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NCERT Solutions for class 10 Science chapter 6 – Life Processes

Back Exercise

Question 1.
The kidneys in human beings are a part of the system for
(a) Nutrition
(b) Respiration
(c) Excretion
(d) Transportation.
Answer:
(c) Excretion

Question 2.
The xylem in plants is responsible for
(a) Transport of water
(b) Transport of food
(c) Transport of amino acids
(d) Transport of oxygen.
Answer:
(a) Transport of water

Question 3.
The autotrophic mode of nutrition requires,
(a) Carbon dioxide and water
(b) Chlorophyll
(c) Sun light
(d) All of the above.
Answer:
(d) All of the above

Question 4.
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) Cytoplasm
(b) Mitochondria
(c) Chloroplast
(d) Nucleus.
Answer:
(b) Mitochondria

Question 5.
How are fats digested in our bodies Where does this process take place ? (CCE 2011)
Answer:
Fats are present in the form of large globules in the small intestine. The small intestine receives the secretions from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzyme lipase can easily act on them. This is referred to as emulsification of fats. This process takes place in the small intestine.

Question 6.
What is the role of saliva in the digestion of food ? (CCE 2011)
Answer:
Saliva is the secretion of salivary glands that is poured in the buccal cavity for :

1. Moistening and softening of food for easy swallowing
2. It contains a digestive enzyme called salivary amylase, which breaks down starch into simpler sugars like maltose.

Question 7.
What are the necessary conditions for autotrophic nutrition and what are its by-products ?
Answer:
Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and O₂ are the by-products of photosynthesis.

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

Aerobic respiration

• The process takes place in the presence of free oxygen
• The products of aerobic respiration are CO₂, water and energy.
• The first step of aerobic respiration (glycolysis) takes place in cytoplasm while the next step takes place in mitochondria.
• The process of aerobic respiration takes place in all higher organisms.
• In this process complete oxidation of glucose takes place.

Anaerobic respiration

• The process takes place in the absence of the free oxygen.
• The products of anaerobic respiration are ethyl alcohol, CO₂ and a little energy.
• Even in anaerobic respiration, the first step takes place in cytoplasm while the next step takes place in mitochondria.
• In this process the glucose molecules is incompletely broken down.
• The process of anaerobic respiration takes place in lower organism like yeast, some species of bacteria and parasites like tapeworm.

Anaerobic Organisms: Yeast (can also perform aerobic respiration), Lactobacillus (bacterium), Ascaris (Roundworm), Taenia (Tapeworm).

Question 9.
How are alveoli designed to maximise the exchange of gases ?
Answer:
Mammals have a double circulatory system. This means that during a single cycle, the blood goes twice in the heart. There are two loops in which blood is circulated. One loop is oxygenated and the other is de-oxygenated. This double circulatory system is important because it ensures provision of oxygenated blood to the muscle and not a mixture of oxygenated and de-oxygenated blood. Hence, this system ensures efficient supply of oxygenated blood to the muscles.

Question 10.
What would be the consequence of deficiency of haemoglobin in our body ?
Answer:
Deficiency of haemoglobin is called anaemia. In anaemia the blood is unable to carry the amount of oxygen required by the body (hypoxia). Lesser energy will be available to the body. The person will feel weak, pale, lethargic and unable to perform vigorous exercise or physical work.

Question 11.
Describe double circulation in human beings. Why is it necessary ?
Answer:
Double circulation is the passage of same blood twice through heart, first from right side to lungs and back to left side for passage to rest of the body to be returned to right side. It consists of two components, pulmonary circulation (from heart to lungs and back) and systemic circulation (from heart to different parts of body and back). In pulmonary circulation deoxygenated blood is converted into oxygenated  blood. In systemic circulation oxygenated blood is supplied to all parts of the body. It gets changed into deoxygenated form.
Mammals have a double circulatory system. This means that during a single cycle, the blood goes twice in the heart. There are two loops in which blood is circulated. One loop is oxygenated and the other is de-oxygenated. This double circulatory system is important because it ensures provision of oxygenated blood to the muscle and not a mixture of oxygenated and de-oxygenated blood. Hence, this system ensures efficient supply of oxygenated blood to the muscles.

Question 12.
What are the differences between the transport of materials in xylem and phloem ? (CCE 2014)
Answer:
Differences in Transport of Materials in Xylem and Phloem

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

In-Text Questions

Question 1.
Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like us ?
Answer:
Every living cell requires oxygen for performing cellular respiration. In unicellular organisms (e.g., Amoeba), the single cell is in direct contact with environment. Oxygen passes into it through diffusion. In simple multicellular organisms (e.g., Hydra), every cell may also get oxygen through diffusion from environment. But this is not possible in complex multicellular organisms like humans. The cells are not in contact with external environment. Therefore, quick diffusion cannot occur. Cell to cell diffusion is a very slow process. Passage of oxygen from lungs to toes through cell to cell diffusion will take about three years. Therefore, diffusion cannot meet the oxygen requirement of multicellular organisms like humans.

Question 2.
What criteria do we use to decide whether something is alive ?
Answer:
Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of molecular movement inside the organisms used to decide whether something is alive or not.

Question 3.
What are outside raw materials used by an organism ?
Answer:
An organism uses outside raw materials mostly in the form of food (Since life on earth depends on carbon based molecules, most of these food sources are also carbon-based) and oxygen. The raw materials required by an organism can be quite varied depending on the complexity of the organism and its environment.

Question 4.
What processes would you consider essential for maintaining life ?
Answer:
Life processes of nutrition, metabolism, respiration, exchange of materials, transportation, excretion.

Question 5.
What are the differences between autotrophic nutrition and heterotrophic nutrition ?
Answer:

Question 6.
Where does the plant get each of the raw materials for photosynthesis ?
Answer:

Plants required the following raw material for photosynthesis

1. CO₂ is obtained from atmosphere through stomata
2. Water is absorbed by plant roots from the soil.
3. Sunlight is an essential raw material for photosynthesis
4. Nutrients are obtained by soil by plant roots

Question 7.
What is the role of acid in our stomach ? (CCE 2012, 2013)
Answer:
HCl present in the stomach dissolves food particles and creates an acidic medium. In acidic environment protein digesting enzymes pepsinogen is converted into pepsin. HCl in the stomach also acts as protective barrier against many disease causing pathogens.

Question 8.
What is the junction of digestive enzymes ? (CCE 2011)
Answer:
Digestive enzymes breaks the complex food molecules into simpler ones. This will make the food absorption process easy and effective.

Question 9.
How is small intestine designed to absorb digested food ?
Answer:
Small intestine has small projections called as micro villi which increases the surface volume which make absorption more effective. Within the villi there are numerous blood vessels that absorb digested food and carry it to blood stream. Blood transports food to each part of our body.

Question 10.
What advantage does a terrestrial organism possess over aquatic organism with regard to obtaining oxygen for respiration ?
Answer:
Terrestrial organisms breathe by using atmospheric oxygen whereas aquatic organism take oxygen dissolved in water. Oxygen level is high in atmosphere when compared to oxygen in water. Hence terrestrial organism need not breathe fast to obtain organism whereas aquatic organisms need to breathe faster to get required oxygen.

Question 11.
What are the different ways in which glucose is oxidised to provide energy in various organisms ?
Answer:

At first glucose (6 carbon molecules) is broken in the cytoplasm of cells of all organisms. This process yields a 3 carbon molecule compound called pyruvate.
Further break down of pyruvate takes place in different manners in different organisms.
→ Anaerobic Respiration: This process takes place in absence of oxygen, e.g. in yeast during fermentation. In this case, pyruvate is converted into ethanol and carbon dioxide.
→ Aerobic Respiration: In aerobic respiration, the breakdown of pyruvate takes place in presence of oxygen to give rise to 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.
→ Lack of Oxygen: Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds). Formation of lactic acid in muscles causes cramp.

Question 12.
How is oxygen and carbon dioxide transported in human beings ? (CBSE AI2008, CCE 2012)
Answer:

→ Transport of Oxygen: The respiratory pigments (haemoglobin) present in red blood cells takes up the oxygen from the air to the lungs. They carry the oxygen to tissues which are deficient in oxygen.

→ Transport of carbon dioxide: Carbon Dioxide is more soluble in water. Hence, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs where it diffuses from blood to air in the lungs and then expelled out through nostrils.

Question 13.
How are lungs designed in human beings to maximise the area for exchange of gases ?
(CBSE AI 2008, CCE 2011)
Answer:
The lungs is an important part of the body. The passage inside the lungs divides into smaller and smaller tubes, which finally terminate in balloon-like structures, called as alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli usually contains an extensive network of blood vessels. We know that, when we breathe in, we lift our ribs, flatten our diaphragm and chest cavity becomes larger. Because of this action, air is sucked into the lungs and fills the expanded alveoli. The blood brings the essential carbon dioxide from rest of the body and supply it to alveoli; the oxygen in the alveolar air is taken up by the blood in the alveolar blood vessels to be transported to the all other cells of the body. During the normal 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 carbon dioxide to be released.

Question 14.
What are the components of the transport system in human beings ? What are the functions of these components ?
(CCE 2011)
Answer:

Heart, blood and blood vessels are the main components of transport system in human beings.

Functions of these components

Heart

Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.

Blood

Blood transports oxygen, nutrients, CO2, and nitrogenous wastes.

Blood vessels

Blood vessels, arteries and veins carry blood to all parts of body.

Question 15.
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ? (CCE 2012)
Answer:
Mammals and birds are warm blooded animals. They constantly use energy to maintain their body temperature. They have a higher energy need and require more oxygenated blood for their cells. Hence it is very important for warm blooded animals to separate oxygenated and deoxygenated blood to keep their circulatory system efficient.

Question 16.
What are the components of the transport system in highly organised plants ? (CCE 2010)
Answer:
Transport system of highly organised plants consists of xylem and phloem.
Xylem: It is used in transport of water and minerals. Xylem is made of tracheids, vessels, xylem fibres and xylem parenchyma. Tracheids and vessels constitute the tracheary elements or channels for transport of water and minerals.
Phloem: It is used for transport or translocation of organic solutes or food. Phloem consists of sieve tubes, companion cells, phloem fibres and phloem parenchyma. Sieve tubes constitute the channels for transport of food materials.

Question 17.
How are water and minerals transported in plants ?
Answer:
Water and minerals are transported through xylem cells from soil to the leaves. The xylem cells of roots, stem and leaves are interconnected to form a continuous conducting channel that reaches all parts of the plant. The root cells take ions from the soil. This creates a difference between the concentration of ions of roots and soil. Therefore, there is a steady movement of water into xylem. An osmotic pressure is formed and water and minerals are transported from one cell to the other cell due to osmosis. The continuous loss of water takes place due to transpiration. Because of transpiration, a suction pressure is created as a result of which water is forced into the xylem cells of roots. The effect of root pressure for transportation in plants is more important in night while during day time transpiration pull becomes the major driving force.

Question 18.
How is food transported in plants ?
Answer:
Food is transported in plants by phloem. Phloem transports food materials from leaf to different parts of a plant. Transportation of food in phloem is achieved by the expenditure of energy from ATP. This increases osmotic pressure in the tissue causing water to move in. This pressure moves material in the Phloem to the tissues with less pressure. This pressure helps to transport food from the area of high concentration to low concentration.

Question 19.
Describe the structure and functions of nephron.
Answer:

Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus, Bowman's capsule, and a long renal tubule.
Functioning of a nephron:
→ The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.
→ The water and solute are transferred to the nephron at Bowman's capsule.
→ In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine.
→ The filtrate then moves down into the loop of Henle, where more water is absorbed.
→ From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct. Collecting duct collects urine from many nephrons.
→ The urine formed in each kidney enters a long tube called ureter. From ureter, it gets transported to the urinary bladder and then into the urethra.

Question 20.
What are the methods used by plants to get rid of excretory products ?
Answer:
Plants can get rid of excess of water by transpiration. Waste materials may be stored in the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that later fall off.

Question 21.
How is the amount of urine produced regulated ?
Answer:
The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Anti-diuretic hormone (ADH) also regulates the amount of urine produced.