bilateral symmetry in larvae but pentamerous rafers symmetry in adult. Fertilization is external. In arthropods body is divided into head thorax and abdomen. Respiratory organs consists of book gills, book lungs and tracheae Notochord is present in chordates at some stage of  their lives. Urinary and anal openings, may or may not be separate.

Parapodia are locomotory structures present in some annelids. Sea urchin belongs to phylum Echinodermata.

Presence of a muscular diaphragm is an exclusive character of class Mammalia. Diaphragm is a complex muscular partition that separates the thoracic cavity from fix abdominal cavity. It increases the efficiency of breathing.

Vertebrates belong to the subphylum Vertebrata of the phylum Chordata. All vertebrates share a common diagnostic character, the elaboration of anterior skill elements into a "cranium" or "skull" which houses varine sense organs and a comples brain. The distinctive vertebrate cranium and brain evolved even before the vertebral colour and are, therefore, more fundamental characteristic of vertebrates than the backbone.

In Cephalochordata, notochored extends from heaft tail and is persistent throughout their life. In Urochordate notochord is present only in larval stage restricted to.

Spongilla is a fresh water sponge in which the inner cellular layer of body consists of highly specialized flagellate cells called choanocytes. These cells are not found in leach dolphin and penguin.

Balaenoptera (Whale) and Delphinus (Dolphin) are auatic mammals. Equus (Horse) is terrestrial and Pteroous (Bat) is a flying mammal.

Lchthyophis (Blind worm) is a limbless amphibian.

Reptiles usually posses 3-chambered heart but crocodiles are an exception with 4-chambered heart. Not all chordates have a mouth with upper and lower jaw. Egg laying mammals include duck-billed platypus. Chondrichtlyes (cartilaginous fishes) are the fishes that have cartilaginous endoskeleton. There is no exception to this.

Humans belong to the phylum Chordata. Animals belonging to the phylum Chordata possess a notochord either during early embryonic life or throughout the embryonic life. In some, it is replaced by vertebral column. In humans, notochord is present only in the embryonic stage, it is replaced by vertebral column in the adult form.

Chordates are those animals that have rod-like notochord. Notochord is also present in vertebrates but in most adult vertebrates, the notochord is replaced by vertebral column, which is the peculiar feature of vertebrates. Thus, we can say that all vertebrates are chordates but as chordates are not vertebrates.

Sea horse and flying fish are fishes and fishes are cold-blooded animals i.e. the temperature of their body varies with the environment. Ornithorhyncus is oviparous, crocodiie has 4-chambered heart, Ascaris and Ancylostoma do not show metameric segmentation.

Testudo (tortoise) belonging to class Reptilia is a poikilotherm.

Hermaphrodite organisms are those organisms in which both male and female sex organs are present in a single individual. Earthworm, tapeworm, leech and sponge are hermaphroditic organisms.

Uricotelic animals are those animals that excrete their waste matter in the form of uric acid. Reptiles, birds, lard snals and insects are uricotelic animals.

Silver fish and cray fish belong to the phylum Arthropoda. Cuttle fish belongs to the phylum Mollusca and jelly fish belongs to the phylum Coelenterata.

A - Pila
B - Balanoglossus
C - Pristis
D - Ornithorhynchus

Animals show four different grades of organization, (i) Protoplasmic grade found in protozoans. (ii) cellular grade is the characteristic of sponges and mesozoans because in a sponge, cells exhibit division of labour for performing specialized functions. (iii) Tissue grade is of two types : Cell-tissue grade is seen in coelenterates as there are cells not only specialized for different functions but also certain similar cells gather together to form tissue as well. Tissue - organ grade appears in flatworms (Platyhelminthes) with arrangement of tissues to form organs, (iv) In organ system level of organisation, organs are joined in a system to perform basic functions. It is found in higher invertebrates and all vertebrates.

Parrot belongs to the class Aves and platypus and kangaroo belong to the class Mammalia. Both aves and mammals are homoiotherms i.e. the temperature of their body remains constant respective of the temperature of the environment.

Frog (Amphibian) is a cold blooded animal i.e. its body temperature varies with the temperatue of the environment. Pigeon (Aves) is a warm blooded animal i.e. its body temperature remains constant irrespective of the temperature of the environment. Wall lizard (Reptile) possesses dry and cornified skin. Earthworm (Annelid) is a dioecious animal i.e. both male and female sex organs are present in the Single individual.

An animal having characters like triploblastic, bilateral symmetry, coelomate, chitinous exoskeleton, head, thorax, abdomen as body parts, and jointed appendages is placed under 'Arthropoda'.

Subphylum Vertebrata is divided into two divisions. They are agnatha (jawless) and gnathostomata (with jaw). Agnatha are further divided into two classes-Ostracodermi, which is extinct and Cydostomata (e.g., hag fish). Jawed vertebrates are divided into two superdasses-Pisces (true fish) and Tetrapoda (four limbs).

The given animal belongs to subphylum hemichordata. The name of the animal is Balanoglossus or acorn worm. In it, true notochord is absent but gill slits are present.

Amphibians do not have scales.

Salamandra belonging to the class Amphibia has a tympanum that represents ear and in it fertilization is external. Ascaris has unsegmented body and it Belongs to the phylum Aschelminthes. Pteropus is viviparous. Aurelia has tissue level of organization.

Osteichthyes is a class of fish that includes bony fish. Some of the characteristics of this class include:

• Body is streamlined and mouth is terminal: This characteristic is correct and would not be excluded from the list of characteristics of Osteichthyes.

• Gills are covered by operculum: This characteristic is correct and would not be excluded from the list of characteristics of Osteichthyes.

• Skin covered with cycloid and placoid scales: This characteristic is incorrect and would be excluded from the list of characteristics of Osteichthyes. Osteichthyes have scales on their skin, but these scales are not necessarily cycloid or placoid.

• Many of them are viviparous: This characteristic is incorrect and would be excluded from the list of characteristics of Osteichthyes. Many Osteichthyes are oviparous, meaning they lay eggs, rather than being viviparous, meaning they give birth to live young.

Therefore, the correct answer is (iii) and (iv).