{"id":22518,"date":"2024-01-18T12:21:48","date_gmt":"2024-01-18T06:51:48","guid":{"rendered":"https:\/\/apboardsolutions.in\/?p=22518"},"modified":"2024-01-19T17:44:15","modified_gmt":"2024-01-19T12:14:15","slug":"ap-inter-1st-year-zoology-study-material-chapter-4","status":"publish","type":"post","link":"https:\/\/apboardsolutions.in\/ap-inter-1st-year-zoology-study-material-chapter-4\/","title":{"rendered":"AP Inter 1st Year Zoology Study Material Chapter 4 Animal Diversity-II: Phylum Chordata"},"content":{"rendered":"

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material<\/a> Lesson 4 Animal Diversity-II: Phylum Chordata Textbook Questions and Answers.<\/p>\n

AP Inter 1st Year Zoology Study Material Lesson 4 Animal Diversity-II: Phylum Chordata<\/h2>\n

Very Short Answer Type Questions<\/span><\/p>\n

Question 1.
\nList out the characters shared by chordates and echinoderms.
\nAnswer:
\nChordates and echinoderms are enterococci, deuterostomes, and bilaterally symmetrical.<\/p>\n

Question 2.
\nWrite four salient features of cyclostomes.
\nAnswer:<\/p>\n

    \n
  1. Cyclostomes are jawless aquatic forms.<\/li>\n
  2. The body is scaleless, long, slender, and eel-like in shape.<\/li>\n
  3. Endoskeleton is cartilaginous.<\/li>\n
  4. Vertebrae are represented by imperfect neural arches in some.<\/li>\n
  5. The mouth is circular and suctorial, Hence there are called Cyclostomes. Ex: Petromyzon.<\/li>\n<\/ol>\n

    Question 3.
    \nWhat is the importance of endostyle in lancelets and ascidians?
    \nAnswer:
    \nEndostyle is useful for accumulating and moving food particles to the oesophagus in lancelets and ascidians.<\/p>\n

    \"AP<\/p>\n

    Question 4.
    \nName the type of caudal fin and scales that are present in a Shark and Catla respectively.
    \nAnswer:
    \nThe caudalfin in shark is heterocercal and scales are placoid. The caudal fin is catla is homocercal and scales are cycloid.<\/p>\n

    Question 5.
    \nWhat is the importance of air bladder in fish?
    \nAnswer:
    \nFishes have an ‘air bladder’ acting as a ‘hydrostatic organ’ helping the fish float easily at the desired level without much expenditure of energy.<\/p>\n

    Question 6.
    \nHow do you justify the statement ‘heart in fishes is a branchial heart’?
    \nAnswer:
    \nThe heart of fish is two-chambered and is described as a branchial heart as it supplies blood only to the gills.<\/p>\n

    Question 7.
    \nWhat are claspers? Which group of fishes possesses them?
    \nAnswer:
    \nClaspers are formed from the posterior portion of pelvic fins in male cartilaginous fish. They serve as intermittent organs used to channel semen into the female’s cloaca during mating.
    \nEx: Chondrichthyes fishes possess Claspers.<\/p>\n

    Question 8.
    \nHow does the heart of an amphibian differ from that of a reptile?
    \nAnswer:
    \nThe heart of an amphibian is three-chambered. The heart of a reptile is incompletely four-chambered.<\/p>\n

    Question 9.
    \nName the structures that appeared for the first time in amphibians, in the course of evolution.
    \nAnswer:
    \nThe two pairs of pentadactyl limbs appeared for the first time in amphibians in the course of evolution.<\/p>\n

    Question 10.
    \nHow do you distinguish a male frog from a female frog?
    \nAnswer:
    \nThe male frog can be distinguished by the presence of sound amplifying vocal sacs and a copulatory pad on the first digit of each forelimb.<\/p>\n

    Question 11.
    \nWhat is a ‘force pump’ in a frog? Why is named so?
    \nAnswer:
    \nIn frogs, during pulmonary respiration, the buccopharyngeal cavity acts like a ‘force pump’. Due to the elevation of the buccopharyngeal cavity the air forces the glottis to open and enter the lungs.<\/p>\n

    Question 12.
    \nWhat are corporabigemina? Mention their chief function.
    \nAnswer:
    \nMidbrain is represented by a pair of optic lobes called corpora bigemina. The optic lobes are associated with the sense of sight.<\/p>\n

    \"AP<\/p>\n

    Question 13.
    \nDistinguish between mesorchium and mesovarium.
    \nAnswer:
    \nThe testes are attached to the kidneys and dorsal body wall by a double fold of the peritoneum called mesorchium.
    \nThe ovaries are attached to the kidneys and dorsal body wall by a double fold of the peritoneum called mesovarium.<\/p>\n

    Question 14.
    \nDistinguish between milt and spawn.
    \nAnswer:
    \nDuring amplexus, the mass of eggs and the mass of sperm released by the female and male are called spawn and milt.<\/p>\n

    Question 15.
    \nWhat are the ‘Golden ages’ of the first jawed vertebrates and the first amniotes?
    \nAnswer:
    \nThe Devonian period is considered the ‘golden age of first jawed vertebrates (Fishes).
    \nThe Mesozoic era is considered the golden age of amniotes (Reptiles).<\/p>\n

    Question 16.
    \nName two poisonous and non-poisonous snakes found in south India.
    \nAnswer:
    \nPoisonous Snakes:<\/p>\n

      \n
    1. Naja naja (Cobra)<\/li>\n
    2. Bungarus (Krait)<\/li>\n
    3. Vipera russelli (Chain viper)<\/li>\n<\/ol>\n

      Non-poisonous Snakes:<\/p>\n

        \n
      1. Ptyas (rat snake)<\/li>\n
      2. Tropidonotus (Pond or grass snake).<\/li>\n<\/ol>\n

        Question 17.
        \nIn which features does the skin of a reptile differ from that of a frog?
        \nAnswer:<\/p>\n

          \n
        • The skin of reptiles is rough and dry, covered by horny epidermal scales, and shields.<\/li>\n
        • The skin of a frog is thin, scaleless, and moist.<\/li>\n<\/ul>\n

          Question 18.
          \nDescribe a cat and a lizard on the basis of their chief nitrogenous wastes excreted.
          \nAnswer:
          \nBased on the nitrogenous wastes excreated by lizards are Uricotelic and cats are ‘Ureotelic’ animals.<\/p>\n

          Question 19.
          \nName the four extraembryonic membranes.
          \nAnswer:
          \nThe extraembryonic membranes namely amnion, allantois, chorion, and yolk sac.<\/p>\n

          Question 20.
          \nWhat are Jacobson’s organs? What is their function?
          \nAnswer:
          \nJacobson’s organs are the specialized olfactory structures, that are highly developed in lizards and snakes.<\/p>\n

          \"AP<\/p>\n

          Question 21.
          \nWhat are pneumatic bones? How do they help birds?
          \nAnswer:
          \nThe main bones in birds are extensions of air sacs without bone marrow are called pneumatic bones. These are helpful in flying birds.<\/p>\n

          Question 22.
          \nWhat is a ‘wishbone? What are the skeletal components that form it?
          \nAnswer:
          \nIn birds, both the clavicles are fused with the interclavicular to form a ‘V-shaped bone, called fiircula or ‘wish hone’ or ‘Merrythought bone’.<\/p>\n

          Question 23.
          \nWhat is continuous oxygenation of the blood? How is it made possible in birds?
          \nAnswer:
          \nThe lungs of birds are compact, spongy, undistensible lungs associated with air sacs. Air sacs facilitate continuous air supply is called ‘continuous oxygenation of the blood.<\/p>\n

          Question 24.
          \nDistinguish between the crop and the gizzard in birds.
          \nAnswer:<\/p>\n

            \n
          • The Oesophagus of birds is often dilated into a crop for the storage of food.<\/li>\n
          • The stomach is usually divided into glandular proventriculus and muscular gizzard a grinding mill.<\/li>\n<\/ul>\n

            Question 25.
            \nDistinguish between altricial and precocial hatchlings.
            \nAnswer:<\/p>\n

              \n
            • Altricial: Young ones of flying birds’ hatchlings are altricial.<\/li>\n
            • Precocial: Young ones of flightless bird hatchlings are precocial.<\/li>\n<\/ul>\n

              Question 26.
              \nIn which group of animals do we find three ear ossicles on each side and what are their names from the innermost to the outermost?
              \nAnswer:
              \nThe middle ear possesses three ear ossicles in the Mammalia group of animals. They are malleus, incus and stapes.<\/p>\n

              Question 27.
              \nHow does a mature RBC of a mammal differ from that of other vertebrates?
              \nAnswer:<\/p>\n

                \n
              • In mammals, mature RBC is enucleated and biconcave.<\/li>\n
              • In other vertebrates RBC is nucleate.<\/li>\n<\/ul>\n

                Question 28.
                \nName the characteristic type of vertebrae found in reptiles, birds, and mammals.
                \nAnswer:<\/p>\n

                  \n
                • Reptiles’ vertebrae are procoelons.<\/li>\n
                • Birds’ vertebrae are heterologous.<\/li>\n
                • Mammalian vertebrae are amphiplatyan.<\/li>\n<\/ul>\n

                  Question 29.
                  \nName the three meninges. In which group of animals do you find all of them?
                  \nAnswer:
                  \nMammals have three meninges. They are the outer dura mater, middle arachnoid mater, and inner diameter.<\/p>\n

                  \"AP<\/p>\n

                  Question 30.
                  \nName the vertebrate groups in which ‘renal portal system1 is absent.
                  \nAnswer:
                  \nThe renal portal system is absent in aves (birds) in vertebrate animals.<\/p>\n

                  Short Answer Type Questions<\/span><\/p>\n

                  Question 1.
                  \nGive three major differences between chordates and non-chordates and draw a sketch of a chordate’s body showing those features.
                  \nAnswer:
                  \nThe major differences between chordates and non-chordates.<\/p>\n\n\n\n\n\n\n\n\n
                  Chordates<\/strong><\/td>\nNon-chordates<\/strong><\/td>\n<\/tr>\n
                  1. Notochord is present.<\/td>\n1. Notochord is absent.<\/td>\n<\/tr>\n
                  2. Central nervous system is dorsal hollow, single and non-ganglionated.<\/td>\n2. Central nervous system is ventral, solid, double, and ganglionated.<\/td>\n<\/tr>\n
                  3. Pharynx is perforated by gill slits.<\/td>\n3. Gill slits are absent.<\/td>\n<\/tr>\n
                  4. Heart is ventral.<\/td>\n4. Heart is dorsal (if present).<\/td>\n<\/tr>\n
                  5. A post-anal tail is present.<\/td>\n5. Post-anal tail is absent.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                  \"AP<\/p>\n

                  Question 2.
                  \nName the four ‘hallmarks’ of chordates and explain the principal function of each of them.
                  \nAnswer:
                  \nThe hallmarks of chordates: All the chordates exhibit four fundamental characteristics. They are Notochord, Dorsal tubular nerve cord, Pharyngeal slits or clefts, and Post-anal tail.<\/p>\n

                  Notochord: It is a flexible rod-like structure situated along the mid-dorsal line between the gut and the nerve cord. It is derived from the embryonic chorda mesoderm. It is firm but flexible. It is present throughout life in the lancelets and cyclostomes. It is present in the tail of the tadpole larva of an ascidian, It is present in embryonic stages, but is replaced partly or wholly by the vertebral column in the adults of higher chordates. Remnants of notochord occur as nucleipulposi in the intervertebral discs of mammals.<\/p>\n

                  Dorsal tubular nerve cord: A single, hollow tubular, and fluid-filled nerve cord is situated above the notochord and below the dorsal body wall. It is derived from the ectoderm of the embryo. In the higher chordates, it gets enlarged to form a distinct brain at the anterior end the rest of it becomes the spinal cord.<\/p>\n

                  Pharyngeal slits of clefts: These are slit openings present on the Pharyngeal wall and meant for the exit of the water from the pharyngeal cavity. They are present throughout life in the protochordate, fishes, and some amphibians. These are present in larval stages in amphibians. They develop by in-pushing of ectoderm and corresponding out pursing of the endoderm. In land vertebrates, the gills become vestigial and nonfunctional and are restricted to embryonic stages only.<\/p>\n

                  Post-anal tail: Chordates have a tail extending posteriorly to the anus. It is lost in many species during late embryonic development. It contains skeletal elements and muscles, coelom and visceral organs are absent in it.<\/p>\n

                  Question 3.
                  \nDescribe the features of a tunicate that reveals its chordate identity.
                  \nAnswer:<\/p>\n

                    \n
                  1. The body of these animals is covered by cellulose-like covering tunicin, hence called tunicates.<\/li>\n
                  2. These possess Notochord in the tail region during the larval stage, hence called Urochordata.<\/li>\n
                  3. These are sedentary or pelagic marine forms.<\/li>\n
                  4. The notochord is present only in larval tails and degenerated in adults.<\/li>\n
                  5. Open type of blood vascular system with blood pigment vanadium.<\/li>\n
                  6. Indirect development with tadpole larva.<\/li>\n
                  7. Adults (mostly) show degenerate characters.<\/li>\n
                  8. The nervous system is represented in the adult by a single dorsal ganglion.<\/li>\n
                  9. They are bisexual or hermaphrodites.<\/li>\n
                  10. Ex: Ascidia, Salpa, Doliolum, Pyrosoma and Oikopleura.<\/li>\n<\/ol>\n

                    \"AP<\/p>\n

                    Question 4.
                    \nCompare and contrast sea squirts and lancelets.
                    \nAnswer:
                    \nSea squirts: These are included in class – Ascadiaceae of subphylum – Urochordata. These are sessile. These are solitary or colonial. The body is enclosed in a permanent test and un-segmented. All these are marine and occur from the surface water to greater depths. Coelom in the absent, pharynx is large and is perforated by numerous gill slits. Branchial aperture in anterior and atrial aperture is dorsal. The digestive tract is ‘complete’. The circulations system is of an open type, the heart is the tubular and the ventral heart. These are bisexual. Development generally includes a free-swimming tadpole larva. Notochordcontinued to the tail hence the name Urochordata.
                    \nEx: Ascidia
                    \n\"AP<\/p>\n

                    Lancelets: Cephalochordates are also called Lancelets. These are marine animals and are small fish without paired fins. These are typical chordates because they possess the notochord, tubular nerve cord, and pharyngeal slits throughout this life. The coelom is enterocoelic respiration mostly across the external body surface. The circulatory system is of a closed type, the heart, blood corpuscles, and respiratory pigments are absent. Excretion by protonephridia fertilization is external and development is indirect.
                    \nEx: Branchiostoma (amphioxus or Lancelet)
                    \n\"AP<\/p>\n

                    \"AP<\/p>\n

                    Question 5.
                    \nList out eight characteristics that help distinguish a fish from the other vertebrates.
                    \nAnswer:
                    \nGeneral characters:<\/p>\n

                      \n
                    1. Fishes are completely aquatic poikilothermic (cold-blooded) animals.<\/li>\n
                    2. The body of a fish is usually streamlined and differentiated into the head, trunk, and tail.<\/li>\n
                    3. The exoskeleton consists of mesodermal scales or bony plates. A few are scaleless.<\/li>\n
                    4. The endoskeleton may be cartilaginous or bony. Skull is monocondylic. Vertebrae are amphicoelous. Centrum is concave at both anterior and posterior faces.<\/li>\n
                    5. Locomotion is assisted by unpaired (median and caudal) fins along with paired (pectoral and pelvic) fins.<\/li>\n
                    6. The mouth is ventral or terminal. Teeth are usually acrodont, homodont, and polyphyodont.<\/li>\n
                    7. The exchange of respiratory gases is performed by the gills. The heart is ‘two-chambered’.<\/li>\n
                    8. Kidneys are mesonephric. Fishes are mostly ammonotelic and some are ureotelic. (cartilaginous fishes).<\/li>\n
                    9. Cranial nerves are 10 pairs, Meninx Primitiva is the only ‘meninx’ enveloping the central nervous system.<\/li>\n
                    10. The internal ear consists of three semicircular canals. Lateral-line sensory system (to detect movement and vibration in the surrounding water) is well-developed.<\/li>\n
                    11. Eyes are without eyelids and each eyeball is protected by a nictitating membrane.<\/li>\n
                    12. Sexes are separate. Fertilization is internal or external. Development may be direct or indirect.<\/li>\n<\/ol>\n

                      \"AP<\/p>\n

                      Question 6.
                      \nCompare and contrast cartilaginous and bony fishes.
                      \nAnswer:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
                      Cartilaginous fishes<\/strong><\/td>\nBony fishes<\/strong><\/td>\n<\/tr>\n
                      1. These are marine farms.<\/td>\n1. These live in all kinds of aquatic habits.<\/td>\n<\/tr>\n
                      2. Endoskeleton made by cartilaginous.<\/td>\n2. Endoskeleton made of bone.<\/td>\n<\/tr>\n
                      3. Body covered by placoid scales.<\/td>\n3. Body covered by cosmid, ganoid, cycloid or ctenoid scales.<\/td>\n<\/tr>\n
                      4. Caudal fin is heterocercal.<\/td>\n4. Caudal fin is homocercal.<\/td>\n<\/tr>\n
                      5. Operculum absent.<\/td>\n5. Operculum present.<\/td>\n<\/tr>\n
                      6. Air bladder absent.<\/td>\n6. Air baldder present.<\/td>\n<\/tr>\n
                      7. Gills are lamelliform and are five to seven on each side.<\/td>\n7. Gills are filamentous and are four on each side.<\/td>\n<\/tr>\n
                      8. These are ureotelic.
                      \nEx: Scoliodon, Pristic, Torpedo.<\/td>\n                      		8. These are mostly ammonotelic.
                      \nEx: Catla, Labeo, Exocetus, Hippocampus.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                      Question 7.
                      \nDescribe the structure of the heart of the frog.
                      \nAnswer:
                      \nThe blood vascular system consists of the heart, blood vessels, and blood. The heart is a muscular organ situated in the upper part of the body cavity. It has two separate atria and a single undivided ventricle. It is covered by a double-layered membrane called the pericardium. A triangular chamber called sinus venosus joins the right atrium on the dorsal side. It receives blood through three vena cavae (caval veins). The ventricle opens into the conus arteriosus on the ventral side. The conus arteriosus bifurcates into two branches and each of them divides into three aortic arches namely carotid, systemic and pulmocutaneous. Blood from the heart is distributed to all parts of the body by the branches of the aortic arches. Three major veins collect blood from the different parts of the body and carry it to the sinus venosus.
                      \n\"AP<\/p>\n

                      Question 8.
                      \nWrite eight salient features of the class – Amphibia.
                      \nAnswer:
                      \nGeneral characters of Amphibia:<\/p>\n

                        \n
                      1. They are the first tetrapods and lead a dual mode of life, i.e. on land and in freshwater.<\/li>\n
                      2. The body is divided into distinct ‘head’ and ‘trunk’. The tail may or may not be present.<\/li>\n
                      3. Skin is soft, scale-less (except for the members of Apoda), moist and glandular.<\/li>\n
                      4. The body bears two pairs of equal or unequal pentadactyle limbs (caecilians are limbless).<\/li>\n
                      5. Skull is dicondylic as in mammals. Vertebrae are mostly precocious (centrum is concave at its anterior face only) in the anurans, amphicoelous in the caecilians, and usually opisthocoelous (centrum is concave at its posterior face) in the urodeles. Sternum appeared for the first time in the amphibians.<\/li>\n
                      6. The mouth is large; teeth are acrodont, homodont, and polyphyodont.<\/li>\n
                      7. Respiratory gaseous exchange is mostly cutaneous; pulmonary and buccopharyngeal respiration also occurs. Branchial respiration is performed by larvae and some adult urodeles.<\/li>\n
                      8. The heart is three-chambered with sinus venosus and conus arteriosus. Three pairs of aortic arches and well-developed portal systems are present; erythrocytes are nucleated.<\/li>\n
                      9. Kidneys are mesonephric; ureotelic.<\/li>\n
                      10. Meninges are the inner pia mater and outer dura mater; cranial nerves are 10 pairs.<\/li>\n
                      11. The middle ear consists of a single ear ossicle, the columella Auris which is the modified ‘hyomandibula’ of the fishes.<\/li>\n
                      12. Tympanum, lacrimal and harderian glands appeared for the first time in the amphibians.<\/li>\n
                      13. Sexes are separate and fertilization is mostly external. Development is mostly indirect.<\/li>\n
                      14. e.g. Bufo (toad), Rana (frog), Hyla (tree frog), Salamandra (salamander), Ichthyophis (limbless amphibian), Rhacophorus (flying frog).<\/li>\n<\/ol>\n

                        \"AP<\/p>\n

                        Question 9.
                        \nDescribe the male reproductive system of a frog with the help of a labelled diagram.
                        \nAnswer:
                        \nMale Reproductive System of frog: The male reproductive system consists of a pair of yellowish and ovoid testes, which are attached to the kidneys and dorsal body wall by a double fold of peritoneum called mesorchium. Each testis is composed of innumerable seminiferous tubules which are connected to form 10 to 12 narrow tubules, the vasa efferentia. They enter the kidneys and open into the Bidders canal which is connected to the ureter through transverse canals of the kidney. The urinogenital ducts of both sides open into the cloaca.
                        \n\"AP<\/p>\n

                        Question 10.
                        \nWrite short notes on organs of special senses in frogs.
                        \nAnswer:
                        \nSpecial senses: Frog has sense organs such as the organs of touch, taste, smell, sight, and hearing. The well-organized structures among them are eyes, and internal ears, and the rest are ‘cellular aggregations’ around nerve endings. The receptors of touch occur in the skin. Organs of taste are called taste buds that lie on small papillae of the tongue. The organs of smell are a pair of nasal chambers.<\/p>\n

                        The organs of sight are a pair of eyes located in the orbits of the skull. Eyes are protected by eyelids. The upper eyelid is immovable. The lower eyelid is folded into a transparent nictitating membrane, which can be drawn across the surface of the eye. The retina of the eye contains both rods and cones. Cones provide ‘colour vision’ and rods are helpful in ‘dim light vision’.<\/p>\n

                        The ear is useful for hearing and balance. It consists of a middle ear closed externally by a large tympanic membrane (ear drum) and a columella that transmits vibrations to the inner ear. The inner ear consists of a utriculus with three semicircular canals and a small sacculus.<\/p>\n

                        \"AP<\/p>\n

                        Question 11.
                        \nList out the salient features of Exo and endoskeleton in reptiles.
                        \nAnswer:
                        \nThe exoskeleton of reptiles occurs in the form of horny epidermal scales, shields, and claws.
                        \nEndoskeleton:<\/p>\n

                          \n
                        1. Skull is monocondylic and many have temporal fossae.<\/li>\n
                        2. Each half of the lower jaws is formed by six bones.<\/li>\n
                        3. Vertebrae are mostly procoelous.<\/li>\n
                        4. The first two cervical vertebrae are specialized into the atlas and axis.<\/li>\n
                        5. The vertebral column is distinguished into cervical, thoracic, lumbar, sacral, and caudal regions.<\/li>\n
                        6. Most living reptiles possess two sacral vertebrae.<\/li>\n
                        7. Interclavicular is associated with the pectoral girdle.<\/li>\n
                        8. Ribs are single-headed except in crocodilians.<\/li>\n<\/ol>\n

                          Question 12.
                          \nList out the extant orders of the Class – Reptilia. Give two examples for each Order.
                          \nAnswer:<\/p>\n

                            \n
                          1. Chelonia – Chelone (marine green turtle), Testudo (terrestrial form), Trionyx (freshwater form)<\/li>\n
                          2. Rhynchocephalia – Sphenodon (a ‘living fossil’, endemic to New Zealand)<\/li>\n
                          3. Crocodilia – Crocodylus pulustris (Indian crocodile or mugger), Alligator (alligator), Gavialis gangeticus (Indian gavial or gharial)<\/li>\n
                          4. Squamata\n
                              \n
                            • Lizards – Hemidactylus (wall lizard), Chameleon, Draco (flying lizard)<\/li>\n
                            • Snakes\n
                                \n
                              • Poisonous Snakes: Naja naja (cobra), Ophiophagus hannah (King cobra), Bungarus (krait), Daboia\/Vipera russelli (chain viper)<\/li>\n
                              • Non-Poisonous Snakes: Ptyas (rat snake), Tropidonotus (grass snake or pond snake)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n

                                \"AP<\/p>\n

                                Question 13.
                                \nWhat are the modifications that are observed in birds that help them in flight?
                                \nAnswer:
                                \nSo many modifications are observed in birds that help them in flight.<\/p>\n

                                  \n
                                1. Exo and endo skeletons and body structure features might have contributed to their successful aerial mode of life.<\/li>\n
                                2. The exoskeleton consists of epidermal feathers. Feathers are unique to birds. They are useful for flight, particularly the Quill feathers help in flight.<\/li>\n
                                3. The body is boat-shaped and streamlined.<\/li>\n
                                4. Four limbs are modified into wings.<\/li>\n
                                5. Many bones are neumatic with extensions of air sacs.<\/li>\n
                                6. All modern flying birds are provided with powerful breast muscles (flight muscles) chiefly the pectoralis major and pectoralis minor.<\/li>\n
                                7. Lungs are associated with air and seas.<\/li>\n<\/ol>\n

                                  Question 14.
                                  \nWhat are the features peculiar to ratite birds? Give two examples of ratite birds.
                                  \nAnswer:
                                  \nRatite birds:<\/p>\n

                                    \n
                                  1. These are modern flightless running birds.<\/li>\n
                                  2. They are ‘discontinuous’ in their distribution like the lungfishes and marsupials.<\/li>\n
                                  3. They are characterized by the presence of reduced wings.<\/li>\n
                                  4. Feathers are without an interlocking mechanism.<\/li>\n
                                  5. Rectrices are absent or irregularly arranged.<\/li>\n
                                  6. Prren gland is absent.<\/li>\n
                                  7. Pygostyle is rudimentary or absent.<\/li>\n
                                  8. The sternum is like without a keel.<\/li>\n
                                  9. Clavicles are absent, and syrinx is absent.<\/li>\n
                                  10. The male animal has a penis.<\/li>\n
                                  11. Young ones are precocial.<\/li>\n
                                  12. Ex: Struthio camelus – (African ostrich); Dromaeus (Emu) Kiwi.<\/li>\n<\/ol>\n

                                    \"AP<\/p>\n

                                    Question 15.
                                    \nMention the most important features of the nervous system and sense organs in mammals.
                                    \nAnswer:<\/p>\n