Important Main Point In Class 7 Science Chapter 2
1. Different Ways Of Taking Food
We have already studied about the┬аnutrition in plants. This part of the content describes the nutritional needs and digestive system in human beings, along with other living beings. As we know that food is needed for every living organism. Plants can prepare their own food but animals cannot. But we know nutrition is required for every organism for energy. The food contains some nutrients like carbohydrate, protein, fat, vitamin and minerals which are required by our body for growth and development, called тАШNutritionтАЩ. Generally, in the process of nutrition, food is taken as a complex substance and break down in simpler substances, called тАШDigestionтАЩ. After that, it is utilised by our body. You may have observed that different types of animals show different modes of nutrition. Such as, eagle tear flesh of prey, hummingbirds suck the nectar from the flower, mosquito and lice suck blood from other organisms. And amoeba capture and swallow tiny aquatic animals, snake-like python swallow others animal on the whole, human and many other animals feed on motherтАЩs milk.
2. Digestion In Human
In this part of the content gives sufficient idea about the journey of food in human beings. As you learnt before in the process of digestion, food is breakdown in simple substances and after it is utilised by our body. The journey of our food starts from the buccal cavity (mouth) then it moves on food pipe or oesophagus and after it reaches to the stomach, small intestine and next to the large intestine and last the anus. Remember, tooth and digestive glands play an important role in our digestion.
3. Process Of Digestion
As you know, food is taken through the mouth with the help of teeth food is breakdown. You must know that our mouth has salivary glands. It secrets a juice, called saliva. We use our tongue for talking beside it mixes saliva with the food and helps in swallowing food. The swallowed food passes into the food pipe and reaches into the stomach. You know digestive juices and acids are present in the stomach which helps the food to digest due to some of the┬аphysical and chemical changes. Partially digested food reaches the small intestine where intestinal juices complete the digestion. You are surprised to know that our small intestine is 7.5 metres long and highly coiled. Similarly, our large intestine is about 1.5 metre-long, and it helps to remove waste material time-to-time through the anus.
4. Digestion In Grass Eating Animals
You may have observed that cows, buffaloes and other grass-eating animals chewing continuously, even when they are not eating. They quickly swallow the grass and store it in a part of a stomach, called тАШRumenтАЩ. Hence, they are called ruminants. You may know that partially digested food or grass present in the rumen of a cow is called тАШCudтАЩ. When this cud is thoroughly chewed in the mouth of the cow and swallowed again and reaches small intestine for complete digestion and absorption of food.
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5. Feeding And Digestion In Amoeba
Have you ever seen amoeba? Your answer will be тАШnoтАЩ. Do you know amoeba cannot see by naked eyes? Amoeba is single-celled microscopic organisms which are found in pond, lakes and other water sources. The body of amoeba has a finger-like projection called pseudopodia or false feet. It captures food and helps in locomotion of amoeba. Then the captured food break-down into simpler substances for digestion. This digested food is then absorbed and used for growth and maintenance by amoeba. In this way, you can see animals obtain their nutrients through a wide variety of feeding patterns. As nutrition is a must for a variety of reasons. Animals need the proper nutrition for growth, maintenance,┬аtransportation of materials┬аand to provide energy for work and vital functions for their survival or existence.
Important Questions For 7th Science Chapter 2
1. 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.
2. Given below from (i) to (iv) are some food items.
(i) Boiled and mashed potato
(ii) Glucose solution
(iii) A slice of bread
(iv) Mustard oil
Which of the above will give blue-black colour when tested with iodine?
(a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iii) (d) (iii) and (iv)
3. 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.
4. 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.
5. 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.
6. The finger-like outgrowths of Amoeba helps to ingest food. However, the finger-like outgrowths of human intestine helps to
(a) digest the fatty food substances.
(b) make the food soluble.
(c) absorb the digested food.
(d) absorb the undigested food.
7. 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
8. Read the following statements with reference to the villi of 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)
9. 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 food pipe.
10. The false feet of Amoeba are used for
(a) movement only.
(b) capture of food only.
(c) capture of food and movement.
(d) exchange of gases only.
Answers Of Important MCQ
1 (b)
2 (b)
3 (b)
4 (a)
5 (b)
6 (c)
7 (a)
8 (a)
9 (d)
10 (c).
Important NCERT Questions Class 7 Science Chapter 2
The 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 bile helps in the digestion of fats.
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7th Science Chapter 2 Important Questions Set тАУ 1
What Do You Mean By Animal Nutrition?
Animals get their food from plants, either directly by eating plants or indirectly by eating animals that eat plants. Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.
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Write Different Modes Of Taking Food In Any Five Animals.
The mode of taking food into the body varies in different organisms. Bees and humming-birds suck the nectar of plants, infants of human and many other animals feed on motherтАЩs milk. Snakes like the python swallow the animals they prey upon. Some aquatic animals filter tiny food particles floating nearby and feed upon them.
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The Food Passes Through Various Compartments In The Human BodyтАЭ- Name Them.
The food passes through a continuous canal which begins at the buccal cavity and ends at the anus. The canal can be divided into various compartments: (1) the buccal cavity, (2) food-pipe or oesophagus, (3) stomach, (4) small intestine, (5) large intestine ending in the rectum and (6) the anus.
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What Do You Mean By Digestive System In Human Body?
The human digestive system consists of the alimentary canal and secretory glands. It consists of the (i) buccal cavity, (ii) oesophagus, (iii) stomach, (iv) small intestine, (v) large intestine ending in rectum and (vi) anus. The main digestive glands which secrete digestive juices are (i) the salivary glands, (ii) the liver and (iii) the pancreas.
The inner walls of the stomach and the small intestine, and the various glands associated with the canal such as salivary glands, the liver and the pancreas secrete digestive juices. The digestive juices convert complex substances of food into simpler ones. The digestive tract and the associated glands together constitute the digestive system.
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Ingestion
Food is taken into the body through the mouth. The process of taking food into the body is called ingestion.
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7th Science Chapter 2 Important Questions Set тАУ 2
Define The Term Milk TEETH And PERMANENT TEETH.
The first set of teeth grows during infancy and they fall off at the age between six to eight years. These are termed milk teeth. The second set that replaces them are the permanent teeth.
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Write The Different Types Of Teeth Found In Human Beings.
Incisors (number 8) for cutting and biting. Canines (number 4) for piercing and tearing. Premolars (number 8) and molars (number 12) for chewing and grinding.
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What Is The Role Of Tongue In Human Body?
The tongue is a fleshy muscular organ attached at the back to the floor of the buccal cavity. It is free at the front and can be moved in all directions. We use our tongue for talking. Besides, it mixes saliva with the food during chewing and helps in swallowing food. We also taste food with our tongue. It has taste buds that detect different tastes of food.
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What Do You Mean By The Tooth Decay?
Normally bacteria are present in our mouth but they are not harmful to us. However, if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it. These bacteria break down the sugars present from the leftover food and release acids. The acids gradually damage the teeth. This is called tooth decay. If it is not treated in time, it causes severe toothache and in extreme cases results in tooth loss.
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Digestion
The components of food such as carbohydrates are complex substances. These complex substances cannot be utilised as such. So, they are broken down into simpler substances. The breakdown of complex components of food into simpler substances is called digestion.
7th Science Chapter 2 Important Questions Set тАУ 3
How Does The Food Pipe Or Oesophagus Help To Taking Food For Digestive System In Human Beings?
The swallowed food passes into the food-pipe or oesophagus. The food-pipe runs along the neck and the chest. Food is pushed down by movement of the wall of the food-pipe. Actually, this movement takes place throughout the alimentary canal and pushes the food downwards.
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What Is тАШVillusтАЩ In Human Body? Write The Role Of The Villus In Digestive System.
The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus).
The 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.
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Write Down The Role Of Stomach In Digestive System.
The stomach is a U-shaped, thick-walled bag. The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices. The mucous protects the lining of the stomach. The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices break down the proteins into simpler substances.
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What Is Egestion?
Absorption And Assimilation
After the stomach, the partly digested food reaches the lower part of the small intestine where the intestinal juice completes the digestion of all components of the food. The digested food can now pass into the blood vessels in the wall of the intestine. This process is called┬аabsorption.
The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). 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. This is called┬аassimilation.
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7th Science Chapter 2 Important Questions Set тАУ 4
What Do You Mean By The Term RUMEN, RUMINATION And RUMINANTSтАЩ?
Grass-eating animals (cows, buffaloes etc.) chewing continuously even when they are not eating. Actually, they quickly swallow the grass and store it in a part of the stomach called 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. So, these animals are called ruminants.
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Why Do We Not Able To Digest Cellulose Like Cattle?
The cellulose of the food is digested by the action of certain bacteria which are not present in humans.
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What Is An тАШAmoebaтАЩ?
Amoeba is a microscopic single-celled organism found in pond water. Amoeba has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm.
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What Do You Mean By Pseudopodia?
Amoeba constantly changes its shape and position. It pushes out one, or more finger-like projections, called pseudopodia or false feet for movement and capture of food.
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Nutrition In Amoeba
Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia (which is false feet) around the food particle and engulfs it. The food becomes trapped in a food vacuole.
Digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed.
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7th Science Chapter 2 Important Questions Set тАУ 5
What Is The Use Of Acid In Stomach?
The inner lining of stomach secretes mucus, hydrochloric acid and digestive juices. Out of these HCL kills any bacteria that may enter the stomach with food and makes the medium acidic.
Mucus protects the stomach lining from HCL and digestive juices break down proteins in food into simpler substances.
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Can We Survive Only On Raw, Leafy Vegetables Or Gram? Discuss.
Raw leafy vegetables and grass are rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose, because they do not have enzymes and certain types of bacteria which can digest cellulose. We cannot survive by taking vegetables in raw form. ThatтАЩs why we boil or cook vegetables which breaks down cellulose into simple carbohydrates. We can only survive by taking in vegetables in boiled or cooked form.
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Ruminants Such As Cow And Buffaloes Swallow Their Food Hurriedly And Then Sit Restfully And Chew Their Food. Can You Give Reason, Why?
Ruminants such as cows and buffaloes swallow their food hurriedly and store it in a part of the stomach called rumen. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
Later, this partially digested food (cud) is returned to the buccal cavity of the animals in small lumps and animal it sitting restfully to complete the process of digestion. This process is called rumination.
The thoroughly chewed cud is swallowed again to other compartment of stomach and then into small intestine for complete digestion and absorption.
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What Is The Function Of Enzymes Present In The Saliva?
The salivary gland present in mouth secretes saliva. It contains the enzyme amylase (ptyalin) that breaks down into simple sugars. Only about 30% starch digestion takes place in the mouth.
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Nutrition in Amoeba and Human beings
Similarity: The basic process of digestion of food and release of energy is the same in amoeba as well as in human beings. In amoeba, digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually, the digested food is absorbed. Similarly, in human beings various digestive juices (mouth, stomach, intestine etc.) act on food and break it down to simpler substances.
Differences: The digestion process in amoeba is simple while in human beings it is a complex process. The process of ingestion and egestion are also quite different. Amoeba engulf its food by surrounding the food particles with its pseudopodia. The undigested food which is largely carbon dioxide gas is expelled out by the vacuole. Which is human beings, the food (which is complex substances) is taken inside the mouth and undergoes a complex process of digestion and absorption. Finally, the undigested food is expelled out in the form of faeces.
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