NCERT Solution Life Processes

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Life Processes

Page no – 101

Solution 1

Autotrophic NutritionHeterotrophic Nutrition
i. Food is synthesized from simple inorganic raw materials such as CO2 and water.i. Food is obtained directly or indirectly from autotrophs. This food is broken down with the help of enzymes.
ii. Presence of green pigment (chlorophyll) is necessary.ii. No pigment is required in this type of nutrition.
iii. Food is generally prepared during day time.iii. Food can be prepared at all times.
Example: All green plants and some bacteria.
Example: All animals and fungi.

Concept comprehension: (i) Differences should always be written in tabular form.(ii) Differences should be written in terms of their significance.(iii) Write only those many numbers of differences as stated in the question.(iv) Give example wherever possible.

Solution 2

Plants need the following things for photosynthesis:

(i) Plants get CO2 from atmosphere through stomata.

(ii) Plants absorb water from soil through roots and transport it to the leaves.
(iii) Sunlight is absorbed by the chlorophyll and other green parts of the plant.        
Concept comprehension:Students should know the process of photosynthesis, raw materials required for photosynthesis and their sources.

Solution 3

Role of Hydrochloric acid in our stomach:i. It provides an acidic medium in our stomach which is necessary for activation of pepsin enzyme.ii. It kills germs present in the food.         
Concept comprehension: Students should know the importance of Hydrochloric acid in stomach.

Solution 4

Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. helps to break the complex food particles into simple ones so that these simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.  

Concept comprehension:   List the various digestive enzymes and their respective functions.

Solution 5

The inner lining of small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for absorption of food and are richly supplied with blood vessels. These blood vessels take the absorbed food to each and every cell of the body where it is used for obtaining energy, building up new tissues and repairing of old tissues.  

Concept comprehension: Remember the structure and function of small intestine.

Page no – 105

Solution 1

Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals that live in water use oxygen dissolved in surrounding water. Since, air dissolved in water has fairly low concentration of oxygen so, the aquatic organisms have to breathe faster to get more oxygen. Terrestrial organisms take oxygen from the oxygen rich atmosphere so, they have much less breathing rate than aquatic organism.  
Concept comprehension:Student should know the respiratory structures of different animals.

Solution 2

Glucose is broken down into a three carbon molecule called pyruvate in the cell cytoplasm. Pyruvate is further broken down by different ways to provide energy in various organisms.   Pyruvate is broken down in different ways in different organisms as shown below:

         

Glucose is broken down into a three carbon molecule called pyruvate 

i.In yeast cells, during fermentation, pyruvate is converted into ethanol and carbon dioxide in the absence of oxygen.

ii. In mitochondria, breakdown of pyruvate takes place in presence of oxygen to give rise three molecules of carbon dioxide and water.

iii. Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid.

Concept comprehension:Students should know various types of respiration.

Solution 3

Transport of Oxygen: The respiratory pigment, haemoglobin present in red blood cells takes up the oxygen from the air to the lungs. They, then carry the oxygen to cells and tissues which are deficient in oxygen.Transport of carbon dioxide: Carbon Dioxide is more soluble in water. Hence, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs where it diffuses from blood to air in the lungs and then expelled out through nostrils.  
Concept comprehension: Students should know the transportation of respiratory gases.

Solution 4

In the lungs, the wind pipe branches into bronchi which, in turn, branches into smaller tubes called bronchioles. Bronchioles have pouch like air-sacs at their ends called alveoli. Each lung contains about 300 – 350 millions of alveoli. The alveoli provides maximum surface area for exchange of gases. They have very thin walls and are surrounded by an extensive network of blood vessels to facilitate exchange of gases.
Concept comprehension:  Remember the structure of human respiratory system.

Page no – 110

Solution 1

The main components of the transport system in human beings are the heart, blood, and blood vessels. (i) Heart receives deoxygenated blood from the various body parts of the body and sends this impure blood to the lungs for oxygenation. After receiving the oxygenated blood, it pumps oxygenated blood to all the parts of the body.  (ii) Blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes throughout the body. WBCs protect the body against infections and diseases.  (iii) The blood vessels (arteries, veins, and capillaries) help in circulating the blood throughout the body.    
Concept comprehension: Student should know the structure and functions of human transport system.

Solution 2

Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. It is therefore necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of oxygen into the body. Hence, these animals require more oxygen (O2) for more cellular respiration so that they can produce more energy to maintain their body temperature.  
Concept comprehension: Students should know the difference between warm blooded and cold blooded organisms.

Solution 3

The transport system in highly organised plants is composed of vascular tissues, xylem and phloem.Xylem helps to conduct water and minerals obtained from the soil to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Concept comprehension: Remember the various vascular tissues, their components and their functions.

Solution 4

The plants take in water containing dissolved minerals from the soil through their roots. The roots of a plant have hairs called root hairs which absorb water and minerals from the soil. The root hairs are directly in contact with the film of water in-between the soil particles  Water and dissolved minerals get into the root hairs by the process of diffusion. The water and minerals absorbed by the root hairs from the soil pass from cell to cell by osmosis through the epidermis, root cortex, endodermis and reach the root xylem.The xylem vessels of the root of the plant are connected to the xylem vessels of its stem. So, the water containing dissolved minerals enters from the root xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the leaves of the plants. So, the water and minerals carried by the xylem vessels in the stem reach the leaves through the branched xylem vessels which enter from the petiole (stalk of the leaf) into each and every part of the leaf. In this way, the water and minerals from the soil reach through the root and stem to the leaves of the plant.

Concept comprehension: Students should know the mechanism of transport of water and minerals in plants.

Solution 5

The transport of food from the leaves to other parts of the plant is called translocation. The food made in leaves is loaded into the sieve tubes of phloem tissue by using energy from ATP. Water now enters into sieve tubes containing sugar by the process of osmosis due to which the pressure in the phloem tissue rises. This high pressure produced in the phloem tissue moves the food to all the parts of the plant having less pressure in their tissues. This allows the phloem to transport food according to the needs of the plant.

Concept comprehension: Students should know the tissues involved in transportation of food and its mechanism in plants.

Page no – 112

Solution 1

Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of nephrons, approximately 1-1.5 million. The main components of the nephron are:
(i) Glomerulus

(ii) Bowman’s capsule

(iii) Long renal tubule

Functioning of a nephron:
(i) The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.(ii) The water and solute are transferred to the nephron at Bowman’s capsule.(iii) In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine.(iv) The filtrate then moves down into the loop of Henle, where more water is absorbed.(v) From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct. Collecting duct collects urine from many nephrons.
Concept comprehension: Remember the structure and function of nephron.

Solution 2

Plants use the following ways to get rid of excretory products:i. Many waste products are stored in vacuoles of the cells.ii. Some waste products are stored in the leaves and they are removed as the leaves fall off.iii. Some waste products such as resins, tannins and gums are stored in non-functional old xylem or bark.iv. Plants also excrete some waste products through roots into the soil around them.v. Plants get rid of excess water through transpiration.
Concept comprehension: Students should know the various waste products of plants and how are they excreted out.

Solution 3

The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Anti-diuretic hormone (ADH) also regulates the amount of urine produced.  
Concept comprehension: Remember the mechanism of urine formation and its regulation in our body.

Page no – 113

Solution 1

(c) In human beings, the kidneys are a part of the system for excretion.  
Concept comprehension: Students should know the various organs of excretory system.

Solution 2

(a) In a plant, the xylem is responsible for transport of water.  
Concept comprehension: Remember the functions of various vascular tissues.

Solution 3

(d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll and sunlight.  

Concept comprehension: Students should know the concept of autotrophic nutrition, organisms that carry out autotrophic mode of nutrition and raw materials required to carry out autotrophic nutrition.

Solution 4

(b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria. 

Concept comprehension:Student should remember the process of aerobic respiration.

Solution 5

Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. Lipase enzyme present in the pancreatic juice causes breakdown of emulsified fats. Glands present in the wall of small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol. This is referred to as emulsification of fats. It takes place in the small intestine.  

Concept comprehension: Remember the various components of food and their digestion.

Solution 6

Saliva is secreted by salivary glands, located under the tongue. It moistens the food for easy swallowing. It contains a digestive enzyme called amylase, which breaks down starch into sugar.

Concept comprehension: Student should know the location and function of saliva.

Solution 7

Conditions necessary for autotrophic nutrition are:(i) Carbon dioxide,(ii) Water,(iii) Chlorophyll pigment(iv) SunlightCarbohydrates (food) and O2 are the by-products of photosynthesis.

Concept comprehension: Students should know the necessary conditions required for photosynthesis and the products formed during this process.

Solution 8

Differences between aerobic and anaerobic respiration:

Aerobic respirationAnaerobic respiration
i. Aerobic respiration takes place in the presence of oxygen.i. Anaerobic respiration takes place in the absence of oxygen.
ii. Complete breakdown of food occurs in aerobic respiration.ii. Partial breakdown of food occurs in anaerobic respiration.
iii. The end products in aerobic respiration are carbon dioxide and water.iii. The end products in anaerobic respiration may be ethanol and carbon dioxide (as in yeast plants), or lactic acid (as in animal muscles).
iv. Aerobic respiration produces a considerable amount of energy.iv. Much less energy is produced in anaerobic respiration.

                                         Yeast and bacteria uses anaerobic mode of nutrition.

(i) Differences should always be written in tabular form.

(ii) Differences should be written in terms of their significance.

(iii) Write only those many numbers of differences as stated in the question.

(iv) Give example wherever possible.

Solution 9

The alveoli have a structure specialised for efficient gaseous exchange:(i) Walls are extremely thin.(ii)They have a large surface area in relation to volume.(iii) They are surrounded by numerous blood capillaries.

Concept comprehension: Students should know the structure and function of alveoli.

Solution 10

Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of haemoglobin in blood can affect its oxygen supplying capacity. This can lead to deficiency of oxygen in the body cells as a result of which the person suffers from anaemia, breathing problems and exhaustion.

Concept comprehension: Student should remember the components of blood and their respective functions.

Solution 11
A circulatory system in which the blood travels twice through the heart in one complete cycle of the body is called double circulation.
Importance of double circulation:
The separation of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the body cells. This efficient system of oxygen supply is very useful in warm-blooded animals such as human beings. Warm-blooded animals have to maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, they require more O2 for more respiration so that they can produce more energy to maintain their body temperature. Thus, the circulatory system of humans is more efficient because of the double circulatory heart.
Concept comprehension: Students should know the structure and functioning of heart and also the flow of blood in human body.

Solution 12

XylemPhloem
i. Xylem conducts water and dissolved minerals from roots to leaves and other parts of the plant.i. Phloem conducts prepared food materials from leaves to other parts of plant in dissolved form.
ii. In xylem, transport of materials take place through vessels and tracheids which are dead tissues.ii. In phloem, transport of materials take place through sieve tubes with the help of companion cells, which are living cells.
iii. Movement of water and dissolved materials is also called ascent of sap.iii. Transportation of food in plants is also called translocation of food.
iv. Movement of water is mainly achieved by transpiration pull and no energy is required.iv. Translocation of food requires energy in the form of ATP.

Concept comprehension:   

(i) Differences should always be written in tabular form. 

(ii) Differences should be written in terms of their significance.

(iii) Write only those many numbers of differences as stated in the question.

(iv) Give example wherever possible.

Solution 13

AlveoliNephron
StructureStructure
Alveoli are small sac-like structures present inside the lungs.Nephrons are tubular structures present inside the kidneys.
The walls of the alveoli are one cell thick and it contains an extensive network of blood capillaries.Nephrons are made of glomerulus, Bowman’s capsule, and a long renal tube. It also contains a cluster of thin-walled blood capillaries.
FunctionFunction
Gas exchange of oxygen and carbon dioxide takes place in the alveoli.Nephrons principal function is to control the absorption of water and soluble substances such as sodium salts by filtering the blood, reabsorbing what is required and excreting the rest as urine.

Concept comprehension:

(i) Differences should always be written in tabular form.

(ii) Differences should be written in terms of their significance.

(iii) Write only those many numbers of differences as stated in the question.

(iv) Give example wherever possible.

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