Human Nutrition

Human nutrition is the process by which our body takes in food and utilizes it to maintain life functions, support growth, and sustain health. It involves various stages including ingestion, digestion, absorption, assimilation, and egestion. The human digestive system plays a key role in breaking down complex food substances into simpler forms that can be absorbed and used by body cells.

Importance of Good Nutrition

• Supports growth and development in children.
• Boosts immune system to fight diseases.
• Maintains energy levels and physical performance.
• Prevents lifestyle diseases like diabetes, obesity, and heart problems.

Steps Involved in Human Nutrition

Nutrition in humans is a complex, multi-step process that ensures the body gets the essential nutrients from the food we eat. These nutrients are used for energy, growth, and maintenance. The five main stages are:

1. Ingestion:

   This is the first step of nutrition where food is taken into the body through the mouth. The process involves chewing (mastication) which breaks down food into smaller pieces, mixing it with saliva to form a soft mass called bolus. Saliva contains enzymes that begin the digestion of carbohydrates even before the food is swallowed.

2. Digestion:

   Digestion is the process of breaking down complex food into simpler, absorbable forms. It includes:

   • Mechanical digestion: Physical breakdown of food by chewing and muscular contractions of the stomach.
   • Chemical digestion: Involves digestive enzymes and acids that break down carbohydrates, proteins, and fats into glucose, amino acids, and fatty acids respectively.

   Digestion starts in the mouth (with salivary enzymes), continues in the stomach (using gastric juices), and is completed in the small intestine with the help of enzymes from the pancreas and bile from the liver.

3. Absorption:

   This is the process by which digested nutrients (glucose, amino acids, fatty acids, vitamins, minerals, and water) are absorbed into the bloodstream or lymph through the walls of the small intestine. Tiny finger-like projections called villi and microvilli greatly increase the surface area for absorption in the small intestine.

4. Assimilation:

   Assimilation refers to the utilization of the absorbed nutrients by body cells. These nutrients are transported via blood to different cells, where:

   • Glucose is used for energy through cellular respiration.
   • Amino acids help in the synthesis of proteins for growth and tissue repair.
   • Fats provide stored energy and are used for insulation and cell membranes.
5. Egestion:

   This is the final step where undigested and unabsorbed food materials (like dietary fiber and waste) are expelled from the body in the form of feces through the rectum and anus. This process is essential to remove unwanted materials and maintain a healthy digestive system.

Major Nutrients Required by the Human Body

• Carbohydrates: Main energy source. Found in rice, wheat, bread, fruits.
• Proteins: Essential for growth and tissue repair. Sources include pulses, meat, eggs, dairy.
• Fats: Provide energy and help absorb vitamins. Found in oils, butter, nuts.
• Vitamins: Required in small amounts for various metabolic functions. Each vitamin has a specific role (e.g., Vitamin C for immunity).
• Minerals: Inorganic substances required for body functions like bone formation (calcium), blood production (iron), etc.
• Water: Maintains hydration, regulates body temperature, and supports metabolic reactions.
• Dietary Fiber: Helps regulate bowel movements and supports digestion.

Balanced Diet

A balanced diet includes the right proportions of carbohydrates, proteins, fats, vitamins, minerals, water, and fiber. It ensures proper body functioning, prevents nutritional deficiencies, and boosts immunity.

Human Digestive System: Structure and Functions

The human digestive system is a complex series of organs and glands that process food to extract nutrients and energy needed by the body. It begins at the mouth and ends at the anus. This system is responsible for ingestion, digestion, absorption, assimilation, and egestion of food.

Main Organs of the Digestive System and Their Functions

1. Mouth (Oral Cavity):
   • First site of digestion where food is chewed and mixed with saliva.
   • Saliva contains the enzyme salivary amylase that starts breaking down starch into sugars.
   • The tongue helps in mixing the food and pushing it into the pharynx. Teeth helps in biting, shearing, cutting and grinding food.
2. Pharynx and Esophagus:
   • Pharynx serves as a passage for food to the esophagus.
   • Esophagus is a muscular tube that moves food to the stomach through rhythmic contractions called peristalsis.
3. Stomach:
   • A muscular organ where food is churned and mixed with gastric juices.
   • Gastric juice contains hydrochloric acid (HCl) and the enzyme pepsin that breaks down proteins into peptides.
   • Food is converted into a semi-liquid substance called chyme.
4. Small Intestine:
   • The longest part of the digestive tract, about 6 meters in length.
   • Divided into three parts: duodenum, jejunum, and ileum.
   • Duodenum receives bile (from liver) and pancreatic juices (from pancreas) for digestion of fats, carbohydrates, and proteins.
   • Most absorption of nutrients takes place in the jejunum and ileum through villi and microvilli.
5. Liver:
   • The largest gland in the body.
   • Produces bile, which helps in emulsification (breakdown) of fats.
   • Also detoxifies harmful substances and stores glucose as glycogen.
6. Gallbladder:
   • Stores and concentrates bile produced by the liver.
   • Releases bile into the duodenum when fatty food is consumed.
7. Pancreas:
   • Secretes pancreatic juice containing enzymes like amylase, lipase, and trypsin.
   • Also has endocrine functions (produces insulin and glucagon).
8. Large Intestine (Colon):
   • Absorbs excess water and salts from the undigested food.
   • Helps in the formation and storage of feces.
   • Houses beneficial bacteria that produce vitamins like Vitamin K.
9. Rectum and Anus:
   • Rectum stores feces temporarily.
   • Feces are expelled through the anus in the process called egestion.

Key Digestive Enzymes and Their Roles

Importance of the Digestive System

• Converts complex food substances into simple absorbable forms.
• Supplies essential nutrients for energy, growth, and repair.
• Helps in maintaining the water and electrolyte balance in opur body.
• Plays a vital role in immunity through gut flora (microorganisms in the intestines).

Excretion in Humans

Excretion is the biological process of removing metabolic waste products from the body. In humans, excretion is vital to maintain internal chemical balance (homeostasis), prevent toxic accumulation, and ensure the proper functioning of body organs.

1. Kidneys

The kidneys are a pair of bean-shaped organs located on either side of the spine, just below the rib cage. Each kidney is about 10 to 12 cm long and reddish to brown in color.

Structure:

• Renal Cortex: The outer region of the kidney; contains parts of nephrons (glomeruli and convoluted tubules).
• Renal Medulla: Inner part made up of renal pyramids, where loops of Henle and collecting ducts are found.
• Renal Pelvis: A funnel-shaped structure that collects urine from the pyramids and channels it to the ureter.
• Nephron: The functional unit of the kidney (about 1 million per kidney), responsible for filtration and urine formation.

Physiology:

• Filtration: Occurs in the glomerulus; removes water, urea, glucose, and salts from the blood.
• Reabsorption: Vital substances like glucose, amino acids, and water are reabsorbed in the tubules.
• Secretion: Hydrogen ions, potassium, and drugs are secreted into the tubule from blood.
• Urine Formation: Final product flows into the collecting ducts, then to the renal pelvis, and finally into the ureter.

2. Ureters

Ureters are muscular tubes (25 to 30 cm long) that transport urine from the kidneys to the urinary bladder using peristaltic movements.

Structure and Function:

• Three layers: Inner mucosa (transitional epithelium), middle muscularis (smooth muscle), and outer adventitia (connective tissue).
• Peristalsis: Rhythmic muscle contractions push urine downward into the bladder.

3. Urinary Bladder

A hollow, muscular organ that temporarily stores urine until it is excreted. The bladder can hold 400 to 600 ml of urine.

Structure:

• Detrusor muscle: Smooth muscle layers in the wall that contract during urination.
• Internal sphincter: Involuntary muscle at the bladder neck controlling urine release.
• External sphincter: Voluntary skeletal muscle allowing conscious control of urination.

Function:

• Stores urine under low pressure
• Contracts during micturition (urination) to expel urine through the urethra

4. Urethra

A thin-walled tube that conveys urine from the bladder to the external body. It is about 3.5 cm long in females and 18 to 20 cm in males.

Structure and Function:

• Urothelium lining: Mucosal layer protecting the epithelium from urine toxins.
• Surrounded by sphincters: Control voluntary and involuntary urine release.
• In males: Also acts as a reproductive passage for semen.

5. Accessory Excretory Organs

Skin:

• Structure: Contains sweat glands that excrete water, salts, and small amounts of urea.
• Function: Helps regulate body temperature and removes excess salts.

Lungs:

• Structure: Alveoli are surrounded by capillaries allowing gaseous exchange.
• Function: Excrete carbon dioxide and water vapor during exhalation.

Liver:

• Structure: Made up of lobules; processes blood and synthesizes bile.
• Function: Converts toxic ammonia into urea and breaks down old RBCs, alcohol, and drugs.

Urine Formation Process in Kidneys:

1. Filtration: Occurs in the glomerulus (Bowman's capsule). Blood pressure forces water, urea, glucose, and salts out of the blood into the nephron.
2. Reabsorption: Essential nutrients like glucose, amino acids, and some water are reabsorbed into the blood in the renal tubule.
3. Secretion: Additional wastes like hydrogen and potassium ions are secr eted into the nephron from blood capillaries.
4. Urine Formation: The remaining fluid, which contains urea, water, and waste ions, is called urine and is passed into the ureter.

Composition of Urine:

• About 95% water
• 2% urea
• 3% salts, creatinine, uric acid, hormones, etc.

Other Forms of Excretion:

• Skin: Sweat glands release sweat composed of water, salt, and small amounts of urea.
• Lungs: Exhalation removes carbon dioxide and excess water vapor.
• Liver: Detoxifies drugs, alcohol, and breaks down old red blood cells, producing bile pigments.

Significance of Excretion:

• Prevents toxic build-up in the body
• Maintains water and ionic balance
• Regulates blood pressure and pH
• Ensures proper cellular function

Life Processes Textbook Solutions

Part -I

1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
   Answer: Diffusion is insufficient to meet the oxygen requirements of multicellular organisms like humans because it is only effective over very short distances, making it far too slow to deliver oxygen to the many cells located deep within the body. Human tissues have high metabolic demands, and oxygen does not dissolve well enough in bodily fluids to diffuse in adequate amounts. As a result, complex organisms require specialized systems—such as lungs to provide a large surface area for gas exchange and a circulatory system with hemoglobin—to rapidly transport oxygen to all cells, something diffusion alone cannot accomplish.

2. What criteria do we use to decide whether something is alive?
   Answer: Living things are identified based on several key criteria. They grow, reproduce, and use energy to carry out life processes. They also respond to stimuli, maintain a stable internal environment (homeostasis), and are made up of one or more cells, which are the basic units of life. Additionally, living organisms adapt and evolve over time. Anything that consistently shows these characteristics is considered alive.

3. What are outside raw materials used by an organism?
   Answer: Food, water and oxygen are outside raw materials mostly used by an organism. Depending on the complexity of the organism its requirement may differ from organism to organism. Food helps to supply energy and provide materials for growth and development of body. Water provides medium in the cells for all metabolic processes necessary for living condition. And oxygen helps to oxidize food to release energy.

4. What processes would you consider essential for maintaining life?
   Answer: The main life processes essential for a living organism are nutrition, respiration, transportation, excretion, reproduction, movement etc. which are considered essential.

Part-2

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

2. Where do plants get each of the raw materials required for photosynthesis?
   Answer: Plants need various raw materials for their survival such as carbon dioxide, water , solar energy and minerals. They get carbon dioxide from the atmosphere through stomata. Roots absorb water and minerals from soil and transports to leaves and chlorophyll absorbs solar energy and converts into chemical energy.

3. What is the role of the acid in our stomach?
   Answer: The acid in our stomach—mainly hydrochloric acid (HCl)—plays several important roles. It helps break down food into simpler forms, making digestion easier. It also creates an acidic environment that activates the enzyme pepsin, which is essential for digesting proteins. Additionally, stomach acid kills harmful bacteria and pathogens that may enter with food, protecting the body from infections. It also helps in the absorption of certain nutrients, such as iron

5. Whatis the function of digestive enzymes?
   Answer: Digestive enzymes help break down complex food molecules into simpler, absorbable forms so the body can use them for energy, growth, and repair. For example, they break proteins into amino acids, carbohydrates into simple sugars, and fats into fatty acids and glycerol. Without digestive enzymes, the body would be unable to properly digest food or absorb nutrients.

6. How is the small intestine designed to absorb digested food?
   Answer: The small intestine is specially designed to absorb digested food efficiently. It is very long and highly coiled, providing a large surface area for absorption. Its inner walls have finger-like projections called villi, and each villus has even smaller microvilli, greatly increasing the surface area further. The walls of the villi contain a rich network of blood capillaries that quickly transport absorbed nutrients into the bloodstream. Additionally, the lining of the small intestine is thin, allowing nutrients to pass through easily, and it has specialized cells that aid in active and passive transport of nutrients. All these features together make the small intestine highly efficient at absorbing digested food.

Part-3

1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtainingoxygen for respiration?
   Answer: A terrestrial organism has an advantage over an aquatic organism because oxygen is much more abundant in air than in water and also diffuses more rapidly. This means land organism can obtain oxygen more easily and efficiently. Air-breathing structures like lungs or tracheae can take in large amounts of oxygen with less effort, while aquatic organisms must extract dissolved oxygen from water, which contains far less oxygen and requires more energy to process.

2. What are the different ways in which glucose is oxidized to provide energy in various organisms?
   Answer: In all living organisms glucose is partially oxidized to form two molecules of pyruvate. Further breakdown of pyruvate takes place in different manners in different organisms. The process occurs in the cytoplasm of the cell. The modes of respiration processes that help in breakdown of glucose is as follows.

• Anaerobic respiration: The pyruvate is converted into ethanol and carbondioxide in the absence of oxygen. This process takes place in yeast during fermentation. Sometimes, during vigorous muscular activities, when oxygen is inadequate for cellular respiration. Pyruvate is converted into Lactic acid.

• Aerobic respiration: It takes place in the mitochondria, where puruvate is completely oxidised in the presence of oxygen. At the end, CO₂, water and large amount of energy is released.

3. How is oxygen and carbon dioxide transported in human beings?
   Answer: In human beings, oxygen and carbon dioxide are transported by the blood in different ways:

Oxygen transport: Oxygen enters the lungs and diffuses into the blood, where it binds to hemoglobin in red blood cells to form oxyhemoglobin. This allows large amounts of oxygen to be carried efficiently through the bloodstream to body tissues, where it is released for cellular respiration.

Carbon dioxide transport: Carbon dioxide produced by cells diffuses into the blood. It is transported in three forms. Mostly as bicarbonate ions (HCO₃⁻) dissolved in the plasma. A smaller amount binds to hemoglobin to form carbaminohemoglobin. A small amount is dissolved directly in the plasma. The blood then carries carbon dioxide back to the lungs, where it is exhaled.

4. How are the lungs designed in human beings to maximize the area for exchange of gases?
   Answer: The lungs in human beings are designed to maximize the area for gas exchange in several ways. They contain millions of tiny air sacs called alveoli, which greatly increase the surface area available for oxygen and carbon dioxide exchange. Each alveolus is surrounded by a dense network of capillaries, allowing gases to diffuse quickly between air and blood. The walls of the alveoli are extremely thin and moist, making diffusion easier and faster. Additionally, the lungs are highly branched, starting from the trachea to bronchi and bronchioles, which ensures that air reaches every part of the lungs. Together, these features create an enormous surface area and an efficient system for gas exchange

Part-4

1. What are the components of the transport system in human beings? What are the functions of thesecomponents?
   Answer : The transport system in human beings, also called the circulatory system, consists of three main components: blood, heart, and blood vessels. Each has specific functions:

1. Blood – a fluid connective tissue that carries oxygen, nutrients, hormones, and waste products throughout the body. It also helps fight infections and maintain body temperature.
2. Heart – a muscular organ that pumps blood continuously through the blood vessels, ensuring circulation to all parts of the body.
3. Blood vessels – a network of tubes that transport blood. Blood vessels includes arteries, veins and capillaries.Arteries carry oxygen-rich blood away from the heart. Veins carry oxygen-poor blood back to the heart. Capillaries are tiny vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues. Together, these components ensure that all cells receive oxygen and nutrients and that wastes are removed efficiently.
4. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
   Answer: It is necessary to separate oxygenated and deoxygenated blood in mammals and birds because they are warm-blooded animals with high energy demands. Keeping the two types of blood separate ensures that only oxygen-rich blood is delivered to body tissues, allowing cells to receive maximum oxygen for efficient energy production through aerobic respiration. If oxygenated and deoxygenated blood mixed, tissues would receive less oxygen, reducing metabolic efficiency and limiting the animal’s ability to maintain a high body temperature and sustain activities like flying or running. This separation is achieved by a four-chambered heart, which prevents mixing and allows efficient circulation.

3. What are the components of the transport system in highly organized plants?
   Answer: The transport system in highly organized plants includes xylem and phloem (vascular tissues). Xylem transports water and mineral ions. Phloem conducts food from leaves to other parts of plants.

4. How are water and minerals transported in plants?
   Answer: The components of xylem tissue (tracheids and vessels) of roots, stems and leaves are interconnected to form a continuous system of water – conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then, there is a steady movement of water from the root xylem to all the plant parts through the interconnected waterconducting channels. Components of xylem tissue helps in the water transport.

5. How is food transported in plants?
   Answer: In plants, food (mainly in the form of sugars like sucrose) is transported through the phloem, one of the two types of vascular tissue. The phloem moves food from leaves, where it is produced by photosynthesis (sources), to other parts of the plant (sinks) such as roots, stems, flowers, and fruits. This process is called translocation. Unlike xylem transport, which moves water mostly upward, phloem transport can occur upward or downward depending on the plant’s needs. The movement is driven by pressure differences created by the active loading and unloading of sugars into and out of the phloem.

Part-5

1. Describe the structure and functioning of nephrons.

Answer: Each kidney has large numbers of filtration units called nephrons packed close together. The nephron is the structural and functional unit of the kidney, responsible for filtering blood and forming urine. Each kidney contains about a million nephrons.

Structure of a Nephron:

1. Bowman’s capsule: A cup-shaped structure that surrounds a network of capillaries called the glomerulus. This is where blood filtration
2. Proximal convoluted tubule (PCT): A twisted tube where most reabsorption of water, glucose, salts, and amino acids
3. Loop of Henle: A U-shaped loop that extends into the kidney’s medulla; it concentrates urine by reabsorbing water and salts.
4. Distal convoluted tubule (DCT): Another twisted segment that regulates salt and pH balance and fine-tunes reabsorption.
5. Collecting duct: Receives urine from several nephrons and carries it to the renal pelvis, from where it passes to the ureter.

Functioning of a Nephron:

1. Filtration: Blood pressure forces water and small molecules from the glomerulus into Bowman’s capsule, forming a filtrate while retaining blood cells and large proteins.
2. Reabsorption: Useful substances like glucose, amino acids, and most water and salts are reabsorbed back into the blood along the PCT and loop of Henle.
3. Secretion: Additional waste products, hydrogen ions, and excess salts are secreted into the tubule from surrounding capillaries.
4. Excretion: The final fluid, urine, flows through the collecting duct to the ureter and eventually to the bladder for storage.

2. What are the methods used by plants to get rid of excretory products?
   Answer:
   Plants get rid of excretory products through several methods, even though they do not have specialized excretory organs like animals:

1. Diffusion through leaves: Gaseous wastes like oxygen, carbon dioxide, and water vapor are released directly into the air through stomata.
2. Storage in leaves, stems, and bark: Some waste products, such as resins, gums, and tannins, are stored in old leaves, bark, or thorns, which may later fall off, removing the wastes from the plant.
3. Excretion into soil: Certain soluble wastes, like oxalates and salts, can be secreted into the cell wall or vacuoles, and eventually leach into the soil.
4. Volatile substances: Some plants release volatile compounds (e.g., essential oils or aromatic substances) into the air, which act as a way to eliminate metabolic by-products.

3. How is the amount of urine produced regulated?
   Answer:Different organisms use varied strategies for excretion. Many unicellular organisms remove the wastes by simple diffusion from the body surface into the surrounding water. Multi cellular organisms use specialised organs to perform the same function. In human beings Nitrogenous waste products are removed by the nephrons in kidneys in the form of urine.

Exercises

1.The kidneys in human beings are a part of the system for
(a) nutrition
(b) respiration
(c) excretion
(d)transportation
Answer: (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.
Answer: (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.
Answer: - 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.
- nucleus.
Answer:(b) mitochondria

5. How are fats digested in our bodies? Where does this process take place?
Answer: Fats are digested in the small intestine. The small intestine gets bile juice and pancreatic juice respectively 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 enzymes can easily act on them. This is referred to as emulsification of fats. It takes place in the small intestine.

6.What is the role of saliva in the digestion of food?
Answer: The saliva contains an enzyme called salivary amylase that breakdown starch which is complex molecule to give simple sugar.

7. What are the necessary conditions for autotrophic nutrition and what are its by products?
Answer: Autotrophs absorbs solar energy and take CO₂and water, prepare their own food.
Glucose, CO₂and water are the byproducts of photosynthesis.
8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use theanaerobic mode of respiration.

Answer: The differences between Aerobic and Anaerobic respiration are:

1. Aerobic respiration occurs in the presence of O₂while anaerobic respiration occurs in the absence of O₂. Aerobic respiration involves the exchange of gases between the organism and the outside environment while in anaerobic respiration exchange of gases is absent.
2. Aerobic respiration occurs in cytoplasm and mitochondria while anaerobic respiration occurs only in cytoplasm.
3. Aerobic respiration always releases CO₂and H₂O while in anaerobic respiration end products vary.
4. Aerobic respiration yields 36 ATPs while anaerobic respiration yields only 2 ATPs.

9.How are the alveoli designed to maximize the exchange of gases?
Answer: The alveoli in human lungs are specially adapted to maximize gas exchange in several ways:


1. Large surface area: The lungs contain millions of alveoli, and each alveolus is tiny and spherical, providing an enormous total surface area for diffusion.
2. Thin walls: Alveolar walls are one cell thick, allowing gases like oxygen and carbon dioxide to diffuse quickly between air and blood.
3. Moist lining: The inner surface of alveoli is moist, which helps gases dissolve and diffuse more efficiently.
4. Rich capillary network: Each alveolus is surrounded by dense capillaries, ensuring a constant flow of blood to carry oxygen away and bring carbon dioxide for removal.
5. Elasticity: Alveoli are elastic, allowing them to expand and recoil, helping air move in and out efficiently.
10. What would be the consequences of a deficiency of haemoglobin in our bodies?
    Answer: Red pigment present in our blood is haemoglobin. It supplies oxygen to all cells of our body Bloodlessness is caused by the deficiency of haemoglobin.

11.Describe double circulation of blood in human beings. Why is it necessary?
Answer: Double circulation in human beings means that blood passes through the heart twice during one complete circuit of the body: once to the lungs and once to the rest of the body.

Pathway of Double Circulation:

• Pulmonary circulation: Deoxygenated blood from the body enters the right atrium and is pumped by the right ventricle to the lungs via the pulmonary artery. In the lungs, blood picks up oxygen and releases carbon dioxide.
• Systemic circulation: Oxygenated blood returns from the lungs to the left atrium, then is pumped by the left ventricle through the aorta to the rest of the body. Oxygen and nutrients are delivered to tissues, and deoxygenated blood returns to the heart.

Why Double Circulation is Necessary:

• It keeps oxygenated and deoxygenated blood separate, ensuring tissues receive blood rich in oxygen.
• It allows high-pressure blood flow to the body, which is essential for efficient delivery of oxygen and nutrients to support the high metabolism of mammals, especially warm-blooded animals.
• It improves overall efficiency of circulation, supporting energy-demanding activities like running, flying, or maintaining body temperature.

12.What are the differences between the transport of materials in xylem and phloem?
Answer:

Xylem	phloem
i) This tissue trans­ports water and mineral salts.	This tissue trans­ports only food.
ii) Roots absorb water and this is carried to all parts of the plant (upward)	Food prepared in to upwards and downwards in both direction.

13.Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to theirstructure and functioning.
Answer:

Feature	Alveoli (Lungs)	Nephrons (Kidneys)
Function	Exchange of gases: oxygen enters blood, carbon dioxide is removed	Filtration of blood, reabsorption of useful substances, and excretion of wastes as urine
Structure	Tiny, balloon-like sacs with thin (one-cell thick) walls and moist lining; surrounded by a dense capillary network	Tubular structure with Bowman’s capsule, glomerulus, proximal & distal tubules, loop of Henle, and collecting duct
Surface area	Large surface area due to millions of alveoli to facilitate rapid gas diffusion	Large combined surface area due to millions of nephrons and long tubules to allow efficient filtration and reabsorption
Mechanism	Diffusion of gases across thin walls between alveoli and blood	Filtration, reabsorption, and secretion of substances between blood and tubules
Role in homeostasis	Maintains oxygen and carbon dioxide levels in blood	Maintains water, electrolyte balance, and removes metabolic wastes

Previous Year Board Papers

1. Under what condition is lactic acid produced in the muscle cells?
2. Draw the diagram showing the structure of nephron and label ‘glomerulus’.
3. Draw the diagram showing the structure of the human brain and label the following parts:
   • Mid-brain
   • Pons
4. Explain the necessity of chemical communication in animals.
5. How is the structure of human heart supportive in transporting oxygenated blood and deoxygenated blood? Explain.
6. Wall of the ventricles in heart is thick. Why? How is blood leakage in the blood vessels prevented?
7. Draw the diagram showing the structure of nephron and label Bowman’s capsule.
8. Write any two differences between biodegradable and non-biodegradable substances.
9. Explain the function of stomach in the human digestive system.
10. Ventricles have thick walls. Give reason.
11. It is necessary to separate oxygenated and deoxygenated blood. Give reason.
12. Which molecule is formed during the first step of cellular respiration by the breakdown of glucose in cytoplasm?
13. Mention the types of respiration and write any two differences between them.
14. Name the products of anaerobic respiration.
15. Diagrams given below represent hearts of three different animals. Observe and answer the questions:

• Among these, which heart is helpful for animals to supply more blood to provide enough energy?
• Which of these is a human heart?
16. The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms. Why?
17. Draw the diagram showing structure of human brain. Label Cerebrum and Cerebellum
18. List any four characteristic features of fishes.
19. Lymph plays an important role in protecting the immune system of the body. Justify this statement.
20. Explain the process of translocation of food materials in plants.
21. Explain the process of digestion in the small intestine of man.
22. Draw the diagram showing the sectional view of the human heart. Label the Aorta and chamber of the heart that receives deoxygenated blood
23. Write the differences between the sex chromosomes of man and the sex chromosomes of woman.
24. Draw the diagram showing the structure of closed stomata.
25. How is vegetative propagation in plants useful to the field of agriculture?
26. How does menstruation in women occur?
27. Draw the diagram showing the structure of human brain. Label the following parts:
• Cerebrum
• Cerebellum
28. What is the important function of 'villi' and 'alveoli' in our body?
29. Draw the diagram of human excretory system and label.
30. Compare the functions of xylem tissue with that of phloem tissue.
31. Explain the process of exchange of gases that takes place through stomata in plants.
32. What is the structure of human heart supporting in transporting oxygenated blood and deoxygenated blood?
33. The body temperature of frogs and lizards depends on the temperature of environment. Justify.
34. Eating chapathi by chewing it very slowly tastes sweeter. Why?
35. How are the functions of arteries, veins, and capillaries interrelated in the circulation of blood? Explain.
36. Explain the structure and function of nephron.
37. What is the importance of transpiration in plants?
38. How does translocation of materials take place by phloem tissue?
39. What are the differences between blood and lymph?
40. How is the sex of a child determined in human beings?
41. Which hormone is produced by having iodine-rich salt in our diet? Mention the gland that secretes this hormone.
42. Compare the functions of xylem tissue with that of phloem tissue.
43. Explain the strategies of excretion in plants.
44. Explain the human male reproductive system.
45. Schematic diagram of circulation in mammals is given below. Answer the questions: Name the blood vessel.
46. Which are the events that occur during photosynthesis?
47. What is the importance of transpiration in the transportation of salts? Mention the different strategies found in plants during the excretion of wastes.
48. What is the function of buccal cavity and stomach in the digestion of food in our body?
49. Mention the role of arteries and capillaries in the transportation of materials in our body.
50. Draw the diagram showing the structure of human brain. Label the following parts:
• Cerebellum
• Hypothalamus

Answers for MCQs

1. The living component of xylem tissue is B. Xylem parenchyma. It is the only living cell type in the xylem tissue, which otherwise consists of dead cells like tracheids, vessels, and xylem fibres.
2. The correct statement related to the digestion in the small intestine is A. acidic food is made alkaline by bile juice. Bile juice emulsifies fats and activates lipase, making the medium alkaline in the small intestine.
3. Plants can get rid of excess water by this process: A. Transpiration is the loss of water vapor from the aerial parts of plants, primarily through stomata.
4. The common passage for both sperms and urine in the human reproductive system is the urethra-Abut this is specific to the male reproductive system. In females, the urethra is exclusively for urine.
5. Which is commonly called the personality hormone: B. Thyroxine. Thyroxine's influence on metabolism, growth, and development impacts an individual's mental and physical characteristics, contributing to aspects of personality.
6. The site of complete digestion of carbohydrates, proteins, and fats is D) small intestine. The small intestine is where these macromolecules are broken down into absorbable units like glucose, amino acids, fatty acids, and glycerol.
7. The plant hormone that causes wilting of leaves is C) abscisic acid. Abscisic acid (ABA) is a stress hormone that promotes stomatal closure, reducing water loss and leading to wilting.
8. The unfertilized egg of a human female contains B) One ‘X’ Chromosome. A human egg is a haploid gamete containing 22 autosomes and one X sex chromosome.
9. The blood vessels that carry blood from all parts of the human body to the heart are D. Veins collect deoxygenated blood (with the exception of pulmonary veins) and return it to the hear

 

Answers for Short Answer Questions

1. Under what condition lactic acid is produced in the muscle cells?

Lactic acid is produced in muscle cells when there is a temporary deficiency of oxygen, especially during intense exercise like fast running, cycling, or weightlifting where the demand for energy exceeds the oxygen supply. During this time, muscle cells respire anaerobically, meaning they break down glucose to produce energy without sufficient oxygen, resulting in the formation of lactic acid as a byproduct. This accumulation of lactic acid can cause muscle cramps. 

2. Draw the diagram showing the structure of nephron and label ‘glomerulus’. 


The diagram of the nephron's structure would include the glomerulus. The glomerulus is a network of capillaries where blood filtration begins. 

3. Draw the diagram showing the structure of the human brain and label the following parts: • Mid-brain • Pons 


A diagram of the human brain would show the mid-brain as the smallest and central part of the brain. The pons is located in the hindbrain, which is the lower part of the brain. 

4. Explain the necessity of chemical communication in animals. 

Chemical communication, primarily through the use of HORMONES, is essential for animals for various reasons: 

1. Mating: Pheromones help individuals find mates and assess their reproductive status.
2. Territory establishment:Animals use chemical signals to mark their territory boundaries and reduce conflicts.
3. Social interactions:Chemical communication helps social animals maintain group interconnection and recognize individuals within their social structure. 
5. How is the structure of the human heart supportive in transporting oxygenated blood and deoxygenated blood? Explain.

The human heart's structure is a four-chambered organ, consisting of two atria and two ventricles, separated by a septum. This design supports efficient transport of oxygenated and deoxygenated blood through two distinct circulatory pathways: 

1. Pulmonary Circulation (Deoxygenated blood): The right side of the heart, specifically the right atrium and right ventricle, receives deoxygenated blood from the body. The right ventricle pumps this blood into the pulmonary artery, which carries it to the lungs for oxygenation. The pulmonary valve prevents backflow into the ventricle.
2. Systemic Circulation (Oxygenated blood): Oxygenated blood returns from the lungs to the left atrium through the pulmonary veins. It then flows into the left ventricle, which has a thicker muscular wall than the right ventricle. This strong left ventricle pumps the oxygenated blood into the aorta, the largest artery, which distributes it to the rest of the body. The aortic valve prevents backflow into the left ventricle. 

This structure ensures that oxygenated and deoxygenated blood remain separated, allowing for efficient delivery of oxygen to the body's tissues. 

6. Wall of the ventricles in heart is thick. Why? How is the blood leakage in the blood vessels prevented?

 The ventricles, especially the left ventricle, have thick muscular walls because they need to pump blood out of the heart against high resistance. The left ventricle, in particular, pumps oxygenated blood to the entire body, which requires high pressure to circulate.Blood leakage from blood vessels is primarily prevented by platelets. When a blood vessel is injured, platelets gather at the site and form a clot, sealing the leak and preventing blood loss. 

7. Draw the diagram showing the structure of nephron and label bowman’s capsule. 


The structure of a nephron includes Bowman's capsule. Bowman's capsule (also known as the glomerular capsule) is a double-walled epithelial cup that surrounds the glomerulus. It collects the filtrate from the glomerulus and channels it into the renal tubule. 

8. Write any two differences between biodegradable and non-biodegradable substances.

Biodegradable Waste	Non-Biodegradable Waste
Can be broken down by natural processes (e.g., microorganisms).	Do not break down naturally and can persist for long periods.
Examples: Food scraps, paper, wood, plant matter.	Examples: Plastic, metal, glass, certain chemicals.

9. Explain the function of stomach in the human digestive system.

The stomach is a muscular, J-shaped organ that plays a crucial role in digestion. Its primary functions include: 

1. Storing food: It acts as a temporary reservoir for food, holding it while it's being digested.
2. Mixing and breaking down food: The muscular walls contract and relax to churn and mix food with digestive juices.
3. Producing digestive enzymes and acid: The stomach produces enzymes (like pepsin) to break down proteins and hydrochloric acid, which further breaks down food and kills bacteria.
10. Ventricles have thick walls give reason 

The ventricles have thick walls because they are responsible for pumping blood out of the heart, which requires considerable pressure, especially for the left ventricle pumping to the entire body. 

11. It is necessary to separate oxygenated and deoxygenated blood , Give reason

It is necessary to separate oxygenated and deoxygenated blood because this allows for a more efficient circulatory system, ensuring that cells receive a rich supply of oxygen to meet their energy needs. This is particularly important for warm-blooded animals like mammals and birds, which need to maintain a constant body temperature and require a high metabolic rate.

12. Which molecule is formed during the first step of cellular respiration by the breakdown of f glucose in cytoplasm

During the first step of cellular respiration in the cytoplasm, glucose is broken down into two molecules of pyruvate through a process called glycolysis.

13. Mention the types of respiration and write any two differences between them

The main types of respiration are aerobic respiration and anaerobic respiration.

• Aerobic respiration: Occurs in the presence of oxygen and produces a large amount of ATP (around 36-38 ATP per glucose molecule). Its end products are carbon dioxide and water.
• Anaerobic respiration: Occurs in the absence of oxygen and produces a smaller amount of ATP (around 2 ATP per glucose molecule). Its end products can be lactic acid (in animals) or ethanol and carbon dioxide (in microorganisms).
14. Name the products of anaerobic respiration

The products of anaerobic respiration depend on the specific type of anaerobic respiration occurring. For example, in lactic acid fermentation, the product is lactic acid. In alcoholic fermentation, the products are ethanol and carbon dioxide.

15. Diagrams given below represents hearts of three different animals observe it and answer the questions below:
16. Among these, which heart is helpful for animals to supply more blood to provide enough energy? Which of these is a human heart?
• To provide enough energy, the heart that is most helpful would be the one in mammals and birds, which have a four-chambered heart that completely separates oxygenated and deoxygenated blood, allowing for a highly efficient oxygen supply for their high energy needs.
• Among the diagrams provided, the human heart would be the one with four chambers, which allows for the complete separation of oxygenated and deoxygenated blood.
17. List any four characteristic features of fishes?

Fishes are aquatic in nature as they live in water. They use gills to extract oxygen from water, and they have paired and unpaired fins for swimming and maintaining balance. Their body is covered with scales for protection.

Lymph plays an important role in protecting the immune system of the body. Justify this statement.
Lymph plays an important role in protecting the immune system because it is a network of vessels and tissues that filters waste products and abnormal cells from the body's tissues. Lymphatic organs, like lymph nodes, produce and store lymphocytes (white blood cells) and other immune cells that fight invaders such as bacteria, viruses, parasites, and fungi.

18. Explain the process of translocation of food materials in plants.

Translocation of food materials in plants is the movement of food (sugars produced during photosynthesis) from the leaves to other parts of the plant where it is needed for growth, storage, or reproduction. This process occurs through the phloem tissue. Sugars are loaded into the phloem at the source (usually the leaves), transported to the sink (where food is needed), and unloaded at the sink.

19. Explain the process of digestion in the small intestine of man.

Digestion in the small intestine begins with the mixing of food with digestive juices from the pancreas, liver, and the walls of the small intestine. The pancreas produces enzymes that break down carbohydrates, proteins, and fats. The liver produces bile, which emulsifies fats. The intestinal juice further breaks down food, and the villi increase the surface area for efficient absorption of digested nutrients into the bloodstream.

20. Draw the diagram showing the sectional view of the human heart. Label the aorta and the chamber that receives deoxygenated blood.

21. Write the differences between the sex chromosomes of man and woman.

Man has one X chromosome and one Y chromosome (XY), whereas a woman has two X chromosomes (XX).

22. How is vegetative propagation in plants useful to the field of agriculture?

Vegetative propagation in plants is useful because it:

• Allows rapid multiplication of plants with desirable traits.
• Ensures genetic uniformity.
• Is useful for plants that do not produce viable seeds.
• Enables quicker growth and maturation.
23. How does menstruation in women occur?

Menstruation occurs as part of the menstrual cycle when the thickened lining of the uterus is shed if pregnancy does not occur. This happens due to hormonal changes, resulting in menstrual blood flowing out through the vagina.

24. Draw the diagram showing the structure of the human brain and label cerebrum and cerebellum.

25. What is the important function of villi and alveoli in our body?

Villi and alveoli provide a large surface area. Villi help in absorption of nutrients in the small intestine, while alveoli help in the exchange of gases in the lungs.

26. Draw the diagram of the human excretory system and label it.

27. Compare the functions of xylem tissue with that of phloem tissue.
• Xylem: Transports water and minerals and provides mechanical support. It consists mainly of dead cells.
• Phloem: Transports food from leaves to other parts of the plant. It consists mainly of living cells.
28. Explain the process of exchange of gases through stomata in plants.


Exchange of gases occurs through tiny pores called stomata. Guard cells control their opening and closing. When stomata are open, carbon dioxide enters and oxygen exits. When guard cells lose water, stomata close to prevent water loss.

29. Explain how the structure of the human heart supports transport of oxygenated and deoxygenated blood.

The heart has four chambers:

• The right atrium receives deoxygenated blood.
• The right ventricle pumps it to the lungs.
• The left atrium receives oxygenated blood.
• The left ventricle pumps it to the body. The septum prevents mixing of blood, and valves ensure one-way flow.
30. The body temperature of frogs and lizards depends on the environment. Justify.

Frogs and lizards are cold-blooded animals. They cannot regulate their body temperature internally, so it depends on environmental temperature.

31. Eating chapathi by chewing slowly tastes sweeter. Why?

Salivary amylase breaks starch into sugars during slow chewing, making the chapathi taste sweeter.

32. How are the functions of arteries, veins, and capillaries interrelated?

Arteries carry blood from the heart, veins return blood to the heart, and capillaries connect them and allow exchange of gases, nutrients, and wastes.

33. Explain the structure and function of nephron.

The nephron is the basic unit of the kidney. It consists of a renal corpuscle and renal tubule. It filters blood, reabsorbs useful substances, and removes waste to form urine.

34. What is the importance of transpiration in plants?

Transpiration helps in transport of water and minerals, cooling the plant, maintaining rigidity, and enabling photosynthesis.

35. How does translocation take place by phloem tissue?

Sugars move from source to sink due to pressure differences created by osmotic movement of water.

36. What are the differences between blood and lymph?

Blood transports oxygen and nutrients, while lymph helps in immunity and fluid balance.

37. How is the sex of a child determined in human beings?

The sperm determines the sex of the child. X chromosome results in a female, and Y chromosome results in a male.

38. Which hormone is produced by iodine-rich salt and which gland secretes it?

Thyroxine is produced with the help of iodine and is secreted by the thyroid gland.

39. Explain the strategies of excretion in plants.

Plants excrete wastes through stomata, lenticels, transpiration, storage in vacuoles, and shedding of leaves and bark.

40. Explain the human male reproductive system.

It includes testes, epididymis, vas deferens, urethra, accessory glands, scrotum, and penis, which together produce and transport sperm and hormones.

41. Which events occur during photosynthesis?
• Absorption of light energy
• Conversion of light energy to chemical energy
• Reduction of carbon dioxide to carbohydrates
42. What is the function of the buccal cavity and stomach in digestion?

The buccal cavity starts digestion by chewing and saliva, while the stomach uses acids and enzymes to continue digestion.

LBA Solutions(Lesson Based Assessment)

Sl. No.	DIFFICULTY LEVEL	NO OF QUESTIONS	MARKS	PERCENTAGE
1	EASY	31	58	30%
2	AVERAGE	48	96	50%
3	DIFFICULTY	23	38	20%

I. Multiple Choice Questions (MCQs)

1. The correct statement regarding digestion that takes place in the small intestine is (JUNE 2019)
   Answer: - Protein is digested by the action of pepsin.
2. The place where carbohydrates, proteins, and fats are completely digested (SEP-2020, JUNE-2020)
   Answer: (A) Stomach
3. Blood vessels that carry blood from all parts of the human body to the heart (JUL-2021)
   Answer: (A) Veins
4. Blood vessels in the human body that carry deoxygenated blood from the heart to the lungs (SEP-2021)
   Answer: - Pulmonary arteries
5. Transport of soluble photosynthesis products in plants (SEP-2021)
   Answer: - Translocation
6. Important function of xylem in plants (JUN-2022)
   Answer: (A) Water transport
7. The main function of the kidney in humans
   Answer: (C) Excretion
8. The place where carbon dioxide and water are released from the breakdown of pyruvate
   Answer: (B) Mitochondria
9. Which of the following is a function of the kidney?
   Answer: (B) Excretion of urea in the form of urine
10. Function of stomata
    Answer: (A) Exchange of gases
11. Structural and functional unit of kidney
    Answer: (B) Nephron
12. A colourless, low-protein fluid in the circulatory system
    Answer: (B) Plasma
13. The blood vessel that carries oxygenated blood from the heart
    Answer: (C) Aorta
14. The important role of stomata in photosynthesis
    Answer: (B) Absorbing carbon dioxide
15. Part of the excretory system that stores nitrogenous wastes dissolved in water
    Answer: (C) Urinary bladder
16. Transpiration process in plant body (SP-2024)
    Answer: - To create osmotic pressure
17. Plants release excess water through this process (2021)
    Answer: (A) Transpiration
18. The need for suction pressure in plants is (AUG-2024)
    Answer: - To remove excess water from the leaves

Short Answer Questions (1/2/3 mark)

1. When is lactic acid produced in muscle cells?
   Answer: (A) Lactic acid is produced during anaerobic respiration in muscle cells when oxygen supply is insufficient. For example, during heavy exercise, muscles perform glycolysis without oxygen, producing lactic acid and energy.
2. How is oxygen supply more efficient in birds and mammals?
   Answer: - Birds and mammals have a four-chambered heart and double circulation system. This allows complete separation of oxygenated and deoxygenated blood, ensuring a continuous, high-efficiency supply of oxygen to body tissues for sustaining high energy demands.
3. Name the products of anaerobic respiration.
   Answer: -
• In animals: Lactic acid + small amount of energy (ATP)
• In plants and yeast: Ethanol + Carbon dioxide + energy
  Anaerobic respiration occurs when oxygen is not available or limited, allowing temporary energy production.
4. Why do deer and rabbits have longer small intestines than tigers/lions?
   Answer: - Herbivores consume cellulose-rich diets which are harder to digest. A longer small intestine allows more time and surface area for enzymatic digestion and absorption of nutrients, whereas carnivores eat protein-rich, easily digestible food and have shorter intestines.
5. Why is the respiration rate of aquatic animals faster than that of terrestrial animals? (A)

Answer : Aquatic animals generally have faster respiration rates than terrestrial animals because water contains less dissolved oxygen than air. To meet their metabolic needs, aquatic animals must breathe more frequently to absorb sufficient oxygen. Also, aquatic animals often maintain high metabolic activity, especially in cold-blooded fish that swim constantly, which increases oxygen demand.

7. What is transpiration?
   Answer: Transpiration is the loss of water in the form of water vapor from the aerial parts of the plant, mainly through the stomata. It helps in cooling the plant, creating transpiration pull for water transport in xylem, and maintaining water balance.
8. Write the type of transport where food material is transported from the leaves to other parts of the plant. (A)
   Answer: The transport of food from leaves (source) to other parts (sink) is called translocation. It occurs in the phloem tissue and is driven by osmotic pressure differences between source and sink regions. Sugars, amino acids, and other nutrients are transported to growing parts and storage organs.
9. What is excretion? -
   Answer: Excretion is the removal of metabolic waste products from the body, such as urea, carbon dioxide, and excess salts. Excretion maintains homeostasis, regulates water and electrolyte balance, and removes harmful substances from the body.
10. What is double circulation?
    Answer: Double circulation refers to the circulation of blood through the heart twice in one complete cycle:
• Pulmonary circulation: Heart → Lungs → Heart (for oxygenation)
• Systemic circulation: Heart → Body → Heart (to supply oxygenated blood to tissues)
  This system ensures efficient oxygen supply and prevents mixing of oxygenated and deoxygenated blood.
11. What is the function of guard cells? (A)
    Answer: Guard cells are specialized cells surrounding stomatal pores. Their main function is to regulate the opening and closing of stomata, controlling gas exchange (CO₂ intake for photosynthesis and O₂ release) and water loss through transpiration.
12. When does stomata close? (A)
    Answer: Stomata close when:
• Water is scarce (to prevent excessive water loss)
• During night, when photosynthesis does not occur and CO₂ intake is not needed
• Under stress conditions such as high temperature or drought
  Closing stomata helps plants conserve water.
13. What is the function of air sacs or alveoli in the lungs? (A)
    Answer: Alveoli are tiny, balloon-like structures at the ends of bronchioles. They:
• Provide a large surface area for gas exchange
• Allow diffusion of oxygen into blood and carbon dioxide out of blood
• Help maintain efficient respiration in humans and mammals
14. “Osmotic pressure in the phloem tissues of plants helps in the transport of materials.” Justify your answer. -
    Answer: Osmotic pressure drives the movement of sugar-rich sap from the source (leaves) to the sink (roots, fruits, storage organs). Sugar molecules are actively loaded into phloem sieve tubes at the source, lowering water potential. Water enters the phloem from xylem via osmosis, generating a pressure gradient. This pressure flow moves nutrients throughout the plant efficiently.
15. “There is a time to absorb oxygen and release carbon dioxide at the beginning of respiration.” Justify -

Answer: At the beginning of respiration, oxygen is absorbed because it is needed to oxidize glucose molecules and release energy in the form of ATP. During this process, carbon dioxide is produced as a byproduct of the breakdown of glucose. This ensures that cells get the required energy for carrying out vital life processes.

16. What are the finger-like structures in the small intestine called? -

Answer: The finger-like projections in the inner lining of the small intestine are called villi.

17. Write the function of villi (A)

Answer: Villi increase the surface area of the small intestine to facilitate efficient absorption of nutrients (like amino acids, glucose, and fatty acids) from digested food into the bloodstream.

18. Humans can't digest grass-like plants. Give reason -

Answer:Humans cannot digest cellulose, the main component of grass, because they lack the enzyme cellulase. This enzyme is required to break the β-1,4-glycosidic bonds in cellulose, so grass passes undigested through the human digestive system.

19. Diffusion is not enough to meet oxygen requirement in multicellular organisms. Why? -

Answer:In multicellular organisms, cells are deep inside the body, so oxygen cannot reach them by diffusion alone. They require specialized transport systems like blood vessels, lungs, or gills to deliver oxygen efficiently to all cells and remove carbon dioxide.

20. Enzymes are biological catalysts. Justify (A)

Answer:Enzymes speed up biochemical reactions without being used up or altered in the process. They lower the activation energy required for reactions, enabling life processes like digestion, respiration, and metabolism to occur efficiently at body temperature.

21. What are life processes? -

Answer: Life processes are essential activities carried out by living organisms to sustain life. These include:

• Nutrition – obtaining energy from food
• Respiration – releasing energy from food
• Transport – moving substances within the organism
• Excretion – removal of waste products
• Reproduction – producing new individuals
22. Name the two types of respiration -

Answer:The two types of respiration are:

1. Aerobic respiration – uses oxygen to break down glucose completely into carbon dioxide and water, releasing energy.
2. Anaerobic respiration – occurs in absence of oxygen, breaking down glucose partially into substances like lactic acid (in animals) or ethanol and carbon dioxide (in plants/yeast), releasing less energy.
23. Name the product released when a 6-carbon glucose molecule is broken down in cytoplasm -

Answer:The 6-carbon glucose molecule is broken down into pyruvate during glycolysis, which occurs in the cytoplasm. Pyruvate then enters mitochondria for further energy production in aerobic respiration.

24. What is nutrition? -

Answer:Nutrition is the process by which organisms obtain food, digest it, absorb nutrients, and use it to obtain energy for growth, repair, and maintenance of body functions.

25. Name the two types of vascular tissues in plants -

Answer:The two vascular tissues are:

• Xylem – transports water and minerals from roots to other parts of the plant
• Phloem – transports food (sugars and other organic nutrients) from leaves to all parts of the plant
26. Enzymes are biological catalysts. Justify.
    Answer: (A) Enzymes accelerate chemical reactions without being consumed. For example, amylase in saliva converts starch into maltose quickly at body temperature, allowing digestion to occur efficiently.
27. What are life processes?

Answer:Life processes are essential activities carried out by all living organisms to sustain life. These processes help organisms to obtain energy, grow, reproduce, and maintain homeostasis. Key life processes include:

• Nutrition – obtaining and using food for energy and growth.
• Respiration – releasing energy from food.
• Transport – moving substances like nutrients, water, and gases within the body.
• Excretion – removing metabolic waste products.
• Reproduction – producing new individuals for species survival.
28. Name the two types of respiration.

Answer: The two types of respiration are:

• Aerobic respiration – occurs in the presence of oxygen. Glucose is completely broken down into carbon dioxide and water, releasing a large amount of energy.
• Anaerobic respiration – occurs in the absence of oxygen. Glucose is partially broken down into substances like lactic acid in animals or ethanol and carbon dioxide in plants/yeast, releasing less energy.
29. What is nutrition?

Answer: Nutrition is the process by which living organisms obtain food, digest it, absorb nutrients, and use them for energy, growth, and repair of tissues. It ensures that the body gets the essential materials for maintaining life processes.

• In autotrophs (plants), nutrition occurs through photosynthesis, where they make their own food.
• In heterotrophs (animals), food is obtained from other organisms.
30. Name the two types of vascular tissues in plants.

Answer: The two vascular tissues are:

• Xylem – transports water and dissolved minerals from roots to other parts of the plant.
• Phloem – transports food (mainly sugars) from leaves to other parts of the plant for growth and storage.
31. What is photosynthesis?

Answer:Photosynthesis is the process by which green plants, algae, and some bacteria use sunlight, carbon dioxide, and water to make food (glucose) and release oxygen.

General equation: 6co₂+6h₂0→c₆h₁₂0₆+60₂.

Function: Produces glucose for energy and growth, and oxygen for respiration.

32. What is cellular respiration?

Answer: Cellular respiration is the process by which cells break down glucose molecules to release energy (ATP) for carrying out life processes. It occurs in all living organisms.

• Aerobic respiration: In mitochondria, glucose + oxygen → CO₂ + H₂O + energy.
• Anaerobic respiration: In cytoplasm, glucose → lactic acid (animals) or ethanol + CO₂ (plants/yeast) + energy.
33. What are parasites?

Answer: Parasites are organisms that live on or inside another organism (the host) and depend on it for food and shelter, often harming the host. Examples: Plasmodium (causes malaria), tapeworm, lice. They may absorb nutrients directly from the host, causing weakness or disease.

34. The haemoglobin content in the blood of two persons A and B is 9 g/dl and 13 g/dl respectively. Which statement is correct regarding oxygen supply?
    Answer: Person B has better oxygen supply because hemoglobin is the protein that binds oxygen in the blood. Higher hemoglobin levels mean more oxygen can be carried to tissues, ensuring better cellular respiration and energy production. Person A, with lower hemoglobin, may experience less efficient oxygen delivery.
35. The schematic representation of blood circulation in mammals


Answer:X – Pulmonary vein: Carries oxygenated blood from lungs to heart. Y – Aorta: Carries oxygenated blood from heart to the rest of the body. Veins have valves to prevent backflow of blood and ensure unidirectional flow toward the heart.

36. Draw the diagram of open stomata and identify parts


Stomata has guard cells: Control opening and closing of the stomatal pore and stomatal pores that allows gas exchange (CO₂ in, O₂ and water vapor out) and transpiration in plants.

37. Approximate lengths of small intestines of animals X and Y
    Answer: X – Herbivorous: Long intestine (20–40 feet) to allow thorough digestion of cellulose-rich plant material. Y – Carnivorous: Short intestine (5–8 feet) because animal protein is easier to digest and absorb.
38. Chapati tastes sweeter when chewed slowly. Why?
    Answer: Salivary glands secrete amylase, an enzyme that breaks down starch in chapati into maltose and simpler sugars, giving a sweet taste when chewed thoroughly.
39. Give reason:
40. a) Ventricles of human heart have thick walls
    Answer: Thick muscular walls generate high pressure to efficiently pump blood to the entire body, especially the systemic circulation.
41. b) Separation of oxygenated and deoxygenated blood in mammals and birds
    Answer: Prevents mixing of blood, ensuring efficient oxygen supply to body tissues, which is vital for high metabolic activity in endothermic animals.
42. Name the enzyme in saliva and its function
    Answer:Enzyme:Function: Digests starch into maltose, beginning the process of carbohydrate digestion in the mouth.
43. Observe pictures – high gas exchange rate, parts X and Y
    Answer: X – Alveoli: Tiny air sacs in lungs where oxygen enters blood and carbon dioxide is removed. High surface area facilitates rapid gas exchange. Y – Bronchioles: Airways that carry air to alveoli.
44. Draw diagram of nephron and label glomerulus
    Answer:Glomerulus: A cluster of capillaries in the nephron where filtration of blood occurs, removing waste products and forming urine.

45. Function of bile juice
    Answer: Bile emulsifies fats in the small intestine, breaking them into smaller droplets to increase surface area for digestion by lipase, aiding fat absorption.
46. How are oxygen and carbon dioxide transported in humans?
    Answer:Oxygen: Bound to hemoglobin in red blood cells as oxyhemoglobin. Carbon dioxide: Mostly transported as bicarbonate ions in plasma, some binds to hemoglobin, and a small fraction dissolves in plasma.
47. Body temperature of frogs and lizards depends on environment
    Answer: These animals are ectotherms, meaning their body temperature varies with environmental temperature. They rely on sunlight or shade to regulate body heat.
48. Why does the heart have different chambers?
    Answer: Separate chambers (atria and ventricles) allow oxygenated and deoxygenated blood to remain separate, ensuring efficient oxygen delivery and preventing mixing.
49. Importance of double circulation
    Answer: Double circulation (pulmonary and systemic) allows:
• Efficient oxygen supply to tissues.
• Prevents mixing of oxygen-rich and oxygen-poor blood.
• Supports high metabolic demand in mammals and birds.
48. If humans had a three-chambered heart
    Answer: Oxygenated and deoxygenated blood would mix, reducing oxygen supply efficiency to tissues, making humans unable to maintain high metabolism.
49. Herbivores have long small intestines; carnivores short
    Answer: Herbivores digest cellulose-rich plant material, which requires more time and surface area, whereas carnivores digest protein and fats, which are easier to break down.
50. Photosynthesis does not occur in desert plants
    Answer: Limited water availability and extreme temperatures prevent normal photosynthesis. Desert plants often have adaptations (like CAM photosynthesis) to minimize water loss.
51. Photosynthesis – product and function
    Answer:Glucose: Used for energy and as a building block for growth. Oxygen: Released into the
52. Lymph role in immunity
    Answer: Lymph transports white blood cells (WBCs) and antibodies, playing a key role in body defense against infections
53. Difference between arteries and veins
    Answer:

Feature	Arteries	Veins
Carry	Blood away from heart	Blood towards heart
Wall thickness	Thick and muscular	Thin and less muscular
Pressure	High	Low
Valves	Absent	Present

54. Explain the role of hydrochloric acid in stomach
    Answer: Provides acidic environment for protein digestion by pepsin. Kills harmful bacteria ingested with food, preventing infections.
55. How is water transported to the higher parts of a plant? Explain..(SEP-2020)

Answer: Water is transported from roots to the higher parts of a plant through xylem tissues by the combined action of root pressure where minerals actively absorbed by roots create osmotic pressure, pushing water upward. Capillary action of narrow xylem vessels allow water to rise due to adhesion and cohesion. Additionally transpiration pull (most important aspect ) causes loss of water through stomata creates a negative pressure that pulls a continuous column of water upward thus, water reaches the highest parts of the plant mainly due to transpiration pull.

56. State the differences between the circulatory systems of fish and humans..(A)-

Feature	Fish	Humans
Type of circulation	Single circulation	Double circulation
Heart chambers	Two (1 atrium, 1 ventricle)	Four (2 atria, 2 ventricles)
Oxygenated blood	Passes through heart once	Passes through heart twice
Efficiency	Less efficient	Highly efficient
Metabolism	Low	High

57. Explain the stages of double circulation in humans.(JUNE-2022)

Answer: Double circulation means blood passes twice through the heart during one complete cycle. It has two stages:

Pulmonary circulation

1. Deoxygenated blood from the body enters the right atrium.
2. It is pumped to the lungs via the pulmonary artery.
3. Blood gets oxygenated in the lungs and returns to the left atrium through pulmonary veins.

Systemic circulation

1. Oxygenated blood moves from the left atrium to the left ventricle.
2. It is pumped to the entire body through the aorta.
3. Deoxygenated blood returns to the right atrium.
58. Explaiun the events in photosynthesis & methods of waste elimination in plants..(A)
events in photosynthesis
1. Absorption of light energy by chlorophyll
2. Conversion of light energy into chemical energy
3. Splitting of water into hydrogen and oxygen
4. Reduction of carbon dioxide to form glucose
 Waste elimination in plants:
1. Oxygen released through stomata
2. Water lost through transpiration
3. Wastes stored in leaves, bark, old xylem
4. Gums, resins and latex excreted
59. In what form do waste products accumulate in old xylem and how are products of photosynthesis transported?

Answer: Waste products accumulate as resins, gums, tannins and crystals in old xylem. Food is transported through phloem by a process called translocation, from leaves to all parts of the plant.

.60. -Explain the structure and function of nephron..(MPQ-2023)-

Answer: A nephron is the structural and functional unit of kidney. It has Bowman’s capsule, Glomerulus, Proximal convoluted tubule, Loop of Henle, Distal convoluted tubule AND Collecting duct

Functions:
1. Filtration of blood
2. Reabsorption of useful substances
3. Secretion of wastes
4. Formation of urine
61. Explain the mode of nutrition in Amoeba..--

Answer: Amoeba shows holozoic nutrition:

1. Ingestion – Food engulfed using pseudopodia
2. Digestion – Enzymes break down food in food vacuole
3. Absorption – Nutrients absorbed into cytoplasm
4. Assimilation – Used for energy and growth
5. Egestion – Undigested food expelled
62. How is urine production controlled in humans?.(A)-

Answer: Urine production is regulated by:

• ADH hormone (controls water reabsorption)
• Blood volume and pressure
• Salt concentration in blood
63. Two animals P (85 ft) and Q (15 ft): where is digestion slow and fast? Why?.--

Answer: In animal P (85 ft): Digestion is slow – herbivore, cellulose digestion takes more time. Animal Q (15 ft) digestion is fast – carnivore, protein digestion is easier

83. Role of digestive enzymes:.(APR-2025)-

Enzyme	Function
Trypsin	Digests proteins into amino acids
Amylase	Breaks starch into maltose
Lipase	Digests fats into fatty acids and glycerol

64. Differences between autotrophic and heterotrophic nutrition..(A)

Autotrophs	Heterotrophs
Make own food	Depend on others
Use sunlight	Cannot photosynthesize
Example: Plants	Example: Animals

65.Schematic diagram of glucose breakdown..(A)-

Glucose(6C) ↓Pyruvate(3C) ↓Aerobic ↓CO₂+H₂O+Energy ( In the case of anaerobic → Lacticacid/Ethanol+Energy)

66.Two methods of excretion in plants
• Through stomata
• Storage in leaves/bark
b) Process transporting water upward.(MAY-2025)-

Answer: Transpiration pull

a) Steps of urine formation in humans.(A)-
1. Ultrafiltration
2. Selective reabsorption
3. Tubular secretion
b) Function of digestive juices

Juice	Function
Gastric juice	Protein digestion
Intestinal juice	Completes digestion

67. Ways parasites/heterotrophs obtain food (3 examples)
1. Holozoic – Amoeba
2. Saprophytic – Fungi
3. Parasitic – Tapeworm
68. First stage of cellular respiration & types of respiration.(APRIL-2022)-

Answer: (a) First stage of cellular respiration: In the cytoplasm, one molecule of glucose (6-carbon) is broken down into two molecules of pyruvate (3-carbon).
This process is called glycolysis and does not require oxygen.

(b) Types of respiration

• Aerobic respiration
• Anaerobic respiration
(c) Differences between aerobic and anaerobic respiration

Aerobic respiration	Anaerobic respiration
Occurs in presence of oxygen	Occurs in absence of oxygen
Releases more energy	Releases less energy

69. Elements required for photosynthesis, events & equation.--

Elements required

• Carbon dioxide
• Water
• Sunlight
• Chlorophyll

 Events in photosynthesis

1. Absorption of light energy by chlorophyll
2. Conversion of light energy into chemical energy
3. Splitting of water into hydrogen and oxygen
4. Reduction of carbon dioxide to glucose

Balanced chemical equation: 6CO₂+6H₂O→sunlight, chlorophyllC₆H₁₂O₆+6O₂

a) Comparison of xylem and phloem.(JUNE-2023)-

Xylem	Phloem
Transports water and minerals	Transports food
Movement is upward	Movement is both ways
Made of dead tissues	Made of living tissues

b) Gas exchange in plants through stomata: Stomata are tiny pores on leaf surfaces. Oxygen and carbon dioxide diffuse through stomata. Guard cells regulate opening and closing. Exchange occurs by diffusion based on concentration gradient. 70. Structure of human heart & blood transport

The human heart has four chambers, right side carries deoxygenated blood and left side carries oxygenated blood. A septum separates the chambers and prevents mixing.
Valves ensure one-way flow, enabling efficient transport.

b) Absorption of digested food & role of blood: digested food is absorbed through villi in the small intestine. Nutrients enter blood capillaries. Blood transports oxygen, nutrients, hormones, and waste to body cells.
71.Components of blood and their functions.--

Component	Function
Plasma	Transports nutrients, hormones, and waste materials
Red Blood Cells (RBC)	Carry oxygen with the help of haemoglobin
White Blood Cells (WBC)	Provide immunity and protect the body from infections
Platelets	Help in blood clotting to prevent blood loss

94. Role of haemoglobin pigment.(A): -Haemoglobin is a red pigment present in RBCs. Itbinds oxygen in the lungs. Transports oxygen to tissues. Releases oxygen for cellular respiration. Thus, haemoglobin plays a vital role in oxygen supply.

72.

a)Comparison: Alveoli and Nephron.--

Alveoli	Nephron
Found in lungs	Found in kidneys
Exchange of gases	Formation of urine
Thin-walled sacs	Tubular structure

b) Reason for muscle cramps: During continuous exercise, muscles undergo anaerobic respiration, producing lactic acid, which causes cramps. a) Anaerobic respiration.--

Anaerobic respiration is respiration without oxygen. In humans: Lactic acid + energy. In plants/yeast: Ethanol + CO₂ + energy

b) Double circulation & usefulness.(MAY-2025)-



Double circulation means blood passes twice through the heart in one cycle. It prevents mixing of blood and ensures efficient oxygen supply. It also supports high metabolism in birds and mammals

73. Advantages of terrestrial animals over aquatic animals.(A)-
• Air has more oxygen than water
• Less energy needed to obtain oxygen
• Faster respiration rate
• More efficient gas exchange
74.Design of lungs for maximum gas exchange

Answer: Human lungs have millions of alveoli, thin walls, rich blood supply and large surface area. These features allow rapid diffusion of oxygen and carbon dioxide.