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ScienceClass 7CBSE

Following statements describe the five steps in animal nutrition. Read each statement and give one word for each statement. Write the terms that describe each process. (a) Transportation of absorbed food to different parts of the body and their utilisation. (b) Breaking of complex food substances into simpler and soluble substances. (c) Removal of undigested and unabsorbed solid residues of food from the body. (d) Taking food into the body. (e) Transport of digested and soluble food from the intestine to blood vessels.

Soln: (a) Assimilation (b) Digestion (c) Egestion (d) Ingestion (e) Absorption

ScienceClass 7CBSE

Q. Fill in the blanks with suitable words: (a) The alimentary canal stretches from to. (b) Teeth are rooted in separate in between the. (c) Digestion of food starts in and gets completed in. (d) is the largest gland in the human body.

Soln: The alimentary canal stretches from Mouth to Anus. Teeth are rooted in separate Sockets in between the Gums. Digestion of food starts in the Buccal cavity and gets completed in Small Intestine. The liver is the largest gland in the human body.

ScienceClass 7CBSE

You were blindfolded and asked to identify the drinks provided in two different glasses. You could identify drink A as lime juice and B as bitter gourd juice. How could you do it in spite of being blindfolded?

Soln: We can identify the juices with the help of different taste buds present in the tongue.

ScienceClass 7CBSE

Choose the odd one out from each group and give reasons. (i) liver, salivary gland, starch, gall bladder (ii) stomach, liver, pancreas, salivary gland (iii) tongue, absorption, taste, swallow (iv) oesophagus, small intestine, large intestine, rectum

Soln: The answer is Starch because starch is a carbohydrate, whereas the liver, salivary gland and gall bladder are the glands. The answer is the stomach because others are digestive glands Absorption is the answer because tongue, swallow and taste are related to the buccal cavity but not absorption. The small intestine is the answer because the oesophagus, large intestine and rectum will not take part in digestion, whereas the small intestine plays the main role in the digestion process.

ScienceClass 7CBSE

Mark the following statements as True or False. If false, write the correct statements. (a) Tongue is attached to the roof of the mouth cavity at the back. (b) The large intestine is longer and wider than the small intestine of the human alimentary canal. (c) Mucus protects the stomach lining from damage. (d) All heterotrophs have a similar basic process of nutrition.

Soln: False – The tongue is attached to the floor of the mouth cavity at the back. False – The large intestine is shorter and wider than the small intestine of the human alimentary canal. True True

ScienceClass 7CBSE

Name the parts of the alimentary canal where (i) water gets absorbed from undigested food. (ii) digested food gets absorbed. (iii) taste of the food is perceived. (iv) bile juice is produced.

Soln: (i) Large intestine (ii) Small intestine (iii) Tongue (iv) Liver

ScienceClass 7CBSE

Cellulose-rich food substances are a good source of roughage in human beings because (a) human beings do not have cellulose-digesting enzymes. (b) cellulose gets absorbed in the human blood and converts into fibres. (c) the cellulose-digesting bacteria convert cellulose into fibres. (d) cellulose breaks down into smaller components which are egested as roughage.

Soln: The answer is (a) human beings do not have cellulose-digesting enzymes.

ScienceClass 7CBSE

Choose the correct order of terms that describes the process of nutrition in ruminants. (a) swallowing → partial digestion → chewing of cud → complete digestion (b) chewing of cud → swallowing → partial digestion → complete digestion (c) chewing of cud → swallowing → mixing with digestive juices → digestion (d) swallowing → chewing and mixing → partial digestion → complete digestion

Soln: The answer is (a) swallowing → partial digestion → chewing of cud → complete digestion

ScienceClass 7CBSE

Cud is the name given to the food of ruminants which is (a) swallowed and undigested. (b) swallowed and partially digested. (c) properly chewed and partially digested. (d) properly chewed and completely digested.

Soln: The answer is (b) swallowed and partially digested. Explanation: Ruminants quickly swallow the grass and store it in a part of the stomach called the rumen. Here the food gets partially digested and is called cud. But later, the cud returns to the mouth in small lumps, and the animal chews it. This process is called rumination.

ScienceClass 7CBSE

The enzymes present in the saliva convert (a) fats into fatty acids and glycerol. (b) starch into simple sugars. (c) proteins into amino acids. (d) complex sugars into simple sugars.

Soln: The answer is (b) starch into simple sugars. Explanation: Saliva consists of salivary amylase enzyme, which breaks starch into simple sugar, which is further digested by enzymes in the stomach and small intestine.

ScienceClass 7CBSE

The false feet of Amoeba are used for (a) movement only. (b) the capture of food only. (c) the capture of food and movement. (d) exchange of gases only.

Soln: The answer is (c) capture of food and movement. Explanation: Amoeba constantly changes their shape and position. It pushes out one, or more finger-like projections, called pseudopodia or false feet, for movement and capture of food. Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it.

ScienceClass 7CBSE

Read the following statements with reference to the villi of the small intestine. (i) They have very thin walls. (ii) They have a network of thin and small blood vessels close to the surface. (iii) They have small pores through which food can easily pass. (iv) They are finger-like projections. Identify those statements which enable the villi to absorb digested food. (a) (i), (ii) and (iv) (b) (ii), (iii) and (iv) (c) (iii) and (iv) (d) (i) and (iv)

Soln: Answer is (a) (i), (ii) and (iv) Explanation: The inner walls of the small intestine have thousands of finger-like outgrowths called villi (singular villus). Villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body, where they are used to build complex substances such as the proteins required by the body.

ScienceClass 7CBSE

The finger-like outgrowths of Amoeba help to ingest food. However, the finger-like outgrowths of the human intestine help to (a) digest the fatty food substances. (b) make the food soluble. (c) absorb the digested food. (d) absorb undigested food.

Soln: The answer is (c) absorb the digested food. Explanation: Fingerlike projection is present in the small intestine, and they are called Villi. Villi absorb nutrients from digested food by increasing the space of the small intestine.

ScienceClass 7CBSE

The acid present in the stomach (a) kills the harmful bacteria that may enter along with the food. (b) protects the stomach lining from harmful substances. (c) digests starch into simpler sugars. (d) makes the medium alkaline.

Soln: The answer is (a) kills the harmful bacteria that may enter along with the food. Explanation: The stomach consists of Hydrochloric acid, which kills the bacteria that enter through food. Thus stomach acid is helping in protecting us from harmful bacteria.

ScienceClass 7CBSE

The swallowed food moves downwards in the alimentary canal because of (a) force provided by the muscular tongue. (b) the flow of water taken with the food. (c) gravitational pull. (d) the contraction of muscles in the wall of the food pipe.

Soln: The answer is (d) the contraction of muscles in the wall of the food pipe. Explanation: Muscles of the Esophagus push food down by the movement of the wall of the food pipe. Actually, this movement takes place throughout the alimentary canal and pushes the food downwards.

ScienceClass 7CBSE

Read carefully the terms given below. Which of the following set is the correct combination of organs that do not carry out any digestive functions? (a) Oesophagus, Large Intestine, Rectum (b) Buccal cavity, Oesophagus, Rectum (c) Buccal cavity, Oesophagus, Large Intestine (d) Small Intestine, Large Intestine, Rectum

Soln: The answer is (a) Oesophagus, Large Intestine, Rectum Explanation: Oesophagus pushes the food downwards, and it is not involved in any digestive functions. The large intestine absorbs water and some salts from the undigested food material, and it is not involved in the digestion process. In the rectum, the remaining waste passes and remains there as semi-solid faeces. It is not involved in any digestive function.

ScienceClass 7CBSE

Which of the following pair of teeth differ in structure but are similar in function? (a) canines and incisors. (b) molars and premolars. (c) incisors and molars. (d) premolars and canines.

Soln: The answer is (b) molars and premolars. Explanation: Our teeth tear and grind the food before swallowing food. There are four types of teeth. Incisors: front eight teeth, 4 in the upper jaw and 4 in the lower jaw. Canines: There are 4 canines, one on each side of each jaw. Premolars: There are 8 premolars. Two premolars in each of the upper and lower jaws. Molars: There are 12 molars, three in each half of both upper and lower jaws.

ScienceClass 7CBSE

Given below from (i) to (iv) are some food items. Boiled and mashed potato Glucose solution A slice of bread Mustard oil Which of the above will give a blue-black colour when tested with iodine? (a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iii) (d) (iii) and (iv)

Soln: The answer is (b) (i) and (iii) Explanation: Mashed potato and bread are rich in starch. On adding iodine, it reacts with starch to give a blue-black colour.

ScienceClass 7CBSE

Write various steps for processing fibres into wool.

Soln: Step I: The fleece of the sheep along with a thin layer of skin is removed from its body [Fig. 3.8 (a)]. This process is called shearing. Machines similar to those used by barbers are used to shave off hair. Usually, hair is removed during the hot weather. This enables sheep to survive without their protective coat of hair. The hair provides woollen fibres. Woollen fibres are then processed to obtain woollen yarn. Shearing does not hurt the sheep just as it does not hurt when you get a hair cut or your father shaves his beard. Do you know why? The uppermost layer of the skin is dead. Also, the hair of sheep grows again just as your hair does. Step II: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring. Nowadays scouring is done by machines [Fig. 3.8 (b) and (c)]. Step III: After scouring, sorting is done. The hairy skin is sent to a factory where the hair of different textures is separated or sorted. Step IV: The small fluffy fibres, called burrs, are picked out from the hair. These are the same burrs which sometimes appear on your sweaters. The fibres are scoured again and dried. This is the wool ready to be drawn into fibres. Step V: The fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white. Step VI: The fibres are straightened, combed and rolled into yarn. The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woollen cloth.

ScienceClass 7CBSE

Explain the phrase – “Unity is Strength” on the basis of the making of fabric from the fibre.

trong>Soln: Fabric is made of a thin hair-like strand called fibres. It is easy to break a fibre thread as it is fragile and easy to break as well. On the other hand, fabric is the accumulation of many fibre threads which are hard to break and needs an enormous amount of energy to break the fabric. Hence, based on making of fabric from fibre it is said that unity is strength.

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