NEET Biology Structural Organisation in Animals Important Questions Set 02

These Class 11 NEET Biology important questions on Structural Organisation in Animals give 23 questions with step-by-step answers, arranged as very short, short and long answer types, taken from a model test paper. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. Name the wings which help in flying in cockroach.
Answer: .Hind-wings or metathoracic wings.

Question 2. What are the finer branches of trachea of cockroach called?
Answer: Tracheoles

Question 3. What term is used for faecal deposits of earthworm?
Answer: Worm castings

Question 4. What is ootheca?
Answer: In cockroach, egg case is present which contains fertilised eggs and is formed by the help of collaterial gland. It is known as ootheca.

Question 5. Why the alimentary canal is shorter in frog?
Answer: Because frogs are carnivorous.

Question 6. Name the glands present in skin of frog.
Answer: Mucous glands

Question 7. Which type of circulatory system present in cockroach?
Answer: Open circulatory system.

Question 8. Mention the term used for the first anterior segment where mouth is present in an earthworm.
Answer: Peristomium

Short Answer Type Questions

Question 9. What is nymph?
Answer: When the young one resembles the adult in its mode of life but differs in structure, it is called nymph. The young one of cockroach is known as nymph.

Question 10. Name the various layers of body wall in earthworm.

Answer:

There are four layers of body wall in earthworm :

Question 11. Name any four endocrine glands of frog.

Answer:

Four endocrine glands of frog are :

Question 12. Mention the term used for the body fluid of cockroach and also mention the components present in the body fluids.
Answer: Body fluid is known as haemolymph. It consists of :
(i) A clear, colourless plasma which is rich in aminoacids etc.
(ii) Different types of cells called haemocytes. Haemolymph does not contain any respiratory pigment and therefore, plays no role in respiration.

Question 13. How is brood pouch formed in female cockroach?
Answer: Brood pouch in female cockroach is located at the hind-end of abdomen. In female, 7th sternum is large, boat-shaped and alongwith 8th and 9th sterna forms brood pouch.

Question 14. What is clitellum? Mention one function of clitellum.
Answer: The mature earthworm, segments 14–16 are covered by a prominent dark band of glandular tissue called clitellum. Clitellum helps in cocoon formation.

Question 15. Name all sense organs of frogs with their respective locations.
Answer: There are five sense organs in a frog. They are :
(i) Tangoreceptors (organs of touch) : They are found in the skin.
(ii) Olfactoreceptors (organs of smell) : They are found in nasal epithelium of the nasal chambers of frog.
(iii) Gustatoreceptors (organs of taste) : They lie in the epithelium of the tongue.
(iv) Eyes (organs of sight) : They are found on the dorso-lateral sides of head.
(v) Ears (organs of hearing and balance) : They are attached to skull, posto-laterally behind eyes represented by tympanum.

Short Answer Type Questions

Question 16. Discuss :
(a) Gizzard in earthworm
(b) Typhlosole
(c) Anterior loops
Answer: (a) Gizzard : The oesophagus continues into a muscular gizzard (8th to 9th segments). It helps in grinding of soil particles and decaying leaves with the help of thick muscles and cuticle.
(b) Typhlosole : In the middle region of the intestine, the mid-dorsal wall is thrown into a longitudinal fold which is known as typhlosole. The typhlosole increases the absorptive surface of the intestine.
(c) Anteriorth loops : There are present two pairs of loop-like vessels called the anterior loops in the 10th and 11 segments. They have no valves. They carry blood from the lateral oesophageal vessels to the supra- oesophageal vessel.

Question 17. Write a short note on :
(a) Morphology of a frog
(b) Excretory system of frog

Answer:

(a) Morphology of frog : Body is divisible into head and trunk. Neck and tail are absent.  Head is flat, roughly triangular in outline and with a short blunt anterior snout terminating in a wide transverse mouth.  Two small openings, the external nares or external nostrils, lie dorsally above the mouth, at the tip of snout and serve in respiration.  Two very large, spherical and protruding eyes are situated dorso-laterally on top of head.  Each eye has a thick, pigmented and almost immovable upper eyelid and a thin semi-transparent and freely movable lower eyelid.  From the lower eyelid arises a transparent third eyelid or nictating membrane, which covers and protects the eye during swimming and keep it moist in air.  Behind and below each eye is a conspicuous, flat and deeply pigmented circular patch of skin, the eardrum or tympanum, that receives sound waves.  An external ear is lacking.  The forelimb and hindlimb help in swimming, walking, leaping and burrowing. The hindlimbs end in five digit while forelimbs have five digits.  Frog exhibits sexual dimorphism.
(b) Frogs have well-developed excretory system which helps in elimination of nitrogenous wastes from its body. Frog is ureotelic as it excretes predominantly urea along with water. Excretory system consists of :

(1) A pair of kidneys : The two kidneys, situated one on either side of the vertebral column in the posterior part of the body cavity. The kidneys are chief excretory organs which are oval, dorsoventrally flattened, dark, red and bean-like structures. Each kidney is a compact mass of innumerable (about
2000) highly twisted microscopic uriniferous tubules or nephrons and blood vessels embedded in connective tissue. These nephrons are the structural and functional units of kidney.
(2) Ureters : From posterior outer margin of each kidney leaves a urinary duct also called ureter. It is a fine, white tube extends backward to open into the dorsal wall of cloaca. In male frog, the ureters are called urinogenital ducts since they pass out sperms as well as urine.
(3) Urinary bladder : A large transparent, bilobed, thin-walled elastic, urinary bladder opens into the ventral wall of cloaca.
(4) Cloaca : It is a small median chamber into which open the anus, urinogenital apertures and urinary bladder. It receives faecal, genital products and urine. Process of Excretion : Frog is ureotelic, it excretes urea along with water. Blood is filtered by nephrons in kidneys. All the wastes is filtered out and useful substances are reabsorbed into blood. The remaining fluid forms urine which is carried out of kidney by collecting vessels into ureter and passes down into cloaca. It is either stored temporarily in urinary bladder or eliminated through cloacal aperture.

Question 18. Describe briefly :
(a) Blood circulation in frog
(b) Functioning of nephridia in earthworm
Answer: (a) Blood circulation in frog : Frogs have three-chambered heart. In heart, firstly sinus venosus contracts and drives the blood to the right auricle. At the same time, left auricle receives oxygenated blood through the pulmonary veins from the lungs. When the two auricles are full of blood, they contract simultaneously and the blood from both auricles is forced into the single ventricle through an aperture. Thus, both oxygenated and deoxygenated blood are mixed in the ventricle. Now, the ventricle contracts and the backward flow of blood into auricles is prevented by the valves. The mixed blood enters the truncus arteriosus (= conus arteriosus). From it, mixed blood goes to all the parts of the body through various arteries.
(b) Functioning of nephridia : The main excretory organs in earthworm are nephridia (singular : nephridium) which performs the function of excretion and osmoregulation. It regulates the volume and composition of blood in earthworm. They are coiled tubular and microscopic structures; consisting
(i) Funnel-shaped part which collects the excess fluid from coelomic cavity, and
(ii) Tubular part where waste material is extracted from the blood through gland cells.

Question 19. Mention the various modifications of foregut and midgut in alimentary canal of cockroach.
Answer: Modifications of foregut : Foregut comprises of mouth, pharynx, crop and gizzard.
(i) The oesophagus dilates in 3rd to 4th abdominal segment to form crop which is large, thin-walled, pear- shaped sac-like structure. It is the largest part of foregut where food is stored, so it resembles to stomach of vertebrates.
(ii) Gizzard (or proventriculus) : Crop open into the gizzard. This part of foregut is modified to help in pulverisation of food. It is thick-walled and round structure whose walls are muscular and greatly folded. It bears six muscular folds which are covered by chitinous conical plates, the teeth used for grinding the food. Its walls consists of strong muscles which are also needed for grinding. In gizzard, the food is crushed into fine particles by the teeth present here. Modification of midgut : Midgut is thin-walled and somewhat coiled tube of alimentary canal which is modified to facilitate efficient digestion and absorption of food. From the junction of midgut and gizzard arises 6 to 8 finger-like blind structure called the hepatic caecae. These are lined by glandular cells which secrete digestive secretion and help in digestion of carbohydrates, proteins and fats.

Question 20. Give details of :
(a) Prostate glands of earthworm
(b) Calciferous glands of earthworm
(c) Mushroom glands of cockroach
Answer: (a) Prostate glands of earthworm : A pair of large prostate glands are present in earthworm. They arethflat and irregularth in outline. These glands are situated on either side of the intestine and extend from the 16 to the 20 segment. They produce a secretion which serves as a medium for transfer of sperms.
(b) Calciferous glands of earthworm : In stomach, a chalky secretion of calciferous glands located in stomach wall, which neutralises the humic acid present in humus, i.e., soil.
(c) Mushroom glands of cockroach : The junction of vasa deferentia and the ejaculatory ductth isthsurrounded by a mushroom-shaped gland which is also known as utricular gland. They lie in the 6 to 7 abdominal segments and consists of long tubules, small tubules and seminal vesicles. Their secretion helps in the nourishment of sperms.

Question 21. Describe various adaptations found in frog.

Answer:

Various adaptations found in frogs are :
(a) Cold-blooded animals : They are cold-blooded animals (i.e., Poikilotherms), so their body temperature changes according to their surroundings. Therefore, they have adapted themselves to live on both; on land and in fresh water. They also show hibernation and aestivation, to cope with the harsh climatic conditions.
(b) Camouflage : They have the ability to camouflage, i.e., to change the colour of the body according to the surroundings, so as to escape from its predators or catch their preys.
(c) Hibernation and aestivation : Frogs are not seen in extreme summer and extreme winter because during these seasons, they live in an inactive state in their deep burrows to protect themselves from the extreme heat which is known as "summer sleep" or aestivation and also in extreme cold which refers to winter sleep or hibernation.
(d) Nictating membrane : Frog's eyes are provided with a third eyelid called nictating membrane which protects their eyes under water and from other infections.

Long Answer Type Questions : [5 Marks]

Question 22. Describe nervous system of earthworm and cockroach.
Answer: (a) Nervous system of earthworm : The nervous system of earthworm is not well-developed. It consists of ganglia arranged segment-wise on the ventral nerve cord. Therefore, basically it has :
(i) Anterior nerve ring
(ii) Posterior ventral nerve cord
(i) Anterior nerve ring (represents brain) : It is formed by a pair of closely united, pear-shapedrd cerebral ganglia which lie dorsally in the depression between buccal cavity and pharynx in the 3 segment of body. They elongate laterally to give risethto a pair of connectives which encircle pharynx and meet ventrally into an another pair of ganglia in 4 segment. They form a complete nerve ring around pharynx.
(ii) Ventral nerve cord : From ganglia of 4th segment arises a nerve cord which runs backward in mid- ventral line and is referred as ventral nerve cord. It bears segmental ganglion in each segment of earthworm's body. This in turn, gives off nerves to various parts of the body.
(b) Nervous system of cockroach : The nervous system of cockroach consists of the brain and ventral nerve cord with its ganglia.
(i) Brain : Brain or supra-oesophageal ganglion is a large bilobed mass located in head above oesophagus. It represents three pairs of ganglia of head region fused together. Remaining three pairs of ganglia of head fuse to form the sub-oesophageal ganglion which lies below oesophagus. Brain and sub-oesophageal ganglion are connected together by paired longitudinal connectives.
(ii) Ventral nerve cord : From sub-oesophageal ganglion runs posteriorly a double ventral nerve cord along the mid-ventral line of thorax and abdomen. It beans 9 ganglion, 3 in thorax and 6 in abdomen.
(iii) Nerves : The nerves are given off from ganglia to all parts of the body. Brain gives off paired optic nerves and antennary nerves to compound eyes and antennae respectively.

Question 23. Describe different blood vessels found in blood vascular system of frog with detailed account of its blood.

Answer:

In frog, two types of blood vessel systems are found, i.e.,
(a) Arterial system : Arteries carry blood away from the heart. The arterial system in frog begins with the truncus arteriosus (= conus arteriosus). The truncus divides into left and right branches each of which sub-divides into vessels.
(b) Venous system : It includes veins or those blood vessels which carry the blood to the heart. In frog, it can be studied in four parts :
(i) Pulmonary veins : They collect oxygenated blood from two lungs and open directly into left auricle.
(ii) Vena cava : They carry deoxygenated blood from the body parts towards heart.
(iii) Renal portal veins : Renal portal vein enters the kidney by several branches which break up into capillaries. The renal portal system collects the blood from hind parts of the body from which the urea and uric acid are first filtered in the kidneys before the blood goes to the heart.
(iv) Hepatic portal veins : A large hepatic portal vein is formed by the confluence of several branches from stomach, intestine, spleen and pancreas. It carries blood of alimentary canal and its glands laden with digested foodstuffs, to the liver into which it breaks up into capillaries. Here, the excess of glucose is converted into glycogen which is stored in the liver for later use. It also produces blood proteins which are put into blood circulation. Along with these two systems, a lymphatic system is also found in frogs which forms another part of circulatory system as it circulates, lymph.
(c) Lymphatic system : Lymph flows through the lymphatic system. Lymph is different from blood and is without RBCs and contains few proteins. It is colourless. Lymph is constantly produced from filtering of blood through capillaries into intercellular spaces. Tissue fluid or lymph bathes the tissues and lubricates many of the internal organs. It functions as the middleman passing over food and oxygen to cells and waste materials to blood. Lymphatic system comprises lymph capillaries (closed at the tip), lymph channels or sinuses (spaces filled with lymph) and lymph nodes.
(d) Blood : Blood carries nutrients, gases and water to the respective sites in the body. Hence, it is the chief circulatory fluid of the body . It contains a clear liquid, called plasma, in which are suspended various types of free cells, called blood corpuscles.
(i) Plasma : It is largely water (90%) in which are dissolved mineral salts, absorbed foods (sugars, proteins), excretory wastes (urea), and other soluble substances.
(ii) Corpuscles : Three types of blood corpuscles are present in the plasma, viz., erythrocytes (RBCs
– red blood corpuscles), leucocytes (WBCs – white blood corpuscles) and thrombocytes – spindle cells or platelets. RBCs are nucleated, oval and biconvex and have haemoglobin (respiratory pigment). This is yellow to red colour, iron-containing protein that serves to carry oxygen in chemical combination to the tissues. WBCs are amoeboid shaped and are protective in function. Thrombocytes or platelets are spindle-shaped and help in blood clotting.