NCERT Solutions for Class 10 Science Chapter 6 Life Processes

NCERT Solutions for Class 10 Science Chapter 6 Life Processes

NCERT Solutions for Class 10 Science Chapter 6 Intext Questions

Page Number: 95

Question 1
Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans ?
Answer:
In multicellular organisms like humans, all the body cells are not in direct contact with the surrounding environment. Therefore, every cell of the body will not get oxygen as per need by the process of diffusion from the environment. Therefore diffusion is insufficient to meet the oxygen requirements of multicellular organisms.

Question 2
What criteria do we use to decide whether something is alive ?
Answer:
The main criteria used to decide whether something is alive are breathing and respiration. However, living beings also show growth and movement.

Question 3
What are outside raw materials used by an organism ?
Answer:
Any organism uses organic molecules as raw material. Heteroptrophs use food and autotrophs use carbon dioxide, minerals, water and all organisms use oxygen (for respiration) as raw materials.

Question 4
What processes would you consider essential for maintaining life ?
Answer:
Processes essential for maintaining life are :
(i) Nutrition
(ii) Respiration
(iii) Transportation
(iv) Excretion

Page Number: 101

Question 1
What are the differences between autotrophic nutrition and heterotrophic nutrition ?
Answer:

Autotrophic nutrition	Heterotrophic nutrition
(i) In this mode of nutrition an organism makes or synthesizes its own food.	(i) In this mode of nutrition an organism cannot make or synthesize its own food
Organisms use simple inorganic materials like carbon dioxide and water and synthesise their food in presence of sunlight.	(ii) Organisms cannot make their own food from simple inorganic matter and depend on other organisms for their food.
(iii) All green plants and some algae undergo this mode of nutrition.	(iii) All the animals, most bacteria and fungi undergo this mode of nutrition.

Question 2
Where do plants get each of the raw materials required for photosynthesis ?
Answer:
(i) Carbon dioxide : Plants get carbon dioxide from the environment/atmosphere through stomata.
(ii) Water : Plants absorb water from the soil through roots and transport to leaves.
(iii) Sunlight : Plants get sunlight from the sun.
(iv) Chlorophyll : It is present in chloroplast found in green leaves and green parts of plants.

Question 3
What is the role of the acid in our stomach ?
Answer:
Role of acid in our stomach is :
(i) To make acidic medium which is necessary for the activation of the enzyme pepsin.
(ii) To kill bacteria which the food may contain.

Question 4
What is the function of digestive enzymes ?
Answer:
The food we eat is complex in nature, i.e., it contains complex molecules. Digestive enzymes break down these complex molecules into smaller simpler molecules so that they can be absorbed by the walls of the intestine.

Question 5
How is the small intestine designed to absorb digested food ?
Answer:
The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body. For this the inner lining of the small intestine has numerous finger-like projections called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

Page Number: 105

Question 1
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration ?
Answer:
Aquatic organisms use oxygen dissolved in surrounding water. Since air dissolved in water has fairly low concentration of oxygen, the aquatic organisms have much faster rate of breathing.
Terrestrial organisms take oxygen from the oxygen-rich atmosphere through respiratory organs. Hence, they have much less breathing rate than aquatic organisms.

Question 2
What are the different ways in which glucose is oxidised to provide energy in various organisms ?
Answer:
First step of breakdown of glucose (6 carbon molecules) takes place in the cytoplasm of cells of all organisms. This process yields a three carbon molecule compound called pyruvate.
Further break down of pyruvate takes place in different ways in different organisms.

(i) Anaerobic respiration : The anaerobic respiration in plants (like yeast) produces ethanol and carbon dioxide as end products.
(ii) Aerobic respiration : In aerobic respiration break down of pyruvate takes place in presence of oxygen to give rise three molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than in anaerobic respiration.
(iii) Lack of oxygen : Sometimes, when there is lack of oxygen especially during physical exercise, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compound). Formation of lactic acid in muscles causes cramp.

Question 3
How is oxygen and carbon dioxide transported in human beings ?
Answer:
(i) Transport of oxygen : Haemoglobin present in the blood takes up the oxygen from the air in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.
(ii) Transport of carbon dioxide : Carbon dioxide is more soluble in water. Therefore, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs. Here it diffuses from blood to air in the lungs.

Question 4
How are the lungs designed in human beings to maximise the area for exchange of gases ?
Answer:
Within the lungs, the air passage divides into smaller and smaller tubes, called bronchi which in turn form bronchioles. The bronchioles terminate in balloon-like structures, called alveoli. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have vary thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.

Page Number: 110

Question 1
What are the components of the transport system in human beings ? What are the functions of these components ?
Answer:
The transport system (circulatory system) in human beings mainly consists of heart, blood and blood vessels.

(i) Function of heart : The heart receives deoxygenated blood from the body parts and pumps it to lungs for enriching with oxygen. It receives purified blood from lungs and pumps it around the body.
(ii) Function of blood : Blood transports oxygen, carbon dioxide, digested food, hormones and nitrogeneous waste like urea. It also protects the body from diseases and regulates the body temperature.
(iii) Function of blood vessels : The blood pushed by the heart flows through the blood vessels (arteries, veins and capillaries) and also comes back to the heart through them.

Question 2
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ?
Answer:
Separation of oxygenated and deoxygenated blood allows good supply of oxygen to the body. This system is useful in animals that have high energy requirement. Mammals and birds constantly need oxygen to get energy to maintain their body temperature constant.

Question 3
What are the components of the transport system in highly organised plants?
Answer:
In highly organised plants there are two conducting tissues xylem and phloem.
Xylem consists of vessels, tracheids and other xylem tissues. The interconnected vessels and tracheids form a continuous system of water conducting channels reaching all parts of the plant. Xylem carries water and minerals.
Phloem conducts soluble products of photosynthesis from leaves to different parts of the plant body.

Question 4
How are water and minerals transport in plants ? [AICBSE 2015]
Answer:
The roots of a plant have hair called root hair.
The root hair are directly in contact with the film of water in between the soil particles. Water and dissolved minerals get into the root hair by the process of diffusion. The water and minerals absorbed by the root hair 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.
Therefore the water containing dissolved minerals enters 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. Thus the water and minerals from the soil reach through the root and stem to the leaves of the plants. Evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.

Question 5
How is food transported in plants ?
Answer:
The movement of food in phloem (or translocation) takes place by utilizing energy. The sugar (food) made in leaves is loaded into the sieve tubes of phloem tissue by using energy from ATR Water now enters the 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 parts of the plant having less pressure in their tissues. This allows the phloem to transport food according to the needs of the plant.

Page Number: 112

Question 1
Describe the structure and functions of nephrons.
Answer:
Structure of nephron : Each nephron is composed of two parts. First one is a cup-shaped bag at its upper end which is called Bowman’s capsule.
The Bowman’s capsule contains a bundle of blood capillaries which is called glomerulus. One end of the glomerulus is attached to the renal artery which brings the impure blood containing the urea waste into it. These impurities are filtered. The other part of the nephron is coiled. In this part, the substances like sugar (glucose), amino acid, ions and excess water which are required by the body, are reabsorbed. The substance remained in the nephron is mainly urine containing dissolved urea in water which is expelled from the body through urethra from time to time.

Functions of nephron : Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and water.
Reabsorption : As the filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule.
Urine : The filtrate which remained after reabsorption is called urine. Urine contains dissolved nitrogenous waste like urea and uric acid, excess salts and water. Urine is collected from nephrons to carry it to the ureter from where it passes into urinary bladder.

Question 2
What are the methods used by plants to get rid of excretory products ?
Answer:
(i) The plants get rid of gaseous products-through stomata in leaves and lenticels in stems.
(ii) The plants get rid of stored solid and liquid waste by the shedding off leaves, peeling off bark and felling off fruits.
(iii) The plants get rid of wastes by secreting them in the form of gums and resins.
(iv) Plants also excrete some waste substances into the soil around them.

Question 3
How is the amount of urine produced regulated ?
Answer:
The amount of urine is regulated by kidney. It depends on the quantity of excess water and wastes dissolved in water.

(i) Quantity of water : When water is abundant in the body tissues, large quantities of dilute urine is excreted out. When water is less in quantity in the body tissues, a small quantity of concentrate urine is excreted.
(ii) Quantity of dissolved wastes : Dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts are excreted from the body. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.
(iii) Hormones : The amount of urine produced is also regulated by certain hormones which control the movement of water and Na+ ions in and out of the nephrons.

NCERT Solutions for Class 10 Science Chapter 6 Textbook Chapter End Questions

Question 1
The kidneys in human beings are a part of the system for
(i) nutrition
(ii) respiration
(iii) excretion
(iv) transportation
Answer:
(iii) Excretion

Question 2
The xylem in plants are responsible for
(i) transport of water
(ii) transport of food
(iii) transport of amino acids
(iv) transport of oxygen
Answer:
(i) Transport of water

Question 3
The autotrophic mode of nutrition requires
(i) carbon dioxide and water
(ii) chlorophyll
(iii) sunlight
(iv) all of the above
Answer:
(iv) All of the above

Question 4
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(i) cytoplasm
(ii) mitochondria
(iii) chloroplast
(iv) nucleus
Answer:
(ii) Mitochondria

Question 5
How are fats digested in our bodies ? Where does this process take place ?
Answer:
Digestion of fats takes place in the small intestine.
Bile juice secreted by the liver poured in the intestine along with pancreatic juice. The bile salts present in the bile juice emulsify fhe large globules of fats. Therefore, by enulsification large globules break down into fine globules to provide larger surface area to act upon by the enzymes.
Lipase enzyme present in the pancreatic juice causes break down 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.

Question 6
What is the role of saliva in the digestion of food ?
Answer:
Saliva contains salivary amylase enzyme that breaks down starch into sugars like maltose.

Saliva keeps the mouth cavity clean and moistens the food that help in chewing and breaking down the big pieces of food into smaller ones.

Question 7
What are the necessary conditions (or autotrophic nutrition and what are its by-products ?
Answer:
Necessary conditions for autotrophic nutrition :
(i) Presence of chlorophyll in the living cells.
(if) Provision of supply of water to green plants or cells of the plant.
(iii) Sufficient sunlight.
(iv) Sufficient supply of carbon dioxide.
By-product of auto tropic nutrition is oxygen.

Question 8
What are the differences between aerobic and anaerobic respiration ? Name some organisms that use the anaerobic mode of respiration.
Answer:

Aerobic respiration	Anaerobic respiration
1. It takes place in the presence of oxygen.	1. It takes place in the absence of oxygen.
2. Complete breakdown of food occurs in aerobic respiration.	2. Partial breakdown of food occurs in anaerobic respiration.
3. The end products in aerobic respiration are carbon dioxide and water.	3. The end products in anaerobic respiration may be ethanol and carbon dioxide (as in yeast plants) or lactic acid (as in animal muscles).
4. Aerobic respiration produces a considerable amount of energy.	4. Much less energy is produced in anaerobic respiration.

Some organisms which use anaerobic respiration are yeast, bacteria etc.

Question 9
How are the alveoli designed to maximise the exchange of gases ?
Answer:
(i) The alveoli are thin walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air filled in alveoli.
(ii) Alveoli have balloon-like structure. Hence, provide maximum surface for exchange of gases.

Question 10
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer:
Due to the deficiency of haemoglobin in blood, its oxygen carrying capacity decreases. As a result the production of energy by oxidation will become slower. Therefore, one would fall sick and would feel fatigue most of the time.

Question 11
Describe double circulation in human beings. Why is it necessary ?
Answer:
In our heart blood enters twice and also pumped out twice from the heart. The deoxygenated blood from the body is brought to the right atrium through vena cava from where it is sent to right ventricle. From right ventricle, the blood is pumped to the lungs for oxygenation through pulmonary artery. The oxygenated blood from lungs again enters the left atrium of the heart through pulmonary veins. From left atrium it is send to left ventricle, from where this oxygenated blood is pumped to different parts of body through the arteries. In this way the blood flows through the heart twice, that’s why it is called ‘double circulation’.

Necessity of double circulation: The right side and the left side of the human heart are useful to keep deoxygenated and oxygenated blood from mixing. This type of separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body. This is useful in case of humans who constantly need energy to maintain their body temperature.

Question 12
What are the differences between the transport of materials in xylem and phloem ?
Answer:

Xylem	Phloem
1.  Xylem conducts water and dissolved minerals from roots to leaves and other parts.	1. Phloem conducts prepared food material from leaves to other parts of plant in dissolved form.
2. In xylem, the transport of material takes place through vessels and tracheids which are dead tissues.	2. In phloem, transport of material takes place through sieve tubes with the help of companion cells, which are living cells.
3. In xylem upward movement of water and dissolved minerals is mainly achieved by transpiration pull. It is caused due to suction created by evaporation of water molecules from the cells of a leaf.	3. In translocation, material is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure that moves the material in the phloem to tissues which have less pressure

Question 13
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer:

Alveoli	Nephron
1. Alveoli are functional unit of lungs.	1. Nephrons are functional unit of kidney.
2. A mature lung has about 30 crore alveoli.	2. A kidney has about 10 lakh nephrons.
3. Alveoli provide a wide surface for gaseous exchange.	3. The surface area of a nephron is not much more.
4. The exchange of O2 and CO2 takes place through the network of capillaries in alveoli.	4. The Bowman’s capsule in nephron regulates the concentration of water and salts.

NCERT Solutions for Class 10 Science Chapter 6 Life Processes

Life processes: ‘Living being’. Basic concept of nutrition, respiration, transport and excretion in plants and animals.

Question 1
How are fats digested in our bodies? Where does this process take place?
Solution:
The small intestine is the site of the complete digestion of carbohydrates, proteins and fats. It receives the secretions of the liver and pancreas for this purpose. The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to acting on fats. Fats are present in the intestine in the form of large globules, which make it difficult for enzymes to act on them. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. The pancreas secretes pancreatic juice, which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats. The walls of the small intestine contain glands, which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

Question 2
What is the role of saliva in the digestion of food?
Solution:
When we eat something we like, our mouth ‘waters’. This is actually not only water, but also a fluid called saliva secreted by the salivary glands. Another aspect of the food we ingest is its complex nature. If it is to be absorbed from the alimentary canal, it has to be broken into smaller molecules. This is done with the help of biological catalysts called enzymes. The saliva contains an enzyme called salivary amylase that breaks down starch, which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing by the muscular tongue.

Question 3
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Solution:
Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis. It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy. This material is taken in the form of carbon dioxide and water, which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilised for providing energy to the plant. The carbohydrates, which are not used immediately, are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant.

Question 4
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Solution:
The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways – some use oxygen to breakdown glucose completely into carbon dioxide and water; some use other pathways that do not involve oxygen. In all cases, the first step is the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm. Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration. The release of energy in this aerobic process is a lot greater than in the anaerobic process.

Question 5
How are the alveoli designed to maximise the exchange of gases?
Solution:
Within the lungs, the passage divides into smaller and smaller tubes, which finally terminate in balloon-like structures, which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood vessels. As we have seen in earlier years, when we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

Question 6
Describe double circulation in human beings. Why is it necessary?
Solution:
The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation.
The adult human heart consists of two separated pumps, the right side with the right atrium and ventricle which pumps deoxygenated blood into the pulmonary circulation.
The oxygenated blood re-enters the left side of the heart through the pulmonary vein into the left atrium and passes to the left ventricle where it is pumped to the rest of the body. This part of the circulation is called as systemic circulation. This type of circulation is called double circulation. The advantage of a double circulatory system is that blood can be pumped to the rest of the body at a higher pressure.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Yeast respires anaerobically using sugar as a substrate. Out of the options given below, choose the correct combination of condition and product?

	Condition	Product
(a)	Aerobic	Alcohol
(b)	Aerobic	Lactic acid
(c)	Anaerobic	Alcohol
(d)	Anaerobic	Lactic acid

Answer:
(c) Under an aerobic condition, yeast respires and converts glucose to alcohol and CO₂.

Question 2.
The table shows the percentage composition of four samples of air. Which sample could have been breathed out by a person after vigorous exercise?

Samples	Oxygen	Carbondioxide	Water Vapour
(a)	16	0.3	Saturated
(b)	16	4	Saturated
(c)	21	0.03	Trace
(d)	21	3	Trace

Answer:
(b) This is because rapid aerobic respiration occurs – during vigorous exercise in order to obtain more energy.

Question 3.
Cramps caused during sudden activities are due to the formation of
(a) lactic acid
(b) acetic acid
(c) excess of water
(d) ethanol
Answer:
(a) Lactic acid is formed by the breakdown of pyruvate when oxygen is insufficient in muscles instead of forming C02 and water. Accumulation of excess lactic acid in the muscles causes cramps.

Question 4.
Which of the following plays nose like function in plants?
(a) Flower
(b) Phloem
(c) Stomata
(d) Chlorophyll
Answer:
(c) Stomata are pores which help in the passage of air in the plants.

Question 5.
Which changes occur when a person breathe in deeply?

	Diaphragm Muscle	External Intercostal Muscles
(a)	Contracts	Contract
(b)	Contracts	No change
(c)	Relaxes	Contract
(d)	Relaxes	Relax

Answer:
(a) When a person breathes deeply the external intercostal muscles contract causing the rib cage to swing up and out. Also, the diaphragm contracts and flattens causing the thoracic cavity to increase in volume and decrease in pressure.

Question 6.

The diagram given above shows part of the lining of the human trachea. What is the function of X?
(a) Gaseous exchange
(b) Mucus removal
(c) Phagocytosis
(d) Secretion of mucus
Answer:
(b) The cilia (X) of the cells lining the air passages move in a sweeping motion to keep the air passages clean. The constant action of these cilia carry mucus and debris upward into the pharynx where they are swallowed.

Question 7.
The table given below shows the percentage composition of a gas in inspired and in expired air.

%Composition
Inspired Air	Expired Air
21.0	16.0

What is the gas?
(a) Carbon dioxide
(b) Nitrogen
(c) Oxygen
(d) Water vapour
Answer:
(c) The gas is oxygen as atmospheric air has approximately 21% of oxygen

NCERT Exemplar Solutions for Class 10 Science Chapter 6 Life Processes

NCERT Exemplar Solutions for Class 10 Science Chapter 6 Short Answer Questions

Question 1.
Name the following :

1. 1. The process in plants that links light energy with chemical energy.

1. Organisms that can prepare their own food.
2. Cells that surround a stomatal pore.
3. The cell organelle where photosynthesis occurs.
4. Organisms that cannot prepare their own food.
5. An enzyme secreted by gastric glands in stomach that acts on proteins.

Answer:

1. Photosynthesis
2. Autotrophs
3. Guard cells
4. Chloroplast
5. Heterotrophs
6. Pepsin.

Question 2.
“All plants give out oxygen during day and carbon dioxide during night.” Do you agree with the statement ? Give reason.
(CCE 2010)
Answer:
Yes. Respiration is going on throughout day and night. Photosynthesis occurs only during the day. Rate of photosynthesis is several times the rate of respiration. All the CO₂ produced in respiration is also consumed in photosynthesis during the day time. Therefore, during day time, plants give out oxygen, which is a product of photosynthesis. However, during night when there is no photosynthesis, plants liberate carbon dioxide.

Question 3.
How do the guard cells regulate opening and closing of stomatal pores ? (CCE 2010, 2012)
Answer:
Opening and closing of stomata is regulated by gain or loss of turgidity of their guard cells. During opening of stomata, guard cells withdraw K⁺ ions from surrounding epidermal cells, followed by absorption of water from them. As a result, guard cells swell up and become turgid. Their outer thin and elastic walls bend outwardly followed by outward movement of thicker inner walls. The latter creates a pore in between the two guard cells.
During closure movement of stomata, guard cells send out K⁺ ions. Water also passes out. Guard cells become flaccid. Their inner thick walls come to touch each other. The stomatal pore gets closed.

Question 4.
Two green plants are kept separately in oxygen free containers, one in dark and the other in continuous light. Which one will live longer ? Give reasons. (CCE 2010)
Answer:
Plant kept in continuous light will live longer due to

1. Manufacture of food and hence its availability to the plant for maintenance and growth,
2. Production of oxygen in photosynthesis and its availability for respiration of the plant. Plant kept in oxygen free container kept in dark will die within a few days due to non-availability of food and oxygen.

Question 5.
If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring ? Justify your answer.
Answer:
A plant releases carbon dioxide and takes in oxygen only when photosynthesis is either absent or too small as not to compensate for respiration.
(In photosynthesis, plants absorb CO₂ and release O₂. The normal rate of photosynthesis is many times the rate of respiration. As a result, CO₂ produced during respiration is consumed and a lot of more is absorbed from outside. Oxygen produced during photosynthesis is much more than required for respiration. Therefore, oxygen passes out.)

Question 6.
Why do fishes die when taken out of water ?
Answer:
Fish taken out of water die due to

1. Inability to obtain oxygen from air
2. Collapsing of gill lamellae so that no space is left for gaseous exchange.

Question 7.
Differentiate between an autotroph and a heterotroph.
Answer:

Autotroph	Heterotroph
1. Food: It manufactures its own food.	It obtains its food from outside sources.
2. Chlorophyll: It has chlorophyll for performing photosynthesis.	Chlorophyll is absent.
3. Energy: It is obtained from sunlight and changed into chemical energy.	It does not require an external source of energy as the same is present in food obtained from outside.
4. Digestion: It is absent.	Food obtained from outside is digested before being absorbed and assimilated.

Question 8.
Is nutrition a necessity for an organism ? Discuss.
Answer:
Yes, nutrition is a must for an organism because of the following reasons :
Importance of Nutrition/Food

1. Food provides energy: Energy is required by the body all the time, whether asleep, taking rest or doing work. When the body is not doing any apparent work, energy is still being consumed in maintaining order. Further, biosynthetic activities continue for replacing materials being consumed or degraded. A number of other activities are going on all the time. Heart is always beating. Breathing movements never stop. Food eaten by a person has to be digested and absorbed. Excretory products are being produced.
2. Body Structure: All body components are built up of materials obtained from food.
3. Food is used in building protoplasm. More protoplasm is required for formation and enlargement of cells that take part in growth of the organism.
4. Food provides materials for replacement and repair of worn out or damaged structures.
5. Hormones and enzymes are formed from ingredients of food. They regulate metabolism and body functions.                                                                ‘
6. Defence system of the body is formed from raw materials got- from food.
7. Food provides materials to form reproductive structures.

Question 9.
What would happen if green plants disappear from earth ?
Answer:
Herbivores will die of starvation followed by carnivores and then decomposers.

Question 10.
Leaves of a healthy plant were coated with vaseline. Will this plant remain healthy for long ? Give reasons for your answer.
Answer:
The plant will not remain healthy for long. Vaseline covers the cuticle and blocks the stomata. As a result

1. It is unable to obtain oxygen from air for respiration,
2. It is unable to perform photosynthesis as no carbon dioxide diffuses from air.
3. In the absence of transpiration, the leaves get heated up and injured.

Question 11.
How does aerobic respiration differ from anaerobic respiration ?
Answer:

Aerobic Respiration	Anaerobic Respiration
1. Method: It is the common method of respiration.	It occurs permanently only in a few organisms. In others it may occur as a temporary measure to overcome shortage of oxygen.
2. Steps: It is completed in 3 steps—glycolysis, Krebs cycle and terminal oxidation.	There are two steps— glycolysis and anaerobic breakdown of pyruvic acid.
3. Oxygen: It requires oxygen.	Oxygen is not required.

Question 12.
Match the words of column A with those of column B

A	B
(a)  Phloem (b)   Nephron (c)  Veins (d)  Platelets	(i)   Excretion (ii)  Translocation of food. (iii)   Clotting of blood (iv)   Deoxygenated blood.

Answer:
a — ii,
b — i,
c —iv,
d —iii.

Question 13.
Differentiate between an artery and a vein. (CCE 2013)
Answer:

Artery	Vein
1. Direction of Flow: It carries blood from heart to an organ.	It brings blood from an organ towards the heart.
2. Speed: Blood flow is rapid in artery.	Blood flow is slow in vein.
3. Jerks: Blood flows with jerks.	Blood flows smoothly.
4. Pressure: Blood flows under pressure	There is little pressure.
5. Internal Valves: They are absent.	Internal valves are present to prevent back flow.
6. Wall: It is thick and elastic.	It is comparatively thinner and little elastic.
7. Lumen: Narrow.	Wide.
8. Type of Blood: Artery carries oxygenated blood except pulmonary arteries.	Vein carries deoxygenated blood except pulmonary veins.
9. Occurrence: It is deep seated.	It is superficial.
10. Collapsibility: Artery is not collapsible.	Vein is collapsible.
11. Blood After Death: It does not contain blood after death.	Vein is full of blood even after death.

Question 14.
What are the adaptations of leaf for photosynthesis ?
Answer:

1. Large Surface Area : Leaf has a large surface area to absorb maximum amount of lift.
2. Leaf Orientation: It is such as to absorb the optimum amount of light.
3. Veins: A number of veins occur in a leaf. They provide mechanical strength to the otherwise soft leaf. Veins also take part in quick transport of substances to and from the mesophyll cells.
4. Transpiration: Leaf is the seat of transpiration. Transpiration cools the surface of leaf for optimum photosynthesis.
5. Gaseous Exchange: A leaf has a large number of stomata for gaseous exchange, required for photosynthesis.
6. Chloroplasts: A very large number of chloroplasts occur in the mesophyll of a leaf for efficient photosynthesis.

Question 15.
Why is small intestine in herbivore longer than in carnivores ? (CCE 2013)
Answer:
Herbivorous diet has a large bulk. It is rich in cellulose. However, cellulose digesting enzymes are absent in them. For digestion
of cellulose, herbivores depend upon bacteria. The food has to be kept for longer period in the intestine for complete digestion of cellulose. Therefore, small intestine where bacterial digestion of cellulose occurs has to be long. There is no such requirement in carnivores as their diet has a smaller bulk which does not contain cellulose. They have a shorter intestine.

Question 16.
What will happen if mucus is not secreted by gastric glands ?
Answer:
Mucus protects the stomach from corrosion by HCl and pepsin of gastric juice. In the absence of mucus, the lining layer of stomach wall will be corroded forming gastric ulcers. There will be excessive acidity and extreme discomfort.

Question 17.
What is the significance of emulsification of fats ?
Answer:
Emulsification of fat is the conversion of large fat pieces into very fine fat globules which can be efficiently acted upon by lipase.

Question 18.
What causes movement of food inside the alimentary canal ?
Answer:
Involuntary movement consisting of rhythmic contraction and expansion of the alimentary canal called peristalsis.

Question 19.
Why does absorption of digested food occur mainly in the small intestine ?
Answer:

1. Digestion of food is completed only in small intestine.
2. Wall of the intestine bears a number of finger-like projections called villi. Villi provide a large surface area to the lining layer for absorption.
3. The epithelium, lining the villi, is made of cells having a number of very fine projections known as microvilli. Microvilli are specialised for absorption.
4. Wall of the intestine, especially the interior of villi, has lymph and blood vessels for carrying the absorbed food to different parts of the body.

Question 20.
Match the articles of columns A and B :

A	B
(a)  Autotrophic nutrition (b)  Heterotrophic nutrition (c) Parasitic nutrition (d)  Digestion in food vacuoles	(i) Leech  (ii) Paramoecium (iii)   Deer (iv)    Green plant.

Answer:
a — iv,
b — iii,
c—i,
d — ii.

Question 21.
Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms ? (CCE 2011, 2012)
Answer:
Most of the aquatic organisms obtain oxygen from water. The amount of dissolved oxygen is quite small as compared to the amount of oxygen in air. Therefore, in order to obtain required oxygen from water, the aquatic animals like fishes have to breathe much faster as compared to the terrestrial organisms.

Question 22.
Why is blood circulation in human heart called double circulation ? (CCE 2011)
Answer:
Blood circulation in human heart is called double circulation as blood passes twice through the heart in order to complete one cycle—once through right side as deoxygenated blood and once through left side as oxygenated blood. Deoxygenated blood passes to lungs. It returns to left side as oxygenated blood. Oxygenated blood is supplied to different parts of the body. It returns to right side of the heart as deoxygenated blood.

Question 23.
What is the advantage of having four chambered heart ? (CCE 2010)
Four chambered heart ensures complete separation of oxygenated and deoxygenated bloods. Only oxygenated blood is pumped out to supply all parts of the body. It is received by left auricle from lungs and pumped out by left ventricle. The blood returns to heart after deoxygenation. It is received by right auricle and pumped out by right ventricle to lungs for oxygenation. The mechanism is useful to animals with high energy needs (due to thermoregulation and higher activity) such as birds mammals.

Question 24.
Mention the major events during photosynthesis. (CCE 2011, 2012)
Answer:

1. Photolysis: With the help of light energy, oxygen evolving Z-complex splits up water into its components —- protons (H⁺), electrons (e^–) and oxygen.
   
2. Absorption of Light Energy: Chlorophyll absorbs light energy.
3. Primary Reaction: Chlorophyll converts the absorbed light energy into chemical energy. It is called primary reaction of photosynthesis. It builds up ATP with the help of excited electrons.
4. Formation of Reducing Power: Coenzyme NADP⁺ is changed to reduced form of NADPH.
   
5. Reduction of CO₂: Carbon dioxide is reduced enzymatically with the help of NADPH and ATP to form carbohydrates.
   

Question 25.
In each of the following situations, what happens to the rate of photosynthesis ?
(a) Cloudy days
(b) No rainfall in the area
(c) Good manuring
(d) Stomata get blocked due to dirt.
Answer:
(a) Cloudy Days: Photosynthesis is reduced due to low light intensity.
(b) No Rainfall: Rate of photosynthesis decreases due to wilting of leaves, closure of stomata and reduced availability of hydration.
(c) Good Manuring: Rate of photosynthesis increases as good manuring increases soil fertility by providing more minerals, moisture and aeration.
(d) Blocked Stomata: It decreases the rate of photosynthesis by reducing gaseous exchange and non-cooling of leaves due to reduced transpiration.

Question 26.
Name the energy currency in the living organisms. When and where is it produced ?
Energy Currency. ATP (adenosine triphosphate) is the energy; currency of the living beings.
It is produced both during respiration (in all organisms) and photosynthesis (in plants only).

Question 27.
What is common amongst Cuscuta, Ticks and Leeches ?
Answer:
All are parasites which obtain their nutrition from their hosts direcdy without killing them.

Question 28.
Explain the role of mouth cavity in digestion of food.
Answer:

1. Moistening of food with saliva,
2. Tongue helps in thorough mixing of food with saliva.
3. Crushing of food into smaller pieces by teeth,
4. Partial digestion of starch by enzyme amylase contained in saliva,
5. Rolling of crushed, moistened and partially digested food into small ball or bolus by the tongue.

Question 29.
What are the functions of gastric glands present in the wall of stomach ? (CCE 2011)
Answer:
Gastric glands produce the following substances :

1. Mucus: Moistening the food and protecting the wall of the stomach from corroding action of HCl and pepsin.
2. HCl: It makes the food soft, sterilised and acidified for pepsin to act upon food.
3. Gastric Lipase: It is active only in infants. It partially breaks down fat into its components.
4. Rennin: It is active in infants where it helps in curdling of milk (casein to paracasein) for action of pepsin.
5. Pepsin: It is secreted in inactive state of pepsinogen. Pepsin hydrolyses proteins into soluble fragments of peptones and proteoses.

Question 30.
Match the items of columns A and B

A	B
(a)  Trypsin (b)  Amylase (c) Bile (d)  Pepsin	(i) Pancreas  (ii) Liver (iii)   Gastric glands (iv)     Saliva

Answer:
a — i,
b — iv,
c — ii,
d — iii.

Question 31.
Name the correct substrates for the following enzymes :
(a) Trypsin
(b) Amylase
(c) Pepsin
(d) Lipase.
Answer:
(a) Trypsin: Proteins, peptones and proteoses,
(b) Amylase: Starch, dextrins.
(c) Pepsin: Proteins.
(d) Lipase: Fats.

Question 32.
Why do veins have thin walls as compared to arteries ?
Answer:
In arteries, blood flows under pressure so that their walls are thick and elastic. In veins the blood is Therefore, their walls are thin. Rather, they possess semilunar valves to check back flow of blood.

Question 33.
What will happen if platelets were absent in the blood ?
Answer:
Blood platelets are a source of thromboplastin which is essential for blood clotting at the place of injury. In the absence of blood platelets, blood clotting will be litde resulting in greater loss of blood from the place of injury.

Question 34.
Plants have low energy needs as compared to animals. Explain.
Answer:
Plants are anchored. They do not move about. Most of their body is made of dead cells and cell walls. Therefore, their requirement for energy is quite low as compared to animals which move about fast in search of food, mate and shelter.

Question 35.
Why and how does water enter continuously into root xylem ?
Answer:
Root cells in the absorbing part of root pick up ions actively from soil. Ions pass inwardly increasing osmotic concentration of xylem. Because of it soil water (which has very low osmotic concentration) continuously passes into root xylem.

Question 36.
Why is transpiration important for plants ?
Answer:
Importance

1. Cooling: Evaporation of water from the aerial parts results in lowering of their temperature which will otherwise rise due to exposure to sun.
2. Concentration of Minerals: Transpiration helps in increasing concentration of minerals present in rising water.
3. Transport: It creates a pull that helps in transport of water and minerals.

Question 37.
How does leaves of plants help in excretion ? (CCE 2016)
Answer:
Waste materials produced in plant cells are stored ’in their vacuoles. In leaves, the waste materials are

1. Stored in vacuoles of mesophyll and epidermal cells,
2. Oxalic acid is crystallised as calcium oxalate.
3.  Nitrogenous wastes are changed into alkaloids
4. Vaste aromatic compounds are changed into tannins. As the old leaves fall, the waste materials are also removed from the plant.

NCERT Exemplar Solutions for Class 10 Science Chapter 6 Long Answer Questions

Question 38.
Explain the process of nutrition in Amoeba.
Answer:

1. Ingestion: (L. ingestus — taken in). It is taking in of solid food with the help of temporary or permanent mouth. Amoeba can ingest food particles from any point on its surface. Paramoecium (another unicellular organism) has fixed point for the same. Amoeba captures food with the help of temporary finger-like processes called pseudopodia. Paramoecium has small hair-like processes called cilia. Beating of cilia creates current in water that pushes food particle through cytostome or cell mouth. The process of ingestion of solid food particle by a cell or unicellular organism is called phagocytosis.
   As soon as Amoeba comes in contact with a food particle or prey, it throws pseudopodia all around the same. The tips of encircling pseudopodia fuse and the prey comes to lie in a vesicle or phagosome.
   
2. Digestion: It is conversion of complex insoluble food ingredients into simple absorbable form. Digestion can be intracellular or intercellular. Intercellular digestion occurs in a digestive tract. Intracellular digestion takes place in the cytoplasm of cells. Here, a lysosome fuses with phagosome to produce a food vacuole, also called gastriole or temporary stomach. Reaction of food vacuole is acidic at first and alkaline later on. Digestion of food occurs with the help of digestive enzymes brought by lysosome. It changes complex insoluble substances of food into simpler absorbable substances.
3. Absorption: The digested simple and soluble substances pass out of food vacuole into the surrounding cytoplasm.
4. The absorbed food materials are converted into various constituents of protoplasm including food reserve.
5. (L. egestus — discharge): It is throwing of undigested components of food out of the body. In Amoeba, the old food vacuole with heavier undigested material reaches the rear end, passes to the surface, fuses with surface membrane and throws out the undigested materials. The process is called egestion. Paramoecium has a definite cytopyge or cell anus.

Question 39.
Describe the alimentary canal of man.
Answer:
Alimentary canal (L. alere-to nourish) is a tubular passage extending from mouth to anus through which food passes during its digestion and absorption. It is about 9 metres in length. Alimentary canal consists of mouth, buccal cavity, oesophagus, stomach, small intestine, large intestine and anus.

1. Mouth: It is a transverse slit like aperture that occurs in between the nose and the chin. Mouth is bounded by two soft, movable sensitive lips, upper and lower. Lips help in holding the food. They also aid in phonation (speech).
2. Buccal or Oral Cavity (L. bucca-cheek): It is anterior part of alimentary canal that extends from mouth to pharynx and lies between two jaws, upper (fixed) and lower (movable). It has palate on upper side, throat and tongue on the lower side and cheeks on the lateral sides. Both the jaws contain teeth in semicircular rows or arches.
   1. It is a muscular, sensory, movable and protrusible flat structure which is attached posteriorly over the lower jaw. Tongue bears taste buds for tasting the quality of food—sweet anteriorly, salt anterio-laterally, sour postero-laterally and bitter posteriorly. It moves food in ‘the buccal cavity for crushing under teeth, mixing with saliva and pushing the food during swallowing. Tongue cleans the teeth. It also aids in phonation (speech). It functions as a movable spoon during drinking.
   2. They are hard structures which are used for cutting, chewing and crushing the food (physical digestion). They are partially embedded in sockets of jaw bones (thecodont). Teeth are made of ivory like substance called dentine. The exposed parts of teeth or crowns are covered by a shining substance called enamel. Enamel is the hardest substance of the body.
   3. Salivary Glands. Three pairs of salivary glands (saliva secreting glands) open into buccal cavity. They are parotid (below ears), sub-maxillary (at the angles of lower jaw) and sublingual (below tongue). About 1-0-1-5 litres of near neutral saliva is poured into buccal cavity every day. Saliva consists of mucus, water, lysozyme and enzyme ptyalin.

Question 40.
Explain the process of breathing in man.
Answer:
Breathing or the process of taking in fresh air and releasing foul air can be easily observed because thorax shows alternate expansion and contraction. It is involuntary though it can be prevented for a brief period. Rate of breathing is controlled by respiratory centre of brain. Expansion of thorax causes fresh air to be drawn in. Contraction of thorax causes foul air to be expelled. Therefore, breathing consists of two steps, inspiration and expiration.

1. Inspiration or Inhalation: It is bringing of fresh air into lungs for exchange of gases. During inhalation, thoracic cavity enlarges due to two types of inspiratory muscles, phrenic and external intercostals. Phrenic muscles straighten the diaphragm by moving its curved part downwards. It increases length of thorax. Contraction of external intercostal muscles pushes the rib cage in outward and upward direction. It increases girth of thorax. Being air tight, increase in size of thoracic cavity causes expansion of lungs. It decreases air pressure in the lungs. As a result outside air rushes into lungs through external nostrils, nasal cavities, internal nostrils, pharynx, larynx, trachea, bronchi, bronchioles to alveoli. While passing through respiratory tract, the incoming air is :
   1. Filtered by hair present in anterior part of nasal cavities.
   2. Cleansed of dust and microbes throughout respiratory tract by lysozyme, mucus and cilia.
   3. Air conditioned (bringing temperature of inhaled air to that of body) with the help of blood capillaries present below nasal epithelium.
   4. Moistened by water vapours from wet epithelium.
2. Exchange of Gases: It occurs in the alveoli. Fresh air has high concentration of oxygen and a very low concentration of carbon dioxide. As a result, oxygen diffuses from alveolar air to blood present in capillaries around the alveoli. Carbon dioxide diffuses from blood into alveolar air.

Question 41.
How do carbohydrates, proteins and fats get digested in human beings ?
Answer:
Carbohydrates:    Glucose.
Proteins:               Amino acids.
Fats:                      Fatty acids and   glycerol.
Hints:

1. Carbohydrates: In mouth cavity (by saliva), duodenum (by pancreatic juice) and jejunum (by intestinal juice).
2. Proteins: In stomach (by gastric juice), duodenum (by pancreatic juice) and jejunum (by intestinal juice).
3. Fats: In duodenum and jejunum (by pancreatic juice aided by bile salts). Also in infants in stomach.

Question 42.
Explain the mechanism of photosynthesis.
Answer:
Mechanism of Photosynthesis:
Photosynthesis is formation of organic food from carbon dioxide and water with the help of sunlight inside chlorophyll containing cells. Oxygen is produced as by-product.

Oxygen comes from water. Hydrogen of water is used to reduce carbon dioxide to form carbohydrate.

Actually, photosynthesis occurs in two steps, photochemical and biochemical.
1. Photochemical Phase (Light or Hill Reaction): The reactions of this phase are driven by light energy. They are of two types— photolysis of water and formation of assimilatory power.
(a) Photolysis of Water. Light energy splits up water into its components. Mn²⁺, CL and Ca²⁺ are required for this.

(b) Formation of Assimilatory Power: Light energy absorbed by chlorophyll molecules is used in synthesis of ATP and NADPH.
Both ATP and NADPH₂ together form assimilatory power.

2. Biosynthetic Phase (Dark or Blackman’s Reaction). It is actually light independent reaction which can occur both in light as well as in dark. It requires the energy and reducing power contained in assimilatory power of light reaction. Common pathway of biosynthetic phase is Calvin cycle. Carbon dioxide combines with ribulose bisphosphate in the presence of enzyme ribulose biphosphate carboxylase or rubisco. It produces two molecules of phosphoglyceric acid (PGA).

3. In the presence of ATP, phosphoglyceric acid is reduced by NADPH₂ to form glyceraldehyde phosphate (GAP).

4. A part of glyceraldehyde phosphate is changed into dihydroxyacetone phosphate. The two condense and form glucose. Ribulose biphosphate is regenerated to combine with carbon dioxide again. Glucose undergoes condensation to form reserve carbohydrate called starch.
5. Other inorganic Raw Materials: Synthesis of carbohydrates during photosynthesis is a mechanism to form food materials for body building and releasing energy.

Plants also require a number of other inorganic raw materials or minerals from soil for building other, e.g., nitrogen, phosphorus, iron, sulphur, magnesium, etc. Nitrogen and sulphur are required for building proteins. Phosphorus is required for synthesis of nucleotides. Minerals are absorbed in the form of ions, e.g., NO₂^– and NH₄⁺ for nitrogen. Some bacteria convert atmospheric nitrogen into compounds of nitrogen. Parts of them become available to plants.

Question 43.
Explain the three pathways of breakdown (respiration) in living organisms.
Answer:
(i) Aerobic Respiration:
It is a multistep complete oxidative breakdown of respiratory substrate into carbon dioxide and water with the help of oxygen acting as a terminal oxidant. Aerobic respiration is the usual mode of respiration in all higher organisms and most of the lower organisms. The reason is that it yields maximum amount of energy. The energy is stored in some 38 molecules of ATP.

Aerobic respiration occurs in two steps, glycolysis and Krebs cycle.

Glycolysis: Glycolysis or EMP (Embden, Meyerhof and Parnas) pathway is the first step of respiration which is common to both aerobic and anaerobic modes of respiration. It occurs in cytoplasm. Respiratory substrate is double phosphorylated before it undergoes lysis to produce 3-carbon compound, glyceraldehyde phosphate. NADH₂ and ATP are produced when glyceraldehyde is changed to pyruvate. The net reaction of glycolysis is :

Krebs Cycle (Krebs, 1940): It is also known as citric acid cycle or tricarboxylic acid cycle (TCA cycle). Pyruvic acid or pyruvate passes into mitochondria. It undergoes oxidative decarboxylation to produce acetyl CoA, carbon dioxide and NADH₂. Acetyl CoA enters Krebs cycle. Here two decarboxylations, four dehydrogenations and one phosphorylation or ATP synthesis occur.

NADH₂ and FADH₂ liberate electrons and hydrogen ions. They are used in building up ATP molecules and activating oxygen molecules to combine with hydrogen for forming water. Synthesis of ATP from ADP and inorganic phosphate with the help of electron generated energy during oxidation of reduced coenzymes (NADH₂, FADH₂) is called oxidative phosphorylation. Water formed in respiration is called metabolic water. As oxygen is used at the end of Krebs cycle for combining with hydrogen, the process is called terminal oxidation.
The overall equation of aerobic respiration using glucose as substrate is

(ii) Anaerobic Respiration Producing Alcohol:
It is a multistep breakdown of respiratory substrate in which atleast one end product is organic and which does not employ oxygen as an oxidant. Anaerobic respiration occurs in many lower organisms, e.g., certain bacteria, yeast. In human body it occurs regularly in red blood cells and during heavy exercise in muscles (striated muscles). Anaerobic respiration occurs entirely in the cytoplasm. It has two steps. The first step is glycolysis. Here, respiratory substrate glucose breaks down into two molecules each of pyruvate, ATP and NADH₂. Pyruvate is converted into ethyl alcohol (C₂H₅OH) in Yeast and certain bacteria. It is changed to lactic acid (CH₃CHOH.COOH) in muscle cells when oxygen utilisation is faster than its availability as during vigorous exercise. It creates an oxygen debt in the body. No such debt occurs in blood corpuscles.

(iii) Anaerobic Respiration Producing Lactic Acid:
Build up of lactic acid in muscles during prolonged activity causes fatigue and results in cramps.
Fermentation (L. fermentum-froth). It is anaerobic breakdown of carbohydrates by microorganisms producing alcohol, organic acids and a variety of other products alongwith heat and waste gases. Fermentation is used in brewing industry (for producing wine, whisky, beer), baking industry (for making bread spongy), curd and yoghurt formation, synthesis of vinegar, citric acid, lactic acid, softening and aromatisation of Tobacco, Tea and other beverages, cleaning of hides and separating or retting of fibres (e.g., Jute, Hemp).

Question 44.
Describe the flow of blood through heart of human beings.
Answer:
It is passage of the same blood twice through the heart first on the right side, then on the left side in order to complete one cycle. Double circulation has two components, pulmonary circulation and systemic circulation.

1. Pulmonary Circulation: It is movement of blood from heart to the lungs and back. Deoxygenated blood of the body enters the right auricle, passes into right ventricle which pumps it into pulmonary arch. With the help of two separate pulmonary arteries the blood passes into the lungs. Here, it is oxygenated. Oxygenated blood comes back to left auricle of heart through four pulmonary veins, two from each lung.
2. Systemic Circulation: It is the circulation of blood between heart and different parts of the body except lungs. Oxygenated blood received by left auricle passes into left ventricle. The left ventricle pumps it into aorta for supply to different body parts including walls of the heart by means of arteries. Inside the organs the blood loses oxygen and nutrients. It picks up carbon dioxide and waste products. This deoxygenated blood is drained by veins and sent to the right auricle of heart.

Question 45.
Describe the process of urine formation in kidneys.
Answer:
Mechanism of Urine Formation: 
It has four components — glomerular filtration, selective reabsorption, tubular secretion and concentration.

1. Glomerular Filtration: Blood flows in glomerulus under pressure due to narrowness of efferent arteriole. As a result it undergoes pressure filtration or ultrafiltration. All small volume solutes (e.g., urea, uric acid, amino acids, hormones, glucose, ions, vitamins) and water are filtered out and enter the Bowman’s capsule. The product is called nephric or glomerular filtrate. Its volume is 125 ml/min (180 litres/day).
2. Reabsorption: Nephric filtrate is also called primary urine. It passes into proximal convoluted tubule. The peritubular capillaries around PCT reabsorb all the useful components of nephric filtrate, e.g, glucose, amino acids, vitamins C, calcium, potassium, sodium, chloride, bicarbonate and water (75%). Selective reabsorption also occurs in the region of distal convoluted tubule. The amount of water absorption depends upon amount of excess water present in the body and the amount of dissolved waste to be excreted.
3. Tubular Secretion (Augmentation): It occurs mostly in the distal convoluted tubule which is also surrounded by peritubular capillaries. Smaller amount of tubular secretion also takes place in the area of proximal convoluted tubule. Tubular secretion is active secretion of waste products by the blood capillaries into the urinary tubule. It ensures removal of all the waste products from blood, viz.,’ urea, uric acid, creatinine. Extra salts, K⁺ and H⁺ are also secreted into urinary tubule to maintain a proper concentration and pH of the urine.
4. Concentration of the Urine: 75% of water content of nephric filtrate is reabsorbed in the region of proximal convoluted tubule. Some 10% of water passes out of the filtrate through osmosis in the area of loop of Henle. It is because loops of Henle are immersed in hyper-osmotic interstitial fluid, Further concentration takes place in the area of collecting tubes in the presence of hormone called antidiuretic hormone (ADH) or vasopressin. The hormone is secreted only when concentrated urine is to be passed out. It is not secreted when a person drinks a lot of water. Absence of antidiuretic  hormone produces a dilute urine. Hormone action, therefore, maintains osmotic concentration of body fluids. Deficiency of ADH causes excessive, repeated, dilute urination (diabetes insipidus).

Life Process Class 10 Science Notes

Nutrition in Plants and Animals – Life Processes Class 10 Notes

• Nutrition: The process by which an organism takes food and utilizes it, is called nutrition.
• Need for Nutrition: Organisms need the energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
• Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
• Modes of Nutrition
  1. Autotrophic Nutrition.
  2. Heterotrophic Nutrition.

Autotrophic Nutrition – Life Processes Class 10 Notes

The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.

• The organisms which carry out autotrophic nutrition are called autotrophs (green plants).
  
• Autotrophic nutrition is fulfilled by the process, by which autotrophs intake CO₂ and H₂O, and convert these into carbohydrates in the presence of chlorophyll, sunlight is called photosynthesis.
• Equation
  

Nutrition in Plants: Green plants prepare their own food. They make food in the presence of sunlight. Sunlight provides energy’, carbon dioxide and water are the raw materials and chloroplast is the site where food is made.

What is Photosynthesis in biology class 10?

Photosynthesis: The process by which green plants prepare food is called photosynthesis.

• During this process, the solar energy is converted into chemical energy and carbohydrates are formed.
• Green leaves are the main site of photosynthesis.
• The green portion of the plant contains a pigment chloroplast, chlorophyll (green pigment).
• The whole process of photosynthesis can be shown by the following equation:
  

Raw Materials for Photosynthesis:

• Sunlight
• Chlorophyll: Sunlight absorbed by chloroplast
• CO₂: Enters through stomata, and oxygen (O₂) is released as a byproduct through stomata on the leaf.
• Water: Water + dissolved minerals like nitrogen, phosphorous etc., are taken up by the roots from the soil.

How do raw materials for photosynthesis become available to the plant?

• Water comes from the soil, through the xylem tissue in roots and stems.
• Carbon dioxide comes in the leaves through stomata.

Site of Photosynthesis: Chloroplast in the leaf. Chloroplast contains chlorophyll (green pigment)

Main Events of Photosynthesis:

• Absorption of light energy by chlorophyll.
• Conversion of light energy into chemical energy + splitting (breaking) of water into hydrogen and oxygen.
• Reduction of CO₂ to carbohydrates.
• Sunlight activates chlorophyll, which leads to splitting of the water molecule.
• The hydrogen, released by the splitting of a water molecule is utilized for the reduction of carbon dioxide to produce carbohydrates.
• Oxygen is the by-product of photosynthesis.
• Carbohydrate is subsequently converted into starch and is stored in leaves and other storage parts.
• The splitting of water molecules is a part of the light reaction.

Other steps are part of the dark reaction during photosynthesis.

Stomata – Life Processes Class 10 Notes

• Stomata: These are tiny pores present in the epidermis of leaf or stem through which gaseous exchange and transpiration occur.

Functions of stomata

• Exchange of gases, O₂ and CO₂.
• Loses a large amount of water (water vapour) during transpiration.
  

Opening and closing of stomatal pores:

• The opening and closing of stomatal pores are controlled by the turgidity of guard cells.
• When guard cells uptake water from surrounding cells, they swell to become a turgid body, which enlarges the pore in between (Stomatal Opening).
• While, when water is released, they become flaccid shrinking to close the pore (Stomatal Closing).
  

Significance of Photosynthesis:

• Photosynthesis is the main way through which solar energy is made available for different living beings.
• Green plants are the main producers of food in the ecosystem. All other organisms directly or indirectly depend on green plants for food.
• The process of photosynthesis also helps in maintaining the balance of carbon dioxide and oxygen in the air.

Heterotrophic Nutrition – Life Processes Class 10 Notes

The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms, other than green plants and blue-green algae follow the heterotrophic mode of nutrition. Heterotrophic nutrition can be further divided into three types, viz. saprophytic nutrition, holozoic nutrition, and parasitic.

• Saprophytic Nutrition: In saprophytic nutrition, the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects, like houseflies, also follow this mode of nutrition.
• Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism. i.e., after the food is ingested. Most of the animals follow this mode of nutrition.
• Parasitic Nutrition: The organism which lives inside or outside another organism (host) and derives nutrition from it is known as parasites and this type of mode of nutrition is called parasitic nutrition. For example Cuscuta, tick etc.

Nutrition in Amoeba

• Amoeba is a unicellular animal which follows the holozoic mode of nutrition.
• In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism.
• Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
  

Steps of Holozoic Nutrition:

• Ingestion: The process of taking in the food is called ingestion.
• Digestion: The process of breaking complex food substances into simple molecules is called digestion. Simple molecules, thus obtained, can be absorbed by the body.
• Absorption: The process of absorption of digested food is called absorption.
• Assimilation: The process of utilization of digested food, for energy and for growth and repair is called assimilation.
• Egestion: The process of removing undigested food from the body is called egestion.

Amoeba is a unicellular animal which follows the holozoic mode of nutrition. The cell membrane of amoeba keeps on protruding into pseudopodia. Amoeba surrounds a food particle with pseudopodia and makes a food vacuole. The food vacuole contains food particle and water. Digestive enzymes are secreted in the food vacuole and digestion takes place. After that, digested food is absorbed from the food vacuole. Finally, the food vacuole moves near the cell membrane and undigested food is expelled out.

Nutrition in Human Beings – Life Processes Class 10 Notes

Human beings are complex animals, which have a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands. The alimentary canal is divided into several parts, like oesophagus, stomach, small intestine, large intestine, rectum and anus. Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal.

Structure of the Human Digestive System:
The human digestive system comprises of the alimentary canal and associated digestive glands.

• Alimentary Canal: It comprises of mouth, oesophagus, stomach, small intestine and large intestine.
• Associated Glands: Main associated glands are
  • Salivary gland
  • Gastric Glands
  • Liver
  • Pancreas

Mouth or Buccal Cavity:

• The mouth has teeth and tongue. Salivary glands are also present in the mouth.
• The tongue has gustatory receptors which perceive the sense of taste.
• The tongue helps in turning over the food so that saliva can be properly mixed in it.
• Teeth help in breaking down the food into smaller particles so that, swallowing of food becomes easier.
• There are four types of teeth in human beings. The incisor teeth are used for cutting the food.
• The canine teeth are used for tearing the food and for cracking hard substances.
• The premolars are used for the coarse grinding of food. The molars are used for fine grinding of food.
  

Salivary glands secrete saliva: Saliva makes the food slippery which makes it easy to swallow the food. Saliva also contains the enzyme salivary amylase or ptyalin. Salivary amylase digests starch and converts it into sucrose, (maltose).

Oesophagus: Taking food from mouth to stomach by Peristaltic movement.

Peristaltic movement: Rhythmic contraction of muscles of the lining of the alimentary canal to push the food forward.

Stomach

• Stomach is a bag-like organ. Highly muscular walls of the stomach help in churning the food.
• The walls of the stomach secrete hydrochloric acid. Hydrochloric acid kills the germs which may be present in food.
• Moreover, it makes the medium inside the stomach as acidic. The acidic medium is necessary for gastric enzymes to work.
• The enzyme pepsin, secreted in the stomach, does partial digestion of protein.
• The mucus, secreted by the walls of the stomach saves the inner lining of the stomach from getting damaged from hydrochloric acid.
  

Small Intestine: It is a highly coiled tube-like structure. The small intestine is longer than the large intestine but its lumen is smaller than that of the large intestine. The small intestine is divided into three parts, like duodenum, jejunum and ileum.

Liver: Liver is the largest organ in the human body. The liver manufactures bile, which gets stored in the gall bladder. From the gall bladder, bile is released as and when required.

Pancreas: Pancreas is situated below the stomach. It secretes pancreatic juice which contains many digestive enzymes.

Bile and pancreatic juice go to the duodenum through a hepatopancreatic duct. Bile breaks down fat into smaller particles. This process is called emulsification of fat. After that, the enzyme lipase digests fat into fatty acids and glycerol. Trypsin and chymotrypsin are enzymes which digest protein into amino acids. Complex carbohydrates are digested into glucose. The major part of digestion takes place in the duodenum.

No digestion takes place in the jejunum: The inner wall in the ileum is projected into numerous finger-like structures, called villi. Villi increase the surface area inside the ileum so that optimum absorption can take place. Moreover, villi also reduce the lumen of the ileum so that food can stay for a longer duration in it, for optimum absorption. Digested food is absorbed by villi.

Large Intestine:

• Large intestine is smaller than the small intestine.
• Undigested food goes into the large intestine.
• Some water and salt are absorbed by the walls of the large intestine. After that, the undigested food goes to the rectum, from where it is expelled out through the anus.
• Large Intestine bbsorb excess of water. The rest of the material is removed from the body via the anus. (Egestion).

Respiration – Life Processes Class 10 Notes

Types of respiration, aerobic and anaerobic respiration, human respiratory system, respiration in plants.

Respiration: The process by which a living being utilises the food to get energy, is called respiration. Respiration is an oxidation reaction in which carbohydrate is oxidized to produce energy. Mitochondria is the site of respiration and the energy released is stored in the form of ATP (adenosine triphosphate). ATP is stored in mitochondria and is released as per need.

Steps of respiration:

• Breaking down of glucose into pyruvate: This step happens in the cytoplasm. Glucose molecule is broken down into pyruvic acid. Glucose molecule is composed of 6 carbon atoms, while pyruvic acid is composed of 3 carbon atoms.
• Fate of Pyruvic Acid: Further breaking down of pyruvic acid takes place in mitochondria and the molecules formed depend on the type of respiration in a particular organism. Respiration is of two types, viz. aerobic respiration and anaerobic respiration.
• Respiration involves
  • Gaseous exchange: Intake of oxygen from the atmosphere and release of CO₂ → Breathing.
  • Breakdown of simple food in order to release energy inside the cell → Cellular respiration

Types of Respiration – Life Processes Class 10 Notes

• Aerobic respiration: This type of respiration happens in the presence of oxygen. Pyruvic acid is converted into carbon dioxide. Energy is released and water molecule is also formed at the end of this process.
• Anaerobic respiration: This type of respiration happens in the absence of oxygen. Pyruvic acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed in case of anaerobic respiration in microbes, like yeast or bacteria. Lactic acid is formed in some microbes as well as in the muscle cells.
  • Glucose (6 carbon molecule) → Pyruvate (3 carbon molecules) + Energy
  • Pyruvate (In yeast, lack of O₂) → Ethyl alcohol + Carbon dioxide + Energy
  • Pyruvate (In muscles, lack of O₂) → Lactic Acid + Energy
  • Pyruvate (In mitochondria; the presence of O₂) → Carbon dioxide + Water + Energy

The equations for the above reactions can be written as follows:

Pain in leg muscles while running:

• When someone runs too fast, he may experience throbbing pain in the leg muscles. This happens because of anaerobic respiration taking place in the muscles.
• During running, the energy demand from the muscle cells increases. This is compensated by anaerobic respiration and lactic acid is formed in the process.
• The deposition of lactic acid causes pain in the leg muscles. The pain subsides after taking rest for some time.

Exchange of gases:

• For aerobic respiration, organisms need a continuous supply of oxygen, and carbon dioxide produced during the process needs to be removed from the body.
• Different organisms use different methods for the intake of oxygen and expulsion of carbon dioxide.
• Diffusion is the method which is utilized by unicellular and some simple organisms for this purpose.
• In plants also, diffusion is utilized for exchange of gases.
• In complex animals, respiratory system does the job of exchange of gases.
• Gills are the respiratory organs for fishes. Fishes take in oxygen which is dissolved in water through gills.
• Since, availability of oxygen is less in the aquatic environment, so the breathing rate of aquatic organisms is faster.
• Insects have a system of spiracles and trachease which is used for taking in oxygen.
• Terrestrial organisms have developed lungs for exchange of gases.
• Availability of oxygen is not a problem in the terrestrial environment so breathing rate is slower as compared to what it is in fishes.

Terrestrial organisms: Use atmospheric oxygen for respiration.
Aquatic organisms: Use dissolve oxygen for respiration.

Human respiratory system – Life Processes Class 10 Notes

The human respiratory system is composed of a pair of lungs. These are attached to a system of tubes which open on the outside through the nostrils.
Following are the main structures in the human respiratory system:

1. Nostrils: There are two nostrils which converge to form a nasal passage. The inner lining of the nostrils is lined by hair and remains wet due to mucus secretion. The mucus and the hair help in filtering the dust particles out from inhaled air. Further, air is warmed up when it enters the nasal passage.
2. Pharynx: It is a tube-like structure which continues after the nasal passage.
3. Larynx: This part comes after the pharynx. This is also called voice box.
4. Trachea: This is composed of rings of cartilage. Cartilaginous rings prevent the collapse of trachea in the absence of air.
5. Bronchi: A pair of bronchi comes out from the trachea, with one bronchus going to each lung.
6. Bronchioles: A bronchus divides into branches and sub-branches inside the lung.
7. Alveoli: These are air sacs at the end of bronchioles. The alveolus is composed of a very thin membrane and is the place where blood capillaries open. This is alveolus, where the oxygen mixes with the blood and carbon dioxide exits from the blood. The exchange of gases, in alveoli, takes place due to the pressure differential.

Passage of air through the respiratory system in human beings:

Breathing Mechanism

• The breathing mechanism of lungs is controlled by the diaphragm and the intercostalis muscles.
• The diaphragm is a membrane which separates the thoracic chamber from the abdominal cavity.
• When the diaphragm moves down, the lungs expand and the air is inhaled.
• When the diaphragm moves up, the lungs contract and air are exhaled.

Transportation – Life Processes Class 10 Notes

Circulatory system of human being, transportation in plants. Human beings like other multicellular organism need a regular supply of foods, oxygen etc. This function is performed by a circulatory system or transport system.

Transportation in Human Beings: The circulatory system is responsible for transport of various substances in human beings. It is composed of the heart, arteries, veins and blood capillaries. Blood plays the role of the carrier of substances.

1. Heart: Heart is a muscular organ, which is composed of cardiac muscles.

• It is so small that, it can fit inside an adult’s wrist. The heart is a pumping organ which pumps the blood.
• The human heart is composed of four chambers, viz. right atrium, right ventricle, left ventricle and left atrium.
• Systole: Contraction of cardiac muscles is called systole.
• Diastole: Relaxation of cardiac muscles is called diastole.

2. Arteries:

• These are thick-walled blood vessels which carry oxygenated blood from the heart to different organs.
• Pulmonary arteries are exceptions because they carry deoxygenated blood from the heart to lungs, where oxygenation of blood takes place.

3. Veins:

• These are thin-walled blood vessels which carry deoxygenated blood from different organs to the heart, pulmonary veins are exceptions because they carry oxygenated blood from lungs to the heart.
• Valves are present in veins to prevent back flow of blood.

4. Capillaries: These are the blood vessels which have single-celled walls.

Blood: Blood is a connective tissue which plays the role of the carrier for various substances in the body. Blood is composed of 1. Plasma 2. Blood cells 3. Platelets.

• Blood plasma: Blood plasma is a pale coloured liquid which is mostly composed of water. Blood plasma forms the matrix of blood.
• Bloods cells: There are two types of blood cells, viz. Red Blood Cells (RBCs) and White Blood Cells (WBCs).
  (a) Red Blood Corpuscles (RBCs): These are of red colour because of the presence of haemoglobin which is a pigment. Haemoglobin readily combines with oxygen and carbon dioxide. The transport of oxygen happens through haemoglobin. Some part of carbon dioxide is also transported through haemoglobin.
  (b) White Blood Corpuscles (WBCs): These are of pale white colour. They play important role in the immunity.
• Platelets: Platelets are responsible for blood coagulation. Blood coagulation is a defense mechanism which prevents excess loss of blood, in case of an injury.

Lymph:

• Lymph is similar to blood but RBCs are absent in lymph.
• Lymph is formed from the fluid which leaks from blood capillaries and goes to the intercellular space in the tissues. This fluid is collected through lymph vessels and finally return to the blood capillaries.
• Lymph also plays an important role in the immune system.
• Lymph a yellowish fluids escape from the blood capillaries into the intercellular spaces contain less proteins than blood.
• Lymph flows from the tissues to the heart assisting in transportation and destroying germs.

Double circulation: In the human heart, blood passes through the heart twice in one cardiac cycle. This type of circulation is called double circulation. One complete heartbeat in which all the chambers of the heart contract and relax once is called cardiac cycle. The heart beats about 72 times per minute in a normal adult. In one cardiac cycle, the heart pumps out 70 mL blood and thus, about 4900 mL blood in a minute. Double circulation ensures complete segregation of oxygenated and deoxygenated blood which is necessary for optimum energy production in warm-blooded animals.

Transportation in plants: Plants have specialized vascular tissues for transportation of substances. There are two types of vascular tissues in plants.

• Xylem: Xylem is responsible for transportation of water and minerals. It is composed of trachids, xylem vessels, xylem parenchyma and xylem fibre. Tracheids and xylem vessels are the conducting elements. The xylem makes a continuous tube in plants which runs from roots to stem and right up to the veins of leaves.
• Carry water and minerals from the leaves to the other part of the plant.
• Phloem: Phloem is responsible for transportation of food. Phloem is composed of sieve tubes, companion cells, phloem parenchyma and bast fibers. Sieve tubes are the conducting elements in phloem.
• Carries product of photosynthesis from roots to other part of the plant.

Transportation in plants

Ascent of sap: The upward movement of water and minerals from roots to different plant parts is called ascent of sap. Many factors are at play in ascent of sap and it takes place in many steps. They are explained as follows :

• Root pressure: The walls of cells of root hairs are very thin. Water from soil enters the root hairs because of osmosis. Root pressure is responsible for movement of water up to the base of the stem.
• Capillary action: A very fine tube is called capillaiy, water, or any liquid, rises in the capillary because of physical forces and this phenomenon is called capillary action. Water, in stem, rises up to some height because of capillaiy action.
• Adhesion-cohesion of water molecules: Water molecules make a continuous column in the xylem because of forces of adhesion and cohesion among the molecules.
• Transpiration pull: Loss of water vapour through stomata and lenticels, in plants, is called transpiration. Transpiration through stomata creates vacuum which creates a suction, called transpiration pull. The transpiration pull sucks the water column from the xylem tubes and thus, water is able to rise to great heights in even the tallest plants.
• Transport of food: Transport of food in plants happens because of utilization of energy. Thus, unlike the transport through xylem, it is a form of active transport. Moreover, the flow of substances through phloem takes place in both directions, i.e., it is a two-way traffic in phloem.
  Transpiration is the process of loss of water as vapour from aerial parts of the plant.

Functions

• Absorption and upward movement of water and minerals by creating pull.
• Helps in temperature regulation in plant.

Transport of food from leaves (food factory) to different parts of the plant is called Translocation.

Excretion – Life Processes Class 10 Notes

Human excretory system, excretion in plants.

Excretion in human beings:

• Removal of harmful waste from the body is called excretion.
• Many wastes are produced during various metabolic activities.
• These need to be removed in time because their accumulation in the body can be harmful and even lethal for an organism.

Human Excretory System:

• The human excretory system is composed of a pair of kidneys.
• A tube, called ureter, comes out of each kidney and goes to the urinary bladder.
• Urine is collected in the urinary bladder, from where it is expelled out through urethra as and when required.

Excretory system of human beings includes :

• A pair of kidneys.
• A urinary bladder.
• A pair of the ureter.
• A urethra.

Kidney:

• Kidney is a bean-shaped organ which lies near the vertebral column in the abdominal cavity.
• The kidney is composed of many filtering units, called nephrons.
• Nephron is called the functional unit of kidney.

Nephron

• It is composed of a tangled mess of tubes and a filtering part, called glomerulus.
• The glomerulus is a network of blood capillaries to which renal artery is attached.
• The artery which takes blood to the glomerulus is called afferent arteriole and the one receiving blood from the glomerulus is called efferent arteriole.
• The glomerulus is enclosed in a capsule like portion, called bowman’s capsule. The bowman’s capsule extends into a fine tube which is highly coiled.
• Tubes from various nephrons converge into collecting duct, which finally goes to the ureter.

Urine formation in the kidney: The urine formation involves three steps:

• Glomerular filtration: Nitrogenous wastes, glucose, water, amino acid filter from the blood into bowman’s capsule of the nephron.
• Tubular reabsorption: Now, useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.
• Secretion: Extra water, salts are secreted into the tubule which opens up into the collecting duct and then into the ureter.

Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.
The purpose of making urine is to filter out waste product from the blood i.e., urea which is produced in the liver.

Haemodialysis: The process of purifying blood by an artificial kidney. It is meant for kidney failure patient.

Excretion in Plants

• Other wastes may be stored in leaves, bark etc. which fall off from the plant.
• Plants excrete some waste into the soil around them.
• Gums, resin → In old xylem
• Some metabolic wastes in the form of crystals of calcium oxalates in the leaves of colocasia and stem of Zamikand.

Nutrition in Plants and Animals

Nutrition: Process of obtaining and utilizing of food is known as nutrition.

Mode of nutrition:

• Autotrophic Nutrition (All green plants)
• Heterotrophic Nutrition (Animals, Man, Non-green plants)
  • Saprotrophic nutrition
  • Parasitic nutrition
  • Holozoic nutrition

Autotrophs: It is a mode of nutrition in which organisms can make their own food from simple raw material. Example, all green plants.

Heterotrophs: It is a mode of nutrition in which organisms cannot prepare their food on their own and depend on others. Example, animals.

Saprotrophic Nutrition: It is the process by which the organism feeds on dead and decaying matter. Example, Rhizopus, Mucor, yeast.

Photosynthesis: It is the process by which green plants prepare their own food.

Raw materials for photosynthesis:

• Water and Minerals: These are absorbed by the roots from the soil.
• Carbon dioxide: Carbon dioxide enters the leaves through tiny pores called stomata.
• Sunlight: Energy from the sun is called solar energy.
• Chlorophyll: Chlorophyll pigment helps leaves to capture solar energy.

Products of Photosynthesis: Carbohydrate-glucose- It is converted to starch.

Symbiotic relationship: Two organisms live in a close association and develop a relationship that is beneficial to both this is called a symbiotic relationship.
Example, Lichen is a living partnership between a fungus an alga. Fungus absorbs water and provides shelter and alga prepare food by photosynthesis

Insectivores: Plants feed on insects for their nitrogen requirements.

Holozoic nutrition: It means feeding on solid food. Organism takes complex organic food into the body. Example, man, amoeba, dog, etc.

• Herbivores: Animals which feed on plants only. Example, deer, cow.
• Carnivores: Animals which feed on flesh or meat. Example, tiger.
• Omnivores: Animals which feed on both plant and flesh. Example, man, dog.

Steps of Holozoic nutrition:

• Ingestion: Taking food into the mouth.
• Digestion: Break down of large insoluble food into small water-soluble molecules by enzymes.
• Absorption: Digested food absorbed through the intestinal wall into the blood.
• Assimilation: Absorbed food is taken by body cells for releasing energy, growth and repair.
• Egestion: Eliminating undigested food from the body.

Digestive organs of human beings: Mouth, oesophagus, stomach, small intestine and large intestine with glands like salivary gland, liver, pancreas.

Teeth: An organ which breaks down the complex food and helps in chewing the food.

• Milk teeth: The first set of 20 small teeth when the baby is 6-7 months old.
• Permanent teeth: The second set of 32 larger teeth, when a child is 6-7 years old and comes by replacing milk teeth.

Enamel: A white, strong, shining, protective material covering on teeth.

Tongue: A muscular organ attached to the floor of the buccal cavity which helps in tasting and mixing the food with saliva for digestion.

Transportation in Plants and Animals

• Vascular tissue: A plant tissue which helps in transportation.
• Xylem tissue: It helps in transporting water and minerals in plants.
• Phloem: It helps in transporting food in plants.
• Translocation: The process of transporting food from leaves to other parts of plants.
• Transpiration: A loss of water from stomata in leaves.
• Blood: A red colour fluid which circulates in the body of animals.
• Plasma: Fluid part of the blood which consists of nutrients, hormones, and waste products.
• Blood vessel: Tube-like structure present in the body for carrying blood inside the body.
• Artery: It carries oxygenated blood from the heart to body parts.
• Vein: It carries deoxygenated blood from body parts to the heart.
• Capillary: A thin-walled narrow tube which connects artery and vein.
• Heart: A muscular organ present in the thoracic cavity and helps in pumping blood in the body.
• Double circulation: A circulatory system in which blood travels twice through the heart in one complete cycle.
• Heartbeat: One complete contraction and relaxation of the heart (72 times in a minute).
• Stethoscope: Instrument which measures heartbeat.
• Systolic pressure: Maximum pressure at which blood flows during contraction of the heart. (120 mm Hg)
• Diastolic pressure: Minimum pressure at which blood flows during relaxation of the heart. (80 mm Hg)
• Sphygmomanometer: Instrument which measures blood pressure.
• Lymph: A light yellow liquid flowing from body tissue to the blood circulatory system and provides immunity.

Excretion in Plants and Animals

• Excretion: It is the process of removing waste products from the body.
• Excretory products of plants: CO₂, O₂, water vapour, peel of bark, fruits, leaves, gum, raisin, etc.
• Excretory products of humans: Carbon dioxide, urea, etc.
• Kidney: Organ which removes the toxic substance urea from blood and filters it.
• Urine: A yellowish liquid which contains water and urea.
• Dialysis: The procedure used for cleaning the blood of a person in case of kidney failure.
• Nephron: Functional unit of excretory system present in the kidney for filtering blood.
• Renal Artery: Blood vessels which bring blood from heart to kidney.
• Renal Vein: Blood vessel which brings blood from kidney to heart.

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