Biology 10th Class Book by Muhammad Ali

Gaseous Exchange in Organisms

All living organisms require energy to sustain life-sustaining activities, the ultimate source of which is sunlight. Photosynthetic organisms capture sunlight to prepare energy-rich organic molecules using carbon dioxide and water, releasing oxygen as a byproduct. Respiration is the cellular process where oxygen is used to break down organic molecules into carbon dioxide and water to release energy. Gaseous exchange refers specifically to the exchange of oxygen and carbon dioxide between an organism and its environment, typically occurring via diffusion, which is the movement of molecules from a region of higher concentration to a region of lower concentration. Breathing is the physical process in higher animals where air is moved into and out of the body to facilitate this exchange. In animals, the lungs serve as the primary organs of breathing, ensuring fresh air with a higher concentration of oxygen is available at the respiratory surface.

In plants, gaseous exchange occurs through the general surface, including the epidermis of roots, stems, and leaves. During the daytime, plant cells carry out both respiration and photosynthesis. Leaves use the carbon dioxide produced during respiration for photosynthesis and release oxygen produced during photosynthesis for respiration. Any excess oxygen is released into the environment, while additional carbon dioxide is taken in from the atmosphere. At night, photosynthesis stops, but respiration continues, meaning plants take in oxygen and release carbon dioxide. Stomata are small pores in leaf and young stem epidermises that facilitate this movement. In woody stems, the bark prevents gas exchange, necessitating special pores called lenticels for interaction with the environment. Roots also perform gaseous exchange with air spaces between soil particles, a process aided by the agricultural practice of tilling, which improves soil drainage and aeration.

The Human Respiratory System and Breathing Mechanism

The human respiratory system is divided into the air passageway and the lungs. The air passageway consists of the nostrils, nasal cavities, pharynx, larynx, trachea, bronchi, and bronchioles. External nostrils allow air into the nasal cavities, where it is warmed, moistened, and filtered by hairs and mucous membranes. The pharynx is a $4.5\text{ inch}$ muscular passage containing tonsils and adenoids to filter microorganisms. The larynx, or voice box, contains the glottis, which is protected by a lid-like epiglottis during swallowing. The trachea, or windpipe, is a ciliated tube kept open by $16$ to $20$ C-shaped cartilaginous rings. It divides into two bronchi that enter the lungs and subdivide into smaller bronchioles, eventually ending in clusters of thin-walled pouches called alveoli. These alveoli are covered in a network of blood capillaries and serve as the site for gaseous exchange.

Breathing involves two phases: inspiration (inhalation) and expiration (exhalation). During inspiration, the volume of the chest cavity increases as the diaphragm muscles contract and flatten, and the intercostal muscles contract to expand the ribcage. This decrease in internal pressure causes atmospheric air to rush into the lungs. During expiration, the ribcage muscles and diaphragm relax, with the diaphragm returning to a dome shape, which increases pressure on the lungs and expels air out. The adult breathing rate at rest is typically $15$ to $20$ times per minute but can increase to $30$ to $40$ times per minute during exercise as the brain's medulla detects increased carbon dioxide levels and signals the muscles to work faster. Inspired air contains approximately $21\%$ oxygen and $0.04\%$ carbon dioxide, while expired air contains around $16\%$ oxygen and $4\%$ carbon dioxide.

Respiratory Disorders and Effects of Smoking

Respiratory health can be disrupted by various factors leading to serious disorders. Bronchitis is the inflammation or infection of the bronchi or bronchioles, causing mucus accumulation and restricted airflow, often treated with antibiotics or anti-virals. Emphysema is a severe condition where the walls of the alveoli are damaged by excessive coughing or pollutants, leading to permanent shortness of breath. Pneumonia is an inflammation of the lungs caused by bacteria, viruses, or fungi that fills the alveoli with pus, often transmitted via airborne droplets. Lung cancer involves the uncontrolled growth of cells in lung tissues. Asthma is characterized by inflammation of the airways making breathing difficult.

Smoking has severe biological consequences, as tobacco smoke contains over $4,000$ different chemicals, including at least $69$ known carcinogens. Tar is a major component that stains teeth and fingers, damages lung tissue, and increases phlegm production. Nicotine increases heart rate and blood pressure, constricts blood vessels, and increases platelet stickiness, leading to coronary diseases. Carbon monoxide in smoke binds to red blood cells, preventing oxygen transport. Major components like benzene and formaldehyde are linked to leukemia and gastrointestinal problems. Passive smoking, the inhalation of smoke by non-smokers, causes eye and throat irritation and is a significant risk factor for cancer.

Homeostasis in Plants and Humans

Homeostasis is the ability of an organism to maintain its internal environment in a constant state despite changes in the external environment. Key components regulated include water, solutes, and temperature. Osmoregulation is the maintenance of water and salt balance, while thermoregulation refers to temperature control centered around an optimal point of $37\,^{\circ}\text{C}$. Excretion is the elimination of nitrogenous wastes and excess water. In plants, osmoregulation is categorized by habitat: Mesophytes live in moderate water and close stomata to prevent transpiration; Hydrophytes live in freshwater and have broad leaves with numerous stomata on top for water removal; Xerophytes live in dry environments and have thick cuticles and specialized succulent stems for water storage; and Halophytes live in salty marshes and use active transport to absorb salts and maintain water intake.

Human homeostasis is primarily managed by the skin, lungs, and kidneys. The lungs regulate carbon dioxide concentration. The skin acts as a thermoregulatory organ; fat cells in the epidermis provide insulation, while sweat glands provide a cooling effect through evaporation. The kidneys act as the chief excretory and osmoregulatory organs by filtering nitrogenous wastes from the blood and adjusting urine volume based on body hydration levels. The liver also assists by breaking down dead red blood cells and converting ammonia into urea, which is then excreted by the kidneys.

The Human Urinary System and Kidney Function

The human urinary system consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra. Each kidney is approximately $10\,\text{cm}$ long, $5\,\text{cm}$ wide, and $4\,\text{cm}$ thick, bean-shaped, and located on the dorsal body wall. The concave side features a hilus where the renal artery enters and the renal vein and ureter exit. Internally, the kidney has an outer renal cortex and an inner renal medulla containing renal pyramids. The functional unit is the nephron, with over one million per kidney. A nephron consists of the renal corpuscle (glomerulus and cup-shaped Bowman's capsule) and the renal tubule (proximal convoluted tubule, Loop of Henle, and distal convoluted tubule). Distal tubules open into collecting ducts leading to the renal pelvis.

Urine formation occurs in three steps: pressure filtration, reabsorption, and tubular secretion. In pressure filtration, high blood pressure in the glomerulus forces water, glucose, and nitrogenous wastes into the Bowman's capsule, forming glomerular filtrate. Blood cells and proteins are too large to filter. In reabsorption, useful substances like glucose and salts are moved back into the blood capillaries surrounding the tubules. Finally, in tubular secretion, waste materials like hydrogen ions and urea are added from the blood to the renal tubule. The resulting urine is stored in the bladder and released through the urethra, controlled by sphincter muscles. Kidneys conserve water by reabsorbing over $99.5\%$ of the glomerular filtrate.

Kidney Disorders and Contributions of Muslim Scientists

Kidney stones are formed when filtered substances like calcium oxalate, uric acid, or ammonium phosphate accumulate into large objects that obstruct the urinary tract. Small stones can be passed with high water intake, while larger ones require surgery or lithotripsy, a non-surgical technique using shock-waves to break stones into tiny pieces. Kidney failure occurs when nephrons are destroyed, often due to long-term diabetes or hypertension, leading to high urea levels in the blood and edema in the limbs. Treatment involves dialysis or transplantation. Haemodialysis uses a machine called a dialyzer with semi-permeable membranes, while peritoneal dialysis utilizes the patient's own peritoneal membrane in the abdomen.

Historical contributions to kidney treatment include the work of Abul-Qasim al-Zahrawi ($936$-$1013\text{ AD}$), who described surgical stone removal in his medical encyclopedia Al-Tasrif. Al-Farabi ($872$-$950\text{ AD}$) wrote extensively on kidney diseases. Abu Bakar Muhammad ibn Al Razi ($865\text{ AD}$) was known for his critical work "The Book of Formation of Small Stones," which explored techniques to remove bladder stones.

Coordination and Control Systems

Coordination integrates different body parts to respond to stimuli. There are two types: nervous coordination, which is electrical and rapid, and chemical coordination, which involves hormones and is typically slower. The process involves three phases: receiving a stimulus via receptors (e.g., sense organs), analyzing information in a coordinator (brain, spinal cord, or endocrine glands), and producing a response via effectors (muscles or glands). The human nervous system consists of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The basic unit is the neuron, comprising a cell body, dendrites to receive impulses, and an axon to transmit them. Myelin sheaths insulate many axons, broken at intervals by nodes of Ranvier. Neurons are classified as sensory, motor, or associative.

The human brain is protected by the cranium and three layers of meninges, bathed in cerebrospinal fluid (CSF). It is divided into the forebrain (cerebrum, thalamus, and limbic system including the hypothalamus), midbrain, and hindbrain (cerebellum, pons, and medulla oblongata). The cerebrum is the largest part, responsible for intelligence and memory, with its outer grey matter known as the cerebral cortex. The cerebellum controls balance, while the medulla oblongata manages automatic functions like heart rate and breathing. The spinal cord, a continuation of the medulla, acts as a coordinator for reflex actions—automatic, involuntary responses performed through a neural pathway called the reflex arc.

Human Receptors and Ophthalmology

Human eyes are photoreceptors located in facial orbits. The eyeball has three layers: the sclera (outer white layer), the choroid (middle layer forming the iris and pupil), and the retina (innermost layer containing photoreceptors). Rods perceive dim light using the pigment rhodopsin (synthesized from Vitamin A), while cones visualize colors using iodopsin. The fovea is the area of highest visual acuity. Vision disorders include myopia (short-sightedness), where the eyeball is too long and light focuses in front of the retina (corrected with concave lenses), and hypermetropia (long-sightedness), where the eyeball is too short and light focuses behind the retina (corrected with convex lenses). Muslim scientists Ibn Al Haitham ($965\text{ AD}$), the father of modern optics, and Ali bin Isa ($940$-$1010\text{ AD}$), author of the "Notebook of the Oculist," made foundational contributions to ophthalmology.

The Human Ear and Hearing Mechanism

The ear acts as a sono-receptor for sound and is essential for balance. It consists of the outer ear (pinna, auditory canal, and ear drum), the middle ear (ossicles: malleus, incus, and stapes), and the inner ear (cochlea and semi-circular canals). Sound waves vibrate the ear drum and ossicles, which transfer vibrations through the oval window to the fluid-filled cochlea. The hair cells in the organ of Corti bend, generating nerve impulses sent via the auditory nerve to the brain. For balance, fluid in the semi-circular canals pushes particles that stimulate hair cells when the head moves, sending orientation signals to the cerebellum.

Chemical Coordination and Endocrine Glands

Chemical coordination is managed by endocrine glands, which are ductless and release hormones directly into the blood. Major glands include the Pituitary (the "master gland"), Thyroid, Pancreas, Adrenal, and Gonads. The Pituitary gland, located at the brain's base, secretes Growth Hormone (TSH), ADH, and oxytocin. Over-secretion of Growth Hormone causes gigantism, while under-secretion causes dwarfism. The Thyroid gland produces thyroxine, which increases metabolism; iodine deficiency in this gland leads to Goitre. The Pancreas secretes insulin to lower blood glucose and glucagon to raise it; failure to produce insulin results in diabetes mellitus. Adrenal glands atop the kidneys produce adrenaline for "fight or flight" responses. Hormone secretion is regulated by feedback mechanisms, such as negative feedback, where the output of a process stops or slows down the process to maintain homeostasis.

Support, Movement, and the Human Skeleton

The human skeleton provides shape, support, protection, and facilitates locomotion. It consists of $206$ bones in adults, categorized into the axial skeleton ($80$ bones including the skull, vertebral column, ribs, and sternum) and the appendicular skeleton ($126$ bones including limbs and girdles). Bones are a rigid form of connective tissue with a hard outer layer of compact bone and an inner spongy bone containing marrow, where blood cells are formed. Cartilage is a flexible connective tissue found at joints, divided into hyaline, elastic, and fibrous types. Joints are classified as immovable (skull sutures), slightly movable (vertebrae), or freely movable (hinge joints in knees/elbows and ball-and-socket joints in hips/shoulders). Ligaments hold bones together at joints, while tendons attach muscles to bones.

Muscles enable movement through contraction. Skeletal muscles are voluntary and often arranged in antagonistic pairs, such as the biceps (flexor) and triceps (extensor). During arm flexion, the biceps contracts while the triceps relaxes. Skeletal disorders include osteoporosis, a mineral depletion that makes bones fragile, and arthritis, the inflammation of joints. Types of arthritis include osteoarthritis (wear of cartilage), rheumatoid arthritis (autoimmune destruction of joints), and gouty arthritis (uric acid crystal accumulation). Arthroplasty is the surgical replacement of diseased joints with artificial ones. Historical anatomical knowledge was greatly advanced by Andreas Vesalius ($1514$-$1564$), who wrote "De Humani Corporis Fabrica."

Reproduction in Plants and Animals

Reproduction ensures species continuity through the transmission of genetic material. Asexual reproduction involves a single parent and produces clones, occurring through binary fission (bacteria, amoeba), multiple fission, budding (yeast, hydra), spore formation (rhizopus), or vegetative propagation. Vegetative propagation in plants can be natural (via stems, bulbs, or leaves) or artificial (via cuttings or grafting). Sexual reproduction in flowering plants involves the alternation of generations between the sporophyte ($2n$) and gametophyte ($n$). Flowers contain stamens (anther/filament) and carpels (stigma/style/ovary). Double fertilization is unique