Tamil Nadu 10th Standard Science Book Solution | Lesson 13 – Structural Organisation of Animals

Lesson 13. Structural Organisation of Animals

Lesson 13. > Structural Organisation of Animals

I. Choose the best answer

1. In leech locomotion is performed by

1. Anterior sucker
2. Posterior sucker
3. Setae
4. None of the above

Ans ; None of the above

2. The segments of leech are known as

1. Metameres (somites)
2. Proglottids
3. Strobila
4. All the above

Ans ; Metameres (somites)

3. Pharyngeal ganglion in leech is a part of

1. Excretory system
2. Nervous system
3. Reproductive system
4. Respiratory system

Ans; Nervous system

4. The brain of leech lies above the

1. Mouth
2. Buccal Cavity
3. Pharynx
4. Crop

Ans ; Pharynx

5. The body of leech has

1. 23 segments
2. 33 segments
3. 38 segments
4. 30 segments

Ans ; 33 segments

6. Mammals are ______________ animals.

1. Cold blooded
2. Warm blooded
3. Poikilothermic
4. All the above

Ans ; Warm blooded

7. The animals which give birth to young ones are

1. Oviparous
2. Viviparous
3. Ovoviviparous
4. All the above

Ans ; Viviparous

II. Fill in the blanks

1. The posterior sucker is formed by the fusion of the __________ segments.

Ans ; last seven

2. The existence of two sets of teeth in the life of an animal is called __________ dentition.

Ans ; Diphyodont

3. The anterior end of leech has a lobe-like structure called __________.

Ans ; Anterior Sucker

4. The blood sucking habit of leech is known as __________.

Ans ; Sanguivorous

5. __________ separate nitrogenous waste from the blood in rabbit.

Ans ; Kidney

6. __________ spinal nerves are present in rabbit.

Ans ; 37 pairs

III. Identify whether the statements are True or False. Correct the false statement

1. An anticoagulant present in saliva of leech is called heparin. ( False )

An anticoagulant present in saliva of leech is called hirudin.

2. The vas deferens serves to transport the ovum. ( False )

• The vas deferens serves to transport the sperms.

3. The rabbit has a third eyelid called tympanic membrane which is movable. ( False )

• The rabbit has a third eyelid called Nictitating membrane which is movable.

4. Diastema is a gap between premolar and molar teeth in rabbit. ( False )

• Diastema is a gap between the incisors and premolar teeth in rabbit.

5. The cerebral hemispheres of rabbit are connected by band of nerve tissue called corpora quadrigemina. ( False )

• The cerebral hemispheres of rabbit are connected by band of nerve tissue called corpus callosum.

IV. Match columns I, II and III correctly

Ans ; 1 – C- D, 2 – B – A, 3 – D – B, 4 – A – C

V. Answer in a sentence

1. Give the common name for Hirudinaria granulosa.

The Indian cattle leech.

2. How does leech respire?

Respiration takes place through skin.

3. Write the dental formula of rabbit.

Dental formula is 

in rabbit which is written as 2033/1023

4. How many pairs of testes are present in leech?

There are eleven pairs of testes in leech.

5. How is diastema formed in rabbit?

Diastema is a gap between incisors and premolar formed due to absence of canine.

6. What organs are attached to the two bronchi?

Lungs are attached to the two bronchi.

7. Which organ acts as suction pump in leech?

Blood is sucked by muscular pharynx, which act as a suction pump.

8. What does CNS stand for?

Central Nervous System.

9. Why is the teeth of rabbit called heterodont?

‘There are different types of teeth in rabbit. Hence, called as heterodont dentition.

10. How does leech suck blood from the host?

The leech makes a triradiate or ‘Y’ shaped incision in the skin of the host by the jaws protruded through the mouth and sucks the blood by muscular pharynx.

VI Short answer questions

1. Why are the rings of cartilages found in trachea of rabbit? *

Rings of cartilages are found in the tracheal walls of rabbit to help in the free passage of air.

2. List out the parasitic adaptations in leech.

Leech is a parasite and sucks the blood of vertebrates and show adaptations.

• Blood is sucked by pharynx.
• Suckers are present in the anterior and posterior ends of the body, by which the animal attaches itself to the body of the host.
• ‘The three jaws inside the mouth causes a triradiate or Y shaped wound in the skin of the host.
• Saliva contains a protein called hirudin which prevents the blood clotting. Thus continuous supply of blood is maintained.
• Parapodia and setae are completely absent.
• Blood is stored in the crop. It gives nourishment to the leech for several months. Hence, there is no digestive juices and enzyme.

VII. Long answer questions

1, Howisthe circulatory system designed in leech to compensate the heart structure?

• Circulation is brought about by haemocoelic system.
• There are no true blood vessels.
• The blood vessels are replaced by haemocoelic channels filled with blood like fluid. This fluid contains haemoglobin.
• There are four longitudinal channels. One lies above the alimentary canal, one below the alimentary canal and two on either side of the alimentary canal, which serve as the heart and has inner valves.

2. How does locomotion take place in leech? aK OK

Locomotion takes place in leech by

• Looping or crawling movement
• Swimming movement.

Looping or crawling movement:

• This type of movement is brought about by the contraction and relaxation of muscles.
• The two suckers help in attachment during the movement.

Swimming movement:

• Leeches swim very actively and perform undulating movements in water.

3. Explain the male reproductive system of rabbit with a labelled diagram.

•  Male reproductive system consists of a pair of testes, which are ovoid in shape.
• Testes is enclosed by scrotal sacs in the abdominal cavity.
• Each testes consists of numerous fine tubules called seminiferous tubules.
• This network of tubules lead into the coiled tubule called epididymis which leads to the sperm duct called vas deferens.
• Below the urinary bladder is the urethra. Vas deferens joins the urethra.
• Urethra runs backward and passes into the penis.
• There are three accessory glands namely prostate gland, cowper’’s gland and perineal gland. Their secretions are involved in reproduction.

Male reproductive system of Rabbit

VIII. Higher Order Thinking skills (HOTS)

1. Arjun is studying in tenth standard. He was down with fever and went to meet the doctor. As he went to the clinic he saw a patient undergoing treatment for severe leech bite. Being curious, Arjun asked the doctor why leech bite was not felt as soon as it attaches to the skin. What would have been the reply given by the doctor?

The leech, while making incision on the skin it also injects an anaesthetic substance that prevents the host from feeling the bite.

2. Shylesh has some pet animals at his home. He has few rabbits too, one day while feeding them he observed something different with the teeth. He asked his grandfather, why is it so? What would have been the explanation of his grandfather?

• Canines are absent.
• Hence, a gap is seen between the incisors and premolars.
• This is called diastema.
• It helps in mastication and chewing of food in herbivorous animals.

IX. Value based questions

1. Leeches do not have an elaborate secretion of digestive juices and enzymes. Why?

• Slime glands are present in the body wall. Their secretion keeps the body moist and slip-pery so that the host can’t remove it easily while it sucks blood.
• The availability of the host to the leeches is not regular. Hence, a large amount of blood is stored in the crop whenever it gets food. Digestion is also very slow.
• It may take more than a year for the complete digestion after a full meal.
• In leech the ingested blood is stored in crop chambers. It may take more than a year for the complete digestion and absorption of a full meal. So there is no need for an elaborate secretion of digestion juices and enzymes.

2. How is the digestive system of rabbit suited for herbivorous mode of feeding?

• Herbivores have a more specialised digestive system than that of a carnivore because it is more difficult to digest vegetarian than meat.
• Plant material is difficult to digest, particularly plant cellulose.
• The herbivorous animals have a longer intestine than the carnivorous animals giving more time for digestion.
• The teeth is also designed to grind the grass and plant material rather than the sharp teeth of carnivores designed to tear flesh.

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