Life ProcessesClass 10 Biology NCERT Solutions
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Q1Exercises
The kidneys in human beings are a part of the system for
(a)
nutrition.
(b)
respiration.
(c)
excretion.
(d)
transportation.
Solution
(c) excretion.
The kidneys are the primary organs of the excretory system, responsible for filtering waste products from the blood to produce urine.
Q2Exercises
The xylem in plants are responsible for
(a)
transport of water.
(b)
transport of food.
(c)
transport of amino acids.
(d)
transport of oxygen.
Solution
(a) transport of water.
The xylem is the vascular tissue in plants that conducts water and dissolved minerals from the roots to the rest of the plant.
Q3Exercises
The autotrophic mode of nutrition requires
(a)
carbon dioxide and water.
(b)
chlorophyll.
(c)
sunlight.
(d)
all of the above.
Solution
(d) all of the above.
Autotrophic nutrition, specifically photosynthesis, requires carbon dioxide, water, chlorophyll to trap sunlight, and sunlight as the energy source.
Q4Exercises
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a)
cytoplasm.
(b)
mitochondria.
(c)
chloroplast.
(d)
nucleus.
Solution
(b) mitochondria.
This process is aerobic respiration. The initial breakdown of glucose to pyruvate occurs in the cytoplasm, but the complete breakdown of pyruvate into carbon dioxide, water, and energy occurs in the mitochondria.
Q5Exercises
How are fats digested in our bodies? Where does this process take place?
Solution
The digestion of fats primarily takes place in the small intestine.
The process involves two main steps:
- Emulsification: Fats arrive in the small intestine in the form of large globules. Bile juice, secreted by the liver, contains bile salts that break down these large fat globules into much smaller globules. This process is called emulsification. It increases the surface area of the fats, making it easier for enzymes to act on them.
- Enzymatic Digestion: The pancreas secretes pancreatic juice, which contains the enzyme lipase. Lipase acts on the emulsified fats and breaks them down into simpler molecules of fatty acids and glycerol. These smaller molecules can then be absorbed by the walls of the small intestine.
Q6Exercises
What is the role of saliva in the digestion of food?
Solution
Saliva plays two important roles in the digestion of food:
- Moistening Food: Saliva wets the food, making it softer and easier to chew and form into a bolus that can be swallowed smoothly.
- Chemical Digestion: Saliva contains an enzyme called salivary amylase. This enzyme begins the chemical digestion of starch (a complex carbohydrate) present in the food, breaking it down into simpler sugars.
Q7Exercises
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Solution
The necessary conditions for autotrophic nutrition (specifically photosynthesis) are:
- Carbon Dioxide (): Obtained from the atmosphere.
- Water (): Absorbed from the soil.
- Sunlight: As a source of energy.
- Chlorophyll: The green pigment that traps sunlight energy.
The byproducts of autotrophic nutrition are:
- Carbohydrates (Glucose, ): Used as a source of energy by the plant and stored as starch.
- Oxygen (): Released into the atmosphere as a waste product.
Q8Exercises
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Solution
The main differences between aerobic and anaerobic respiration are:
| Feature | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen Requirement | Occurs in the presence of oxygen. | Occurs in the absence of oxygen. |
| Location in Cell | Occurs in the cytoplasm and mitochondria. | Occurs only in the cytoplasm. |
| End Products | Carbon dioxide () and water (). | Ethanol and (in yeast) or Lactic acid (in muscle cells). |
| Energy Released | A large amount of energy is released (approx. 38 ATP). | A very small amount of energy is released (approx. 2 ATP). |
| Breakdown of Glucose | Complete breakdown of glucose. | Incomplete breakdown of glucose. |
Some organisms that use the anaerobic mode of respiration are:
- Yeast (used in fermentation for making bread and alcoholic beverages).
- Certain bacteria (like those causing tetanus).
Q9Exercises
How are the alveoli designed to maximise the exchange of gases?
Solution
The alveoli are designed to maximise the exchange of gases in several ways:
- Large Surface Area: There are millions of alveoli in the lungs, which collectively provide an enormous surface area (about 80 ) for gas exchange to occur.
- Thin Walls: The wall of each alveolus is extremely thin, only one cell thick. This shortens the diffusion distance, allowing for rapid and efficient exchange of oxygen and carbon dioxide between the air and the blood.
- Rich Blood Supply: The alveoli are covered with an extensive network of blood capillaries. This ensures that a large volume of blood is constantly flowing past the alveoli, maintaining a steep concentration gradient for the diffusion of gases.
- Moist Surface: The inner surface of the alveoli is moist, which helps gases like oxygen to dissolve before diffusing across the membrane.
Q10Exercises
What would be the consequences of a deficiency of haemoglobin in our bodies?
Solution
Haemoglobin is the respiratory pigment in our red blood cells responsible for transporting oxygen from the lungs to all the body tissues. A deficiency of haemoglobin would lead to a condition called anemia.
The consequences would be:
- Reduced Oxygen Supply: The oxygen-carrying capacity of the blood would be significantly reduced. This means that body cells would not receive enough oxygen to carry out cellular respiration efficiently.
- Lack of Energy: Due to insufficient oxygen, less energy would be produced in the cells. This would cause symptoms like fatigue, weakness, and getting tired easily.
- Other Symptoms: A person with haemoglobin deficiency may also experience breathlessness (especially on exertion), pale skin, and dizziness, as the body tries to compensate for the lack of oxygen.
Q11Exercises
Describe double circulation of blood in human beings. Why is it necessary?
Solution
Double Circulation:
Double circulation is a system in which the blood passes through the heart twice during one complete cycle of circulation through the body. The human heart is divided into four chambers, and the pathway consists of two distinct circuits:
-
Pulmonary Circulation: This circuit moves blood between the heart and the lungs. Deoxygenated blood from the body enters the right atrium, is pumped to the right ventricle, and then sent to the lungs via the pulmonary artery. In the lungs, the blood releases carbon dioxide and picks up oxygen. The now oxygenated blood returns to the left atrium of the heart through the pulmonary vein.
-
Systemic Circulation: This circuit moves blood between the heart and the rest of the body. The oxygenated blood from the left atrium is pumped to the left ventricle, which then pumps it with great force into the aorta. The aorta branches into smaller arteries that supply oxygenated blood to all body tissues. Deoxygenated blood from the tissues is collected by veins and returned to the right atrium of the heart, completing the circuit.
Necessity of Double Circulation:
Double circulation is necessary for warm-blooded animals like humans because it prevents the mixing of oxygenated and deoxygenated blood. This separation ensures a highly efficient supply of oxygen to the body's cells, which is crucial for meeting their high energy demands required for maintaining a constant body temperature.
Q12Exercises
What are the differences between the transport of materials in xylem and phloem?
Solution
The differences between the transport of materials in xylem and phloem are as follows:
| Feature | Transport in Xylem | Transport in Phloem |
|---|---|---|
| Substances Transported | Water and dissolved minerals. | Food (sucrose) and other substances like amino acids. |
| Direction of Flow | Unidirectional: from roots upwards to other plant parts. | Bidirectional: from leaves to storage organs or growing parts (upwards or downwards). |
| Driving Force | It is a passive process driven by physical forces like transpiration pull and root pressure. | It is an active process that requires energy in the form of ATP to move substances. |
| Conducting Cells | Tracheids and vessels (which are dead cells). | Sieve tubes and companion cells (which are living cells). |
Q13Exercises
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Solution
A comparison between the alveoli and nephrons is as follows:
| Feature | Alveoli in the Lungs | Nephrons in the Kidneys |
|---|---|---|
| Basic Structure | Tiny, thin-walled, balloon-like air sacs. | A long, coiled tubule with a cup-shaped Bowman's capsule containing a capillary cluster (glomerulus). |
| Number | Millions in each lung. | Millions in each kidney. |
| Surface Area | Both structures vastly increase the surface area for their respective functions. | Both structures vastly increase the surface area for their respective functions. |
| Blood Supply | Surrounded by an extensive network of blood capillaries. | The glomerulus is a capillary cluster, and the tubule is surrounded by capillaries. |
| Primary Function | Gaseous Exchange: Exchange of oxygen and carbon dioxide between the air and the blood. | Blood Filtration and Urine Formation: Filtering waste products from the blood and forming urine. |
| Mechanism | Works on the principle of diffusion down a concentration gradient. | Works by ultrafiltration under pressure, followed by selective reabsorption. |
| Substances Handled | Oxygen () and Carbon Dioxide (). | Water, salts, glucose, amino acids, and nitrogenous wastes (like urea). |
| Outcome | Blood is oxygenated and carbon dioxide is removed. | Harmful wastes are removed from the blood, and useful substances are reabsorbed, regulating water and salt balance. |
Q1In-text Questions 1
Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Solution
In large multicellular organisms like humans, all the cells are not in direct contact with the surrounding environment. Simple diffusion is a very slow process and would take an extremely long time for oxygen to reach all the cells of the body. For instance, the text mentions it would take about 3 years for an oxygen molecule to diffuse from our lungs to our toes. Therefore, diffusion is insufficient to meet the oxygen requirements of all the body cells efficiently, and a specialized respiratory and transport system is required.
Q2In-text Questions 1
What criteria do we use to decide whether something is alive?
Solution
The criteria used to decide whether something is alive include:
- Visible Movements: Obvious movements like running, breathing, or growth are common indicators of life.
- Molecular Movements: The most fundamental criterion is the presence of molecular movements. Living structures are highly organised and tend to break down over time due to environmental effects. To counter this, living organisms must constantly repair and maintain their structures by moving molecules around. This invisible molecular movement is considered necessary for life.
Q3In-text Questions 1
What are outside raw materials used for by an organism?
Solution
An organism uses outside raw materials for two main purposes:
- Source of Energy: Raw materials, which we call food, are broken down through processes like respiration to provide energy. This energy is essential for carrying out various life processes and maintaining the organised structure of the organism.
- Growth and Synthesis: Additional raw materials are needed for the growth and development of the body. These materials are used to build new cells and synthesize substances like proteins required by the body.
Q4In-text Questions 1
What processes would you consider essential for maintaining life?
Solution
The processes essential for maintaining life, collectively known as life processes, are:
- Nutrition: The process of taking in food (a source of energy and raw materials) from outside the body.
- Respiration: The process of breaking down food sources to release energy for cellular needs.
- Transportation: The process of carrying food, oxygen, and other essential substances from one part of the body to another.
- Excretion: The process of removing harmful metabolic waste products from the body.
Q1In-text Questions 2
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Solution
The differences between autotrophic and heterotrophic nutrition are as follows:
| Feature | Autotrophic Nutrition | Heterotrophic Nutrition |
|---|---|---|
| Food Source | Organisms synthesise their own food from simple inorganic raw materials like and water. | Organisms obtain complex organic food directly or indirectly from autotrophs. |
| Energy Source | Uses an external energy source, typically sunlight (photosynthesis). | Derives energy by breaking down the complex food substances it consumes. |
| Organisms | Includes green plants and some bacteria. | Includes animals, fungi, and most other bacteria. |
| Process | Food is produced within the organism. | Food is taken in from an external source and then digested. |
Q2In-text Questions 2
Where do plants get each of the raw materials required for photosynthesis?
Solution
Plants obtain the raw materials for photosynthesis from the following sources:
- Carbon Dioxide (): Taken from the atmosphere through tiny pores on the surface of the leaves called stomata.
- Water (): Absorbed from the soil by the roots.
- Sunlight: Absorbed by chlorophyll, the green pigment present in cell organelles called chloroplasts.
- Other Minerals: Nutrients like nitrogen, phosphorus, iron, and magnesium are also taken up from the soil by the roots.
Q3In-text Questions 2
What is the role of the acid in our stomach?
Solution
The acid in our stomach, which is hydrochloric acid (HCl), has two main roles:
- Activates Pepsin: It creates an acidic medium in the stomach, which is necessary for the protein-digesting enzyme pepsin to function effectively.
- Kills Germs: It kills any harmful bacteria or other microorganisms that may have entered the body along with the food, thus preventing infections.
Q4In-text Questions 2
What is the function of digestive enzymes?
Solution
Digestive enzymes are biological catalysts that speed up the breakdown of complex, insoluble food molecules into simpler, smaller, soluble molecules. This process is essential because the body can only absorb these smaller molecules. For example, salivary amylase breaks down starch into sugar, pepsin breaks down proteins into smaller peptides, and lipase breaks down fats into fatty acids and glycerol.
Q5In-text Questions 2
How is the small intestine designed to absorb digested food?
Solution
The small intestine is specially designed for efficient absorption of digested food in the following ways:
- Large Surface Area: It is a very long, coiled tube. Its inner lining has numerous tiny, finger-like projections called villi, which vastly increase the surface area available for absorption.
- Rich Blood Supply: The villi are richly supplied with a network of blood vessels. This allows the absorbed food to quickly enter the bloodstream and be transported to all the cells in the body.
- Thin Walls: The walls of the villi are very thin, which reduces the diffusion distance for the nutrients to pass into the blood.
Q1In-text Questions 3
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Solution
The primary advantage a terrestrial organism has over an aquatic organism is the higher concentration of oxygen in the environment. The amount of oxygen in the air (about 21%) is much higher than the amount of dissolved oxygen in water. Because of this, terrestrial organisms can obtain sufficient oxygen with a relatively slower breathing rate, whereas aquatic organisms have to breathe much faster to get the same amount of oxygen.
Q2In-text Questions 3
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Solution
The first step in cellular respiration is the breakdown of glucose (a 6-carbon molecule) into pyruvate (a 3-carbon molecule) in the cytoplasm. From there, pyruvate is broken down in three different ways:
-
Aerobic Respiration (in the presence of oxygen): This occurs in the mitochondria. Pyruvate is completely broken down into carbon dioxide (), water (), and a large amount of energy is released.
-
Anaerobic Respiration (in the absence of oxygen): This occurs in organisms like yeast during fermentation. Pyruvate is converted into ethanol, carbon dioxide, and a smaller amount of energy.
-
Anaerobic Respiration in Muscle Cells (lack of oxygen): During strenuous physical activity, when there is a lack of oxygen in muscle cells, pyruvate is converted into lactic acid and a small amount of energy. This build-up of lactic acid causes muscle cramps.
Q3In-text Questions 3
How is oxygen and carbon dioxide transported in human beings?
Solution
In human beings, oxygen and carbon dioxide are transported by the blood:
-
Oxygen Transport: Oxygen is primarily transported by the red blood corpuscles (RBCs). RBCs contain a respiratory pigment called haemoglobin, which has a high affinity for oxygen. It binds with oxygen in the lungs and carries it to the tissues.
-
Carbon Dioxide Transport: Carbon dioxide is more soluble in water than oxygen. Therefore, it is mostly transported in the dissolved form in the blood plasma from the body tissues to the lungs.
Q4In-text Questions 3
How are the lungs designed in human beings to maximise the area for exchange of gases?
Solution
The lungs in human beings are designed to maximise the area for gaseous exchange in the following ways:
- Branching Network: The air passage (trachea) divides into smaller and smaller tubes (bronchi and bronchioles), spreading throughout the lungs.
- Alveoli: These tubes terminate in millions of tiny, balloon-like structures called alveoli. The presence of millions of alveoli provides a very large surface area for gas exchange (about 80 ).
- Thin Walls: The walls of the alveoli are extremely thin (one-cell thick) to allow for rapid diffusion of gases between the air in the alveoli and the blood.
- Rich Blood Supply: Each alveolus is covered by an extensive network of blood capillaries, ensuring efficient exchange and transport of gases.
Q1In-text Questions 4
What are the components of the transport system in human beings? What are the functions of these components?
Solution
The components of the transport system (circulatory system) in human beings are the heart, blood, and blood vessels.
Their functions are:
-
Heart: A muscular pumping organ that pumps blood throughout the body. It ensures that blood circulates continuously, reaching all tissues and organs.
-
Blood: A fluid connective tissue that acts as the medium of transport. Its functions include:
- Transporting oxygen from the lungs to the body cells.
- Transporting carbon dioxide from the cells to the lungs.
- Transporting digested food (nutrients) from the small intestine to all parts of the body.
- Transporting metabolic wastes (like urea) from the tissues to the kidneys for excretion.
- Transporting hormones and salts.
-
Blood Vessels (Arteries, Veins, and Capillaries): A network of tubes through which blood flows.
- Arteries: Carry oxygenated blood (except pulmonary artery) away from the heart to various organs under high pressure.
- Veins: Collect deoxygenated blood (except pulmonary vein) from different organs and bring it back to the heart.
- Capillaries: Extremely narrow, thin-walled vessels that form a network within tissues. They are the site where the exchange of materials (food, oxygen, waste products) between the blood and body cells takes place.
Q2In-text Questions 4
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Solution
It is necessary to separate oxygenated and deoxygenated blood in mammals and birds because they are warm-blooded animals. They have high energy needs to constantly maintain their body temperature, irrespective of the environmental temperature. The separation of oxygenated and deoxygenated blood by a four-chambered heart ensures a highly efficient supply of oxygen to the body's cells. This efficient oxygen supply allows for effective respiration, which releases the large amount of energy required to maintain a constant body temperature.
Q3In-text Questions 4
What are the components of the transport system in highly organised plants?
Solution
The transport system in highly organised plants consists of a network of conducting tissues called vascular tissues. The two main components are:
- Xylem: This tissue forms a continuous network of channels that transports water and dissolved minerals from the roots to all other parts of the plant, especially the leaves.
- Phloem: This tissue transports the soluble products of photosynthesis (food, such as sucrose) from the leaves to other parts of the plant, including storage organs (like roots and fruits) and growing regions.
Q4In-text Questions 4
How are water and minerals transported in plants?
Solution
Water and minerals are transported in plants through the xylem tissue. The transport occurs through two main mechanisms:
- Root Pressure: Cells in the roots actively take up ions from the soil. This creates a concentration difference, causing water to move into the root xylem from the soil through osmosis. This continuous movement of water creates a pressure that pushes the water column upwards to a certain height. This effect is more significant at night.
- Transpiration Pull: During the day, water evaporates from the surface of the leaves through the stomata (a process called transpiration). This evaporation creates a suction force, or pull, which pulls water up through the xylem vessels from the roots to the leaves. This transpiration pull is the major driving force for water movement over long distances in tall plants.
Q5In-text Questions 4
How is food transported in plants?
Solution
The transport of food (soluble products of photosynthesis) in plants is called translocation, and it occurs through the phloem tissue. This process is different from transport in the xylem as it requires energy.
- Loading: Food, such as sucrose, is actively transferred from the leaf cells into the sieve tubes of the phloem using energy from ATP.
- Pressure Gradient: This loading of sugar increases the osmotic pressure in the phloem, causing water to move into it from the adjacent xylem tissue.
- Movement: The increased pressure moves the material in the phloem to tissues with lower pressure, such as storage organs (roots, fruits) or growing regions (buds).
- Unloading: At the destination, the food is actively transported out of the phloem, according to the plant's needs. This transport can occur in both upward and downward directions.
Q1In-text Questions 5
Describe the structure and functioning of nephrons.
Solution
Structure of a Nephron:
A nephron is the basic filtration unit of the kidney. Each kidney contains millions of nephrons. Its main parts are:
- Bowman's Capsule: A cup-shaped structure at the beginning of the nephron.
- Glomerulus: A dense cluster of very thin-walled blood capillaries located inside the Bowman's capsule.
- Long Coiled Tubule: A long, coiled tube that extends from the Bowman's capsule. This tubule eventually joins a collecting duct.
Functioning of a Nephron:
The process of urine formation involves three main steps:
- Glomerular Filtration: Blood enters the glomerulus under high pressure. This pressure forces water and small solutes (like glucose, amino acids, salts, and nitrogenous wastes like urea) from the blood into the Bowman's capsule. This filtered fluid is called the initial filtrate.
- Selective Reabsorption: As the filtrate passes through the long tubule, useful substances such as glucose, amino acids, salts, and a major amount of water are selectively reabsorbed back into the blood capillaries surrounding the tubule.
- Secretion: The remaining fluid, which contains metabolic wastes like urea, excess salts, and water, forms the urine. The urine from all nephrons is collected in the collecting ducts, which then pass it to the ureter.
Q2In-text Questions 5
What are the methods used by plants to get rid of excretory products?
Solution
Plants use a variety of different strategies to get rid of excretory products:
- Gaseous Wastes: Oxygen (a byproduct of photosynthesis) and carbon dioxide (a byproduct of respiration) are removed through stomata in leaves and lenticels in stems.
- Excess Water: Excess water is removed by the process of transpiration.
- Storage in Dead Tissues: Many waste products are stored in tissues consisting of dead cells, such as old xylem, which may be stored as resins and gums.
- Shedding of Leaves: Some waste products are stored in the vacuoles of leaf cells. These wastes are removed when the leaves fall off.
- Excretion into Soil: Plants also excrete some waste substances into the soil around them.
Q3In-text Questions 5
How is the amount of urine produced regulated?
Solution
The amount of urine produced is regulated by the process of selective reabsorption in the kidney tubules. The amount of water reabsorbed depends on two main factors:
- Amount of Excess Water in the Body: If the body has excess water, less water is reabsorbed, and a large amount of dilute urine is produced. If the body is dehydrated, more water is reabsorbed to conserve it, and a small amount of concentrated urine is produced.
- Amount of Dissolved Waste to be Excreted: The amount of nitrogenous wastes (like urea) and salts that need to be removed from the body also influences the volume of urine. This regulation is controlled by hormones like Antidiuretic Hormone (ADH).