NCERT Solutions for Class 10 Science Chapter 6 Life Processes

Q1 ) Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Answer :

Diffusion is a passive mode of transport of substances like ions, atoms etc. from higher concentration to lower concentration region.This process takes place slowly and can only transfer substances up to a very small distance.The size of the multicellular organisms is very large compared to unicellular organisms and also the body cells are not in direct contact with the surrounding environment so, 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.

Q2 ) What criteria do we use to decide whether something is alive?

Answer :

Breathing, respiration, transportation and excretion are the main criteria to decide whether something is alive. Also few factors like growth and movement in living beings also are considered important.

Q3 ) What are outside raw materials used by an organism ?

Answer :

The raw materials required by an organism depends upon the complexity of the organism and its environment. Minerals ,water and gases like carbon dioxide ,Oxygen etc. are outside raw materials used by an organism. For e.g. Heterotrophs use food and autotrophs use carbon dioxide, minerals and water. Also organisms use oxygen (for respiration) as raw materials.

Q4 ) What processes would you consider essential for maintaining life?

Answer :

Essential processes for maintaining life are as follows:

1. Nutrition
2. Respiration
3. Transportation(oxygen and nutrition)
4. Reproduction
5. Excretion

Q5 ) What are the differences between autotrophic nutrition and heterotrophic nutrition?

Answer :

Autotrophic nutrition:
i. organisms makes or synthesizes their own food In this mode of nutrition .

ii.organisms depends on raw materials like carbon dioxide and water and synthesise their food in presence of sunlight.

iii.Green plants and algae undergo this type of nutrition process.

Heterotrophic nutrition:
i.organisms do not make or synthesizes their own food In this mode of nutrition

ii. as organisms don't prepare their own food so they depend on other organisms for their food.

iii.all the animals , bacteria and fungi undergo this mode of nutrition

Q6 ) Where do plants get each of the raw materials required for photosynthesis?

Answer :

Plants use water, minerals and carbon dioxide as raw materials in the presence of sunlight and chlorophyll to perform photosynthesis. Water and minerals are obtained from the soil and carbon dioxide from the atmosphere. Chlorophyll is already present in green plants and sunlight reaching the plant directly is absorbed by the plants.

Q7 ) What is the role of the acid in our stomach?

Answer :

The hydrochloric acid is found in our stomach This provides an acidic medium for digestion and absorption of certain nutrients . Also It helps in killing harmful germs which may enter the stomach with intake of food.

Q8 ) What is the function of digestive enzymes?

Answer :

Digestive enzymes help in breaking large food particles which are complex in nature into smaller and simpler particles which are then easily absorbed by blood and transported to body cells. For example- amylase and pepsin.

Q9 ) 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. In the small intestine the innermost layer is in the shape of finger-like projections known as villi.The villis are richly supplied with blood vessels which take the absorbed food to each and every cell of the body via the bloodstream..

Q10 ) What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration ?

Answer :

Terrestrial organisms take oxygen from the oxygen-rich atmosphere where the oxygen content is quite high whereas aquatic organisms use oxygen dissolved in water which is very low as compared to the amount in the atmosphere. Since air dissolved in water has quite low concentration of oxygen, the rate of breathing is much faster in aquatic organisms to obtain as much oxygen as possible than terrestrial organisms and thus, terrestrial organisms spend less energy than aquatic organisms for respiration.

Q11 ) What are the different ways in which glucose is oxidised to provide energy in various organisms?

Answer :

First step takes place is breakdown of glucose in the cytoplasm giving rise to pyruvate which is a three carbon molecule.This pyruvate is further broken down in three different ways:
(a) Aerobic respiration: This involves breakdown of pyruvate in the presence of oxygen and Pyruvate gets converted into carbon dioxide and water.Release of energy in this is much more than in anaerobic respiration..Example: In mitochondria.

(b) Anaerobic respiration: This involves breakdown of pyruvate taking place in the absence of oxygen hence Pyruvate is broken down into ethanol and carbon dioxide.Example: Yeast during fermentation.

(c)Lack of oxygen:This state may be reached due to vigorous activities and leads to lack of oxygen which results in conversion of pyruvate into lactic acid(3 carbon molecule compound).Accumulation of lactic acid leads to muscle cramps.Example: In human muscle cells.

Q12 ) How is oxygen and carbon dioxide transported in human beings?

Answer :

Haemoglobin present in blood aids in the transportation of these gases.The blood serves as a transport system for both carbon dioxide and oxygen. Oxygen is carried to the cells whereas carbon dioxide is carried away from the cells.
(i) Transport of oxygen :

The oxygen molecule can bind to the haemoglobin molecules easily.One molecule of haemoglobin binds four molecules 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 :

Similarly, 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 in the form of carboxyhemoglobin. Here it diffuses from blood to air in the lungs.

Q13 ) How are the lungs designed in human beings to maximize the area for exchange of gases?

Answer :

The structure of the lung is as follow:
In each lung the air passage is divided into smaller and smaller tubes, named as bronchi which divide into bronchioles. These bronchioles further terminate in balloon-like structures, called alveoli . These alveoli provide maximum surface for exchange of gases and occupy less volume. They are further connected with veins and arteries to facilitate exchange of gases.

Q14 ) What are the components of the transport system in human beings? What are the functions of these components?

Answer :

The transport system in human beings mainly involves heart, blood and blood vessels.Functions of these are:
(i) Function of heart :The heart pumps oxygenated blood to all cells of the body.Also, during cellular respiration,the blood gets deoxygenated due to the release of \( CO_2 \) from cells so, the heart receives deoxygenated blood from the body parts and sends the deoxygenated blood to lungs for purification/oxygenation.

(ii) Function of blood : Blood helps in the transport of oxygen to the cells, exhaling carbon dioxide by picking it from cells, transport of nutrients and nitrogenous waste like urea. It also helps in the protection of the body from diseases and regulation the body temperature.

(iii) Function of blood vessels : The blood pushed by the heart flows through the blood vessels (arteries, veins and capillaries) and are responsible for carrying blood through the tissues and organs.

Q15 ) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Answer :

Birds and mammals are warm blooded animals.They constantly need large amount of oxygen to get energy for maintaining their body temperature constant and for good supply of oxygen, it is required to separate the oxygenated and deoxygenated blood.This system is useful in animals that have high energy requirements.

Q16 ) What are the components of the transport system in highly organized plants?

Answer :

In highly organised plants there are two conducting tissues named as xylem and phloem.
Xylem tissues: Xylem consists of vessels, tracheids and other xylem tissues and is responsible for the transport of water and minerals from the root to the other parts of the plant.

Phloem tissue: The Phloem tissue is made of sieve tubes, companion cells and phloem fibres ,and is responsible for the transportation of food from the leaves to all parts of the body.

Q17 ) How are water and minerals transported in plants?

Answer :

Transportation of water and minerals in plants takes place as follows:
The roots of a plant have hair called root hair which absorbs water and dissolved minerals by the process of diffusion.These further passes 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 and the xylem vessels of its stem are connected.Therefore, the water containing dissolved minerals enters the stem xylem vessels.Further the water and dissolved minerals are carried by the xylem vessels in the stem reaching 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.This continuous uptake creates a root pressure which allows water to be pushed upwards from the root to the plant body. In tall plants, like trees, transpiration is responsible for the pull of water.Transpiration includes the evaporation of water molecules from the cells of a leaf which creates a suction and pulls water from the xylem cells of roots.

Q18 ) How is food transported in plants?

Answer :

The movement of food in phloem takes place by utilizing energy and this energy is obtained from ATP.Food is stored in plants in the form of sucrose but sucrose is a heavy molecule and can’t be transported so it is broken down into simple molecules called glucose. The transportation of food is achieved in plants via the phloem with the help of ATP by decreasing the water concentration in the required part of the plant. As a result, water enters the cell by the process of diffusion.As the cellular content increases, the pressure increases on the cell wall . Food is pushed into other cells where the pressure is low because of the increased pressure. In this way, the Phloem helps to transport food from the area of high concentration to low concentration.This allows the phloem to transport food according to the needs of the plant.

Q19 ) Describe the structure and functioning of nephrons.

Answer :

Structure of nephron :
Each nephron is composed of two parts. First one is called Bowman’s capsule.The Bowman’s capsule is a cup-shaped bag at its upper end which contains a bundle of blood capillaries which is called glomerulus. Glomerulus has two parts in which one part is attached to Renal Artery responsible for bringing in the dirty blood(Containing Urea) while the other end comes out of Bowman's Capsule containing the clean blood.

The other part of the nephron is coiled where the substances which are required by the body like sugar (glucose), amino acid, ions and excess water are reabsorbed. The substance remaining in the nephron is mainly urine ,which contains dissolved nitrogenous waste like urea and uric acid, excess salts and water.

Functions of nephron :

• Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus.
• Re-absorption : As the filtrate flows along the tubule, useful substances are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule.These substances include glucose, amino acids, salts and water.
• Urine : Urine is remained after reabsorption which 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 the urinary bladder.

Q20 ) What are the methods used by plants to get rid of excretory products?

Answer :

(i) The plants get rid of Gaseous products or moisture through stomata in leaves and lenticels in stems.
(ii) Shedding off leaves, peeling off bark and felling off fruits is the way in which the plants get rid of stored solid and liquid waste. Plants also excrete some waste substances into the soil around them.

(iii) The plants get rid of other wastes by secreting them in the form of gums and resins stored on barks are eliminated by peeling of the bark.

Q21 ) How is the amount of urine produced regulated?

Answer :

The amount of urine is regulated by the kidney. It depends on the following factors:
(i) Quantity of water : When water is excess in the body tissues,the quantity of dilute urine excreted out is high. When water is less in quantity in the body tissues, a small quantity of concentrate urine is excreted.

(ii) Quantity of dissolved wastes : When there is more quantity of dissolved wastes in the body, especially nitrogenous wastes, like urea and uric acid and salts , more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.

(iii) Urine produced also depends on the following factors like hormones(Anti-diuretic hormone (ADH)) and habitat of an entity.