Answer The Following Question.
1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Ans: Diffusion is insufficient in multi-cellular organisms because:
Cells are not in direct contact with the environment.
The body is large and complex, increasing the distance oxygen needs to travel.
Diffusion is a slow process and cannot meet the high oxygen demand of all cells.
Specialized respiratory and circulatory systems ensure efficient oxygen delivery to every part of the body.
3. What are outside raw materials used for by an organism?
Ans: Organisms use outside raw materials for various life processes:
Food – Provides energy and essential materials for growth and repair.
Oxygen – Helps in the breakdown of food to release energy.
Water – Aids in digestion and other metabolic activities within the body.
The type and amount of raw materials needed depend on the organism’s complexity and its environment.
4. What processes would you consider essential for maintaining life?
Ans: The essential processes for maintaining life include:
Nutrition – For obtaining energy and materials.
Respiration – To release energy from food.
Transportation – To distribute nutrients, gases, and waste within the body.
Excretion – To remove metabolic waste from the body.
These processes ensure the survival and proper functioning of an organism.
5. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans: Autotrophic Nutrition:
Food is synthesized from simple inorganic raw materials like CO₂ and water.
Chlorophyll is required for the process.
Food is generally prepared during the daytime (photosynthesis).
It occurs in all green plants and some bacteria.
Heterotrophic Nutrition:
Food is obtained directly or indirectly from autotrophs and broken down with the help of enzymes.
Chlorophyll is not required.
Food can be obtained at any time.
It occurs in all animals, fungi, and most microorganisms.
5. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans: Autotrophic Nutrition:
Food is synthesized from simple inorganic raw materials like CO₂ and water.
Chlorophyll is required for the process.
Food is generally prepared during the daytime (photosynthesis).
It occurs in all green plants and some bacteria.
Heterotrophic Nutrition:
Food is obtained directly or indirectly from autotrophs and broken down with the help of enzymes.
Chlorophyll is not required.
Food can be obtained at any time.
It occurs in all animals, fungi, and most microorganisms.
6. Where do plants get each of the raw materials required for photosynthesis?
Ans: The raw materials required for photosynthesis are:
Carbon Dioxide (CO₂): Plants obtain CO₂ from the atmosphere through stomata present on leaves.
Water: Water is absorbed from the soil by roots and transported to the leaves through xylem.
Sunlight: Sunlight is absorbed by chlorophyll present in the green parts of the plant, mainly the leaves.
7. What is the role of the acid in our stomach?
Ans: The roles of acid in our stomach are:
Dissolving food and creating an acidic medium: The hydrochloric acid in the stomach dissolves food particles and creates an acidic environment, which helps activate the enzyme pepsinogen, converting it into pepsin. Pepsin is a protein-digesting enzyme.
Killing harmful microorganisms: The acid helps kill many bacteria and microorganisms that enter the stomach with food, preventing infections.
8. What is the function of digestive enzymes?
Ans: Digestive enzymes break down complex food particles into simpler molecules.
Amylase helps break down carbohydrates into sugars.
Lipase breaks down fats into fatty acids and glycerol.
Pepsin and trypsin help break down proteins into amino acids.
The simpler molecules are absorbed by the bloodstream and transported to the body’s cells for energy and growth.
9. How is the small intestine designed to absorb digested food?
Ans: The small intestine has millions of tiny finger-like projections called villi, which increase the surface area for more efficient absorption of digested food.
Inside the villi, there are many blood vessels that absorb the digested food.
The absorbed nutrients are then carried through the bloodstream and delivered to all cells of the body.
10. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Ans: Terrestrial organisms obtain oxygen from the atmosphere, while aquatic organisms extract oxygen from water.
Air contains a higher concentration of oxygen (O₂) compared to water.
Due to the higher O₂ content in air, terrestrial animals do not need to breathe as fast as aquatic animals to obtain enough oxygen.
Unlike aquatic animals, terrestrial animals do not require specialized adaptations for gaseous exchange, as oxygen is more readily available in the air.
11. What are the different ways in which glucose is oxidized to provide energy in various organisms?
Ans: Glycolysis: Glucose (6 carbon molecules) is initially broken down in the cytoplasm of cells to form pyruvate (a 3-carbon molecule).
Anaerobic Respiration:
Occurs in the absence of oxygen (e.g., in yeast during fermentation).
Pyruvate is converted into ethanol and carbon dioxide, releasing a small amount of energy.
Aerobic Respiration:
Takes place in the presence of oxygen.
Pyruvate is further broken down into 3 molecules of carbon dioxide and water, releasing a much larger amount of energy.
Lack of Oxygen (Lactic Acid Fermentation):
Occurs when oxygen is insufficient, especially during vigorous activity in muscles.
Pyruvate is converted into lactic acid (a 3-carbon compound), which can cause muscle cramps.
12. How is oxygen and carbon dioxide transported in human beings?
Ans: Transport of Oxygen:
Hemoglobin, the respiratory pigment present in red blood cells, binds to oxygen in the lungs.
It carries oxygen to tissues that are deficient in oxygen, where it is released for cellular respiration.
Transport of Carbon Dioxide:
Carbon dioxide is more soluble in water, so it is mostly transported in the blood plasma in its dissolved form.
It is carried from body tissues to the lungs, where it diffuses from the blood into the air in the lungs and is then expelled out through the nostrils.
13. How are the lungs designed in human beings to maximize the area for exchange of gases?
Ans:
The lungs contain millions of tiny, sac-like structures called alveoli, which provide a large surface area for gas exchange.
An extensive network of blood vessels surrounds the walls of the alveoli, facilitating the exchange of gases between the air and the blood.
During breathing, when the ribs lift and the diaphragm flattens, the chest cavity expands, allowing air to be sucked into the lungs and alveoli.
Oxygen from the inhaled air diffuses into the blood, while carbon dioxide from the blood diffuses into the air in the alveoli to be expelled.
14. What are the components of the transport system in human beings? What are the functions of these components?
Ans:
The main components of the transport system in human beings are the heart, blood, and blood vessels.
Heart:
Pumps oxygenated blood throughout the body.
Receives deoxygenated blood from various body parts and sends it to the lungs for oxygenation.
Blood:
Transports oxygen, nutrients, carbon dioxide, and nitrogenous wastes throughout the body.
Blood Vessels (Arteries, Veins, and Capillaries):
Arteries carry oxygenated blood away from the heart to various organs.
Veins carry deoxygenated blood back to the heart.
Capillaries are the tiny blood vessels where the exchange of gases, nutrients, and waste products occurs between blood and tissues.
15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans: Efficient Oxygen Supply: Separating oxygenated and deoxygenated blood ensures a constant and efficient supply of oxygen to tissues.
High Energy Needs: Mammals and birds have high energy demands due to their active lifestyles.
Temperature Regulation: These animals use energy to maintain their body temperature, requiring an effective circulatory system.
Double Circulatory System: The separation of blood types allows for more efficient circulation, essential for the survival of high-energy animals.
16. What are the components of the transport system in highly organised plants?
In highly organized plants, the transport system consists of two main conducting tissues.
Xylem:
Transports water and minerals absorbed from the soil (via roots) to the rest of the plant.
Phloem:
Transports food materials, such as sugars produced in the leaves, to different parts of the plant body.
17. How are water and minerals transported in plants?
Ans:Transport through Xylem:
Water and minerals are transported through xylem cells from the soil to the leaves.
Xylem cells of roots, stems, and leaves form a continuous conducting channel that reaches all parts of the plant.
Movement of Water into Xylem:
Root cells absorb ions from the soil, creating a concentration difference between the root and soil.
This difference causes a steady movement of water into the xylem via osmosis, forming osmotic pressure.
Transpiration:
Water continuously evaporates from the leaves, causing a loss of water through transpiration.
The loss of water creates a suction pressure, which pulls water into the xylem cells of the roots.
Role of Root Pressure and Transpiration Pull:
Root pressure is more significant at night, aiding in the transport of water.
During the day, transpiration pull becomes the major driving force for water and mineral transport.
18. How is food transported in plants?
Ans:
Phloem Transport:
Food materials (mainly sugars) are transported through phloem from the leaves to various parts of the plant.
echanism of Transport:
The transport of food in phloem is an active process that requires energy from ATP.
ATP helps create osmotic pressure, which moves food from areas of high concentration (such as leaves) to areas of low concentration (such as roots or other parts of the plant)
19. Describe the structure and functioning of nephrons.
Ans: Nephrons are the basic functional and filtering units of the kidneys, with each kidney containing approximately 1 to 1.5 million nephrons. The main components of a nephron are:
Glomerulus:
Bowman’s Capsule:
Renal Tubule (which includes proximal tubule, loop of Henle, distal tubule, and collecting duct)
Functioning of a nephron:
Blood Filtration:
Blood enters the kidney through the renal artery, which branches into capillaries that form the glomerulus.
Filtrate Formation:
Water and solutes are filtered from the blood into the Bowman’s capsule.
Selective Reabsorption:
In the proximal tubule, substances like amino acids, glucose, and salts are selectively reabsorbed into the blood, while unwanted molecules are added to the urine.
Water Reabsorption:
The filtrate moves into the loop of Henle, where more water is absorbed back into the blood.
Final Adjustment:
The filtrate moves upward into the distal tubule, where further adjustments are made to maintain electrolyte balance.
Collecting Duct:
The filtrate then enters the collecting duct, which collects urine from multiple nephrons.
Urine Transport:
The urine formed in the kidneys travels to the ureter, then to the urinary bladder, and finally is expelled through the urethra.:
20. What are the methods used by plants to get rid of excretory products?
Ans:
Transpiration:
Plants get rid of excess water through transpiration, a process where water evaporates from the leaves and other aerial parts.
Storage in Vacuoles:
Waste materials may be stored in cell vacuoles, which act as storage spaces for unwanted substances.
Storage in Xylem:
Waste products may be stored as gum and resin, particularly in the old xylem tissue.
Leaf Shedding:
Some waste materials are stored in the leaves, which eventually fall off as part of the plant’s natural process of shedding.
21. How is the amount of urine produced regulated?
Ans:
The amount of urine produced is primarily determined by the excess water and dissolved wastes in the body.
Habitat of the organism: The environment in which an organism lives (e.g., desert or aquatic) affects water availability and urine production.
Hormones:
Anti-diuretic hormone (ADH) plays a key role in regulating urine production.
ADH helps control the amount of water reabsorbed by the kidneys, reducing urine output when the body needs to conserve water.
Page No: 113
Exercise
1. The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
Ans: (c) excretion.
2. The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Ans: (a) transport of water.
3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Ans: (d) all of the above.
4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Ans: (b) mitochondria.
22. How are fats digested in our bodies? Where does this process take place?
Ans:
Emulsification of Fats:
Fats enter the small intestine in the form of large globules.
Bile salts, secreted by the liver, break down these large fat globules into smaller ones, a process known as emulsification.
Action of Lipase:
The pancreatic enzyme lipase acts on these smaller fat globules, breaking them down into fatty acids and glycerol.
Location of the Process:
This process of fat digestion occurs in the small intestine.
23. What is the role of saliva in the digestion of food?
Ans:
Moistening Food:
Saliva moistens the food, making it easier to swallow.
Enzymatic Action:
Saliva contains the enzyme salivary amylase, which breaks down starch into simpler sugars, beginning the process of carbohydrate digestion.
24. What are the necessary conditions for autotrophic nutrition and what are its by-products?
Ans:
Necessary Conditions for Autotrophic Nutrition:
Carbon dioxide
Water
Chlorophyll pigment
Sunlight
By-products of Autotrophic Nutrition (Photosynthesis):
Carbohydrates (food)
Oxygen (O₂)
25. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Ans:
Aerobic Respiration
Occurs in the presence of Oxygen (O₂).
Involves the exchange of gases between the organism and the outside environment.
Takes place in both the cytoplasm and mitochondria.
Always releases CO₂ and H₂O as by-products.
Anaerobic Respiration
Occurs in the absence of Oxygen (O₂).
Gas exchange is absent.
Occurs only in the cytoplasm.
The end products vary (e.g., ethanol and CO₂ in yeast, lactic acid in muscles).
Organisms that use Anaerobic Respiration:
Yeast (during fermentation)
Some bacteria
Muscle cells in humans (during strenuous activity)
26. How are the alveoli designed to maximise the exchange of gases?
Ans:
Large Surface Area:
The alveoli provide a large surface area for the exchange of gases, facilitating efficient oxygen and carbon dioxide transfer.
Thin Walls:
The walls of the alveoli are very thin, allowing gases to diffuse easily between the air and the blood.
Rich Blood Supply:
An extensive network of blood vessels (capillaries) is present around the alveoli, ensuring a constant flow of blood for gas exchange.
Breathing Mechanism:
When we breathe, the diaphragm flattens and the ribs lift, expanding the chest cavity, which allows air to flow into the lungs and alveoli. Oxygen diffuses from the air into the blood, while carbon dioxide diffuses from the blood into the air to be exhaled.
27. What would be the consequences of a deficiency of haemoglobin in our bodies?
Ans:
educed Oxygen Supply:
Hemoglobin is responsible for transporting oxygen to body cells for cellular respiration. A deficiency in hemoglobin reduces the oxygen-carrying capacity of the blood.
Oxygen Deficiency in Cells:
As a result, body cells may not receive enough oxygen, affecting their ability to perform necessary functions.
Anaemia:
A lack of sufficient hemoglobin leads to a condition called anaemia, which causes symptoms like fatigue, weakness, and shortness of breath.
28. Describe double circulation in human beings. Why is it necessary?
Ans:
Double Circulation:
In humans, blood passes through the heart twice during one complete cycle. This is known as double circulation.
In the first circulation, deoxygenated blood is pumped from the heart to the lungs for oxygenation.
In the second circulation, oxygenated blood is pumped from the heart to the rest of the body to supply oxygen to the cells.
Necessity of Double Circulation:
Separation of Oxygenated and Deoxygenated Blood: Double circulation ensures that oxygenated blood and deoxygenated blood are kept separate, making the circulatory system more efficient.
Efficient Oxygen Supply: This separation allows for the efficient delivery of oxygen to body tissues and ensures that the heart functions optimally.
Maintaining Constant Body Temperature: Double circulation helps in maintaining a stable and constant body temperature by efficiently distributing oxygen and nutrients to cells.1
29. What are the differences between the transport of materials in xylem and phloem?
Ans:
Function:
Xylem: Transports water and minerals from the roots to the rest of the plant.
Phloem: Transports food (mainly sugars) produced during photosynthesis from the leaves to other parts of the plant.
Direction of Transport:
Xylem: Transport is unidirectional, from roots to leaves.
Phloem: Transport is bidirectional, carrying food both upwards and downwards in the plant.
Composition:
Xylem: Made up of dead cells (such as tracheids and vessel elements) that form tubes for water transport.
Phloem: Made up of living cells (such as sieve tube elements and companion cells) that facilitate food transport.
Transport Mechanism:
Xylem: Movement is driven mainly by transpiration (evaporation of water from leaves), creating a suction pull.
Phloem: Movement is driven by pressure flow from areas of high sugar concentration (source) to areas of low sugar concentration (sink).
Presence of Lignin:
Xylem: Contains lignin, which provides strength and supports the plant structure.
Phloem: Does not contain lignin, as it needs to maintain the flow of nutrients in living cells.
30. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Ans:
Function:
Alveoli (in Lungs): Their primary function is gas exchange. Oxygen from the air diffuses into the blood, while carbon dioxide from the blood diffuses into the air to be exhaled.
Nephrons (in Kidneys): Their primary function is filtration of blood to remove waste products and excess substances, forming urine. They help in regulating the balance of water, salts, and other substances in the body.
Structure:
Alveoli:
Tiny, thin-walled sacs surrounded by a dense network of capillaries.
Their thin walls (only one cell thick) allow efficient gas exchange.
Large surface area to maximize the contact with air and blood for gas exchange.
Nephrons:
Each nephron consists of a glomerulus (a network of capillaries) and a renal tubule (which includes the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct).
The glomerulus filters blood, while the renal tubule reabsorbs useful substances and secretes wastes.
The renal tubules are surrounded by capillaries to absorb reabsorbed substances.
Functioning:
Alveoli:
Air enters the lungs during inhalation, and oxygen diffuses through the thin alveolar walls into the blood, while carbon dioxide diffuses in the opposite direction into the alveoli for exhalation.
The presence of hemoglobin in red blood cells helps transport oxygen through the bloodstream.
Nephrons:
Blood enters the glomerulus, where filtration occurs, and the filtrate moves into the renal tubule.
Useful substances like glucose, amino acids, and water are reabsorbed back into the blood.
Wastes like urea are secreted into the filtrate, forming urine, which is transported to the urinary bladder via the collecting duct.
Special Features for Efficient Functioning:
Alveoli:
Large surface area for gas exchange.
Thin walls and the proximity of capillaries allow for fast diffusion of gases.
Moist surface aids gas exchange.
Nephrons:
Filtration at the glomerulus ensures removal of waste.
Selective reabsorption in the renal tubule ensures that essential nutrients and water are retained.
The loop of Henle creates a concentration gradient to help in water reabsorption, ensuring water balance.