NCERT Science Notes - Class 10
Chapter 5 - Life Processes

Welcome to AJs Chalo Seekhen. This webpage is dedicated to Class 10 | Science | Chapter 5 - Life Processes. The chapter delves into the intricacies of life as we unravel the essential processes that define living organisms. From respiration to growth, reproduction to response, and metabolism to organization, our comprehensive notes provide a deep understanding of the mechanisms that sustain life. Explore this enlightening chapter and unlock the secrets of vitality.

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NOTES

NCERT Science Notes - Class 10
Chapter 5 - Life Processes

    5.0 Introduction

    To differentiate between living and non-living entities, we often look for certain characteristics or evidence of life. Here are some common criteria used to determine if something is alive:

    1. Movement: Visible movement is a clear sign of life in many cases. For example, animals like dogs and cows exhibit noticeable movements, which indicate their vitality. However, as mentioned in your text, some organisms may not show visible movement, and microscopic movements at the molecular level are essential for life.
    2. Growth: The ability to grow and develop over time is another characteristic of living organisms. Plants, for instance, may not always exhibit visible movement, but they do grow, which is a sign of life.
    3. Breathing or Respiration: The process of respiration, where organisms exchange gases (like oxygen and carbon dioxide) with their environment, is a vital sign of life. Breathing may involve visible lung expansion and contraction in animals or cellular respiration in all living cells.
    4. Reproduction: Many living organisms have the ability to reproduce and create offspring, ensuring the continuation of their species. Reproduction is a fundamental characteristic of life.
    5. Response to Stimuli: Living organisms often respond to external stimuli, such as light, temperature changes, or touch. This responsiveness is known as irritability and is a sign of life.
    6. Metabolism: All living organisms have metabolic processes that involve chemical reactions to obtain energy, grow, and maintain their structures. These metabolic processes include digestion, circulation, and other cellular activities.
    7. Organization: Living organisms are highly organized, from cells to tissues to organs, ensuring that their structures function efficiently. Maintaining this organization is crucial for life.
    8. Homeostasis: Living organisms maintain internal stability through processes like temperature regulation and pH balance. This ability to keep a constant internal environment is essential for life.

    Regarding your mention of molecular movements, yes, molecular movement is essential for life, especially at the cellular level. Cells constantly undergo molecular movements to transport nutrients, eliminate waste, and carry out various biochemical processes necessary for survival. 

    Viruses, as you noted, are a unique case because they lack metabolic processes and cannot independently reproduce. Their status as living or non-living entities is a subject of debate among scientists.

    In summary, the characteristics of life involve a combination of visible and microscopic features, and the presence of one or more of these criteria can help determine whether an entity is alive or not.

    5.1 - What are Life Processes?

    Life processes are essential functions that maintain life in living organisms, whether they are actively doing something or at rest. These processes include:

    1. Nutrition: The process of transferring energy from outside the body to the inside. This involves obtaining food, which is typically carbon-based, and converting it into a form that the body can use. Different organisms have different nutritional processes depending on the complexity of their food sources.
    2. Respiration: This is the process of acquiring oxygen from outside the body and using it to break down food sources for cellular needs. It involves a series of chemical reactions, primarily oxidising-reducing reactions, to convert food into a uniform source of energy.
    3. Transportation: In multicellular organisms, not all cells are in direct contact with the environment, so a transportation system is necessary to carry food, oxygen, and waste products to and from different parts of the body.
    4. Excretion: This involves the removal and discarding of waste by-products from the body. In multicellular organisms, specialized tissues typically handle excretion, and the transportation system carries waste away from cells to these excretory tissues.

    In single-celled organisms, these processes are simpler because the entire surface of the organism is in contact with the environment, allowing direct exchange of materials. However, in multicellular organisms, the complexity increases due to the need for specialized tissues and systems to perform these life processes efficiently. These processes are vital for maintaining the structure and function of living organisms, and they require energy to occur.

    5.2 NUTRITION

    Nutrition in Organisms

    1. Energy Requirement: All organisms need energy for activities and maintaining bodily functions. This energy comes from food.
    2. Autotrophs: These organisms, like green plants and some bacteria, make their own food from simple inorganic substances (carbon dioxide and water) through photosynthesis.
    3. Heterotrophs: Animals and fungi belong to this group. They consume complex substances and break them down into simpler forms using enzymes. Their survival depends on autotrophs for food.
    4. Interdependence: Heterotrophs rely on autotrophs for their nutritional needs, highlighting an ecosystem's interconnected nature.

    Autotrophic Nutrition

    Autotrophs are organisms that can produce their own food using light, water, carbon dioxide, or other chemicals. Plants and some bacteria are common examples. The process they use is known as photosynthesis.

    Photosynthesis

    • Process: Photosynthesis is the process by which autotrophs convert carbon dioxide and water into carbohydrates in the presence of sunlight and chlorophyll.
    • Chemical Equation: The basic chemical equation for photosynthesis is:
    • This represents the conversion of carbon dioxide and water into glucose (C6​H12​O6) and oxygen.
    • Energy Storage: The carbohydrates produced are used for energy. Excess carbohydrates are often stored as starch in plants, similar to how humans store excess energy as glycogen.

    Steps in Photosynthesis

    1. Absorption of Light Energy by Chlorophyll: Chlorophyll in the chloroplasts of plant cells absorbs sunlight.

    2. Conversion of Light Energy to Chemical Energy: The absorbed light energy is used to split water molecules into hydrogen and oxygen.

    3. Reduction of Carbon Dioxide to Carbohydrates: The energy from step 2 is used to convert carbon dioxide into carbohydrates like glucose.

    Timing of Photosynthesis Steps

    • In some plants, like desert plants, these steps can occur at different times. For example, they might take up CO2 at night and process it during the day when sunlight is available.

    Chlorophyll and Chloroplasts

    • Chloroplasts are the cell organelles in plants where photosynthesis occurs. They contain chlorophyll, which is crucial for the process. Experiments can demonstrate that chlorophyll is essential for photosynthesis.

    Overview

    This detailed explanation of autotrophic nutrition, specifically through the process of photosynthesis, highlights the importance of autotrophs in the ecosystem. They not only provide their own energy but also serve as the primary producers in the food chain, supporting heterotrophs (like animals and fungi) that cannot produce their own food.

    Activity 5.1 : Summary

    1. Objective: To demonstrate starch production in leaves through photosynthesis.
    2. Procedure:
      • Use a variegated leaf plant (e.g., money plant, croton).
      • First, store the plant in darkness for three days to deplete starch.
      • Then, expose it to sunlight for about six hours.
      • Pluck a leaf, trace its green areas on paper, and note the color changes through the following steps:
        1.  Boil the leaf to kill it.
        2.  Immerse it in alcohol and heat in a water bath to remove chlorophyll.
        3.  Observe the color change in the leaf and the alcohol.
        4.  Soak the leaf in iodine solution, then rinse.
        5.  Compare the final leaf color to the initial tracing.
    3. Observation and Conclusion:
      • The experiment shows where starch is stored in the leaf, indicated by color changes due to the iodine test. This helps understand photosynthesis areas.

    4. Carbon Dioxide Uptake and Stomata Function

      • Stomata: Plants have tiny pores on their leaf surfaces called stomata, which are crucial for gas exchange, including the uptake of carbon dioxide necessary for photosynthesis.
      • Gaseous Exchange: While stomata are mainly found on leaves, gas exchange also occurs across the surfaces of stems and roots to a lesser extent.
      • Water Loss: Stomata also play a role in transpiration, which is the loss of water vapor from the plant. This can be significant, so plants have adapted to regulate it.
      • Guard Cells: The opening and closing of stomata are controlled by guard cells, which surround each stomatal pore. When guard cells take in water, they swell and open the pore, allowing gas exchange. When they lose water and shrink, the pore closes, reducing water loss and carbon dioxide exchange.

      This system allows the plant to balance its need for carbon dioxide for photosynthesis with the need to minimize water loss, especially in conditions where water is scarce or during times when photosynthesis is not occurring, such as at night.

    Activity 5.2 : Summary

      1. Objective: To show that carbon dioxide is needed for photosynthesis.
      2. Method:
        • Select two similar-sized healthy potted plants.
        • Store them in darkness for three days to deplete stored starch.
        • Place them on separate glass plates with a watch-glass containing potassium hydroxide next to one plant to absorb CO2.
        • Cover each plant with bell-jars sealed with vaseline to ensure an air-tight environment.
        • Expose to sunlight for about two hours.
        • Test a leaf from each plant for starch presence.
      3. Observations:
        • The leaf from the plant with potassium hydroxide (which absorbs CO2) should show less or no starch presence compared to the other plant.
      4. Conclusions:
        • Carbon dioxide is necessary for photosynthesis, as the plant without CO2 will not perform photosynthesis efficiently and thus, not produce starch.


      Designing an Experiment for Sunlight's Role in Photosynthesis

      Based on the above activities, an experiment to demonstrate the role of sunlight could be as follows:
      1. Take two similar-sized healthy potted plants and keep them in a dark room for three days.
      2. Cover one plant with a material that allows air but no light (a black bag or box) and leave the other exposed to sunlight.
      3. After a few hours, test leaves from both plants for starch.
      4. The plant exposed to sunlight should show starch presence, while the one kept in the dark should not, demonstrating that sunlight is essential for photosynthesis.


      Nutrient Uptake in Autotrophs

      Beyond energy requirements, autotrophs also absorb water and minerals from the soil for growth and maintenance:
      • Water: Absorbed through the roots and used in photosynthesis.
      • Minerals: Such as nitrogen, phosphorus, iron, and magnesium, are essential for synthesizing proteins and other compounds. Nitrogen is absorbed as inorganic nitrates or nitrites, or as organic compounds synthesized by bacteria from atmospheric nitrogen.

      5.2.2 - Heterotrophic Nutrition

      Definition: Heterotrophic nutrition is the mode of nutrition in which organisms rely on other living organisms for their food, as they cannot produce their own.

      Adaptation to Environment: Each organism is adapted to its environment, and the type of nutrition depends on:

      • The kind and availability of food
      • How food is obtained, such as whether it is stationary (e.g., grass) or mobile (e.g., a deer).
      Types of Heterotrophic Nutrition:
      1. Saprophytic Nutrition:
        • Some organisms, like fungi (e.g., bread moulds, yeast, mushrooms), break down food outside their bodies and then absorb the nutrients.
      2. Holozoic Nutrition:
        • In this method, organisms take in whole food material and break it down within their bodies.
        • The type of food ingested depends on the organism's body design and digestive system.
      3. Parasitic Nutrition:
        • Certain organisms, such as cuscuta (amar-bel), ticks, lice, leeches, and tapeworms, derive their nutrition from plants or animals without killing the host.
        • This strategy involves feeding on a host organism for sustenance without providing any benefit in return.

      5.2.3 - How Do Organisms Obtain Their Nutrition?

      Overview: The process of obtaining and digesting food varies across organisms, largely depending on their complexity and structure. In simple, single-celled organisms, food intake and digestion occur differently compared to multicellular organisms.

      Nutrition in Single-Celled Organisms:

      1. Amoeba:
        • Method of Food Intake: Uses temporary finger-like extensions of its cell surface called pseudopodia to engulf food.
        • Digestion: Forms a food vacuole around the food particle where complex substances are broken down into simpler ones.
        • Absorption: The digested nutrients diffuse into the cytoplasm.
        • Egestion: The remaining undigested material is expelled from the cell.
      2. Paramoecium:
        • Method of Food Intake: Has a definite shape with a specific spot for food intake.
        • Role of Cilia: Tiny hair-like structures (cilia) on the surface of the cell help move food to the designated spot for ingestion.
        • Digestion: Similar to Amoeba, digestion occurs within a food vacuole, where nutrients are absorbed, and waste is expelled.
      Summary: In unicellular organisms like Amoeba and Paramoecium, the entire cell surface or specific cell parts are adapted to obtain, digest, and absorb food. The complexity of digestion increases with the complexity of the organism's body structure.

      5.2.4 - Nutrition in Human Beings

      The Alimentary Canal: The human digestive system, or alimentary canal, is a long tube extending from the mouth to the anus, with different sections specialized for various functions involved in digestion and nutrient absorption.

      Process of Digestion: When food enters the body, it moves through the different parts of the alimentary canal, each performing a specific role in breaking down the food so that nutrients can be absorbed.


      Activity 5.3 - Investigating the Action of Saliva on Starch
      1. Materials Needed:
        • 1 mL of 1% starch solution
        • Two test tubes (A and B)
        • 1 mL saliva
        • Dilute iodine solution
      2. Procedure:
        • Pour 1 mL of starch solution into both test tubes, A and B.
        • Add 1 mL of saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes.
        • After the waiting period, add a few drops of dilute iodine solution to both test tubes.
      3. Observation:
        • Look for a color change in the test tubes after adding iodine solution.
      4. Results and Conclusion:
        • Color Change: Iodine reacts with starch to produce a blue-black color. If no starch is present, there will be no blue-black coloration.
        • Interpretation:
          • If test tube A does not change color while test tube B does, it indicates that saliva in test tube A has broken down the starch, showing that saliva contains enzymes (such as amylase) that act on starch.

      5.2.4 - Nutrition in Human Beings

      In humans, various types of food pass through the same digestive tract and are processed to ensure they become small, uniform particles. This is achieved by:

      1. Chewing: The food is crushed by teeth, and saliva from salivary glands moistens it, making it easier to swallow and digest.
      2. Saliva and Enzymes: Saliva contains the enzyme salivary amylase, which starts breaking down starch into simple sugars.
      3. Peristalsis: The rhythmic contraction of muscles along the alimentary canal, known as peristaltic movement, pushes the food forward.
      Path of Digestion:
      • Mouth to Stomach: After chewing, the food moves through the oesophagus to the stomach. In the stomach, gastric glands release:
        • Hydrochloric acid to create an acidic environment,
        • Pepsin to digest proteins,
        • Mucus to protect the stomach lining from the acid.
      • Stomach to Small Intestine: Food exits the stomach in small amounts through a sphincter muscle and enters the small intestine:
        • The liver secretes bile juice to neutralize the stomach acid and emulsify fats.
        • The pancreas releases pancreatic juice containing trypsin (for proteins) and lipase (for fats).
        • The small intestine’s walls release intestinal juice, which completes the digestion, converting proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol.
      • Absorption: The inner lining of the small intestine has finger-like structures called villi that absorb nutrients, which are then transported through blood vessels to cells for energy, tissue growth, and repair.
      • Large Intestine: Unabsorbed food moves into the large intestine, where water is absorbed. The remaining waste exits the body through the anus, regulated by the anal sphincter.

      Dental Caries

      Dental caries, or tooth decay, is the gradual softening of the enamel and dentine layers of the tooth. The process begins when bacteria act on sugars, producing acids that lead to enamel demineralization.

      • Formation of Plaque: Bacterial cells and food particles adhere to the teeth, forming a sticky layer known as dental plaque.
      • Effect on Saliva: Plaque prevents saliva from reaching the tooth surface, limiting its ability to neutralize acids and protect enamel.
      • Prevention: Brushing after meals helps remove plaque before bacteria can produce harmful acids.
      • If Left Untreated: The bacteria may reach the pulp of the tooth, leading to inflammation and infection.

      5.3 - Respiration

      Respiration is the process where cells utilize nutrients to release energy essential for life processes. Different organisms carry out respiration in various ways, often depending on the availability of oxygen.


      Activity 5.4: Observing Carbon Dioxide in Exhaled Air

      1. Fresh lime water is taken in a test tube.
      2. Air is blown through the lime water, causing it to turn milky, indicating the presence of carbon dioxide.
      3. A syringe or pichkari with fresh air is also used in another test tube with lime water to compare how long it takes to turn milky.
      Conclusion: This activity shows the higher concentration of carbon dioxide in exhaled air compared to regular air.


      Activity 5.5: Observing Fermentation by Yeast

      1. Add yeast to fruit juice or sugar solution in a test tube.
      2. Fit a bent glass tube to the cork, directing the other end into lime water.
      3. Observe the lime water as the fermentation produces carbon dioxide, which turns it milky.
      Conclusion: The milky change in lime water confirms that carbon dioxide is a product of fermentation.
      Types of Respiration
      1. Anaerobic Respiration:
        • Occurs in Absence of Oxygen: Takes place in organisms like yeast during fermentation.
        • Products: Ethanol and carbon dioxide.
        • Energy Output: Low energy release.
      2. Aerobic Respiration:
        • Occurs in Presence of Oxygen: Happens in the mitochondria of cells.
        • Products: Carbon dioxide and water.
        • Energy Output: High energy release, more than in anaerobic respiration.
      3. Lactic Acid Formation in Muscles:
        • Occurs in Low Oxygen Conditions: During intense physical activity, muscles may lack sufficient oxygen.
        • Product: Lactic acid, leading to muscle cramps.


      Role of ATP
      • ATP (Adenosine Triphosphate): Energy released from respiration is used to synthesize ATP.
      • Function: ATP stores and provides energy for cellular reactions, particularly endothermic reactions.

      More to Know About Respiration and ATP

      ATP (Adenosine Triphosphate):

      • ATP is often called the "energy currency" of the cell because it provides energy for most cellular processes.
      • Formation: During respiration, energy is used to convert ADP (Adenosine Diphosphate) and inorganic phosphate into ATP.
      • Energy Release: Breaking the terminal phosphate bond in ATP releases 30.5 kJ/mol of energy, which powers cellular functions.
      • Analogy: Like a battery powering various devices, ATP provides energy for processes like muscle contraction, protein synthesis, and nerve signal transmission.

      Gas Exchange in Plants and Animals
      1. In Plants:
        • Daytime: CO₂ from respiration is used in photosynthesis; oxygen is released.
        • Night: With no photosynthesis, CO₂ is expelled as the primary gas exchange.
        • Mechanism: Exchange of gases occurs through stomata and by diffusion, depending on environmental needs.
      2. In Animals:
        • Aquatic Organisms: Fish take in water through their mouths and pass it over gills, where blood absorbs dissolved oxygen. Due to lower oxygen levels in water, fish breathe more frequently than terrestrial animals.
        • Terrestrial Organisms: Animals on land breathe in atmospheric oxygen, which is absorbed by specific respiratory organs, such as lungs in humans. These organs maximize the surface area for efficient gas exchange.


      Activity 5.6: Observing Fish Respiration
      • Watch how fish coordinate their mouth and gill-slit movements, counting how often they open and close their mouths in a minute.
      • Compare this with human breathing rates.


      Human Respiratory System

      1. Pathway:
        • Nostrils: Air enters through the nostrils, where fine hairs and mucus filter it.
        • Throat: Air travels through the throat into the lungs.
        • Cartilage Rings: These rings keep the air passage open, preventing collapse.
      2. Function:
        • Structure: Respiratory organs in terrestrial animals are structured to increase surface area for gas exchange, with delicate surfaces placed inside the body for protection.
        • Mechanism: Special passages and mechanisms in the body move air in and out of the lungs, enabling oxygen absorption and carbon dioxide release efficiently.

      More to Know About the Effects of Tobacco and Smoking

      Harmful Effects of Tobacco:

      • Using tobacco products such as cigars, cigarettes, bidis, hookah, and gutkha can damage multiple organs, including the tongue, lungs, heart, and liver.
      • Health Risks: Both smoking and smokeless tobacco increase the risk of heart attacks, strokes, respiratory diseases, and various cancers, especially oral cancer due to chewing tobacco products like gutkha.
      • Prevention: Saying "NO" to tobacco is essential for maintaining good health and preventing these severe health issues.
      Impact of Smoking on the Respiratory System:
      • Cilia Damage: The upper respiratory tract has hair-like structures called cilia that filter out germs, dust, and harmful particles from the air we inhale. Smoking destroys these cilia, allowing harmful particles to enter the lungs, leading to infections, coughing, and even lung cancer.

      Structure and Function of the Lungs
      1. Alveoli:
        • The lungs contain tiny air sacs called alveoli, where the exchange of gases (oxygen and carbon dioxide) occurs. Alveoli are surrounded by blood vessels to facilitate gas transfer.
        • Mechanism: During inhalation, the ribs lift, and the diaphragm flattens, increasing the chest cavity’s volume, causing air to fill the expanded alveoli. Blood flowing around the alveoli absorbs oxygen and releases carbon dioxide.
      2. Breathing Cycle:
        • Residual Air: Lungs always retain a small amount of air, allowing continuous oxygen absorption and carbon dioxide release.
        • Respiratory Pigments: In larger animals, respiratory pigments are necessary to transport oxygen throughout the body. In humans, haemoglobin in red blood cells binds with oxygen, delivering it to tissues and organs efficiently.
      Interesting Facts:
      • The surface area of the alveoli in the lungs can cover about 80 m², far greater than the surface area of our skin, which maximizes the efficiency of gas exchange.
      • Without haemoglobin, if oxygen relied on simple diffusion, it would take three years for an oxygen molecule to reach the toes from the lungs, highlighting the efficiency of haemoglobin in oxygen transport.

      5.4 - TRANSPORTATION

      5.4.1 - Transportation in Human Beings

      Activity 5.7

      1. Haemoglobin Content:
        • Visit a health center to determine the normal haemoglobin range for human beings.
        • Compare haemoglobin levels across children, adults, men, and women.
      2. Animal Comparison:
        • Visit a veterinary clinic to check haemoglobin levels in animals like cows or buffaloes.
        • Compare levels in calves, male, and female animals.
        • Consider possible explanations for observed differences between male and female humans and animals.

      Transportation System in Humans

      Role of Blood in Transport:

      • Blood serves as a transport medium for food, oxygen, and waste products.
      • Blood, a fluid connective tissue, consists of plasma (a fluid medium) in which cells are suspended.
        • Plasma: Transports dissolved food, carbon dioxide, and nitrogenous wastes.
        • Red Blood Cells (RBCs): Carry oxygen to various tissues.
        • Other Components: Blood also transports salts and other essential substances.
      Circulatory System:
      • A pumping organ (heart) is needed to move blood throughout the body.
      • A network of blood vessels reaches all body tissues, supplying nutrients and oxygen while removing waste.
      • A repair system is essential to maintain the integrity of the blood vessel network if damaged.
      This system ensures continuous circulation, enabling all cells to receive essential nutrients and oxygen while waste products are effectively removed.

      Our Pump — The Heart

      The heart is a muscular organ, roughly the size of a fist, that pumps blood throughout the body. It ensures the circulation of oxygen-rich blood and carbon dioxide-rich blood without mixing the two, maintaining efficient oxygen delivery and carbon dioxide removal.


      Structure and Chambers of the Heart:

      • The heart is divided into four chambers: two upper chambers (atria) and two lower chambers (ventricles).
      • The left side of the heart handles oxygen-rich blood from the lungs, while the right side deals with deoxygenated blood from the body.


      Circulatory Process
      :
      1. Oxygenated Blood Pathway:
        • Left Atrium: Oxygen-rich blood from the lungs enters the left atrium.
        • Left Ventricle: The left atrium contracts, pushing blood into the left ventricle.
        • The left ventricle then contracts, pumping oxygenated blood to the entire body.
      2. Deoxygenated Blood Pathway:
        • Right Atrium: Deoxygenated blood returns from the body to the right atrium.
        • Right Ventricle: The right atrium contracts, transferring blood to the right ventricle.
        • The right ventricle pumps blood to the lungs, where carbon dioxide is removed, and oxygen is absorbed.


      Special Features
      :
      • Thick Muscular Walls: Ventricles have thicker walls than atria because they need to pump blood with greater force.
      • Valves: Valves between chambers prevent the backflow of blood, ensuring a one-way circulation when the heart chambers contract.
      This efficient structure and process allow the heart to sustain the vital exchange of gases, nutrients, and waste products essential for the body’s functions.


      Oxygen Enters the Blood in the Lungs

      The heart's separation into the right and left sides plays a crucial role in preventing the mixing of oxygenated and deoxygenated blood, which enhances the efficiency of oxygen supply to the body. This separation is particularly advantageous for animals with high energy demands, such as birds and mammals, which require a constant energy supply to maintain their body temperature.


      Heart Structures in Different Animals

      1. Mammals and Birds:
        • Four-Chambered Heart: They possess a four-chambered heart (two atria and two ventricles), ensuring complete separation of oxygen-rich blood from oxygen-poor blood.
        • Benefit: This allows for a highly efficient delivery of oxygen to the tissues, supporting their high metabolic rates.
      2. Amphibians and Some Reptiles:
        • Three-Chambered Heart: These animals have a three-chambered heart (two atria and one ventricle), allowing for some mixing of oxygenated and deoxygenated blood.
        • Adaptation: They can tolerate this mixing as their body temperature depends on the surrounding environment, reducing their overall energy requirements.
      3. Fish:
        • Two-Chambered Heart: Fish possess a simpler two-chambered heart (one atrium and one ventricle).
        • Circulation: Blood is pumped from the heart to the gills, where it is oxygenated before being distributed to the rest of the body. In this case, blood only passes through the heart once during each complete cycle of circulation.


      Double Circulation

      In vertebrates with four-chambered hearts (like mammals and birds), blood circulation is referred to as double circulation because:

      • Blood passes through the heart twice during each complete circuit through the body:
        • First Passage: Blood is pumped from the heart to the lungs for oxygenation (pulmonary circulation).
        • Second Passage: Oxygenated blood returns to the heart and is pumped to the rest of the body (systemic circulation).
      This efficient system ensures that tissues receive a continuous and adequate supply of oxygen, which is essential for sustaining high levels of activity and metabolic processes in these animals.


      Blood Pressure

      Definition: Blood pressure is the force exerted by circulating blood against the walls of blood vessels.


      Types of Blood Pressure

      1. Systolic Pressure:
        • This is the pressure in the arteries during ventricular systole, which is the contraction phase of the heart.
        • Normal Value: Approximately 120 mm of Hg.
      2. Diastolic Pressure:
        • This is the pressure in the arteries during ventricular diastole, which is the relaxation phase of the heart.
        • Normal Value: Approximately 80 mm of Hg.

      Measurement
      • Blood pressure is measured using a device called a sphygmomanometer.

      Significance of Blood Pressure
      • High Blood Pressure (Hypertension):
        • Hypertension is defined as elevated blood pressure, often resulting from the constriction of arterioles, leading to increased resistance to blood flow.
        • Potential Complications:
          • Can cause the rupture of arteries, resulting in internal bleeding.
          • Associated with increased risk of cardiovascular diseases, stroke, and other health issues.
      Summary: Maintaining normal blood pressure is crucial for overall health, as both high and low blood pressure can have significant effects on bodily functions and organ health. Regular monitoring is essential, especially for individuals at risk for hypertension.


      Blood Vessels

      Definition: Blood vessels are the network of tubes that transport blood throughout the body, playing a crucial role in the circulatory system.

      Types of Blood Vessels

      1. Arteries:
        • Function: Carry blood away from the heart to various organs.
        • Structure:
          • Have thick, elastic walls to withstand high pressure from the blood ejected by the heart.
          • The elasticity allows them to expand and contract as blood is pumped through.
      2. Veins:
        • Function: Collect blood from various organs and return it to the heart.
        • Structure:
          • Have thinner walls compared to arteries since the blood is under lower pressure.
          • Contain valves that ensure blood flows in only one direction, preventing backflow.
      3. Capillaries:
        • Function: Facilitate the exchange of materials (oxygen, nutrients, waste) between blood and surrounding cells.
        • Structure:
          • The smallest blood vessels with walls that are only one cell thick.
          • This thin structure allows for efficient diffusion of substances between blood and tissues.


      Blood Flow Process

      • As arteries transport blood away from the heart, they progressively branch into smaller vessels, eventually leading to capillaries where the exchange of materials occurs.
      • After passing through the capillaries, blood is collected by veins, which transport it back to the heart.

      Summary:
      The circulatory system's efficiency is largely due to the specialized structures of arteries, veins, and capillaries, ensuring that oxygen, nutrients, and waste products are effectively transported to and from tissues throughout the body.


      Maintenance by Platelets

      Definition: Platelets, or thrombocytes, are small, disc-shaped cell fragments in the blood that play a crucial role in hemostasis (the process of stopping bleeding).


      Function of Platelets

      • Clotting Mechanism: When there is an injury to a blood vessel, platelets are activated and quickly gather at the site of the leak. They perform the following functions:
        1. Adhesion: Platelets adhere to the exposed collagen fibers in the damaged blood vessel wall.
        2. Aggregation: Activated platelets release chemical signals that attract more platelets to the site, causing them to stick together and form a temporary "platelet plug."
        3. Coagulation Cascade: The aggregation of platelets initiates a complex series of reactions (coagulation cascade) that ultimately leads to the conversion of fibrinogen (a soluble plasma protein) into fibrin (an insoluble protein), forming a stable clot that seals the wound.

      Importance of Platelets
      • Minimizing Blood Loss: By plugging leaks, platelets help to minimize blood loss from the circulatory system during injuries.
      • Maintaining Blood Pressure: Preventing leakage ensures that blood pressure remains stable, allowing for efficient circulation and proper functioning of the cardiovascular system.
      SummaryPlatelets are vital components of the blood that prevent excessive bleeding by forming clots at injury sites, thereby maintaining the integrity of the circulatory system and ensuring efficient blood flow throughout the body.


      Lymph

      Definition: Lymph, also known as tissue fluid, is a clear, colorless fluid that is similar to blood plasma but contains fewer proteins and is found in the intercellular spaces of tissues.


      Formation of Lymph

      • Process: Lymph is formed when plasma, along with some proteins and blood cells, leaks through the pores in the walls of capillaries into the intercellular spaces, creating tissue fluid.
      • Components: While similar to blood plasma, lymph is colorless and has a lower concentration of proteins.

      Functions of Lymph

      1. Transportation of Substances:
        • Lymph carries digested and absorbed fats from the intestine. These fats are emulsified and transported as chyle, a milky fluid.
      2. Drainage of Excess Fluid:
        • Lymph plays a crucial role in draining excess fluid from the extracellular space back into the bloodstream, helping to maintain fluid balance in the body.
      3. Immune Function:
        • Lymph contains lymphocytes (a type of white blood cell) that are essential for the immune response, helping to fight infections and disease.

      Lymphatic System
      • Structure: Lymph drains into lymphatic capillaries, which are small vessels that collect lymph from the intercellular spaces.
      • Transportation: These capillaries converge to form larger lymphatic vessels that eventually open into larger veins, facilitating the return of lymph to the circulatory system.

      Summary:
      Lymph is an essential fluid involved in transportation within the body, contributing to nutrient absorption, fluid balance, and immune responses. It originates from plasma that leaks into tissue spaces and is collected by lymphatic vessels, ultimately returning to the bloodstream.


      5.4.2 - Transportation in Plants

      Plants require various raw materials for growth and energy, primarily absorbed through their roots from the soil. The transportation of these materials, along with energy, occurs through specialized tissues in the plant. Here’s an overview of the transportation systems in plants:


      Absorption of Raw Materials

      • Source: The soil serves as the nearest and richest source of raw materials such as nitrogen, phosphorus, and other minerals.
      • Process: Roots, which are in contact with the soil, absorb these essential nutrients and minerals.

      Diffusion Limitations
      • Short Distances: When the distances between soil-contacting organs (roots) and chlorophyll-containing organs (leaves) are short, nutrients and energy can diffuse easily throughout the plant.
      • Long Distances: As plants grow larger, diffusion alone becomes insufficient to transport materials over longer distances, necessitating a more efficient transport system.

      Energy Needs in Plants
      • Low Energy Requirements: Unlike animals, plants do not move and have a significant proportion of dead cells in many tissues, resulting in relatively low energy needs.
      • Transport Systems: Despite low energy needs, transport systems must operate over large distances, especially in tall trees.


      Transportation Tissues

      Plants have two main types of vascular tissues responsible for transportation:

      1. Xylem
        • Function: Transports water and minerals absorbed from the soil.
        • Direction of Flow: Moves upwards from the roots to the leaves.
        • Structure: Composed of specialized cells (tracheids and vessel elements) that facilitate the movement of water and minerals.
      2. Phloem
        • Function: Transports the products of photosynthesis (mainly sugars) from the leaves to other parts of the plant.
        • Direction of Flow: Can move both upwards and downwards, depending on the plant's needs.
        • Structure: Composed of sieve tube elements and companion cells, which help in the transport of nutrients.
      Summary: Plants have specialized transportation systems (xylem and phloem) that allow for the efficient movement of water, minerals, and photosynthetic products throughout their bodies. These systems are essential for sustaining plant growth and functioning, especially in larger plants where distances between organs are considerable.


      Transport of Water in Plants

      The transport of water in plants primarily occurs through xylem tissue, which consists of interconnected vessels and tracheids. This system facilitates the movement of water from the roots to the leaves and other parts of the plant. Here’s how the process works:

      Mechanism of Water Transport

      1. Continuous System: Xylem vessels and tracheids form a continuous network that extends from the roots, through the stems, and into the leaves, allowing for efficient water conduction.
      2. Active Ion Uptake:
        • Cells in the root, in contact with the soil, actively absorb ions (such as potassium, sodium, etc.) from the soil.
        • This ion uptake creates a concentration gradient, leading to a lower concentration of ions inside the root compared to the surrounding soil.
      3. Water Movement:
        • To balance this difference, water from the soil moves into the root through osmosis, creating a steady influx of water into the root xylem.
        • This influx generates a column of water that is pushed upwards through the xylem.
      4. Role of Transpiration:
        • Although root pressure helps move water upwards, it is often insufficient to reach the heights of tall plants.
        • Transpiration plays a crucial role in enhancing water movement. This process involves the evaporation of water from the stomata (small openings on leaves).
        • As water vapor escapes, it creates a suction effect that pulls water from the xylem in the roots up through the plant.
      5. Driving Forces:
        • During the night, root pressure can contribute to water transport.
        • During the day, when stomata are open for photosynthesis, transpiration pull becomes the dominant force, facilitating the upward movement of water.


      Activity 5.8: Observing Water Transport

      Objective: Compare the effects of transpiration in a potted plant and a stick.

      • Materials: Two small pots of the same size with equal amounts of soil; one pot contains a plant, and the other contains a stick of the same height.
      • Procedure:
        1. Cover the soil in both pots with a plastic sheet to prevent moisture loss through evaporation.
        2. Cover both pots (plant and stick) with plastic sheets and place them in bright sunlight for half an hour.
        3. Observe any differences between the two cases.
      Expected Observation:
      • The pot with the plant should show signs of moisture loss from the soil due to transpiration, whereas the pot with the stick will remain unchanged, demonstrating that transpiration is vital for water transport in plants.
      Summary: Water transport in plants occurs through xylem tissue via a combination of root pressure and transpiration. This system not only enables the upward movement of water and minerals but also plays a critical role in regulating plant temperature. Transpiration serves as a key mechanism by creating a suction effect, ensuring efficient water delivery throughout the plant.


      Transport of Food and Other Substances in Plants

      While we have discussed the transport of water and minerals through xylem, it's equally important to understand how plants transport the products of photosynthesis and other metabolic substances. This process is known as translocation, which occurs in the phloem.

      Key Aspects of Translocation

      1. Phloem Tissue:
        • The phloem is the vascular tissue responsible for transporting soluble products of photosynthesis (like sugars), amino acids, and other substances throughout the plant.
        • It delivers these substances primarily to storage organs such as roots, fruits, and seeds, as well as to actively growing tissues.
      2. Mechanism of Translocation:
        • Sieve Tubes and Companion Cells: Translocation occurs in sieve tubes, which are long tubular structures in the phloem. Adjacent companion cells assist in the process.
        • Unlike xylem transport, which relies on physical forces like pressure and osmosis, translocation in phloem requires energy, specifically from ATP (adenosine triphosphate).
      3. Energy Utilization:
        • For example, when sucrose (a type of sugar) is transported into the phloem tissue, energy from ATP is used to actively transport it.
        • This action increases the osmotic pressure within the phloem tissue, causing water to move in from surrounding cells. This results in a higher pressure in the phloem.
      4. Pressure Gradient:
        • The increase in osmotic pressure causes a movement of materials within the phloem from areas of higher pressure to areas of lower pressure.
        • This pressure-driven flow allows the phloem to distribute nutrients according to the plant's immediate needs.
      5. Seasonal Changes:
        • During different seasons, the direction of translocation can change. For instance, in spring, stored sugars in the roots or stems are transported to budding leaves, which require energy for growth.
        • This adaptability ensures that the plant can efficiently manage its resources throughout its growth cycle.
      Summary: Translocation is the process through which plants transport soluble products of photosynthesis and other substances via the phloem. This process involves the active transport of materials, driven by energy from ATP, leading to changes in osmotic pressure that facilitate the movement of substances to various parts of the plant. The phloem's ability to transport materials both upwards and downwards according to the plant's needs is essential for growth, storage, and overall health.


      5.5 - Excretion

      Excretion is the biological process through which organisms remove harmful metabolic wastes from their bodies. While gaseous wastes from photosynthesis or respiration can be eliminated easily, nitrogenous wastes generated from metabolic activities need to be specifically removed.

      5.5.1 - Excretion in Human Beings

      The excretory system in humans consists of:

      • Kidneys: A pair of organs located in the abdomen on either side of the backbone.
      • Ureters: Tubes that carry urine from the kidneys to the urinary bladder.
      • Urinary Bladder: Stores urine until it is expelled from the body.
      • Urethra: The tube through which urine is released from the bladder.


      Urine Production
      :
      • Urine is produced to filter waste products from the blood, primarily nitrogenous wastes such as urea or uric acid.
      • Each kidney contains a large number of filtration units called nephrons. The filtration process occurs in a structure called Bowman’s capsule, which surrounds a cluster of thin-walled blood capillaries.
      • As the initial filtrate (containing glucose, amino acids, salts, and water) flows through the nephron, selective reabsorption occurs, allowing the body to reclaim needed substances and water.
      • The volume of water reabsorbed depends on the body’s hydration status and the concentration of dissolved waste.
      • Urine produced in the kidneys travels down the ureters to the urinary bladder, where it is stored until excretion.


      Control of Urination
      :
      • The urinary bladder is muscular and is under nervous control, allowing for voluntary regulation of urination.
      Artificial Kidney (Hemodialysis)In cases of kidney failure—due to infections, injury, or restricted blood flow—an artificial kidney can be utilized to perform dialysis. This device works as follows:
      • It contains tubes with a semi-permeable lining, immersed in a tank of dialysing fluid that has the same osmotic pressure as blood but lacks nitrogenous wastes.
      • The patient’s blood passes through these tubes, allowing waste products to diffuse into the dialysing fluid.
      • The purified blood is then returned to the patient. Unlike natural kidney function, this process does not involve reabsorption.
      On average, a healthy adult’s kidneys filter about 180 liters of fluid daily, but only 1 to 2 liters are excreted as urine due to reabsorption.


      Think it Over! 

      Organ Donation is a noble act of giving an organ to someone in need, often due to organ failure caused by disease or injury. Key points include:

      • Consent: Organ donation typically requires the consent of the donor and their family.
      • Eligibility: Anyone can become a donor, regardless of age or gender.
      • Types of Donations: Commonly donated organs include kidneys, corneas, heart, liver, pancreas, lungs, intestines, and bone marrow.
      • Timing: Most donations occur posthumously, but certain organs (like a kidney or part of the liver) can be donated while the donor is alive.
      • Impact: Organ transplants can save lives and significantly improve the quality of life for recipients.


      5.5.2 - Excretion in Plants

      Plants utilize distinct strategies for excretion compared to animals. Key points regarding plant excretion include:

      • Oxygen as Waste: Oxygen is produced as a byproduct of photosynthesis and can be considered a waste product that plants release into the atmosphere.
      • Transpiration: Excess water is eliminated through the process of transpiration, where water vapor is released from the plant's aerial parts, primarily through small openings called stomata.
      • Utilization of Dead Cells: Many plant tissues are composed of dead cells, which can serve as storage sites for waste products. Plants can also shed parts of themselves, such as leaves, to remove waste.
      • Storage of Waste Products: Waste materials are often stored in cellular vacuoles, which are compartments within plant cells.
      • Gums and Resins: Some waste products are stored in the form of resins and gums, particularly in older xylem tissues.
      • Excretion into Soil: Plants can also release certain waste substances into the surrounding soil, contributing to nutrient cycling.
      These strategies help plants manage waste without the specialized organs found in animals, allowing them to efficiently cope with metabolic byproducts.

      CBSE Class 10 | Science | Chapter 5 - Life Processes


      CBSE Class 10 | Science | Chapter 5 - Life Processes

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