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The correct option is (d) The necessary condition for being a mammal is to give birth to their young ones

The explanation: African ELEPHANT is the largest mammal on the Earth. Mammalia derives its origin from Latin word MAMMA which means BREAST. MAMMALS have HAIR or fur and are warm-blooded. The necessary condition for being a mammal is to feed their young ones with milk. Although most animals reproduce by laying eggs there are few exceptions to this.

Right answer is (b) Left AURICLE deals with deoxygenated blood

Explanation: 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.

Right ANSWER is (b) Warm blooded ANIMALS

The best I can EXPLAIN: Homoiothermous are the warm blooded animals i.e. they can generate heat internally. Examples of the warm-blooded include aves and mammals and examples of COLD blooded animals include reptiles and Pisces.

Right option is (b) Scales

To elaborate: SCUTES are also called scales. Reptiles are COVERED with scales and HELP them in movement and in RESPIRATION. Vipera, garden lizard, chelone, testudo, alligator and hemicydactylus are examples of scales.

Right OPTION is (a) Chondrichthytes are jawless fishes

The explanation: Chondrichthytes have powerful jaws. They have stream-lined BODY. Notochord is present through-out their LIFE. Their skin is covered with pointed denticles. Some chondrichthytes like Tripado have electric organs to paralyze the prey. Some of them also use POISONOUS STING to catch prey.

The correct option is (b) They are cold-blooded animals and can regulate the BODY temperature

Easiest EXPLANATION: PISCES have a streamlined body and a muscular tail that helps them in their MOVEMENT. They are cold-blooded animals and can regulate the body temperature. Their heart is 2 chambered. Their skeleton is made of cartilage and bone.

Right option is (a) True

The best I can EXPLAIN: Mammals are the milk feeding animals. Mammals are derived from the Latin WORD “mamma” which means BREAST. All the mammals feed the animals with milk. Sometimes, mammals lay eggs to reproduce and MAY give BIRTH to reproduce.

Correct answer is (b) Latin

Explanation: The WORD Chordata derives its origin from the Latin word Chordate which means those that POSSES’ chord. In most of the chordates spinal CORD might gradually MATURE to FORM back bone.

The correct option is (c) Amphibians

Explanation: SALAMANDER is an example of the phylum AMPHIBIA. Salamander can survive both in WATER and on LAND. They use their GILLS when inside water and they use lungs when on land. Their skin is moist.

The correct OPTION is (b) All of them have a three-CHAMBERED heart

Easiest explanation: Reptiles are cold-blooded animals with SCALES on them. Most of them have three-chambered heart except crocodile. Crocodile has a four chambered heart. KIDNEYS are present for excretion. These are oviparous.

Correct choice is (C) They have cold-blooded animals

The explanation: SCALES are ABSENT and skin is dry except at the one end there is an OIL gland. Endoskeleton is made of BONES and they respire through lungs. They are warm-blooded animals. They are dioecious and oviparous.

The CORRECT answer is (a) Endoskeleton composition

Explanation: PISCES are sub-classified into CHONDRICHTHYTES and OSTEICHTHYTES based on the composition of endoskeleton. In Chondrichthytes or CARTILAGINOUS fishes, endoskeleton is made of cartilage. In Osteichthytes, endoskeleton is made of bone.

Correct answer is (d) REPTILES are warm blooded ANIMALS

To explain: Reptiles cannot generate their body heat internally like humans do. Reptiles cannot sense smell like humans do instead they flick their tongue out in order to sense chemo receptors. Reptiles DERIVE its origin from the WORD reptum which MEANS creep or crawl. Reptiles are cold blooded animals.

The correct answer is (b) They are warm-blooded animals

Explanation: AMPHIBIANS can live both on land and water. They are cold-blooded animals i.e. they can’t regulate temperature. They have three chambered HEART. They have GILLS/ LUNGS to respire.

The correct answer is (d) Bats are the only mammals that lay eggs and feed their young ones with milk

The best I can EXPLAIN: Mammals are mostly TERRESTRIAL and feed their young ones with milk. Scales are absent, instead hairs, SWEAT and oil glands on skin. They RESPIRE through lungs and their heart is four-chambered. Platypus is the only mammal that LAYS eggs and feed its young ones with milk.

The CORRECT choice is (b) Air sacs are sites of gas exchange in Avian Dinosaurs

The explanation is: The AVES have hollow BONES and help them to fly. Air sacs are not sites of gas exchange in Avian Dinosaurs. Humming BIRD is the smallest bird. Ostrich and penguins are few birds that can’t fly.

The correct answer is (C) GILLS are SEPARATE without operculum

Best explanation: Swim bladder HELPS them retain buoyancy. Many of them are edible. Gills have operculum. Skin covered with cycloid/ ctenoid SCALES. Most of the Osteichthyes like Katla and Rhono are edible.

Right CHOICE is (b) This super class is classified into PISCES and tetrapods based on their type of blood

Explanation: Gnathostomata are vertebrates with jaws. This super class is classified into psices and tetrapods based on the ORGANS they USE for their movement. Pisces use FINS for their movement. Tetrapods use limbs for their movement.

Right answer is (c) The WORD TETRAPODA MEANS those that have four chambered heart

The best I can explain: 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.

Correct choice is (C) They have a dorsal heart ALONG with dorsal and ventral blood vessels

Explanation: Mollusks constitute the second largest phylum of Animal KINGDOM. They have organ system LEVEL of organization. They have open type of circulatory system. Their body is covered with calcareous shell.

The correct answer is (a) Nereis is a monoecious and Pheretima are dioecious

To explain I would say: Nereis is a dioecious and Pheretima are monoecious. Annelids have a complete digestive system with Pharynx, Esophagus, Stomach and Intestines. Annelids possess HEART and blood vessels i.e. they have a CLOSED circulatory system. LOCUSTA is ONE of the sociable Arthropods.

Correct option is (a) Hemichordates

Best explanation: ANIMALS are classified considering several factors like level of organization in the organism, symmetry, ARRANGEMENT of CELLS in the embryo, presence or absence of coelom, segmentation in the organism and presence or absence of notochord. Hemichordate is ONE such organism which has organ SYSTEM level of organization, bilateral symmetry and body cavity.

Right choice is (b) Post anal tail must be PRESENT in CHORDATES

Easy explanation: Chordates have PAIRED muscles. Post anal tail is present at the embryo but might VANISH after certain period of time. Their notochord also vanishes after certain period of time. Pharyngeal gill slits are present.

Correct CHOICE is (C) Dorsal nerves act as sensory nerves of the body

For explanation I would say: Nerve ring made of FOUR GANGLIA serves as brain. Nerve chords are PRESENT on the dorsal and ventral side of their body. Dorsal nerves act as motor nerves of the body. Ventral nerves act as both motor controllers and sensory nerves of the body.

Correct CHOICE is (a) True

The explanation: Ascidia, Salpa, Doliolum ETC. are examples of Urochordata. Branchiostoma which resembles like finless FISH is actually an example of Cephalochordata. The Cephalochordates and UROCHORDATES are grouped under Protochordates.

Right answer is (a) Obelia (POLYP) PRODUCES medusa by fragmentation

Explanation: Obelia (polyp) produces medusa by budding. Medusae undergoes sexual reproduction to PRODUCE polyp. Obelia exists in both the forms in alternate GENERATIONS. This process is called METAGENESIS.

The correct CHOICE is (b) False

The BEST I can explain: In an open circulatory system, INTERSTITIAL fluids and blood has no specific distinction and therefore CALLED as hemolymph. Whereas in closed circulatory system, interstitial fluids and blood has specific distinction. Because in closed circulatory system, blood flows through blood vessels.

Right answer is (a) True

For explanation I would say: Most of the sponges are ASYMMETRIC WHEREAS few sponges are radially symmetrical.For EXAMPLE, in CASE of sea stars bilateral symmetry is SEEN in the initial stage and radial symmetry in adult forms.

Correct CHOICE is (a) True

The best I can explain: Some animals have a SINGLE OPENING both for INGESTION and egestion. This TYPE of digestive system is called as incomplete digestive system. Incomplete digestive system is found in animals like tapeworm.

Right option is (c) They adopt tracheal mode of respiration

The explanation: The DIGESTIVE SYSTEM in hemichordates is complete with both MOUTH and anus. They are bilaterally symmetrical and are coelomates. They use their gills to respire. These organisms are also CALLED as ACORN worms.

Right CHOICE is (d) CLOSED circulatory SYSTEM is exhibited by arthropods

The explanation: In open circulatory system, BLOOD is pumped by heart into blood cavity. In closed circulatory system, blood is enclosed in blood vessels. Interstitial fluid is separated from blood in the case of closed circulatory system. Closed circulatory system is exhibited by CHORDATES and open circulatory system is exhibited by mollusca and arthropods.

Right choice is (d) HYDRA exhibits this level of organization

The explanation: In cellular level of organization, a group of cells combine to FORM the whole body. Each cell carries over a specific FUNCTION. This level of organization is also CALLED as cell aggregate of body plan. Sponges exhibit this level of organization. Hydra exhibits TISSUE level of organization.

The correct answer is (d) All of these animals have a cavity between their digestive tract and body wall called as coelom

Easiest explanation: Organs group to form organ systems. Each and every organ SYSTEM is specialized to PERFORM a specific physiological activity. Annelids exhibit this level of organization. Some of these animals are COELOMATES, few others are pseudo coelomates and others are ACOELOMATES.

Correct option is (d) Levels of organization

For explanation I would say: Levels of organization, SYMMETRY, arrangement of cells in embryo, presence of coelom, segmentation and presence of notochord are the BASIS for the classification in ANIMALIA. SINCE all the animals are heterotrophic, there is no need to classify Animalia based on their mode of nutrition.

Right option is (d) They are monoecious

For explanation: EMBRYO development is indirect i.e. they have an INTERMEDIATE larval stage. The circulatory SYSTEM is of closed type i.e. they have a dorsal heart and BLOOD vessels. They have dorsal and ventral nerves that help in coordination. They are DIOECIOUS.

The correct option is (d) The circulatory system is closed and they have a heart along with BLOOD vessels

To explain I would say: The word “Echino” MEANS spiny and “dermata” means skinned. Echinoderms are dioecious with fertilization being EXTERNAL in most cases. They have a central nerve ring that extends throughout their body. The circulatory system in Echinoderms is of open type.

The correct CHOICE is (a) They must have notochord at every point of their LIFE

For EXPLANATION I would say: In chordates, notochord at some point of their life and may vanish after certain period of time. They have a post anal tail. They have a dorsal NERVE cord. They have a ventral HEART.

Correct CHOICE is (a) True

The explanation: Mollusks have a file like rasping organ called as RADULA that helps them in CATCHING prey. Mollusks have GANGLIA at important parts of their body which helps them perform important FUNCTIONS.

The correct option is (c) They reproduce both sexually and asexually

Best EXPLANATION: CTENOPHORES are radially symmetrical. They are diploblastic. They reproduce only by SEXUAL reproduction. They have eight rows of ciliated comb PLATES on their BODY. Examples of Ctenophores are Ctenoplana and Pleurobrachia.

The CORRECT answer is (d) Hemichordates are organisms that contain NOTOCHORD like chordates but lack in all other features

The EXPLANATION: Hemichordates have three main parts in their body, namely, Proboscis, Collar and a long trunk. Open circulatory system is present in these organisms. EXCRETION takes place through proboscis gland. Hemichordates don’t have a notochord instead have a structure similar to notochord called as stomochord.

Correct answer is (d) Their brain is MADE up of 4 NERVE rings

Best explanation: Radial nerves extend through the ARMS from the central nerve RING that surrounds the mouth. Sensory tentacles help in sense of touch. Epidermis contains sensory CELLS that help in sense of touch. In Echinoderms, brain is absent.

Correct answer is (d) They have a heart and blood vessels to supply blood to the organs of the body

Explanation: ARTHROPODS consist of three parts, namely, head, THORAX and abdomen. Their respiratory organs can be either LUNGS or gills. Their digestive SYSTEM is complete with mouth, esophagus, intestines and rectum. Their circulatory system is of open TYPE i.e. they don’t have either heart or blood vessels to supply blood to the organs of the body.

The correct CHOICE is (a) All CHORDATES are vertebrates

To elaborate: All vertebrates are chordates but the vice-versa is not TRUE. Notochord is present during embryonic period. It is replaced by vertebral column in ADULTS. They might also not have post-anal tail after a certain period of time.

The CORRECT choice is (c) Notochord is formed from epidermal cells

To explain I WOULD say: Notochord is a rod-like structure formed on the dorsal side of animals. During the embryonic DEVELOPMENT, notochord GETS developed from mesodermal cells. Animals are classified as chordates and non-chordates based on the presence or absence of notochord. Pisces are an example for chordates.

Correct CHOICE is (a) True

The best explanation: In organ LEVEL of organization, organs are specialized to perform a specific action. Tissues are GROUPED to form organs. Example for this level of organization is Platyhelmenthes.