13. Structural Organisation of Animals

I. Choose the correct answer.

1. In leech, locomotion is performed by _____.

(a) Anterior sucker
(b) Posterior sucker
(c) Setae
(d) None of the above.

2. The segments of leech are known as:

(a) Metameres (somites)
(b) Proglottids
(c) Strobila
(d) All the above

3. Pharyngeal ganglion in leech is a part of _____.

(a) Excretory system
(b) Nervous system
(c) Reproductive system
(d) Respiratory system.

4. The brain of leech lies above the:

(a) Mouth
(b) Buccal Cavity
(c) Pharynx
(d) Crop

5. The body of leech has _____.

(a) 23 segments
(b) 33 segments
(c) 38 segments
(d) 30 segments.

6. Mammals are ______ animals.

(a) Cold – blooded
(b) Warm – blooded
(c) Poikilothermic
(d) All the above.

7. The animals which give birth to young ones are:

(a) Oviparous
(b) Viviparous
(c) Ovoviviparous
(d) All the above

II. Fill in the blanks.

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

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

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

4. The blood-sucking habit of a leech is known as Sanguivorous.

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

6. 37 pairs of spinal nerves are present in the rabbit.

III. Identify whether the statements are true or false. Correct the false statement.

1. An anticoagulant present in the saliva of the leech is called heparin.
   Answer:        False.
Correct Statement: The anticoagulant present in the saliva of the leech is called Hirudin.

2. The vas deferens serves to transport the ovum.
   Answer:        False.
Correct Statement: The vas deferens serves to transport the sperm.

3. The rabbit has a third eyelid called tympanic membrane which is movable.
   Answer:        False.
Correct Statement: The rabbit has a third eyelid called Nictitating membrane, which is movable.

4. Diastema is a gap between premolar and molar teeth in rabbit.
   Answer:        True.

5. The cerebral hemispheres of the rabbit are connected by a band of nerve tissue called corpora quadrigemina.
   Answer:        False.
Correct Statement: The cerebral hemisphere of the rabbit are connected by a band of nerve tissue called Corpus callosum.

IV. Match the Columns I, II and III correctly.

Organs

Membranous Covering

Location

Brain

Pleura

abdominal cavity

Kidney

Capsule

Mediastinum

Heart

Meninges

enclosed in the thoracic cavity

Lungs

Pericardium

cranial cavity

Answer:

Organs

Membranous Covering

Location

Brain

Meninges

cranial cavity

Kidney

Capsule

abdominal cavity

Heart

Pericardium

enclosed in the thoracic cavity

Lungs

Pleura

mediastinum

V. Answer in a sentence.

1. Give the common name of the Hirudinaria granulosa.

Indian Cattle Leech.

2. How does leech respire?

The leech respire through skin (diffusion).

3. Write the dental formula of the rabbit.



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

In leech, there are eleven pairs of testes. One pair in each segment from 12 to 22 segments.

5. How is diastema formed in rabbit?

The diastema is formed in Rabbit, as a gap between the incisors and premolars,

6. What organs are attached to the two bronchi?

Lung, Bronchioles and Alveoli are the Organs, attached to Bronchi.

7. Which organ acts as suction pump in leech?

Pharynx acts as suction pump in leech.

8. What does CNS stand for?

CNS stands for Central Nervous System.

9. Why are the teeth of a rabbit called heterodont?

The teeth of Rabbit are of different types. So it is called heterodont.

10. How does leech suck blood from the host?

Leech attaches itself to the body of the host by suckers. Jaws of mouth causes wound. Then the blood is sucked by pharynx.

VI. Short Answer Questions.

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

Tracheal walls are supported by rings of cartilage, which help in the free passage of air.

2. List out the parasitic adaptations in leech.

The suckers are the primary organ of the blood sucking.

  1. The blood is sucked by muscular pharynx.
  2. Leeches attaches itself to the body of host by Anterior and Posterior ends of the body.
  3. The three jaws inside the mouth, causes a painless triradiate or Y shaped incision in the skin of the host.
  4. A protein called hirudin is produced in the salivary gland of leech to prevent blood coagulation. Thus, a continuous supply of the blood is maintained.
  5. Parapodia and setae are completely absent.
  6. Leeches also inject an anaesthetic substances that prevents the host from feeling their bite.
  7. In the crop, blood is stored which gives nourishment to the leech for several months. Due to this reason there is no eloborate secretion of the digestive juices and enzymes.

VII. Long Answer Questions.

1. How is the circulatory system designed in leech to compensate the heart structure?

There are no true blood vessels in leeches. The blood vessels are replaced by canals called haemocoelic canals. These canals are filled with haemocoelic fluid. There are four longitudinal canals. One is dorsal lying above the alimentary canal, another is ventral lying below the alimentary canal. The remaining two are lateral lying on either side of the alimentary canal. These four canals are connected together at the posterior end. There is no heart, but the lateral channels serve as a heart by being contractile. They have values inside. The dorsal and ventral channels are non-contractile having no muscular walls.

2. How does locomotion take place in leech?

Locomotion in leech takes place by:

  • Looping or Crawling movement: This type of movement is brought about, by the contraction and relaxation of muscles. The two suckers, serve for attachment, during movement on a substratum.
  • Swimming movement: Leeches swim very actively and perform undulating movements in the water.

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

A pair of Testes, which are ovoid in shape, are enclosed by Scrotal Sac, in the abdominal cavity. Each testis consists of numerous fine tubules called Seminiferous tubules. This network of tubules leads into a coiled tubule called Epididymis, which lead into the sperm duct called vas deferens. The vas deferens join in the urethra, just below the Urinary Bladder. The Urethra runs backwards and passes into the penis.

The Prostate gland, Cowper’s gland and Perineal gland are the three accessory glands, whose secretions are involved in reproduction.


VIII. Higher Order Thinking Skills (HOTS) Questions

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 makes a wound with the jaws by making a rasping movement. The blood is sucked by the muscular pharynx. The salivary secretion is poured in the wound. They inject an anaesthetic substances that prevents the host from feeling their bite. The saliva contains an active substances called hirudin which prevents the coagulation of the blood.

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?

The explanation of the grandfather would have been as follows: Teeth are hard bone – like structures, used to cut, tear and grind the food. There are incisors, canines, premolars and molars teeth are seen. Canines are absent. Something different from the teeth is the gap between incisors and premolar, which is called Diastema. It helps in mastication and chewing the food.

IX. Value-Based Questions.

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

The blood sucked by the leech is stored up in the crop. The blood gets haemolysed in the crop. Then the blood is passed drop by drop into the stomach where it is digested slowly by the peptolytic enzyme. The digested blood is absorbed slowly by the intestine.

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

The caecum is a thin – walled sac present at the Junction of the small intestine and large intestine. It contains bacteria, that helps in digestion of cellulose. So the digestive system of Rabbit is suited for a herbivorous mode of feeding.