Class - 10 Science (Biology) Chapter - 06 Life Processes Notes, NCERT Solutions & Frequently Asked Questions

                                                                          Class - 10

Science (Biology) 

Chapter - 06

                                           Life Processes

Notes, NCERT Solutions & Frequently Asked Questions 

-- Notes --

 

All the processes such as respiration, nutrition, circulation, excretion etc. that are necessary for the survival of the living organisms are known as life processes.

 

Modes of Nutrition

The two most common types of nutrition are autotrophic nutrition and heterotrophic nutrition.

 

Autotrophic Nutrition

It is a type of nutrition in which inorganic materials such as carbon dioxide, is used up to synthesise organic food by a process known as photosynthesis. For example, green plants use an autotrophic mode of nutrition. Organisms that use the autotrophic mode of nutrition are known as autotrophs.

 

Now the question arises how does autotrophic nutrition occur in plants using photosynthesis?

For photosynthesis to occur, carbon dioxide, water, sunlight and chlorophyll are the required raw materials. Sunlight provides energy, chlorophyll is used to absorb the sunlight, carbon dioxide is reduced to carbohydrates and water is oxidised to release the oxygen. Water is taken up from the soil through the roots.

The site where photosynthesis occurs is known as chloroplast. They contain a green colour pigment known as chlorophyll that traps sunlight for photosynthesis.

The steps of photosynthesis are as follows-

• Absorption of light by chlorophyll.
• Conversion of light energy into chemical energy.
• Splitting of water into hydrogen and oxygen.
• Finally, reduction of carbon dioxide into carbohydrates.

Leaves contain small openings known as stomata which helps in the exchange of gases. The stomata/stoma is surrounded by a guard cell which guards the opening and closing of stomata. Guard cells also contain chloroplast.

Fig.1. Structure of Stomata

 

The overall equation of photosynthesis is:

Fig.2. Overall Equation of Photosynthesis

 

Heterotrophic Nutrition

In this mode of nutrition, an organism is unable to synthesise its food. It is of the following types-

1. Holozoic nutrition is a type of nutrition where an organism takes in whole food and breaks it inside the body. For example, Amoeba.
2. Saprophytic nutrition is nutrition in which organisms feed on dead and decaying matter. For example, fungi.
3. Parasitic nutrition is nutrition in which an organism feeds on a living host. For example, Cuscuta. 

 

Nutrition in Human Beings

Humans consist of the alimentary canal which starts from the mouth and ends at the anus. The parts of the alimentary canal are as follows-

1. Mouth
2. Pharynx
3. Oesophagus/food pipe
4. Stomach
5. Small intestine
6. Large intestine
7. Rectum
8. Anus

Fig.3. Human Digestive System

Mouth is the first portion of the alimentary canal. The mouth consists of a muscular tongue and teeth. The cavity inside the mouth is known as the oral cavity.

Fig.4. Human Mouth Parts

 

Mechanism of Digestion of Food

• Food digestion process begins in the mouth. Food is complex in nature.
• To break down food and absorb it, we need biological catalysts known as enzymes.
• The mouth contains salivary glands that secrete saliva. Saliva contains an important enzyme known as the salivary enzyme that breaks down starch into simple sugars.
• The food then passes via the oesophagus into the stomach. The movement of the food inside the oesophagus occurs via rhythmic contraction of muscles, this is known as peristalsis.
•  The stomach contains gastric glands that secrete mucus, hydrochloric acid and pepsin. Pepsin is a protein-digesting enzyme.
• After the stomach, food then enters the small intestine. The small intestine is larger in herbivores due to cellulose digestion compared to carnivores.
• Complete digestion of carbohydrates, proteins and fats occurs in the small intestine.
• The small intestine receives secretions from the pancreas and bile from the liver. Bile helps in the emulsification of fats whereas the pancreas secretes enzymes such as trypsin for protein digestion. The intestinal wall also contains glands that secrete intestinal juice.
• The small intestine has villi that increase the surface area for the absorption of food.
• The unabsorbed food is then transferred to the large intestine where water is absorbed.
• Undigested food is then expelled out from the anus.

 

Respiration

• It is a metabolic process that involves the breakdown of food to release energy is known as respiration.

Fig.5. Breakdown of glucose by different pathways

• The breakdown of pyruvate into ethanol and carbon dioxide in absence of oxygen is known as fermentation. As this process occurs in absence of oxygen, it is known as anaerobic respiration. When the pyruvate is broken down into carbon dioxide and water in presence of oxygen it is known as aerobic respiration.
• The energy released during the process is used up to synthesise the ATP (adenosine triphosphate).
• Compared to animals, plants used stomata to exchange carbon dioxide and oxygen. This exchange occurs through diffusion.

 

Respiration in Human Beings

Human respiratory system starts with the nostrils, nasal cavity, pharynx, trachea, bronchi, bronchioles and then lungs. In the lungs, alveoli are present, where an exchange between oxygen and carbon dioxide takes place.

Fig.6. Passage of air in Humans

Humans have a respiratory pigment known as haemoglobin to carry the oxygen to different parts of the body and to remove carbon dioxide from the body. Compared to oxygen, carbon dioxide is more soluble in water, so it is usually transported in dissolved form.

 

Transportation in Human Beings

Blood is a fluid connective tissue that transports food, oxygen, carbon dioxide, nitrogenous waste etc. Blood contains plasma and blood cells. Red blood cells carry oxygen throughout the body. The heart is the pumping organ in the body.

• The human heart is 4 chambered, with two atriums and two ventricles.
• The left atrium receives the oxygen-rich blood from the lungs. While receiving the blood it relaxes.
• The left ventricle pumps oxygen-rich blood throughout the body.
• Deoxygenated blood comes from the body to the upper right atrium. It contracts to pump the blood to the right ventricle.
• The right ventricle pumps the blood to the lungs for oxygenation.

Fig.7. Structure of Human Heart

Note: Fishes have a two-chambered heart, amphibians and reptiles have a three-chambered heart except crocodiles which possess a 4 chambered heart. Birds and mammals also have 4 chambered hearts.

 

Double Circulation

The right side and left side of the heart are separated to prevent the mixing of oxygenated and deoxygenated blood. In vertebrates, blood goes through the heart twice during each cycle. This is defined as double circulation.  (NTSE)

Fig.8. Double Circulation

Note: The force that the blood exerts against the wall of the vessel is known as blood pressure. The pressure of blood inside the artery during ventricular contraction is known as systolic pressure whereas the pressure in the artery during ventricular relaxation is known as diastolic pressure. The normal blood pressure is 120/80 mm of Hg.

Artery	Capillary	Vein
They carry blood away from the heart	One cell thick smallest vessels	They carry blood towards the heart
They carry oxygenated blood except for the pulmonary artery.	Help in the exchange of the material between the blood and surrounding cells.	They carry deoxygenated blood except for the pulmonary vein.
They have thick walls and do not have valves.	They do not have valves	They have thin walls and also possess valves.

 

• Platelets are blood cells that help in blood clotting.
• Lymph is also known as interstitial fluid is a fluid that leaks out from the pores of the capillaries.

 

Transport in Plants

• Plants have the xylem tissue for the transportation of water. Xylem transports water from the roots to different parts of the plants. Xylem tissue consists of vessels and tracheids.
• Loss of water in the form of water vapour from the aerial parts of the plants is known as transpiration. The transpiration creates a suction that pulls the water up to the higher plants.
•  Similarly, the transport of food in plants occurs via the phloem. It transports food from the leaves to different parts of the plants.

Fig.9. Transport in Plants

 

Excretion

• The process involved in the removal of nitrogenous waste from the body is known as excretion.
• The excretory system of humans consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra.
• The basic filtration unit of the kidneys is known as nephrons.
• The nephron is the structural and functional unit of the kidneys.
• They consist of a bowman's capsule and a renal tubule.
• For the formation of urine, some substances such as glucose and amino acids are selectively reabsorbed.
• The amount of water reabsorbed depends on how much water is there in the body.
• The urinary bladder is a muscular structure and it is under nervous control

                                                Fig.10. Human Excretory System

Note: Plants excrete their waste through transpiration. Plants also produce other excretory waste in the form of gums, resins etc.

---NCERT Solution---

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. Heterotrophs 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
(i) 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 (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) 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 ? 
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.

-- Textbook 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.