Biology PDF - Gaseous Exchange in Plants and Humans

Summary

This document covers gaseous exchange in plants and humans, including the processes of photosynthesis and respiration, the role of stomata, and different respiratory disorders such as bronchitis, emphysema, and pneumonia.

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12/1/2024 LEARN WITH ME [BIOLOGY] HAMZA AND UMAIR [PARADOX] [BIOLOGY] [PARADOX] [CLASS] -:GASEOUS EXCHANGE:- -:CH-1:- -:INTRODUCTION:- Gaseous exchange...

12/1/2024 LEARN WITH ME [BIOLOGY] HAMZA AND UMAIR [PARADOX] [BIOLOGY] [PARADOX] [CLASS] -:GASEOUS EXCHANGE:- -:CH-1:- -:INTRODUCTION:- Gaseous exchange is the biological process by which oxygen and carbon dioxide are exchanged between an organism and its environment. This process is essential for respiration, which provides energy to cells. GASEOUS EXCHANGE IN PLANTS Gaseous exchange in plants is the process where they exchange oxygen (O₂) and carbon dioxide (CO₂) with the air. This process happens mainly through stomata, which are tiny openings on the surface of leaves, and sometimes through pores called lenticels on stems. 1 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] When and How Does It Happen? 1. During the Day (Photosynthesis): Plants perform photosynthesis in the presence of sunlight. They take in carbon dioxide (CO₂) from the air through stomata. This CO₂ is used to produce glucose (food) and oxygen (O₂) is released as a byproduct. This means during the day, plants take in CO₂ and release O₂. 2. At Night (Respiration): In the absence of sunlight, photosynthesis stops. Plants carry out respiration to get energy from stored food. During respiration, plants take in oxygen (O₂) and release carbon dioxide (CO₂), just like animals. At night, plants take in O₂ and release CO₂. 2 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] How Does Gaseous Exchange Occur? Stomata: o These are small pores on the surface of leaves. They can open and close to control the exchange of gases. o Guard cells around the stomata control their opening and closing, depending on the time of day and environmental conditions. Diffusion: o The movement of gases happens naturally through diffusion, where gases move from an area of high concentration to low concentration. Importance of Gaseous Exchange: It provides the CO₂ needed for photosynthesis to make food for the plant. It allows plants to get O₂ for respiration, which releases energy for growth and survival. It maintains the balance of oxygen and carbon dioxide in the atmosphere. 3 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Feature Photosynthesis Respiration Purpose To make food (glucose). To release energy. Only plants, algae, and Occurs In All living organisms. some bacteria. Time Only in the daytime. All the time. Uses CO₂, H₂O, sunlight. Glucose and O₂. Produces Glucose and O₂. Energy, CO₂, and H₂O. STOMATA Stomata are tiny pores on the surface of plant leaves and stems. They are like small openings that allow plants to "breathe." Key Points: What Do They Do? o Stomata let plants take in carbon dioxide (CO₂) for photosynthesis. o They release oxygen (O₂) and water vapor. 4 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] How Do They Work? o Stomata are surrounded by guard cells that open and close the pores. o They are usually open during the day to let in CO₂ and closed at night or when the plant needs to save water. Why Are They Important? o Stomata help plants make food (photosynthesis). They control water loss through evaporation (transpiration). In short, stomata are like the "mouths" of plants, helping them take in air and release water! 5 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] GASEOUS EXCHANGE IN HUMANS Gaseous exchange in humans is the process of swapping oxygen (O₂) and carbon dioxide (CO₂) between the lungs and the blood. It takes place in the lungs, specifically in tiny air sacs called alveoli. How It Happens: Breathing In (Inhalation): o Air enters the lungs through the nose or mouth, passes the windpipe (trachea), and reaches the bronchi, which lead to the lungs. o This air contains oxygen (O₂). At the Alveoli: o The lungs contain millions of alveoli (tiny air sacs), surrounded by a network of blood capillaries. o Oxygen from the inhaled air moves from the alveoli into the blood in the capillaries. o At the same time, carbon dioxide (CO₂) from the blood moves into the alveoli to be exhaled. 6 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Breathing Out (Exhalation): o The CO₂, a waste product of respiration, is removed from the body when we exhale. Why It Happens: The exchange occurs due to diffusion, where gases move from areas of high concentration to low concentration: Oxygen is higher in the alveoli than in the blood, so it diffuses into the blood. Carbon dioxide is higher in the blood than in the alveoli, so it diffuses out. Importance of Gaseous Exchange: 1. Oxygen Delivery: Provides oxygen to the blood, which is carried to the body cells for energy production (respiration). 2. Waste Removal: Removes carbon dioxide, which is toxic if it builds up in the body. 3. Maintains Balance: Keeps oxygen and carbon dioxide levels stable in the blood. 7 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] In short, gaseous exchange in humans ensures that cells get the oxygen they need while getting rid of harmful carbon dioxide. THE MECHANISM OF BREATHING Inspiration: Ribs muscles contract Diaphragm less dome like Pressure in lungs reduce Surface area of chest increase Expiration: Ribs muscles relax Diaphragm dome like Pressure increase Surface area reduces 8 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] RESPIRATORY DISORDERS Bronchitis Bronchitis is a condition where the lining of the bronchial tubes (the airways that carry air to and from your lungs) becomes inflamed. This inflammation leads to swelling and increased mucus production, which can block airflow and make breathing difficult. Depending on the cause and duration, bronchitis is classified as either acute or chronic: Acute Bronchitis: o Short-term condition, usually caused by infections (like viruses or bacteria). o It often develops after a cold or flu and typically lasts 1-3 weeks. Chronic Bronchitis: o Long-term inflammation, often linked to smoking or long-term exposure to irritants like pollution. o It’s a type of chronic obstructive pulmonary disease (COPD) and lasts for months or recurs over years. 9 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Key Points: o The main feature of bronchitis is persistent coughing, which helps clear mucus from the airways. o Acute bronchitis is temporary and often resolves on its own, while chronic bronchitis requires medical management and lifestyle changes. Causes o Viruses: Like the ones that cause colds or flu. o Bacteria: Sometimes, bacteria can also cause bronchitis. o Smoking: Irritates and damages the airways. o Air Pollution: Dust, fumes, or chemicals can trigger it. o Allergies: Pollen or mold can irritate the lungs. Symptoms o Coughing (often with mucus that may be clear, yellow, or green). o Feeling short of breath or wheezing. o Chest tightness or discomfort. o Fever or chills (sometimes). o Fatigue or feeling tired. 10 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] EMPHYSEMEA Emphysema is a long-term lung condition that is part of a group of diseases called chronic obstructive pulmonary disease (COPD). It happens when the tiny air sacs (alveoli) in the lungs become damaged. These air sacs stretch out, lose their elasticity, and can’t work properly, making it hard for the lungs to exchange oxygen and carbon dioxide. Causes of Emphysema 1. Smoking: The most common cause; damages lung tissues over time. 2. Air Pollution: Long-term exposure to polluted air or chemical fumes. 3. Genetics: A rare condition called Alpha-1 Antitrypsin Deficiency can increase the risk. 4. Secondhand Smoke: Breathing in smoke from others. Symptoms of Emphysema Shortness of breath, especially during physical activity. A long-lasting cough (often called a smoker’s cough). Wheezing or a whistling sound when breathing. 11 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Fatigue and difficulty with daily activities. Weight loss in advanced stages. Key Effects With emphysema, the lungs can’t fully expel air, leading to a buildup of carbon dioxide. The damage is permanent and gets worse over time, but treatment can help manage symptoms. PNEUMONIA Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs. These air sacs can fill with fluid or pus, making it hard to breathe and reducing the amount of oxygen that reaches your blood. Causes of Pneumonia 1. Bacteria: Most common in adults, e.g., Streptococcus pneumoniae. 2. Viruses: Like the flu or respiratory syncytial virus (RSV), often in children. 12 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 3. Fungi: Rare, usually affects people with weakened immune systems. 4. Aspiration Pneumonia: Caused by inhaling food, liquids, or vomit into the lungs. Symptoms of Pneumonia Cough (may produce yellow, green, or bloody mucus). Fever, chills, or sweating. Shortness of breath or rapid breathing. Chest pain, especially when breathing deeply or coughing. Fatigue and weakness. Nausea, vomiting, or diarrhea (sometimes). Confusion (especially in older adults). How Serious Is It? Mild Cases: Can feel like a bad cold or flu. Severe Cases: Can lead to complications like difficulty breathing, sepsis, or lung abscesses. 13 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] People at higher risk include the elderly, infants, smokers, and those with chronic illnesses like diabetes or heart disease. LUNGS CANCER Lung cancer is a type of cancer that begins in the cells of the lungs. It happens when abnormal cells grow uncontrollably, forming tumors that can interfere with normal lung functions like breathing and oxygen exchange. Lung cancer can spread to other parts of the body if not treated. Types of Lung Cancer 1. Non-Small Cell Lung Cancer (NSCLC): o Most common type (85% of cases). o Includes subtypes like adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. 2. Small Cell Lung Cancer (SCLC): o Less common but more aggressive. o Often linked to smoking and spreads rapidly. 14 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Causes of Lung Cancer 1. Smoking: The biggest risk factor (85-90% of cases), as tobacco contains harmful chemicals that damage lung cells. 2. Secondhand Smoke: Breathing smoke from others increases the risk. 3. Air Pollution: Long-term exposure to polluted air or industrial fumes. 4. Asbestos and Radon Exposure: These harmful substances can increase the risk. 5. Family History: Genetics may play a role. Symptoms of Lung Cancer Persistent cough that doesn’t go away. Coughing up blood (even a small amount). Shortness of breath or wheezing. Chest pain or discomfort. Hoarseness or voice changes. Unexplained weight loss and fatigue. Frequent lung infections (like pneumonia or bronchitis). 15 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] HOMEOSTASIS CH-2 INTRODUCTION Homeostasis is how your body keeps things balanced so it can work properly. It makes sure things like your body temperature, blood sugar, and water levels stay just right, even if the environment around you changes. Simple Examples: Body Temperature: If you get too hot, your body cools you down by sweating. If you're too cold, you shiver to warm up. Blood Sugar: After you eat, your body lowers your blood sugar by using insulin. If your blood sugar drops too low, it releases stored energy to bring it back up. Water Levels: If you're dehydrated, you feel thirsty, so you drink water. Your body also makes less urine to save water. 16 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] OSMOREGULATION Osmoregulation is the process by which living organisms control the balance of water and salts (electrolytes) in their bodies. This helps keep cells and the body functioning properly. THERMOREGULATION Thermoregulation is how your body keeps its temperature within a healthy range, even if the temperature outside changes. This is important because your body needs to stay at the right temperature (around 37°C or 98.6°F) for your organs to work properly. 17 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] HOMEOSTASIS IN PLANTS Homeostasis in plants is how they keep their internal systems stable and balanced to survive in changing conditions. Here are the main ways plants do this: Water Control 1. Plants open and close tiny holes on their leaves called stomata to control water loss and let in carbon dioxide for photosynthesis. 2. Their roots absorb water from the soil when needed. 3. A waxy layer on leaves, called the cuticle, helps reduce water loss. Nutrient Balance 1. Roots take in essential nutrients like nitrogen and potassium while keeping out harmful substances. 2. Plants move nutrients through special tubes called xylem and phloem to where they are needed. Temperature Control 1. Plants release water vapor through their leaves (transpiration) to cool down. 18 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] They make special proteins to protect themselves when it gets too hot. Why It Matters Homeostasis helps plants stay healthy, grow, and survive even when their environment changes, like during a drought or extreme heat. It’s also important for farming and nature because healthy plants support life on Earth. TRANSPIRATION Transpiration is the process by which plants lose water in the form of water vapor through tiny openings in their leaves called stomata. It is an essential part of how plants function and stay healthy. Steps of Transpiration: 1. Water is absorbed by the plant roots from the soil. 2. This water travels up through the plant via the xylem, reaching the leaves. 19 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 3. In the leaves, some of this water evaporates from the cells and escapes into the air through the stomata. Why is Transpiration Important? 1. Cooling the Plant: It helps plants cool down, especially on hot days. 2. Water Movement: Transpiration pulls water and nutrients up from the roots to the rest of the plant. 3. Photosynthesis: By opening their stomata for transpiration, plants can also take in carbon dioxide, which is needed for photosynthesis. Factors Affecting Transpiration: Temperature: Warmer temperatures increase transpiration. Humidity: High humidity slows it down, while dry air speeds it up. Wind: Wind removes water vapor around leaves, increasing transpiration. Light: Bright light causes stomata to open, leading to more transpiration. 20 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] HOMEOSTASIS IN HUMAN Homeostasis in humans is the process by which the body maintains a stable internal environment, ensuring that conditions remain within a range that allows the body to function properly. It helps balance things like temperature, water levels, pH, and blood sugar, even when the outside environment changes. Steps of Homeostasis: Sensors (Detect Changes) o Specialized cells or organs act as sensors to detect changes in the body or environment. o For example: ▪ Thermoreceptors detect changes in body temperature. ▪ Baroreceptors monitor blood pressure. ▪ Chemoreceptors detect changes in oxygen or carbon dioxide levels. Control Center (Decides the Response) 21 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o The brain or specific glands (like the hypothalamus or pancreas) process the information from the sensors. o The control center compares the current condition to the ideal state (called the set point, e.g., 37°C for body temperature). o If there's a difference, it sends signals to trigger a response. Effectors (Act to Restore Balance) o Effectors are organs, tissues, or cells that carry out the response to bring the body back to its normal state. o For example: ▪ Sweat glands produce sweat to cool the body when it’s hot. ▪ Muscles shiver to generate heat when it’s cold. ▪ Kidneys adjust how much water is retained or excreted to balance hydration. 22 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] KIDNEY What is a Kidney? The kidney is a bean-shaped organ in your body that filters blood, removes waste, and balances water and salts. Humans have two kidneys, located on either side of the spine, just below the ribcage. They are essential for cleaning your blood and keeping your body healthy. Structure of the Kidney A kidney is about the size of a fist and has the following main parts: Cortex o The outer layer of the kidney. o It contains tiny filtering units called nephrons. Medulla o The middle layer of the kidney. o It contains tubes that collect filtered waste and water. 23 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Renal Pelvis o The innermost part of the kidney. o It collects urine before it moves to the bladder. Nephrons o The functional units of the kidney (each kidney has about a million). o They filter blood and make urine. Each nephron has: ▪ A glomerulus: Filters blood. ▪ A tubule: Adjusts water, salts, and nutrients. Function of the Kidney The kidneys perform several important tasks: 1. Filter Blood: Remove waste products like urea, toxins, and extra salts. 2. Make Urine: Convert waste and excess water into urine. 3. Balance Water and Salts: Keep the right levels of water, salt, and minerals in the blood. 4. Control Blood Pressure: Regulate blood pressure by adjusting fluid levels. 5. Produce Hormones: 24 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Erythropoietin: Helps make red blood cells. o Renin: Regulates blood pressure. o Vitamin D Activation: Helps keep bones strong. How Does the Kidney Work? Blood Enters o Blood flows into the kidney through the renal artery. o It carries waste, excess water, and salts. Filtration o Inside the nephron, the glomerulus acts like a filter. o It removes waste, water, and small molecules from the blood while keeping useful things like blood cells and proteins. Reabsorption o The tubule adjusts the mix, returning useful substances like water, glucose, and salts back to the blood. Formation of Urine 25 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Waste products and extra water are left in the tubule, forming urine. o Urine collects in the renal pelvis, travels down the ureter, and is stored in the bladder until it's expelled. Clean Blood Exits o The clean blood leaves the kidney through the renal vein and goes back to the body. KIDNEY STONE A kidney stone is a hard, pebble-like substance that forms in the kidneys when minerals and salts in the urine clump together. These stones can vary in size, from as small as a grain of sand to as large as a marble, and they can cause pain and discomfort when they move through the urinary tract. 26 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] C-OORDINATION & CONTROL CH-3 INTRODUCTION Coordination and control refer to how living organisms detect changes in their environment (both inside and outside the body) and respond to them in a well-organized way. These processes ensure that the body functions smoothly and can adapt to different situations. RESPONSE A response in humans is how the body reacts to a stimulus—a change in the environment (internal or external). Responses help humans adapt, protect themselves, and maintain balance (homeostasis). 27 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] NERVOUS CO-ORDINATION Nervous Coordination What it is: Coordination that uses the nervous system to send electrical signals (nerve impulses) between the brain, spinal cord, and body. Features: o Speed: Very fast, almost instant. o Duration: Short-term responses. o Mechanism: Involves nerve cells (neurons) transmitting signals. Examples: o Reflex actions (like pulling your hand away from something hot). o Voluntary movements (like walking or writing). 28 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] CHEMICAL CO-ORDINATION Chemical coordination is the process by which living organisms regulate their body functions using chemical messengers called hormones. These hormones are produced by specific organs or glands, released into the bloodstream, and carried to target organs or tissues to trigger a response. Features of Chemical Coordination 1. Involves Hormones: Hormones are chemical messengers that regulate various body functions. 2. Slower Process: Compared to nervous coordination, it takes more time to produce and transport hormones. 3. Long-lasting Effects: The effects of hormones last longer (e.g., growth, metabolism). 4. Widespread Influence: Hormones can affect multiple organs or tissues at the same time. Chemical Coordination in Humans 29 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] In humans, chemical coordination is managed by the endocrine system, which consists of glands that release hormones. Endocrine Glands and Their Hormones Gland Hormone Function Controls growth, and Pituitary Growth hormone, regulates other Gland others glands. Controls metabolism Thyroid Gland Thyroxine and energy levels. Regulates blood sugar Pancreas Insulin, Glucagon levels. Prepares the body for Adrenal Adrenaline stress ("fight or Glands flight"). Regulates Ovaries/Testes Estrogen/Testosterone reproduction and sexual traits. 30 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] How It Works 1. A stimulus is detected (e.g., low blood sugar). 2. A specific gland releases a hormone (e.g., pancreas releases glucagon). 3. The hormone travels through the bloodstream to the target organ or tissue. 4. The target organ responds (e.g., liver releases stored sugar into the blood). Examples of Chemical Coordination Blood Sugar Regulation: o When blood sugar is high, the pancreas releases insulin to lower it. o When blood sugar is low, the pancreas releases glucagon to raise it. Stress Response: o When stressed, the adrenal glands release adrenaline, increasing heart rate and energy. Growth: o The pituitary gland releases growth hormone, controlling the body's growth during childhood. 31 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] CO-ORDINATION IN PLANTS Coordination in Plants Plants lack a nervous system but still coordinate their responses using: Hormones: o Auxins: Control growth towards light (phototropism). o Abscisic Acid: Helps the plant respond to stress, like drought. External Stimuli: o Plants grow towards light (phototropism). o Roots grow downward in response to gravity (geotropism). 32 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] HUMAN NERVOUS SYSTEM The nervous system is like the body's control center and communication network. It helps the body stay coordinated and work smoothly by sending and receiving messages. Main Parts: 1. Brain: It’s the boss! It controls what you think, feel, and do, like moving your hand or solving a problem. 2. Spinal Cord: It’s the messenger! It carries messages between your brain and the rest of your body. The nervous system helps you: Sense things (like touch, sound, and sight). React quickly (like pulling your hand back from something hot). Control movements (like walking or writing). Stay balanced and keep everything working together inside your body. 33 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] CENTRAL NERVOUS SYSTEM The Central Nervous System (CNS) is like the body’s main computer system that controls and coordinates everything you do. It has two main parts: 1. Brain: It’s the control center of your body. It helps you think, remember, and feel emotions. It controls voluntary actions like talking, walking, and writing. It also manages involuntary actions like breathing, heartbeats, and digestion. Different parts of the brain handle specific tasks. For example: o Cerebrum: Thinking, learning, memory, and voluntary movements. o Cerebellum: Balance and coordination. o Brainstem: Basic functions like breathing and heartbeat. 34 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 2. Spinal Cord: It’s like a highway that connects the brain to the rest of the body. It carries signals from the brain to your muscles and organs and sends back messages like pain or touch. It also handles reflexes — quick, automatic actions to protect you (e.g., pulling your hand away from fire). The CNS works with the peripheral nervous system (nerves outside the brain and spinal cord) to sense the world around you, make decisions, and control your body. It’s what keeps everything in sync! PARTS OF BRAIN The brain is the most important part of the central nervous system. It is divided into three main parts, each with specific functions: 35 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 1. Cerebrum (Largest Part): Structure: Divided into two halves called the left and right hemispheres. Each hemisphere controls the opposite side of the body. Functions: o Thinking, learning, and decision-making. o Memory, language, and speech. o Sensing touch, temperature, and pain. o Voluntary movements like walking or writing. Lobes of the Cerebrum: o Frontal Lobe: Thinking, planning, problem-solving, emotions, and voluntary movement. o Parietal Lobe: Senses like touch, pressure, and spatial awareness. o Temporal Lobe: Hearing, language, and memory. o Occipital Lobe: Vision and interpreting what you see. 2. Cerebellum (Coordination Center): Location: Below the cerebrum at the back of the brain. Functions: 36 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Maintains balance and posture. o Coordinates smooth and precise movements (like riding a bike or playing an instrument). 3. Brainstem (Life Support System): Location: Connects the brain to the spinal cord. Functions: o Controls basic, involuntary functions like breathing, heartbeat, and blood pressure. o Manages reflexes like swallowing and blinking. o Contains three parts: ▪ Midbrain: Controls vision and hearing reflexes. ▪ Pons: Helps with breathing and communication between brain parts. ▪ Medulla Oblongata: Controls vital processes like heart rate and digestion. The brain also has protective layers and fluids: Meninges: Three protective layers around the brain. 37 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Cerebrospinal Fluid (CSF): Cushions the brain and removes waste. PERIPHERAL NERVOUS SYSTEM The Peripheral Nervous System (PNS) is the part of the nervous system outside the brain and spinal cord. It acts as a communication network, connecting the central nervous system (CNS) to the rest of the body. The Peripheral Nervous System (PNS) is divided into two main parts based on its function: 1. Somatic Nervous System (SNS): This part handles voluntary movements and sensory input. Main Features: Sensory Nerves: o Carry information from sense organs (skin, eyes, ears, etc.) to the brain and spinal cord. o Example: Feeling heat when you touch something hot. 38 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Motor Nerves: o Send commands from the brain and spinal cord to your muscles. o Example: Moving your hand away from something hot. 2. Autonomic Nervous System (ANS): This part controls involuntary actions like heartbeat, breathing, and digestion. It is further divided into: a) Sympathetic Nervous System: Prepares the body for stress or emergencies ("fight or flight"). Increases heart rate, dilates pupils, and slows digestion. Example: Feeling alert and ready to run when scared. b) Parasympathetic Nervous System: Helps the body relax and conserve energy ("rest and digest"). Slows the heart rate, stimulates digestion, and calms the body. Example: Relaxing after eating a meal. 39 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] c) Enteric Nervous System (ENS): Manages the digestive system independently of the brain. Controls digestion, nutrient absorption, and gut reflexes. Summary of PNS Parts: Somatic Nervous System: o Voluntary actions (walking, writing). o Senses (touch, pain). Autonomic Nervous System: o Involuntary actions (breathing, digestion). o Divided into: ▪ Sympathetic: Stress and emergency responses. ▪ Parasympathetic: Relaxation and recovery. ▪ Enteric: Digestion control. The PNS ensures smooth coordination between the body and the brain! 40 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] NEURON A neuron is the basic building block of the nervous system. It is a specialized cell that carries messages, or signals, throughout the body using electrical and chemical processes. These messages help the body respond to its surroundings and control various activities. Parts of a Neuron: Cell Body (Soma): o The main part of the neuron that contains the nucleus. o It processes information and keeps the neuron alive. Dendrites: o Branch-like structures extending from the cell body. o They receive signals from other neurons and send them to the cell body. 41 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Axon: o A long, tail-like structure that carries signals away from the cell body to other neurons, muscles, or glands. o Axons are covered by a myelin sheath, which acts like insulation to speed up the signal transmission. Axon Terminals: o The endpoints of the axon. o They release chemicals (neurotransmitters) to send signals to other neurons or target cells. How Neurons Work: Signal Transmission: o Neurons receive information through dendrites. o The signal is processed in the cell body and then travels along the axon. Synapse: o The gap between the axon terminal of one neuron and the dendrites of another. 42 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Neurotransmitters are released into the synapse to pass the signal to the next neuron. Types of Neurons: 1. Sensory Neurons: Carry signals from sensory organs (eyes, skin, etc.) to the brain and spinal cord. 2. Motor Neurons: Send commands from the brain and spinal cord to muscles and glands. 3. Interneurons: Connect sensory and motor neurons within the brain and spinal cord to process information. Neurons are like messengers, working together to keep the body connected, coordinated, and responsive! REFLEX ACTION A reflex action is a quick, automatic response to a stimulus that happens without thinking. It helps protect the body from harm 43 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] and allows it to react quickly to sudden changes in the environment. How Reflex Actions Work: Reflex actions follow a specific pathway called the reflex arc: 1. Stimulus: A change in the environment triggers the reaction (e.g., touching a hot object). 2. Receptor: Sensory organs (like skin) detect the stimulus and send a signal to sensory neurons. 3. Sensory Neuron: Carries the signal to the spinal cord or brain. 4. Interneuron: In the spinal cord, this neuron processes the information and decides the response. 5. Motor Neuron: Sends the command from the spinal cord to a muscle or gland. 6. Effector: The muscle or gland carries out the response (e.g., pulling your hand away). 44 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] EYE The eye is the organ that enables vision, allowing us to see and interpret the world around us. It works like a camera, capturing light and sending signals to the brain, where the image is processed. Parts of the Eye and Their Functions: Cornea: o The clear, dome-shaped surface covering the front of the eye. o Focuses incoming light onto the lens. Iris: o The colored part of the eye (e.g., brown, blue). o Controls the size of the pupil and regulates how much light enters the eye. Pupil: o The black circular opening in the center of the iris. o Adjusts size based on light: ▪ Bright light: Shrinks to reduce light entry. 45 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] ▪ Dim light: Enlarges to allow more light in. Lens: o A transparent, flexible structure behind the iris. o Focuses light onto the retina by changing shape (accommodation). Retina: o A thin layer of light-sensitive tissue at the back of the eye. o Contains two types of cells: ▪ Rods: Help see in dim light and detect black and white. ▪ Cones: Detect color and function in bright light. Optic Nerve: o Transmits visual signals from the retina to the brain, where they are interpreted as images. Sclera: o The tough, white outer layer of the eye that provides structure and protection. 46 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Choroid: o A layer between the retina and sclera. o Supplies blood and nutrients to the eye. Aqueous Humor: o A clear fluid between the cornea and lens. o Maintains pressure and nourishes the eye. Vitreous Humor: o A gel-like substance inside the eye. o Helps maintain the eye's shape and keeps the retina in place. How the Eye Works: 1. Light enters the eye through the cornea and passes through the pupil. 2. The lens focuses the light onto the retina at the back of the eye. 3. The retina's rods and cones detect light and color, converting it into electrical signals. 4. The signals travel via the optic nerve to the brain, which interprets them as images. 47 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] EAR The ear is the organ responsible for hearing and balance. It detects sound and helps maintain your balance by providing information about your body’s position. The ear is divided into three parts: the outer ear, middle ear, and inner ear. Parts of the Ear and Their Functions: 1. Outer Ear: Auricle (Pinna): o The visible, outer part of the ear. o Collects sound waves and directs them into the ear canal. Ear Canal (External Auditory Canal): o The tube that carries sound from the outer ear to the middle ear. o Also helps protect the inner ear from dust and foreign objects. 48 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 2. Middle Ear: Eardrum (Tympanic Membrane): o A thin membrane that vibrates when sound waves hit it. o These vibrations are transmitted to the bones of the middle ear. Ossicles: o Three small bones in the middle ear: Malleus (hammer), Incus (anvil), and Stapes (stirrup). o These bones amplify the vibrations from the eardrum and transmit them to the inner ear. 3. Inner Ear: Cochlea: o A spiral-shaped, fluid-filled structure that converts sound vibrations into electrical signals. o Inside the cochlea, tiny hair cells move with the fluid and send signals to the auditory nerve. Auditory Nerve: 49 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Carries the electrical signals from the cochlea to the brain, where they are interpreted as sound. Semicircular Canals: o Fluid-filled tubes in the inner ear that help control balance. o They detect changes in head position (e.g., tilting or rotating your head). Vestibule: o The part of the inner ear that detects motion and helps with balance. How the Ear Works: 1. Sound waves enter the ear through the auricle and travel down the ear canal. 2. The eardrum vibrates as the sound hits it, and these vibrations are transferred to the ossicles. 3. The ossicles amplify the vibrations and pass them to the cochlea in the inner ear. 50 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 4. The cochlea converts the vibrations into electrical signals, which are sent to the brain via the auditory nerve. 5. The brain processes these signals as sound. Balance Function: The semicircular canals and vestibule in the inner ear send information about the position and movement of your head to the brain, helping you maintain balance. ENDOCRINE GLANDS The endocrine glands are specialized organs in the body that produce and release hormones. Hormones are chemical messengers that travel through the bloodstream to regulate various bodily functions, such as growth, metabolism, mood, and reproduction. 51 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Here are the main endocrine glands and their functions: 1. Hypothalamus: Location: In the brain, just below the thalamus. Function: o Controls the release of hormones from the pituitary gland. o Helps regulate body temperature, hunger, thirst, sleep, and emotional responses. 2. Pituitary Gland (Master Gland): Location: At the base of the brain, just below the hypothalamus. Function: o Releases hormones that control other endocrine glands, like the thyroid, adrenal glands, and reproductive organs. o Important hormones: ▪ Growth Hormone (GH): Stimulates growth and development. ▪ Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland. 52 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] ▪ Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal glands. 3. Thyroid Gland: Location: In the neck, in front of the windpipe. Function: o Regulates metabolism, energy levels, and body temperature. o Produces hormones: ▪ Thyroxine (T4) and Triiodothyronine (T3): Control the rate of metabolism. ▪ Calcitonin: Helps control calcium levels in the blood. 4. Parathyroid Glands: Location: Four small glands behind the thyroid. Function: o Regulates calcium levels in the blood by releasing parathyroid hormone (PTH), which increases calcium levels when they are too low. 53 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 5. Adrenal Glands: Location: On top of each kidney. Function: o Release hormones in response to stress and regulate various functions. o Key hormones include: ▪ Adrenaline (Epinephrine) and Norepinephrine: Increase heart rate, blood pressure, and energy during stress ("fight or flight"). ▪ Cortisol: Helps manage stress and regulate metabolism and immune response. ▪ Aldosterone: Regulates salt and water balance, affecting blood pressure. 6. Pancreas: Location: Behind the stomach. Function: o Regulates blood sugar levels by producing hormones: ▪ Insulin: Lowers blood sugar by allowing cells to take in glucose. 54 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] ▪ Glucagon: Increases blood sugar by signaling the liver to release stored glucose. 7. Ovaries (in females): Location: In the pelvic region. Function: o Produce eggs and release hormones involved in reproduction and sexual development. o Key hormones: ▪ Estrogen: Regulates the menstrual cycle and promotes female sexual characteristics. ▪ Progesterone: Prepares the uterus for pregnancy. 8. Testes (in males): Location: In the scrotum. Function: o Produce sperm and release hormones involved in male reproduction and sexual development. o Key hormone: ▪ Testosterone: Regulates sperm production and male sexual characteristics. 55 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 9. Pineal Gland: Location: In the brain, near the center. Function: o Produces melatonin, which helps regulate sleep- wake cycles (circadian rhythms). 10. Thymus Gland: Location: Behind the sternum, between the lungs. Function: o Produces hormones like thymosin, which help develop and maintain the immune system, especially during childhood. Summary: The endocrine system is a collection of glands that secrete hormones into the bloodstream to regulate various processes in the body. These include growth, metabolism, reproduction, and mood, and they help maintain balance and homeostasis within the body. 56 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] SUPPORT AND MOVEMENT CH-4 INTRODUCTION The support and movement system in the human body is made up of two main structures: the skeletal system and the muscular system. Together, these systems allow the body to maintain its shape, support organs, and enable movement. 1. Skeletal System (Support): The skeletal system is made up of bones, cartilage, ligaments, and joints. It provides structure, support, and protection for the body. Functions of the Skeletal System: Support: The skeleton acts as a framework, giving the body its shape and supporting soft tissues. Protection: Bones protect vital organs (e.g., the skull protects the brain, ribs protect the heart and lungs). 57 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Movement: The skeleton provides points of attachment for muscles, enabling movement when muscles contract. Mineral Storage: Bones store important minerals like calcium and phosphorus, releasing them into the bloodstream as needed. Blood Cell Production: The bone marrow produces red blood cells, white blood cells, and platelets. Parts of the Skeletal System: Bones: Rigid structures that form the skeleton. There are 206 bones in the adult human body. Joints: Areas where two or more bones meet, allowing movement (e.g., knee, elbow). Cartilage: A flexible tissue that cushions joints and prevents bones from rubbing together. Ligaments: Strong bands of connective tissue that connect bones to other bones, stabilizing joints. 2. Muscular System (Movement): The muscular system is made up of muscles that work with the bones to enable movement. Muscles contract and relax to produce movement. 58 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Functions of the Muscular System: Movement: Muscles contract and pull on bones, causing movement of body parts. Posture: Muscles help maintain body posture and stability, even when standing still. Heat Production: Muscle contractions generate heat, helping to maintain body temperature. Joint Stabilization: Muscles support joints and help stabilize them during movement. Types of Muscles: 1. Skeletal Muscles: o These muscles are attached to bones and are responsible for voluntary movements (e.g., walking, lifting). o They are striated (striped) and work in pairs (one muscle contracts, and the other relaxes). 2. Smooth Muscles: o Found in the walls of internal organs like the stomach, intestines, and blood vessels. o These muscles are involuntary and control functions like digestion and blood flow. 3. Cardiac Muscle: 59 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Found in the heart. It is involuntary and specialized to pump blood throughout the body. o It is striated like skeletal muscle but works automatically without conscious control. How Support and Movement Work Together: Bones and Muscles: The muscles are attached to bones via tendons. When muscles contract, they pull on bones, creating movement at the joints. Joints and Movement: The joints act as levers, allowing the bones to move in various directions. Ligaments and cartilage help keep joints stable and prevent injury. Example of Movement: When you bend your arm, the bicep muscle (a skeletal muscle) contracts, pulling the radius (one of the bones in the forearm) towards the shoulder, while the triceps muscle relaxes. This movement is possible because of the joints, bones, and muscles working together. 60 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Summary: The skeletal system provides the body with structure, support, and protection, while the muscular system enables movement. Together, they allow the body to perform a wide range of activities, from simple movements to complex actions. MOVEMENT AND LOCOMOTION Movement and locomotion are both ways organisms move, but they are different: Movement: Movement is any kind of change in position or action. It doesn't always mean moving from one place to another. Examples: o Bending your arm or lifting your leg are movements of body parts. o Food moving through your stomach or blood flowing are internal movements in your body. Locomotion: 61 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Locomotion is the movement that helps an organism move from one place to another. It means travel or movement through space. Examples: o Humans walking or running to move around. o Fish swimming in water. o Birds flying in the sky. o Snakes slithering on the ground. How Locomotion Works: For locomotion, muscles and bones work together to help the body move. The muscles contract (tighten) to create movement, and the bones provide a structure for muscles to pull against. SEKELETON AND IT’S TYPE The skeleton is the structure that supports and protects an animal’s body. Different animals have different types of skeletons based on their body needs and environment. Here are the main types of skeletons found in animals: 62 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 1. Endoskeleton (Internal Skeleton): Location: Inside the body. Structure: Made of bones and cartilage. Function: Supports the body, protects organs, and allows movement. Examples: Humans: We have an internal skeleton made of bones like the skull and spine. Mammals (like dogs, elephants), Birds, Fish, and Reptiles also have internal skeletons. 2. Exoskeleton (External Skeleton): Location: On the outside of the body. Structure: Made of a hard outer covering, usually made of chitin or calcium carbonate. Function: Protects the body and supports its structure. Animals with exoskeletons must shed (molting) to grow. 63 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Examples: Insects (like ants, beetles, and butterflies) have exoskeletons. Crustaceans (like crabs and lobsters) also have external skeletons. 3. Hydrostatic Skeleton (Fluid-based Skeleton): Location: Inside the body, but there are no bones. Structure: The body is filled with fluid (like water) that is under pressure. Function: The pressure from the fluid gives the animal shape and helps it move by using muscles around the fluid-filled body. Examples: Worms and jellyfish have a hydrostatic skeleton. Summary: 1. Endoskeleton (inside the body) - Found in humans, mammals, birds, fish, and reptiles. 64 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 2. Exoskeleton (outside the body) - Found in insects (like ants) and crustaceans (like crabs). 3. Hydrostatic Skeleton (fluid inside the body) - Found in soft-bodied animals like worms and jellyfish. DIFFERENCE BETWEEN BONES AND CARTILAGE Feature Bones Cartilage Hard, rigid, made of Flexible, rubbery, made of Structure calcium salts and collagen fibers and collagen fibers. proteoglycans. Supports body, Cushions joints, supports protects organs, flexible structures like nose Function enables movement, and ears, and helps with and produces blood smooth movement in joints. cells. Flexible and can bend Flexibility Inflexible and rigid. without breaking. Grows through Grows through appositional Growth ossification and interstitial growth. 65 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Feature Bones Cartilage (hardening) at growth plates. Heals relatively Heals slowly or may not heal Healing quickly due to blood at all due to lack of blood supply. supply. Vascular (has blood Avascular (lacks blood Vascularity vessels). vessels). Skull, ribs, arms, legs, Nose, ears, joints (like knee), Examples spine. and rib cage. HUMAN SKELETON The human skeleton is the internal framework that provides structure, protects vital organs, and enables movement. It is made up of bones and cartilage and consists of 206 bones in an adult. The skeleton is divided into two main parts: 1. Axial Skeleton: 66 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] The axial skeleton forms the central axis of the body and includes bones that protect the brain, heart, and lungs. Skull: Composed of the bones of the head and face. The cranium protects the brain, and the facial bones form the face. Vertebral Column (Spine): Made up of 33 vertebrae, it protects the spinal cord and provides support for the body. Ribs: 12 pairs of ribs protect the heart and lungs. Sternum (Chest Bone): Located in the center of the chest, it connects to the ribs and helps protect the heart and lungs. 2. Appendicular Skeleton: The appendicular skeleton includes bones of the limbs (arms and legs) and the structures that connect them to the axial skeleton. Shoulder Girdle: Includes the clavicles (collarbones) and scapulae (shoulder blades), which attach the arms to the body. Arms and Hands: The humerus is the upper arm bone, and the radius and ulna are the forearm bones. The 67 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] hands are made up of carpals (wrist bones), metacarpals (bones in the palm), and phalanges (finger bones). Pelvic Girdle: Made up of two hip bones, it supports the weight of the upper body and connects the spine to the legs. Legs and Feet: The femur is the thigh bone, the tibia and fibula are the lower leg bones, and the patella is the kneecap. The feet are made of tarsals (ankle bones), metatarsals (bones in the foot), and phalanges (toe bones). Key Functions of the Human Skeleton: 1. Support: Provides structure and shape to the body. 2. Protection: Protects vital organs like the brain, heart, and lungs. 3. Movement: Muscles are attached to bones, allowing for movement. 4. Blood Cell Production: Bone marrow produces red blood cells, white blood cells, and platelets. 5. Mineral Storage: Stores minerals like calcium and phosphorus, which can be released into the bloodstream when needed. 68 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Major Bone Groups: Long Bones: Found in arms and legs (e.g., femur, humerus). Short Bones: Found in wrists and ankles (e.g., carpals, tarsals). Flat Bones: Protect organs (e.g., skull, ribs). Irregular Bones: Have complex shapes (e.g., vertebrae, pelvis). Sesamoid Bones: Embedded in tendons (e.g., patella). Summary: The human skeleton provides structure, protection, and mobility. It is made of bones and cartilage and is divided into the axial skeleton (skull, spine, ribs) and the appendicular skeleton (limbs and girdles). The bones work together with muscles to allow movement, while also protecting organs and producing blood cells. 69 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] JOINTS Joints are where two or more bones meet, allowing movement. There are different types: 1. Fixed Joints: No movement (e.g., skull). 2. Hinge Joints: Move in one direction (e.g., knee, elbow). 3. Ball-and-Socket Joints: Move in all directions (e.g., shoulder, hip). 4. Pivot Joints: Rotate around each other (e.g., neck). 5. Gliding Joints: Slide over each other (e.g., wrist, ankle). 6. Saddle Joints: Move side to side and back and forth (e.g., thumb). Joints allow bones to move and provide flexibility to the body. TENDEN AND LIGAMENT Tendons and ligaments are both types of connective tissues, but they have different functions and locations: 70 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Tendons: Function: Connect muscles to bones. Description: Tendons are strong, flexible tissues that help muscles move bones when they contract. Example: The Achilles tendon connects the calf muscle to the heel bone. Ligaments: Function: Connect bones to other bones at joints. Description: Ligaments are tough, elastic tissues that stabilize and support joints by keeping bones in place. Example: The ACL (anterior cruciate ligament) in the knee connects the thigh bone to the shin bone. Summary: Tendons = Muscle to bone. Ligaments = Bone to bone. 71 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] INHERITANCE CH-6 INTRODUCTION Inheritance in genetics is the process by which parents pass their traits to their children through genes. Genes are tiny units of information in our DNA that determine things like hair color, eye color, height, and even some health conditions. Key Points: Genes and DNA: o Genes are like instructions found in our DNA. Each parent gives half of their genes to their child. Traits: o Traits can be physical (like eye color or height) or hidden (like blood type or a risk for certain diseases). 72 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Dominant and Recessive Genes: o Dominant genes are stronger and usually determine a trait. o Recessive genes are weaker and only show up if both parents pass them down. Types of Inheritance: o Simple inheritance: Some traits depend on a single gene, like attached or detached earlobes. o Complex inheritance: Traits like height or skin color depend on many genes and environmental factors. In simple terms, inheritance is how we get a mix of traits from our parents, which makes each person unique! CONTROL OF GENES IN INHERITANCE The control of genes in inheritance refers to how genes are regulated and determine the traits that are passed from parents to offspring. Not all genes are active all the time, and their expression depends on various factors. Here's a simple explanation: 73 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Key Concepts: 1. Genes and Alleles: Genes come in different forms called alleles, which are inherited from both parents. For example, one allele might code for blue eyes, and another for brown eyes. 2. Dominant and Recessive Alleles: Dominant alleles "control" a trait because they overpower recessive alleles. Recessive alleles only show their effect if both alleles are recessive (e.g., blue eyes). 3. Gene Expression: Not all genes are "turned on" (active) in every cell. For example, the genes for eye color are active in eye cells but not in skin cells. The environment and other regulatory mechanisms can influence whether a gene is expressed. 4. Polygenic Traits: Some traits, like height or skin color, are controlled by multiple genes working together. 74 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 5. Epigenetics: External factors, such as diet, stress, or toxins, can influence how genes are expressed without changing the DNA sequence. This is known as epigenetic control. CHROMOSOMES AND GENES Chromosomes and Genes in Simple Words: 1. What Are Chromosomes? Chromosomes are like storage units for our DNA. They are found in the center (nucleus) of every cell in our body. Humans have 46 chromosomes in total, organized into 23 pairs. We get one chromosome in each pair from our mother and the other from our father. 2. What Are Genes? Genes are like instructions stored on the chromosomes. 75 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Each gene carries information that determines a specific trait, like eye color, hair type, or height. They are small segments of DNA. 3. How Do They Work Together? Chromosomes hold thousands of genes. Think of a chromosome as a book, and the genes are the individual pages with instructions for building and running the body. 4. Why Are They Important? Chromosomes and genes carry the blueprint for how our bodies are built and function. They determine our inherited traits (passed down from parents). Example: If your DNA is a library, chromosomes are the books, and genes are the chapters explaining specific traits! 76 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] CHEMICAL COMPOSITION OF CHROMOSOMES The chemical composition of chromosomes is primarily made up of the following components: 1. DNA (Deoxyribonucleic Acid): DNA is the main chemical in chromosomes and carries genetic information. It has a double-helix structure made of: o Sugar (deoxyribose) o Phosphate group o Nitrogenous bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). 2. Proteins (Histones): DNA is tightly wrapped around histone proteins to form a compact structure. Histones help organize DNA and control gene activity. 77 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 3. RNA (Ribonucleic Acid): Small amounts of RNA are sometimes associated with chromosomes, especially during gene expression. 4. Other Components: Lipids and Enzymes: Found in small amounts, helping with chromosome maintenance and replication. Ions (like magnesium): Stabilize the chromosome structure. Summary of Composition (in percentages): DNA: ~40% Proteins: ~60% Small amounts of RNA and other molecules. Chromosomes are essentially a mix of genetic material (DNA) and structural proteins that work together to store and manage genetic information! 78 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] DNA What is DNA? DNA stands for Deoxyribonucleic Acid. It is the molecule that carries the genetic instructions for the growth, development, functioning, and reproduction of all living organisms and many viruses. Key Features of DNA: 1. Structure: o DNA is shaped like a double helix (a twisted ladder). o It is made up of two long strands of nucleotides that run in opposite directions. 2. Components: DNA is composed of smaller units called nucleotides, and each nucleotide has three parts: o Sugar (deoxyribose): Acts as the backbone. o Phosphate group: Links the sugars together. o Nitrogenous bases: The "rungs" of the ladder. ▪ Adenine (A) pairs with Thymine (T) 79 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] ▪ Cytosine (C) pairs with Guanine (G) 3. Function: o DNA contains instructions to make proteins, which are essential for building and operating the body. o It passes genetic information from parents to offspring. 4. Location: o Found in the nucleus of cells in the form of chromosomes. o Small amounts of DNA are also found in mitochondria (mitochondrial DNA). 5. Replication: o DNA can make exact copies of itself, ensuring genetic information is passed on during cell division. Why is DNA Important? DNA is like a blueprint for life, determining traits such as eye color, height, and even the risk of certain diseases. 80 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] It is also vital for the production of proteins, which carry out most of the body's functions. In simple terms, DNA is the master code of life! GENE What is a Gene? A gene is a small section of DNA that acts as a set of instructions for making proteins or controlling traits in an organism. Genes are the basic units of heredity, meaning they are passed from parents to their children and determine how the body grows, develops, and functions. Key Features of a Gene: 1. Location: o Genes are located on chromosomes inside the nucleus of a cell. 2. Composition: o Made up of DNA sequences (combinations of the four nitrogenous bases: A, T, C, and G). 81 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 3. Function: o Each gene contains instructions for making a specific protein or molecule that the body needs to work properly. o Proteins influence traits like eye color, height, or how the body fights disease. 4. Expression: o Not all genes are "active" all the time. Gene expression determines which genes are turned on or off in different cells. 5. Heredity: o Genes are passed from parents to offspring, with each parent contributing half of the child’s genes. o Variations in genes lead to different traits. Why Are Genes Important? Determine Traits: Genes control physical features like eye color, hair texture, and more. 82 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Health: Genes play a role in determining susceptibility to certain diseases or conditions. Instructions for Life: Genes help the body function properly by guiding the production of essential molecules. Example of a Gene: The eye color gene determines whether a person has blue, green, or brown eyes. Different versions of the gene (called alleles) lead to different eye colors. In simple terms, a gene is like a recipe that tells your body how to make a specific trait or function! REPLICATION What is DNA Replication? DNA replication is the process by which a cell makes an exact copy of its DNA before it divides. This ensures that each new cell receives the same genetic information as the parent cell. 83 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] How Does DNA Replication Work? DNA replication follows a semi-conservative model, meaning each new DNA molecule consists of one original (old) strand and one newly made strand. Steps of DNA Replication: 1. Unwinding the DNA: o The enzyme helicase breaks the hydrogen bonds between the two DNA strands, "unzipping" the double helix to form a replication fork (Y-shaped structure). 2. Binding of Primers: o Primase adds a short RNA primer to the DNA strand. This serves as a starting point for DNA synthesis. 3. Building the New DNA Strand: o The enzyme DNA polymerase adds nucleotides (A, T, C, G) to the new strand by matching them with the complementary bases on the original strand: ▪ A pairs with T 84 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] ▪ C pairs with G o Replication happens in the 5' to 3' direction (the leading strand is synthesized continuously, while the lagging strand is synthesized in small fragments called Okazaki fragments). 4. Joining Fragments: o On the lagging strand, the enzyme ligase joins the Okazaki fragments into a continuous strand. 5. Proofreading: o DNA polymerase checks and corrects any mistakes to ensure the new DNA strand is accurate. Result of DNA Replication: Two identical DNA molecules are formed, each containing: o One original strand. o One newly synthesized strand. Why is DNA Replication Important? 85 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] It ensures that every new cell has the same genetic material as the original cell. It is crucial for growth, development, and repair in living organisms. In simple terms, DNA replication is like photocopying your genetic code so it can be passed on to new cells! TRANSCRIPTION What is Transcription? Transcription is when a copy of DNA's instructions is made in the form of mRNA (messenger RNA). This copy is needed to make proteins. Steps (Simply): 1. Unzipping DNA: A part of the DNA strand opens up. 86 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 2. Making a Copy: An enzyme (RNA polymerase) reads the DNA and makes a copy called mRNA. o In RNA, A pairs with U and T pairs with A. 3. Sending the Message: The mRNA leaves the nucleus and goes to a ribosome, where it helps make a protein. Why It’s Important? Transcription is how cells read DNA and turn it into instructions to build proteins, which do most of the work in the body. Think of transcription as writing a short note from a big instruction manual! MENDEL’S LAW OF HERITATION Mendel's Laws of Heredity Gregor Mendel was an Austrian scientist who is considered the father of modern genetics. He discovered the basic principles 87 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] of heredity through experiments with pea plants. His work laid the foundation for understanding how traits are inherited from one generation to the next. Mendel's findings are summarized in three laws: 1. Law of Segregation Definition: Each individual has two alleles (versions of a gene) for a given trait, one inherited from each parent. These alleles separate (segregate) during the formation of gametes (egg or sperm cells), so each gamete carries only one allele for each trait. Key Point: An offspring inherits one allele from each parent, and the two alleles are separated during reproduction. Example: For a plant with a gene for flower color (where P = purple and p = white), the plant might have Pp alleles. When the plant produces gametes, the alleles segregate so half of the gametes will carry P and half will carry p. 88 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 2. Law of Independent Assortment Definition: The alleles for different traits are inherited independently of each other. This means that the inheritance of one trait does not affect the inheritance of another trait. Key Point: Genes located on different chromosomes assort independently during gamete formation, leading to genetic variation. Example: If a pea plant has the following alleles: Pp for flower color and Tt for height, the inheritance of flower color and height will occur independently, meaning a gamete could carry P and T, or P and t, or p and T, or p and t. 3. Law of Dominance Definition: In a pair of alleles, one allele may be dominant and the other recessive. The dominant allele masks the effect of the recessive allele in the heterozygous state. Key Point: The dominant allele determines the organism's trait if at least one dominant allele is present, while the 89 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] recessive allele only shows its effect if both alleles are recessive. Example: For flower color, P (purple) is dominant and p (white) is recessive. A plant with Pp will have purple flowers because P is dominant. Summary: 1. Law of Segregation: Each parent contributes one allele per gene. 2. Law of Independent Assortment: Alleles for different traits are inherited independently. 3. Law of Dominance: Dominant alleles mask the effects of recessive alleles. These laws explain how traits are passed down through generations and form the foundation of Mendelian genetics! 90 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] MULTIPLE ALLELE Multiple Alleles Multiple alleles refer to the existence of more than two possible forms of a gene that can occupy the same gene locus (position) on a chromosome. While an individual can only inherit two alleles for each gene (one from each parent), the population can have more than two versions of a particular gene. Key Points About Multiple Alleles: 1. More than Two Alleles in the Population: o While each individual can have at most two alleles for a gene (one from each parent), there can be more than two alleles in the overall population. o Example: For the blood type gene, there are three possible alleles: A, B, and O. 2. Inheritance: o Each person still inherits only two alleles for a gene, one from each parent, but the possible combinations 91 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] come from the multiple alleles available in the population. Example: Blood Group in Humans The gene for blood type in humans has three alleles: A, B, and O. o A and B are dominant, while O is recessive. Possible Genotypes and Phenotypes: o AA → Type A blood o AO → Type A blood o BB → Type B blood o BO → Type B blood o AB → Type AB blood (co-dominant) o OO → Type O blood Even though there are three alleles (A, B, and O), each person only has two alleles for this gene (one from each parent). This is an example of multiple alleles in a population, but each individual has a combination of only two alleles. 92 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Why It’s Important: Multiple alleles increase genetic variation in a population. It helps explain traits that don't follow simple dominant- recessive inheritance patterns and allows for more complex inheritance. In simple terms, multiple alleles are just different versions of a gene that exist in a population, even though each individual only has two alleles for that gene. RECESSIVE ALLELE A recessive allele is a version of a gene that is masked or hidden when a dominant allele is present. For a recessive trait to show in an individual, that person must inherit two copies of the recessive allele—one from each parent. Key Points About Recessive Alleles: 1. Hidden in the Presence of Dominant Alleles: o If an individual has one dominant allele and one recessive allele (heterozygous), the dominant allele will "cover up" the effect of the recessive allele. 93 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o Example: In the case of eye color, B (brown) is dominant, and b (blue) is recessive. If someone has Bb alleles, they will have brown eyes because B is dominant. 2. Requires Two Copies for Expression: o A recessive trait will only be expressed if both alleles are recessive. This means an individual must have two copies of the recessive allele (homozygous recessive) for the trait to appear. o Example: If a person has bb alleles, they will show the recessive trait, such as blue eyes in the example above. Example of a Recessive Trait: Cystic fibrosis, a genetic disorder, is caused by a recessive allele. A person must inherit the defective gene from both parents (having the cc genotype) to develop the disease. 94 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Summary: A recessive allele is one that is masked by a dominant allele in a heterozygous individual. It only shows its effect if both alleles are recessive (homozygous). CO-DOMINANCES Co-Dominance Co-dominance is a genetic scenario in which both alleles of a gene are expressed equally in the phenotype of an individual. This means that neither allele is dominant or recessive, and both contribute to the organism's trait, resulting in a mixed or combined expression of both alleles. Key Points About Co-Dominance: 1. Both Alleles Are Expressed: o In co-dominance, both alleles show their traits without one being masked by the other. 95 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o The traits of both alleles appear together in the organism’s phenotype. 2. Example of Co-Dominance: o A classic example of co-dominance is seen in the inheritance of blood types in humans, specifically the AB blood group: ▪ A and B alleles are co-dominant. ▪ If a person inherits one A allele from one parent and one B allele from the other parent, both alleles are expressed, and the person will have AB blood type. 3. No Dominant or Recessive Allele: o In co-dominance, both alleles are expressed equally, unlike in dominant-recessive inheritance, where one allele masks the other. Example: Co-Dominance in Cattle (Roan Coat Color) In cattle, the red (R) and white (W) coat color genes exhibit co-dominance: o RR results in a red coat. o WW results in a white coat. 96 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o RW results in a roan coat (a mixture of both red and white hairs). Summary: Co-dominance occurs when both alleles in a gene pair are expressed equally, resulting in a phenotype that shows both traits simultaneously, such as in the case of AB blood type or roan coat color in cattle. INCOMPLETE DOMINANCE Incomplete Dominance: Incomplete dominance is a type of inheritance where neither allele is completely dominant over the other. Instead, the resulting phenotype is a blend of the two parental traits. In this case, the heterozygous phenotype (the offspring with two different alleles) is intermediate between the two homozygous phenotypes. 97 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Key Points About Incomplete Dominance: 1. Blended Phenotype: o In incomplete dominance, the offspring displays a phenotype that is a mixture of the two parent traits. o Neither allele is completely dominant or recessive. 2. Example of Incomplete Dominance: o One of the most famous examples is the flower color in snapdragons (a type of plant). ▪ Red (RR) and white (WW) flowers produce pink (RW) flowers when crossed. The pink color is a blend of red and white. 3. No Pure Dominant or Recessive Trait: o In this form of inheritance, the heterozygous condition (RW) results in a third phenotype, which is a mixture of the two pure forms (red and white). Example: Incomplete Dominance in Snapdragons (Flower Color) In snapdragons: o RR = Red flowers. 98 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] o WW = White flowers. o RW = Pink flowers (a blend of red and white). This is an example of incomplete dominance because the heterozygous flower (RW) is neither red nor white but a blend of both. Summary: Incomplete dominance occurs when two alleles blend together to create a new phenotype in heterozygous individuals, resulting in a mixture of the traits from both parents. This is different from both co-dominance (where both traits are fully expressed) and dominant-recessive inheritance (where one trait is completely masked by the other). VARIATION AND EVOLUTION Variation and Evolution: Variation and evolution are key concepts in understanding how species change over time and how new species come into existence. Here's a breakdown of both: 99 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 1. Variation Variation refers to the differences in characteristics or traits among individuals within a population. These differences can be in physical appearance, behavior, or biochemical processes and can arise due to genetic differences or environmental factors. Types of Variation: 1. Genetic Variation: o Genetic variation comes from differences in the genes (DNA) that individuals inherit from their parents. This is the main source of variation in populations and includes mutations, recombination, and genetic drift. o Example: Eye color, blood type, or resistance to diseases. 2. Environmental Variation: o This type of variation occurs due to differences in the environment in which individuals live, affecting traits like body size, skin color, or behavior. Environmental 100 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] factors, such as diet or climate, can influence how traits develop. o Example: A plant may grow taller if it receives more sunlight or water. Why is Variation Important? Variation is essential for the process of evolution, as it provides the raw material (different traits) for natural selection to act upon. It helps populations adapt to changing environments and improves their chances of survival. 2. Evolution Evolution is the process by which species change over generations through variations in traits and the survival and reproduction of individuals with advantageous traits. It is driven by mechanisms like natural selection, genetic drift, mutation, and gene flow. 101 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] Key Concepts in Evolution: 1. Natural Selection: o Natural selection is the process by which individuals with traits that are better suited to their environment are more likely to survive and reproduce, passing on those advantageous traits to their offspring. o Example: A population of birds with different beak shapes will have individuals with better beak shapes for eating available food. Over time, these traits become more common in the population. 2. Mutation: o Mutations are random changes in the DNA sequence that can introduce new traits in a population. Some mutations may be beneficial, while others may be harmful or neutral. o Example: A mutation that makes a bacteria resistant to an antibiotic. 102 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] 3. Genetic Drift: o Genetic drift refers to random changes in the frequency of alleles in a small population. It can lead to the loss of genetic diversity over time. o Example: A natural disaster kills many individuals in a population, causing a random reduction in genetic diversity. 4. Gene Flow: o Gene flow is the transfer of genetic material between different populations. This can introduce new genetic variations into a population, influencing its evolutionary path. o Example: When individuals from one population migrate to another and interbreed, they introduce new alleles into the gene pool. Why is Evolution Important? Evolution explains the diversity of life on Earth and how organisms adapt to changing environments. Over long periods, evolution can lead to the formation of new species (speciation). 103 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] It provides a framework for understanding how complex traits and behaviors evolve and how life forms are interconnected. Summary: Variation refers to the differences in traits among individuals within a population. These differences can be genetic or environmental and are important for the process of evolution. Evolution is the change in species over time, driven by natural selection, mutations, genetic drift, and gene flow, allowing species to adapt and evolve to their environments. In simple terms: Variation is about the different traits you find in a group of individuals. Evolution is the process by which those traits change in the population over generations. 104 UMAIR HAMZA [BIOLOGY] [PARADOX] [CLASS] MAN AND HIS ENVIRONMENT CH-7 INTRODUCTION Man and His Environment: Introduction The relationship between man (humans) and the environment is one of interdependence. Humans depend on the environment for resources like food, water, and shelter, while also affecting and shaping the environment through their actions. Understanding this relationship is crucial because it influences both human development and the health of the planet. Key Points of Man and His Environment: 1. Human Impact on the Environment: o Humans have a significant impact on the environment, both positive and negative. Activities 105 UMAIR HAMZA [BIOLOGY] [PARADOX]

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