Life Processes Class 10 Science Chapter 5 Notes

Life Processes Class 10 Science Chapter 5 Notes are available here. Our team of subject experts has created these notes to assist you in understanding the concepts in the chapter.

Life Processes Class 10 Science Chapter 5 Notes

Introduction

• Distinguishing between living and non-living entities involves observing movement.
• Breathing is a common indicator of life, but not all life exhibits visible movement.
• Movement at molecular levels is crucial for life, even though it may not be visible to the naked eye.
• Viruses, lacking molecular movement until they infect a cell, pose a challenge to the definition of life.
• Living organisms require continuous maintenance and repair of their organized structures to remain alive.
• Maintenance of these structures involves constant movement of molecules within living organisms.

Life Processes

• Living organisms require ongoing maintenance even during periods of inactivity.
• Maintenance activities are collectively referred to as life processes.
• Maintenance processes require energy to prevent damage and breakdown.
• Energy for these processes comes from external sources, usually food.
• Nutrition is the process of transferring energy and raw materials from outside the organism to the inside.
• Organisms may require additional raw materials from outside to support growth.
• Carbon-based molecules are essential for life on Earth, and most food sources are carbon-based.
• Different organisms use different nutritional processes depending on the complexity of carbon sources.
• External energy sources vary due to the uncontrollable nature of the environment.
• Energy from external sources must undergo breakdown or synthesis within the organism.
• The converted energy serves the purpose of fueling molecular movements for maintaining living structures and supporting growth.
• Chemical reactions, particularly oxidizing-reducing reactions, are vital for breaking down molecules.
• Many organisms utilize oxygen from outside the body for these chemical reactions.
• The process of acquiring oxygen and utilizing it in breaking down food sources for cellular needs is known as respiration.
• Single-celled organisms rely on their entire surface for interactions with the environment, eliminating the need for specific organs for food intake, gas exchange, or waste removal.
• As organisms grow larger and become more complex, with multiple cells, direct contact between all cells and the environment is not possible.
• Consequently, simple diffusion cannot adequately fulfill the needs of all cells in multicellular organisms.
• Multicellular organisms have specialized body parts for various functions.
• Specialized tissues are responsible for functions like food and oxygen uptake.
• Food and oxygen are taken up at specific locations in the organism’s body, but all parts require them.
• This situation necessitates a transportation system to carry food and oxygen from uptake sites to all parts of the body.
• Chemical reactions involving carbon sources and oxygen for energy production produce waste by-products.
• These waste by-products are useless or potentially harmful to the cells and must be removed from the body.
• The removal process is called excretion.
• In multicellular organisms, specialized tissues for excretion develop according to basic body design rules.
• The transportation system must carry waste from cells to specialized excretory tissues.

Nutrition

• Energy is expended during activities such as walking or cycling.
• Even during periods of apparent inactivity, energy is required to maintain bodily order.
• External materials are necessary for growth, development, and synthesis of essential substances in the body.
• Food serves as the primary source of energy and materials for the body.
• All organisms require energy and materials for survival and growth.
• Different organisms fulfill these requirements in various ways.
• Autotrophs, such as green plants and some bacteria, use simple inorganic sources like carbon dioxide and water for food.
• Heterotrophs rely on complex substances that need to be broken down into simpler forms before use.
• Enzymes act as bio-catalysts to facilitate the breakdown of complex substances in heterotrophs.
• Heterotrophic organisms, including animals and fungi, depend directly or indirectly on autotrophs for their survival.

Autotrophic Nutrition

• Autotrophic organisms fulfill their carbon and energy requirements through photosynthesis.
• Photosynthesis involves taking in carbon dioxide and water from the outside and converting them into carbohydrates in the presence of sunlight and chlorophyll.
• Carbohydrates produced are utilized by the plant for providing energy.
• Excess carbohydrates are stored in the form of starch as an internal energy reserve.
• Stored energy in the form of glycogen is also observed in humans, derived from the food we eat.
• Photosynthesis involves several key steps: (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy into chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.
• These steps may not occur immediately one after the other. For instance, desert plants take up carbon dioxide at night and prepare an intermediate compound that undergoes further processing during the day.
• Chlorophyll, found in chloroplasts within plant cells, is crucial for photosynthesis.
• The activity involves demonstrating the essential role of chlorophyll in photosynthesis, which can be observed by examining a leaf cross-section under a microscope.
• Stomata are small pores found on the surface of leaves, facilitating significant gaseous exchange for photosynthesis.
• Gas exchange also occurs across the surfaces of stems, roots, and leaves.
• Stomata can lead to significant water loss, so plants close these pores when they don’t need carbon dioxide for photosynthesis.
• The opening and closing of stomatal pores are regulated by guard cells.
• When water flows into guard cells, they swell, causing stomatal pores to open.
• Conversely, when guard cells shrink, the stomatal pores close.

Heterotrophic Nutrition

• Organisms are adapted to their environments, influencing their nutritional strategies.
• The type and availability of food material, as well as how it’s obtained, determine an organism’s nutritional approach.
• Differences in accessing food arise based on whether the food source is stationary (like grass) or mobile (like a deer), impacting the nutritive apparatus used.
• Various strategies exist for food intake and utilization by organisms.
• Some organisms externally break down food material before absorbing it, as seen in fungi like bread molds, yeast, and mushrooms.
• Others ingest whole material and break it down internally, depending on their body design and functioning.
• Some organisms derive nutrition from plants or animals without killing them, known as parasitic nutritive strategy, utilized by organisms like cuscuta (amar-bel), ticks, lice, leeches, and tapeworms.

How do Organisms obtain their Nutrition?

• The digestive system varies among organisms due to differences in food type and acquisition.
• In single-celled organisms, such as Amoeba, food may be ingested through the entire surface.
• As organism complexity increases, different parts become specialized for different functions.
• Amoeba uses temporary finger-like extensions of the cell surface to take in food, which forms a food vacuole.
• Inside the food vacuole, complex substances are broken down into simpler ones that diffuse into the cytoplasm.
• Undigested material is expelled from the cell surface.
• In Paramoecium, another unicellular organism, food is ingested at a specific spot facilitated by the movement of cilia covering the cell’s surface.

Nutrition in Human Beings

• Food consumed must pass through the digestive tract, which processes it into small, uniform particles.
• This processing involves crushing food with teeth and wetting it with saliva for smooth passage.
• Saliva, secreted by salivary glands, aids in food digestion and lubrication.
• Saliva contains enzymes like salivary amylase, which breaks down complex starch molecules into simple sugars.
• The tongue assists in mixing food thoroughly with saliva and moving it around the mouth during chewing.
• Food must be moved in a regulated manner along the digestive tract for proper processing.
• Muscles in the lining of the digestive canal contract rhythmically to push food forward.
• These rhythmic contractions, known as peristaltic movements, occur throughout the digestive tract.
• Food travels from the mouth to the stomach through the esophagus or food pipe.
• The stomach is a large organ that expands upon food entry.
• Muscular walls of the stomach aid in thoroughly mixing food with digestive juices.
• Digestion in the stomach is facilitated by gastric glands located in the stomach wall.
• Gastric glands release hydrochloric acid, pepsin (a protein-digesting enzyme), and mucus.
• Hydrochloric acid creates an acidic environment that aids pepsin’s action.
• The mucus secreted by gastric glands protects the stomach’s inner lining from the acidic environment.
• Acid reflux or heartburn, commonly referred to as ‘acidity’, is a common complaint among adults.
• The exit of food from the stomach is regulated by a sphincter muscle, releasing it in small amounts into the small intestine.
• The small intestine is the longest part of the alimentary canal and is compactly coiled to fit into a confined space.
• The length of the small intestine varies among animals based on their diet.
• Herbivores, such as grass-eating animals, require a longer small intestine to digest cellulose effectively.
• Carnivores, like tigers, have a shorter small intestine because meat is easier to digest.
• The small intestine is where complete digestion of carbohydrates, proteins, and fats occurs.
• Secretions from the liver and pancreas aid in digestion in the small intestine.
• Bile juice from the liver alkalizes acidic stomach contents for pancreatic enzyme action and acts on fats.
• Bile salts emulsify fats, breaking them into smaller globules for more efficient enzyme action, similar to the emulsifying action of soaps.
• Pancreatic juice contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.
• Glands in the walls of the small intestine secrete intestinal juice containing enzymes that convert proteins into amino acids, complex carbohydrates into glucose, and fats into fatty acids and glycerol.
• Digested food is absorbed by the walls of the intestine.
• The inner lining of the small intestine contains numerous finger-like projections called villi, which increase the surface area for absorption.
• Villi are densely supplied with blood vessels, facilitating the transport of absorbed nutrients to every cell of the body.
• Absorbed nutrients are utilized by cells for energy, building new tissues, and repairing old tissues.
• Unabsorbed food enters the large intestine, where its walls absorb more water from the material.
• The remaining material, now waste, is expelled from the body through the anus.
• The exit of waste material is controlled by the anal sphincter.

Dental Caries

• Dental caries, or tooth decay, results in the gradual softening of enamel and dentine.
• Bacteria act on sugars, producing acids that demineralize the enamel, initiating decay.
• Dental plaque forms when bacterial cells and food particles adhere to teeth.
• Plaque prevents saliva from neutralizing acid on tooth surfaces.
• Brushing teeth after eating helps remove plaque before bacteria produce acids.
• Untreated decay can lead to microorganisms invading the pulp, causing inflammation and infection.

Respiration

• Nutrition provides food material used by cells to generate energy for various life processes.
• Different organisms utilize different pathways for energy production, some involving oxygen (aerobic) and others not (anaerobic).
• The initial step in both aerobic and anaerobic respiration is the breakdown of glucose into pyruvate in the cytoplasm.
• Anaerobic respiration occurs in the absence of oxygen and may result in the conversion of pyruvate into ethanol and carbon dioxide, as seen in yeast during fermentation.
• Aerobic respiration occurs in the presence of oxygen, taking place in the mitochondria, where pyruvate is broken down into carbon dioxide and water.
• Aerobic respiration yields significantly more energy compared to anaerobic respiration.
• In the absence of sufficient oxygen in muscle cells, pyruvate may be converted into lactic acid through another pathway, causing muscle cramps during strenuous activity.
• Energy released during cellular respiration is utilized to synthesize ATP (adenosine triphosphate), a molecule used to fuel all cellular activities.
• ATP is broken down during cellular processes, releasing a fixed amount of energy that drives endothermic reactions occurring within the cell.
• Aerobic organisms rely on oxygen for aerobic respiration.
• Plants exchange gases through stomata and large intercellular spaces, ensuring all cells are in contact with air.
• Carbon dioxide and oxygen are exchanged by diffusion, with direction depending on environmental conditions and plant requirements.
• At night, when photosynthesis doesn’t occur, carbon dioxide elimination is the major exchange activity.
• During the day, carbon dioxide generated during respiration is used for photosynthesis, resulting in oxygen release as the major event.
• Animals have evolved different organs for oxygen uptake and carbon dioxide elimination.
• Terrestrial animals can breathe oxygen from the atmosphere.
• Animals living in water need to extract oxygen dissolved in water for respiration.
• Dissolved oxygen levels in water are lower than in the air, requiring aquatic organisms to have faster breathing rates.
• Aquatic organisms, like fish, take in water through their mouths and force it past their gills.
• Oxygen dissolved in water is absorbed by the blood in the gills.
• Terrestrial organisms use atmospheric oxygen for respiration.
• Different animals have organs adapted for oxygen absorption, all with structures increasing the surface area in contact with oxygen.
• The surface for gas exchange is delicate and protected within the body, requiring passages for air to reach it.
• Mechanisms exist for moving air in and out of the area where oxygen is absorbed.
• In humans, air enters the body through the nostrils, where it is filtered by fine hairs and mucus.
• The air then moves through the throat and into the lungs.
• Rings of cartilage in the throat prevent the collapse of the air passage.
• The passage within the lungs divides into smaller tubes, eventually leading to balloon-like structures called alveoli.
• Alveoli provide a surface for gas exchange, containing an extensive network of blood vessels.
• Breathing involves lifting the ribs, flattening the diaphragm, and expanding the chest cavity, allowing air to be sucked into the lungs and fill the alveoli.
• Carbon dioxide from the body is transported to the alveoli, while oxygen in the alveolar air is absorbed by blood vessels for distribution to body cells.
• During the breathing cycle, the lungs maintain a residual volume of air to ensure sufficient time for gas exchange.
• In larger animals, diffusion pressure alone cannot adequately deliver oxygen to all body parts.
• Respiratory pigments, such as hemoglobin in humans, bind with oxygen in the lungs and transport it to oxygen-deficient tissues before releasing it.
• Hemoglobin, present in red blood corpuscles, has a high affinity for oxygen.
• Carbon dioxide, more soluble in water than oxygen, is primarily transported in dissolved form in blood.
• The surface area of the alveolar surface is approximately 80 m², providing a large area for gas exchange.
• The efficiency of gas exchange is enhanced by the large surface area available for exchange to occur.
• Diffusion alone would take approximately 3 years for a molecule of oxygen to reach our toes from our lungs.
• The presence of hemoglobin facilitates efficient oxygen transport, significantly speeding up the process compared to diffusion alone.

ATP

• ATP serves as the primary energy currency for most cellular processes.
• Energy released during respiration is used to convert ADP (adenosine diphosphate) and inorganic phosphate into ATP.
• Endothermic processes within the cell utilize ATP to drive reactions.
• When the terminal phosphate linkage in ATP is hydrolyzed with water, releasing energy equivalent to 30.5 kJ/mol.
• ATP functions similarly to a battery, providing energy for various cellular activities such as muscle contraction, protein synthesis, and nerve impulse conduction.

Smoking

• Smoking is harmful to health.
• Lung cancer is a common cause of death worldwide.
• The upper respiratory tract has small hair-like structures called cilia.
• Cilia help remove germs, dust, and other harmful particles from inhaled air.
• Smoking destroys these cilia, allowing harmful substances to enter the lungs and cause infection, coughing, and potentially lung cancer.

Transportation in Human Beings

• Blood serves as a transport medium for food, oxygen, and waste materials in the body.
• Blood is a fluid connective tissue consisting of plasma and suspended cells.
• Plasma transports food, carbon dioxide, and nitrogenous wastes in dissolved form.
• Oxygen is carried by red blood corpuscles.
• Blood also transports many other substances like salts.
• The body requires a pumping organ to push blood around the body, a network of tubes to reach all tissues, and a system for repairing this network if damaged.

Heart

• The heart is a muscular organ approximately the size of a fist.
• The heart has different chambers to prevent the mixing of oxygen-rich blood with blood containing carbon dioxide.
• Carbon dioxide-rich blood must reach the lungs for carbon dioxide removal, while oxygenated blood from the lungs is returned to the heart.
• Oxygen-rich blood is pumped from the heart to the rest of the body.
• Oxygen-rich blood from the lungs enters the thin-walled upper chamber of the heart on the left, known as the left atrium.
• The left atrium relaxes to collect blood, then contracts to transfer it to the next chamber, the left ventricle.
• The left ventricle contracts to pump oxygen-rich blood out to the body.
• Deoxygenated blood from the body enters the upper chamber on the right, the right atrium, as it relaxes.
• As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates to receive blood.
• The right ventricle pumps deoxygenated blood to the lungs for oxygenation.
• Ventricles have thicker muscular walls than the atria because they pump blood into various organs.
• Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Blood In The Lungs

• The separation of the right and left sides of the heart prevents oxygenated and deoxygenated blood from mixing.
• This separation allows for a highly efficient supply of oxygen to the body, particularly in animals with high energy needs like birds and mammals.
• Animals that maintain body temperature through energy use typically have four-chambered hearts.
• Animals whose body temperature depends on the environment, such as amphibians or many reptiles, often have three-chambered hearts and tolerate some mixing of oxygenated and deoxygenated blood.
• Fish have two-chambered hearts, where blood is pumped to the gills for oxygenation and then directly to the body, resulting in blood passing through the heart only once during each cycle through the body.
• Other vertebrates, including birds and mammals, have double circulation, where blood passes through the heart twice during each cycle.

Blood Vessels

• Arteries carry blood away from the heart to various organs of the body.
• Arteries have thick, elastic walls to withstand the high pressure of blood emerging from the heart.
• Veins collect blood from different organs and bring it back to the heart.
• Veins have valves to ensure one-way flow of blood, as blood is no longer under pressure.
• Arteries divide into smaller vessels to reach individual cells within organs or tissues.
• The smallest vessels, called capillaries, have thin walls (one-cell thick) where exchange of materials between blood and surrounding cells occurs.
• Capillaries join together to form veins that carry blood away from organs or tissues.

Platelets

• The system of blood vessels functions like a network of tubes in the body.
• Injuries or leaks in this system can lead to bleeding, which must be minimized.
• Leakage would reduce pressure, diminishing the efficiency of the heart’s pumping.
• Platelet cells circulate in the blood and help to clot blood at points of injury.
• Platelets plug leaks in blood vessels, preventing excessive bleeding and maintaining pressure.

Lymph

• Lymph, also known as tissue fluid, plays a role in transportation in the body.
• Plasma, proteins, and blood cells escape from capillaries into intercellular spaces to form lymph.
• Lymph is similar to blood plasma but is colorless and contains fewer proteins.
• Lymph drains into lymphatic capillaries and then into larger lymph vessels.
• Lymphatic vessels eventually open into larger veins, returning lymph back to the bloodstream.
• Lymph carries digested and absorbed fat from the intestine and drains excess fluid from the extracellular space back into the blood.

Transportation in Plants

• Plants absorb raw materials such as nitrogen, phosphorus, and minerals from the soil.
• Absorption of these substances happens through the roots, which are in contact with the soil.
• Energy stored in chlorophyll-containing organs, like leaves, is generated through photosynthesis.
• When the distances between soil-contacting organs (roots) and chlorophyll-containing organs (leaves) are small, diffusion can effectively transport energy and raw materials.
• If these distances become large due to changes in plant body design, diffusion processes may not be sufficient.
• In such cases, a proper transportation system becomes essential to ensure the distribution of raw materials and energy throughout the plant body.
• Plants have different energy needs compared to animals due to their stationary nature.
• Plant bodies contain a large proportion of dead cells in many tissues.
• Plants have relatively low energy needs compared to animals.
• Plant transport systems can operate relatively slowly due to their lower energy requirements.
• Despite lower energy needs, tall trees may require efficient transport systems due to the large distances over which they operate.
• Plant transport systems move energy stores from leaves and raw materials from roots.
• Two independently organized conducting tubes are involved in this process.
• Xylem transports water and minerals obtained from the soil.
• Phloem transports products of photosynthesis from leaves to other parts of the plant.

Transport Of Water In Plants

• Xylem tissue consists of interconnected vessels and tracheids in roots, stems, and leaves, forming a continuous system of water-conducting channels.
• Cells in contact with the soil at the roots actively take up ions, creating a concentration gradient between the root and the soil.
• Water moves into the root from the soil to equalize this ion concentration difference.
• This creates a steady movement of water into the root xylem, forming a column of water pushed upwards.
• Plant use additional strategies to move water in the xylem upwards to reach the highest points of the plant body.
• Water lost through stomata is replaced by water from xylem vessels in the leaf.
• Evaporation of water molecules from leaf cells creates suction, pulling water from xylem cells in roots.
• The loss of water in the form of vapor from aerial parts of the plant is termed transpiration.
• Transpiration aids in the absorption and upward movement of water and minerals from roots to leaves.
• Transpiration helps regulate temperature.
• Root pressure is more significant in water transport at night.
• During the day, when stomata are open, transpiration pull becomes the primary driving force for water movement in the xylem.

Transport Of Food And Other Substances In Plants

• Translocation is the transport of soluble products of photosynthesis from leaves to other parts of the plant.
• Translocation occurs in the phloem, a part of the vascular tissue.
• Besides photosynthesis products, phloem transports amino acids and other substances.
• Substances transported by phloem are delivered to storage organs like roots, fruits, seeds, and growing organs.
• Translocation in sieve tubes involves adjacent companion cells aiding in both upward and downward directions.
• Translocation in phloem involves the utilization of energy.
• Sucrose is transferred into phloem tissue using energy from ATP.
• This process increases the osmotic pressure of the tissue, causing water to move into it.
• The pressure generated moves the material in the phloem to tissues with lower pressure.
• Phloem can transport material according to the plant’s needs, such as transferring stored sugar to buds in spring for growth.

Excretion

• Excretion is the biological process of removing harmful metabolic wastes from the body.
• Gaseous wastes generated during photosynthesis or respiration are eliminated through various mechanisms.
• Nitrogenous materials produced during metabolic activities also need to be removed.
• Different organisms employ varied strategies for excretion.
• Unicellular organisms typically remove wastes by simple diffusion from the body surface into surrounding water.
• Complex multicellular organisms utilize specialized organs to perform excretory functions.

Excretion in Human Beings

• The human excretory system comprises kidneys, ureters, urinary bladder, and urethra.
• Kidneys are positioned in the abdomen, one on each side of the backbone.
• Urine formed in the kidneys travels through the ureters to the urinary bladder.
• The urinary bladder stores urine until it’s expelled through the urethra.
• Urine production involves filtering waste products from the blood.
• Similar to how CO2 is removed from the blood in the lungs, nitrogenous waste like urea or uric acid is removed in the kidneys.
• The basic filtration unit in the kidneys, like in the lungs, consists of thin-walled blood capillaries.
• Each capillary cluster in the kidney is associated with Bowman’s capsule, a coiled tube that collects the filtrate.
• Each kidney contains numerous filtration units called nephrons.
• Nephrons selectively reabsorb substances like glucose, amino acids, salts, and water from the initial filtrate.
• The amount of water reabsorbed depends on the body’s water balance and the quantity of dissolved waste to be excreted.
• Urine from each kidney enters the ureter, a long tube connecting the kidneys to the urinary bladder.
• Urine is stored in the urinary bladder until pressure from its expansion triggers the urge to urinate.
• The urinary bladder is muscular and under nervous control, allowing us to control the urge to urinate.

Artificial kidney (Hemodialysis)

• Kidneys are crucial for survival.
• Various factors such as infections, injury, or restricted blood flow can impair kidney function.
• Reduced kidney activity leads to the buildup of poisonous wastes in the body.
• This accumulation can potentially result in death.
• In cases of kidney failure, artificial kidneys can be employed.
• Artificial kidneys function by removing nitrogenous waste products from the blood through dialysis.
• Artificial kidneys consist of tubes with a semi-permeable lining in a tank filled with dialysing fluid.
• The dialysing fluid matches blood osmotic pressure but lacks nitrogenous wastes.
• Patient’s blood is circulated through these tubes, allowing waste products to diffuse into the dialysing fluid.
• Purified blood is returned to the patient, mimicking kidney function without reabsorption.
• In healthy adults, kidneys initially filter about 180 liters of fluid daily, but only a liter or two is excreted due to tubular reabsorption.

Excretion in Plants

• Plants employ different excretion strategies compared to animals.
• Oxygen, a byproduct of photosynthesis, can be considered a waste product for plants.
• Plants eliminate excess water through transpiration.
• Many plant tissues contain dead cells, allowing them to shed parts like leaves to discard waste.
• Plant waste products are often stored in cellular vacuoles or in leaves that fall off.
• Resins and gums, particularly in old xylem, serve as storage for waste products.
• Some waste substances are excreted into the surrounding soil by plants.