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Right answer is (d) AGNATHA

The best I can explain: Urochordata, Cephalochordata and VERTEBRATA are sub-phyla of Chordata. These sub-phyla are classified based on the period of presence of NOTOCHORD in Chordates. Whereas unlike other three OPTIONS, Agnatha is a super CLASS in Chordates.

The correct answer is (b) False

Explanation: Transport or canal SYSTEM in Porifera helps in exchange of GASES, distribution of food, water removal, gathering of food. Canal system can’t help in FORMATION of new individual. Porifera undergoes either fragmentation or sexual REPRODUCTION to form a new individual.

Right CHOICE is (c) PLATYHELMENTHES have a complete digestive system

Best explanation: A digestive system with one OPENING to outside is called an incomplete digestive system and a digestive system with separate openings for ingestion and egestion is called complete digestive system. Platyhelmenthes and sea sponges have an incomplete digestive system.

The correct option is (a) MUSCULAR tissues

For EXPLANATION I would say: Mesoderm gives rise to skeletal and MUSCLE tissues, blood, lymph and connective tissues. Ectoderm gives rise to epidermis, hair, mammary glands and CNS. Endoderm gives rise to ORGANS like stomach, pancreas, urinary bladder and intestines.

Correct choice is (B) All the mollusks exhibit cephalization

For explanation I would say: Most of the mollusks don’t exhibit cephalization. Ganglia are present at IMPORTANT parts of their body. Many of them have eyespots that act as PHOTORECEPTORS. The anterior HEAD region has sensory tentacles that help in sense of touch.

Right OPTION is (c) Excretion OCCURS through malpighian tubules

To elaborate: Pair of MAIN nerve cords extends throughout their body. MOLLUSKS respire either through gills or MANTLE cavity. Excretion occurs through nephridia. They have an open type of circulatory system.

Right choice is (b) SCALES and FINS are present

Easiest EXPLANATION: Agnatha are also called as jawless fishes. Scales and fins are absent. They adopt parasitic mode of nutrition. Their circular mouth ACTS as sucker. They are aquatic and most of them are extinct. The only class that exists in this super-class is cyclostomata.

Right choice is (a) True

Explanation: ANIMALS classified into COELOMATES, PSEUDOCOELOMATES and acoelomates based on the PRESENCE or absence of pseudocoelom. ECHINODERMS, annelids, mollusks and arthropods are examples of coelomates.

The correct CHOICE is (b) COLLAR CELLS

To explain: Choanocytes are ALSO called as collar cells. They filter the food materials present in the water that enters the central CAVITY through minute spores called Ostia. This water leaves the central cavity through an opening called Osculum.

Correct choice is (c) These are mostly viviparous organisms

Easy EXPLANATION: Arthropods are dioecious animals. In most of the TERRESTRIAL arthropods, internal fertilization occurs whereas in the CASE of AQUATIC arthropods EXTERNAL fertilization occurs. Development of Embryo is either direct or indirect. These are mostly oviparous.

Right choice is (a) True

To EXPLAIN: GANGLIA FUSE to form brain in Arthropods. Ladder like nervous SYSTEM is present in these ORGANISMS. Paired ventral nerve cord run through different segments of the body. Paired Ganglia is noticed I each segment.

The correct OPTION is (a) Medusa

Easiest explanation: Coelenterates that are umbrella shaped are called Medusa and those that are cylindrical are called POLYP. Some cnidarians exhibit METAGENESIS i.e. both FORMS exist in alternative GENERATIONS.

Correct choice is (c) Some of these ANIMALS are dioecious and others are monoecious

The EXPLANATION: Arthropoda are triploblastic, segmented and hemocoelomate animals. Their Exoskeleton is made of chitin which helps them from EXTREME CONDITIONS. They are dioecious and internal FERTILIZATION is seen in terrestrial arthropods whereas external fertilization is noticed in aquatic arthropods.

Correct answer is (c) Their digestive SYSTEM is COMPLETE with stomach, food pipe and intestines

Explanation: Vertebral COLUMN is made of CARTILAGE in Cyclostomata. They don’t have a stomach. Their circulatory system is closed with a 2 chambered heart. Lamprey and hagfish are examples of this class.

The correct choice is (d) They have a COMPLETE digestive system

The explanation is: Tissue level of organization is present in Coelenterata. Sea anemone exists in colonies. Coelenterates have TWO layers of CELLS in their BODY i.e. they are diploblastic. They have an incomplete digestive system.

Correct option is (b) The functions of each and every segment are UNIQUE and don’t intersect in their functions

To EXPLAIN: Some animal bodies are divided into segments both internally and externally. ALONG with few specific functions each and every segment has many common functions. The phenomenon of segmentation is termed as metamerism. Segmentation HELPS few animals in LOCOMOTION.

The correct option is (d) In coelomates, cavities between the GUT WALL and mesoderm is absent

Easy explanation: Coelom is the cavity between the body wall and gut wall. It is the fluid filled space other than lymph vessels and BLOOD vessels. Animals are divided into coelomates, acoelomates and pseudocoelomates BASED on the presence or absence of the coelom or false coelom respectively.

Right choice is (c) Tissue LEVEL of organization REFERS to the way tissues combine to form organs which in TURN form ANIMAL body

To elaborate: Tissue level of organization refers to the grouping of cells to form tissues that combine to form an animal body. There are no organs PRESENT in this level of organization. Example: Platyhelmenthes.

Right OPTION is (c) The LARVAE is IMMOBILE and bilaterally SYMMETRICAL

Best explanation: Larval stage is bilaterally symmetrical and adults are RADIALLY symmetrical. They are dioecious and most of the times the fertilization is external. The larvae is immobile and bilaterally symmetrical. They have a complete digestive system with mouth on the ventral side and anus on the dorsal side.

Correct choice is (d) The DIGESTIVE system in Porifera is incomplete

The best explanation: The name Porifera comes from the pores present on the SURFACE of sponges. A hard and PROTECTIVE skeleton made up of sponging or spicules supports the BODY. Development of embryo takes place through an intermediate larval stage. The digestive system in Porifera is ABSENT.

Right answer is (c) Collar cells help in the distribution and filtering of food materials

The explanation: Water enters the central cavity through minute pores called as OSTIA and leaves the cavity through Osculum. FLAGELLATED cells CREATE water currents inside SPONGOCOEL. Collar cells filter the food materials and AMOEBOID cells distribute food materials.

Right answer is (a) Mesodermal cells

For explanation: Animals are CLASSIFIED as CHORDATES and non-chordates BASED on the presence or absence of notochord RESPECTIVELY. Notochord is a rod-like structure formed from mesodermal cells.

The correct choice is (a) OSCULUM

For explanation I would say: Minute pores called OSTIA let water into a central CAVITY called SPONGOCOEL. An opening on the upper side of the spongocoel that HELPS in egestion of water is called as Osculum.

Correct answer is (a) Hermaphrodite

Best EXPLANATION: The property of not having separate sexes in an organism is called Hermaphrodite. In organisms of this kind eggs and SPERMS are PRODUCED by the same individual. Example: SPONGES

Right choice is (b) Radially SYMMETRICAL

The best explanation: Sponges are asymmetrical. They contain UNEVEN branches growing on their surface that MAKES them asymmetrical. Symmetry is also considered as the basis of classification. An animal is considered to be radially symmetrical if their body looks similar when cut in any radial direction. Examples: Colentrates and echinodermata. An animal is considered to be bilaterally symmetrical if their body looks when cut along the LATERAL direction. Examples: Annelids, Arthropods and humans.

The correct option is (C) PLANARIA EXHIBITS this level of organization

To elaborate: Cells performing same FUNCTIONS group TOGETHER to form a tissue. Organs are absent in this level of organization. Cells are specialized with division of labour. Example for this level of organization is Hydra. Planaria exhibits organ level of organization.

Correct answer is (d) Agnatha

The best explanation: Urochordata, Cephalochordata and Vertebrata are sub-phyla of CHORDATA. These sub-phyla are CLASSIFIED based on the PERIOD of presence of notochord in Chordates. Whereas unlike other three options, Agnatha is a super CLASS in Chordates.

The correct option is (c) In most of the CASES, medusa is sessile

Easy explanation: Coelenterates are acoelomates. Tentacles have stinging capsules CALLED cnidocytes that help in CATCHING of PREY. In most of the cases, POLYP is sessile. Corals have skeleton that is made up of CaCO3.

The CORRECT option is (a) This is the second largest phylum of Animalia KINGDOM

The EXPLANATION: Arthropoda is the second largest phylum of Animalia Kingdom. They have jointed legs due to which they are named Arthropoda. Their jointed legs help them in FAST mobility. Their body is BILATERALLY symmetrical.

Correct choice is (d) The pigmented photo receptors are CALLED Oceli

Explanation: Annelids have ganglia in each segment that help in the muscular movements. They have TWO VENTRAL NERVE chords throughout the body. Specialized sensory receptors are present to help in sense of touch and LIGHT. Pigmented photo receptors called Oceli are present in Annelids.

The correct choice is (c) Mesoderm HOLDS the INTERNAL ORGANS in its own place

To elaborate: Body CAVITY is absent in acoelomates. In this type of animals, mesoderm HELPS in holding the internal organs in its own place. Coelenterates, platyhelminthes and porifera are the best examples for acoelomates.

Right ANSWER is (d) PORIFERA is the best example for coelomates

For explanation: Coelomates is also CALLED as Eucoelomates which MEANS true coelom. Body cavity is lined by mesoderm. Internal ORGANS are suspended in the coelom and are attached through peritoneum. Hemichordates, chordates, annelids and arthropods are the best examples for coelomates.

Right choice is (b) Mantle

Explanation: The soft spongy LAYER of skin over the hump is called Mantle. The gap between hump and the mantle is called mantle cavity. In some MOLLUSKS, mantle cavity acts as the RESPIRATORY ORGANS of the body.

The correct option is (c) Adamsia

Easy EXPLANATION: Pennatula, PHYSALIA, Adamsia and Meandrina are also called as Sea-pen, Portuguese MAN of war, Sea anemone and BRAIN coral respectively. All the above organisms belong to the phylum Coelenterata.

Correct answer is (d) In diploblastic organisms, mesoglea, a well differentiated substance, is present between ENDODERM and ECTODERM

For explanation: The word “blasted” derives its origin from the word blastula which means a hollow ball of cells formed during the early stage of embryo. If the NUMBER of cell layers in blastula is two in number, i.e. ectoderm and endoderm, then such organisms are considered to diploblastic. If the number of cell layers in blastula is three in number, i.e. ectoderm, MESODERM and endoderm, then such organisms are considered to triploblastic. In diploblastic organisms, mesoglea, an undifferentiated substance, is present between endoderm and ectoderm.