Grade 9 Science – Key Concepts ( condensed overview )
Micro-organisms
Definition: Unicellular or multicellular microscopic organisms, to micrometers, requiring a microscope. Ubiquitous in diverse habitats.
Major groups:
Bacteria: Unicellular prokaryotes (no nucleus/organelles). Varied shapes (cocci, bacilli, spirilla, vibrios). Peptidoglycan cell walls. Rapid asexual binary fission. E.g., Lactobacillus bulgaricus (yogurt), Bacillus anthracis (anthrax), Acetobacter aceti (vinegar), Vibrio cholerae (cholera).
Fungi: Eukaryotes (true nucleus/organelles). Unicellular (yeasts) or multicellular (molds, mushrooms). Heterotrophic (absorb nutrients), decomposers/parasites. Chitin cell walls. E.g., Mucor (bread mold), Saccharomyces cerevisiae (yeast).
Protozoa: Unicellular eukaryotes, motile, heterotrophic, aquatic/moist. Locomotion by cilia (Paramecium), pseudopodia (Amoeba), or flagella (Euglena). Many free-living, some parasitic (Plasmodium - malaria).
Algae: Unicellular or multicellular eukaryotes; contain chlorophyll, perform photosynthesis. Primarily aquatic. Lack true roots/stems/leaves. Base of aquatic food chains (phytoplankton). E.g., Chlamydomonas, Spirogyra, Diatoms, Ulva.
Viruses: Non-cellular, obligate intracellular parasites. Genetic material (DNA/RNA) in a protein capsid, sometimes lipid envelope. Microscopic size, cause diseases.
Environment and substrates: Found universally (soil, water, air, living organisms). Exhibit high adaptability, thriving in extreme conditions (extremophiles: thermophiles, halophiles, acidophiles, barophiles, anaerobes, chemoautotrophs). Form biofilms.
Beneficial effects (applications):
Agriculture:
Nitrogen fixation: Rhizobium, Azotobacter, cyanobacteria convert atmospheric to usable forms (, ) for plants.
Bio-fertilizers: Microbes (nitrogen-fixing/phosphate-solubilizing bacteria, Mycorrhiza fungi) enhance soil nutrients, reducing chemical fertilizers.
Crop Improvement: Genetic engineering (e.g., Bt toxin from Bacillus thuringiensis for pest resistance, Erwinia uredovora for Golden Rice Vitamin A).
Biological pesticides: Microbes (e.g., Alternaria, Bacillus thuringiensis) control pests naturally.
Composting/Waste decomposition: Decomposers (bacteria, fungi) break down organic waste, enriching soil nutrients.
Medicine and Pharmaceuticals:
Antibiotics: Microbe-produced compounds (e.g., Penicillin from Penicillium notatum) inhibit or kill harmful microbes by inhibiting bacterial cell wall synthesis.
Vaccines: Weakened/killed microbes or components stimulate immune response, providing immunity (e.g., recombinant hepatitis B vaccine).
Anti-toxins: Antibodies neutralize microbial toxins (e.g., diphtheria anti-toxin).
Food Industry:
Dairy fermentation: Lactic acid bacteria ferment lactose (milk to yogurt, curd, cheese).
Fermented foods/beverages: Yeast in bread (CO2), beer/wine (alcohol); Acetobacter aceti in vinegar (acetic acid).
Biogas production: Methanogenic bacteria anaerobically digest organic matter (waste, manure) to produce methane (biogas) and fertilizer.
Environment Conservation (Bioremediation):
Oil degradation: Bacteria/fungi (Pseudomonas, Rhodococcus) break down hydrocarbons in oil spills.
Heavy metal removal: Microbes sequester/transform toxic heavy metals from water/soil.
Biodegradable plastics: Research focuses on microbes producing/degrading eco-friendly plastics.
Waste water treatment: Aerobic/anaerobic microbes break down organic matter in sewage, remove nutrients, reduce pathogens.
Other Industrial Uses: Retting (jute, flax fibre separation), bio-leaching/bio-mining (metal extraction from low-grade ores).
Adverse effects:
Pathogens: Micro-organisms causing diseases in humans, plants, animals via toxins, tissue invasion, or function disruption.
Human Diseases: Spread airborne (TB, Influenza), water/foodborne (Typhoid, Cholera), vector-borne (Dengue, Malaria), sexual/blood (AIDS). E.g., Dengue (virus, Aedes mosquito), TB (Mycobacterium tuberculosis, airborne), AIDS (HIV, sexual/blood), Typhoid (Salmonella typhi, food/water), Malaria (Plasmodium, Anopheles mosquito), Amoebic dysentery (Entamoeba histolytica, water/food), Leishmaniasis (Leishmania, sand flies).
Food Spoilage: Microbes (bacteria, yeasts, molds) cause undesirable changes (odor, taste, texture, appearance), leading to economic losses, nutritional reduction, and health risks (e.g., botulism from Clostridium botulinum).
Economic Losses: Pathogenic microbes damage crops, livestock, stored products, and infrastructure (e.g., blight, rot, foot-and-mouth disease, biodeterioration).
Biological Weapons: Virulent microbes/toxins weaponized for harm (e.g., anthrax, smallpox virus, botulinum toxin).
Summary takeaway: Micro-organisms are highly diverse with rapid reproduction, profoundly impacting Earth's ecosystems. They are crucial for industry, agriculture, medicine, and environmental health (nutrient cycles), but also major threats as pathogens and spoilage agents, showcasing their dual nature.
Eye and Ear (2)
Structure and function of the human eye (2.1):
The eye is a complex sensory organ for vision, detecting light, converting it to neural signals for brain interpretation. Protected by skull orbits, eyelids, eyelashes, and tears.
Sclerotic layer (Sclera): Outermost, tough, opaque, fibrous protective layer (white of eye). Maintains shape, provides rigidity, attachment for extrinsic eye muscles.
Cornea: Transparent, dome-shaped front part. Major role in light refraction (approx. total power) before light enters the eye.
Choroid: Middle layer, between retina and sclera. Highly vascularized (supplies retina), contains dark pigments to absorb excess light and prevent blurring.
Retina: Innermost, light-sensitive neural layer. Contains photoreceptor cells (rods and cones) for phototransduction (light to electrical signals).
Rod cells: ~ million, peripheral. High sensitivity to dim light, scotopic (black-and-white) vision, night vision, peripheral vision. No color.
Cone cells: ~ million, concentrated in fovea. Responsible for photopic (color) vision and high-acuity in bright light. Three types (red, green, blue sensitive).
Aqueous humour: Clear, watery fluid (anterior/posterior chambers). Nourishes cornea/lens, maintains intraocular pressure, some refractive power.
Lens: Transparent, flexible, biconvex structure behind iris. Focuses light onto retina by changing curvature (accommodation) for varied distances.
Iris: Colored muscular diaphragm, controls pupil size (regulates light entry).
Pupil: Adjustable, central opening in iris for light entry.
Ciliary muscle: Smooth muscle around lens. Alters suspensory ligament tension to change lens curvature/focal length, enabling accommodation.
Vitreous humour: Clear, jelly-like substance in posterior cavity. Maintains eyeball shape, supports retina, contributes to optical properties.
Fovea (Yellow spot/Macula lutea): Central retinal depression, sharpest vision due to dense cone concentration and absence of light-scattering layers.
Blind spot (Optic disc): Area where optic nerve exits; no photoreceptors, thus no vision.
Optic nerve: Bundle of nerve fibers transmitting electrical signals from retina to brain's visual cortex for image interpretation.
Eye muscles (Extrinsic ocular muscles): Six muscles attached to sclera. Coordinate precise eyeball movements (vertical, horizontal, circular) to widen visual field.
Refraction and image formation (2.1–2.2):
Vision begins as light rays refract sequentially through cornea (most significant), aqueous humor, lens, and vitreous humor, converging on the retina.
The cornea performs primary focusing; the lens fine-tunes via accommodation.
Combined refraction forms a real, inverted, diminished image on the retina. Brain interprets this as upright.
Convex lens: Converging lens, thicker middle. Parallel rays converge to focal point. Eye's lens is convex.
Concave lens: Diverging lens, thinner middle. Parallel rays diverge as if from virtual focal point.
Eye's lens dynamically changes curvature to focus: relaxes for distant (flatter, longer focal length); contracts for near (curved, shorter focal length). Image always forms on retina.
Defects of vision (2.4–2.5):
Hypermetropia (Long-sight/Farsightedness): Clear distant vision, blurry near. Eyeball too short or lens too weak, light focuses behind retina. Corrected with convex lens (adds converging power).
Myopia (Short-sight/Nearsightedness): Clear near vision, blurry distant. Eyeball too long or lens too strong, light focuses in front of retina. Corrected with concave lens (diverges light).
Presbyopia: Age-related farsightedness (~mid-s). Hardening lens/weakening ciliary muscles reduce accommodation for near vision. Corrected with reading glasses (convex lenses) or bifocals.
Astigmatism: Blurred vision at all distances. Irregularly shaped cornea or lens causes uneven light focus. Corrected with cylindrical or toric lenses.
Eye diseases (2.3):
Cataract: Progressive clouding of eye's natural lens. Leads to blurred vision, decreased color, glare, night vision difficulty. Age, UV, diabetes are risk factors. Treated by surgical lens removal and IOL replacement.
Glaucoma: Irreversible optic nerve damage, often due to high intraocular pressure (IOP). Causes gradual, irreversible vision loss (peripheral first); can lead to blindness. Early detection and treatment (drops, laser, surgery) are vital.
Conjunctivitis (Pinkeye): Inflammation of conjunctiva. Caused by bacterial/viral infections (contagious), allergies, irritants. Symptoms: redness, itching, watering, gritty sensation, discharge.
Eye infections and precautionary care:
Protection from harmful light: Use sunglasses blocking UVA/UVB. Avoid direct exposure to bright sources (welding, lasers, sun) to prevent retinal damage.
Wearing safety glasses: Essential in hazardous environments (industrial, labs, sports) to prevent injuries.
Maintaining strict personal hygiene: Avoid touching/rubbing eyes with unwashed hands. Do not share eye makeup, towels, or contact lenses; follow strict contact lens care.
Regular eye check-ups: Especially for those at risk (glaucoma, diabetes, hypertension) for early detection and intervention.
Anatomy and function of the human ear (2)
The ear performs hearing (sound detection/interpretation) and balance (equilibrium).
Structure:
Outer ear: Collects and funnels sound waves.
Pinna (Auricle): Visible external part. Collects and directs sound into ear canal.
External Auditory Canal (Ear Canal): Channels sound to tympanic membrane, amplifies frequencies. Lined with hair and ceruminous glands (earwax) for protection.
Tympanic Membrane (Eardrum): Thin membrane separating outer/middle ear. Vibrates with sound waves, converting sound to mechanical vibrations.
Middle ear (Tympanic cavity): Air-filled cavity. Transmits and amplifies vibrations from eardrum to inner ear.
Ossicles: Chain of three tiny bones (malleus, incus, stapes). Transmit and amplify vibrations (~x force) from tympanic membrane to oval window.
Malleus (Hammer): Largest ossicle, attached to eardrum.
Incus (Anvil): Middle ossicle, between malleus and stapes.
Stapes (Stirrup): Smallest, footplate fits into cochlea's oval window.
Eustachian Tube (Auditory Tube): Connects middle ear to nasopharynx. Equalizes atmospheric pressure, allowing eardrum free vibration.
Inner ear (Labyrinth): Fluid-filled, converts mechanical vibrations to electrical signals (hearing) and maintains balance.
Cochlea: Snail-shaped, fluid-filled structure for hearing. Contains Organ of Corti with hair cells that transduce vibrations from oval window into nerve impulses.
Auditory Nerve (Vestibulocochlear Nerve / Cranial Nerve VIII): Transmits electrical signals from cochlea (hearing) and vestibule/semicircular canals (balance) to brain.
Semicircular Canals: Three fluid-filled loops. Detect rotational head movements for dynamic equilibrium (balance during motion).
Vestibule: Central chamber (utricle and saccule). Detects linear acceleration and static equilibrium (head position relative to gravity).
Hearing mechanism: Sound waves -> external auditory canal -> vibrate tympanic membrane -> ossicles transmit/amplify -> stapes vibrates oval window -> pressure waves in cochlear fluid -> hair cells in Organ of Corti stimulated -> electrical impulses -> auditory nerve -> brain (temporal lobe's auditory cortex) for sound interpretation.
Auditory range: Human hearing: Hz to Hz ( kHz). Intensity in decibels (dB), dB threshold. Frequencies < Hz (infrasound), > Hz (ultrasound). High frequency sensitivity declines with age.
Ear disorders and protection:
Otitis Media: Middle ear infection/inflammation (common in children). Causes ear pain, fever, muffled hearing. Recurrent episodes can lead to temporary/permanent hearing loss.
Tinnitus: Perception of sounds (ringing, buzzing) without external source. Symptom linked to hearing loss/inner ear damage.
Hearing Loss: Reduced hearing ability, conductive (outer/middle ear issue) or sensorineural (inner ear/auditory nerve damage, often irreversible). Hearing aids for amplification, cochlear implants for profound loss.
Protection: Avoid loud noises (> dB), use hearing protection (earplugs/earmuffs) in noisy environments. Never insert objects into ear canal. Maintain outer ear hygiene.
Eye–ear summary: Vision and hearing are critical primary senses. Each uses specialized structures (eye, ear) to detect light/sound waves and convert them to neural signals for brain processing. Both organs are delicate and require protection and regular care for optimal function.
3 Nature and Properties of Matter
3.1 Elements
Definition: Pure substance of one atom type, cannot be broken down chemically/physically. Uniquely characterized by atomic number (Z, number of protons).
Symbols: Standardized 1- or 2-letter abbreviations (e.g., H, C, O, Na (natrium), Fe (ferrum)).
Building units: Atoms are smallest units retaining chemical properties. Can exist individually (Noble gases) or combine into molecules.
Homo-atomic molecules: Two+ atoms of the same element chemically bonded (e.g., , , , , , ).
Elements vs compounds:
Elements: Only one atom type, simplest form of matter (e.g., Au, ). Cannot be decomposed.
Compounds: Two+ different elements chemically combined in fixed ratios. Properties distinct from constituents (e.g., from flammable H and combustion-supporting O; from reactive Na and toxic Cl; ).
3.1.3 Atomic structure
Atom: Basic unit of matter retaining element's chemical identity. Central nucleus (protons, neutrons) surrounded by electron cloud.
Nucleus: Dense, positively charged core. Contains protons (p) and neutrons (n). Most of atom's mass, tiny volume.
Protons (p): charge, relative mass ~ amu. Number defines atomic number (Z) and element identity.
Neutrons (n): charge, relative mass ~ amu. Stabilize nucleus, contribute to mass.
Electrons (e): charge, relative mass ~ amu. Orbit nucleus in energy levels, determine chemical properties.
Atomic Number (Z): Number of protons in nucleus. Identifies element. Z = electrons in neutral atom.
Mass Number (A): Total protons + neutrons in nucleus. . Also nucleon number.
Isotopes: Atoms of same element (same Z, protons) but different neutrons (different A). E.g., Carbon-12 () vs. Carbon-14 (). Similar chemical, differing physical properties.
Notation: (e.g., ) or Symbol-A (e.g., Na-23, Carbon-14).
3.2 Compounds
Definition: Substances formed when two+ different elements bond chemically in fixed proportions. Resulting substance has unique properties distinct from constituents.
Examples: Water (), Glucose (), Sodium Chloride (), Copper Sulfate ().
Chemical Formulae: Represent types and number of atoms for each element in a molecule/formula unit, indicating fixed combo ratios.
3.3 Mixtures
Definition: Physical combinations of two+ pure substances (elements/compounds). Components retain identity and can be physically separated.
Homogeneous mixtures (Solutions): Uniform composition, components indistinguishable (e.g., salt water, air, brass).
Heterogeneous mixtures: Non-uniform composition, visibly distinct components (e.g., mud, sand/iron filings, salad).
Separation Methods: Physical methods based on property differences (boiling point, density, etc.). Common methods: filtration, distillation, evaporation, magnetism, decantation, chromatography.
3.4 Quick recall
Distinguish elements vs. compounds (one type atom vs. multiple types chemically bonded).
Recognize homo-atomic molecules (same element atoms, e.g., ) vs. hetero-atomic molecules (different element atoms, e.g., ).
Differentiate mixtures (physical combo, properties retained, physically separable) from pure substances (fixed composition/properties, not easily separable).
4 Force
4.1 Force: A push or pull on an object, an interaction. A net force causes acceleration (change in motion). A vector quantity (magnitude & direction).
Forces can cause:
Cause motion (start moving).
Change speed (speed up/slow down).
Change direction (alter path).
Change shape or size (deformation).
Types of Forces:
Contact Forces: Direct physical contact.
Friction: Resists relative motion between surfaces (e.g., book on table).
Tension: Pulling force via string/cable (e.g., rope pulling bucket).
Normal force: Perpendicular force from surface supporting an object (e.g., floor on standing person).
Applied force: Direct push/pull by person/object (e.g., pushing a door).
Air resistance (Drag force): Frictional force by air opposing motion (e.g., skydiver).
Non-contact Forces (Action-at-a-distance forces): Act between objects not in contact, via fields.
Gravitational force: Attractive force between any two masses (e.g., ball falling).
Electromagnetic force: Force between charged particles (magnets, electricity, chemistry).
Strong nuclear force: Holds atomic nuclei together.
Weak nuclear force: Involved in radioactive decay.
4.2 Magnitude of force: Strength of force, measured by Newton spring balance. SI unit: Newton (N). . (Note: scales often show mass, implicitly measuring weight).
4.3 Direction and point of application: Crucial for effect. Same magnitude, different direction/point yields different results (e.g., pushing a door near hinges vs. handle; kicking a ball center vs. off-center).
4.4 Graphical representation: Arrow. Length proportional to magnitude, arrowhead shows direction. Tail marks point of application.
4.5 Everyday implications: Practical in daily life/engineering. Designing simple machines (levers, door handles, wrenches) utilizes optimal force application point/direction for maximal effect/ease.
4.6 Summary: Force = push/pull, causes/tends to cause motion/shape change. Vector (magnitude, direction, point of application). Represented by arrows. Causes acceleration, direction change, or deformation. SI unit: Newton (N).
5 Pressure
5.1 Pressure: Perpendicular force exerted per unit area. . SI unit: Pascal (Pa). . Other units: kPa, psi, atm, bar, mmHg.
5.2 Factors affecting pressure: Directly proportional to force (), inversely proportional to area ().
Increasing Force: Increases pressure (constant A) (e.g., hitting nail harder).
Increasing Area: Decreases pressure (constant F) (e.g., snowshoes).
Decreasing Area: Significantly increases pressure (constant F) (e.g., sharp needle).
5.3 Applications and examples:
Narrow vs. Broad Straps: Broad straps on bags increase contact area, reducing pressure on shoulders (comfortable).
Knives and Cutting Tools: Sharp, thin edges have tiny contact area, generating high pressure to cut with minimal force.
Foundations of Buildings: Wide foundations spread massive weight over large area, reducing pressure on soil, preventing sinking.
Road Damage by Heavy Vehicles: Many wheels/wide tires distribute weight, reducing pressure on roads, minimizing damage.
Drawing Pins/Nails: Broad head transmits force to tiny sharp point, concentrating tremendous pressure to penetrate surfaces easily.
5.4 Changing pressure:
To Increase Pressure: Increase applied force OR decrease contact area.
To Decrease Pressure: Decrease applied force OR increase contact area.
5.5 Problems and practice: Students solve problems and explain real-world pressure phenomena.
Pressure in Liquids (Fluid Pressure):
Liquids exert pressure in all directions (random molecular motion/collisions).
Hydrostatic pressure () depends on depth (), liquid density (), and gravity ().
Explains: pressure increases with depth; pressure at given depth is uniform in all directions; pressure depends on liquid density. (E.g., thick dam walls at bottom).
6 The Human Circulatory System
The human circulatory (cardiovascular) system: Closed transport system. Transports blood throughout body, delivering oxygen/nutrients/hormones/enzymes to cells and removing waste (CO2, urea, lactic acid).
6.1 Heart structure: Powerful, muscular, four-chambered organ (clenched fist size), acts as double pump for efficient oxygenated/deoxygenated blood separation.
Four Chambers: Divided by septum into right/left halves, each with an atrium (upper) and ventricle (lower).
Right Atrium (RA): Receives deoxygenated blood from body via superior/inferior vena cava.
Right Ventricle (RV): Pumps deoxygenated blood from RA to lungs via pulmonary artery (pulmonary circulation).
Left Atrium (LA): Receives oxygenated blood from lungs via four pulmonary veins.
Left Ventricle (LV): Pumps oxygenated blood from LA to rest of body via aorta (systemic circulation). Thickest wall (myocardium) for high pressure.
Valves: Ensure unidirectional blood flow, prevent backflow. Contribute to heart sounds.
Atrioventricular (AV) Valves: Between atria and ventricles.
Tricuspid Valve: Between RA and RV (3 cusps).
Bicuspid Valve (Mitral Valve): Between LA and LV (2 cusps). Regulates oxygenated blood flow to powerful LV.
Semilunar Valves: At major artery origins from ventricles.
Pulmonary Valve: RV to pulmonary artery (3 pocket-like cusps).
Aortic Valve: LV to aorta (3 cusps).
Major Vessels (Directly Connected to the Heart):
Aorta: Largest artery from LV. Carries oxygenated blood to systemic arteries under high pressure.
Pulmonary Arteries: Carry deoxygenated blood from RV to lungs (unique).
Pulmonary Veins: Carry oxygenated blood from lungs to LA (unique).
Vena Cava (Superior and Inferior): Largest veins. Collect deoxygenated blood from upper/lower body to RA.
Blood Flow Path (Pulmonary and Systemic Circulation): Heart pumps blood through two continuous loops:
Systemic Circulation (Body Cycle): Deoxygenated blood enters RA (vena cava) -> Tricuspid valve -> RV -> Pulmonary valve -> Pulmonary Artery -> lungs.
Pulmonary Circulation (Lung Cycle): In lungs, blood exchanges CO2 for O2. Oxygenated blood from lungs -> Pulmonary Veins -> LA -> Mitral valve -> LV -> Aortic valve -> Aorta -> body. Deoxygenated blood returns to RA via vena cava.
6.2 Arteries, veins and capillaries: Blood vessels adapted for specific roles.
Arteries: Thick-walled, muscular, elastic. Carry oxygenated blood away from heart (except pulmonary artery). Withstand high pressure, maintain flow. Branch into arterioles.
Veins: Thinner-walled, less muscular/elastic. Carry deoxygenated blood towards heart (except pulmonary veins). Lower pressure. Contain one-way valves to prevent backflow; aided by muscle contractions and breathing.
Capillaries: Smallest, most numerous networks. Extremely thin walls (1 cell thick) for rapid gas/nutrient/waste exchange between blood and cells. Slow blood flow for efficient exchange.
Blood Flow Pathway: Large arteries -> arterioles -> capillary beds (exchange) -> venules -> larger veins -> heart.
6.3 Blood components and functions: Blood is fluid connective tissue (plasma + formed elements).
Plasma: Straw-colored liquid matrix (~ blood volume), water. Contains proteins (albumin, globulins, fibrinogen), salts, hormones, antibodies, nutrients, gases, waste. Transports substances, maintains volume/pH/temperature.
Red Blood Cells (Erythrocytes): Most numerous (~ million/µL). Biconcave discs for efficient gas exchange, anucleated (mammals). Packed with haemoglobin (iron-containing protein) for oxygen transport from lungs to tissues. Minor CO2 transport. Produced in red bone marrow, ~120-day lifespan.
White Blood Cells (Leukocytes): Larger, nucleated (~/µL). Crucial for immune defense. Granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes). Roles: phagocytosis, debris removal, antibody production, immune responses.
Platelets (Thrombocytes): Small, irregular, anucleated cell fragments from megakaryocytes. Crucial for hemostasis (stopping bleeding) by forming platelet plug and releasing clotting factors (fibrin mesh formation).
6.4 Blood transfusion: Transferring blood/components from donor to recipient. Requires compatibility to prevent immune reactions.
ABO Blood Groups: Based on A/B antigens on RBCs and anti-A/anti-B antibodies in plasma. Incompatible transfusion causes agglutination/hemolysis.
Type A: A antigens, anti-B antibodies. Receives A, O.
Type B: B antigens, anti-A antibodies. Receives B, O.
Type AB: A & B antigens, no antibodies. Universal recipient (theoretically for RBCs).
Type O: No A/B antigens, both anti-A/anti-B antibodies. Universal donor (RBCs). Receives only O.
Rh Factor (Rhesus factor): Presence (Rh+) or absence (Rh-) of D antigen on RBCs. Anti-Rh antibodies only produced upon exposure/sensitization.
Rh-negative (Rh-): Lacks D antigen. Must receive Rh- blood, especially if sensitized (risk of HDN in pregnancy).
Rh-positive (Rh+): Possesses D antigen. Can receive Rh+ or Rh-.
NBTS (National Blood Transfusion Service) Procedures: Strict protocols: donor screening (diseases), accurate ABO/Rh typing, cross-matching (recipient plasma vs. donor RBCs), proper storage/handling/administration. Donor health questionnaires are vital.
7 Plant Growth Substances
Plant growth substances (phytohormones): Naturally occurring organic compounds in plants found in low concentrations. Regulate plant growth, development, and responses to stimuli. Some promote growth, others inhibit.
Main promoters:
Auxins (e.g., IAA): Synthesized in shoot tips, young leaves, developing seeds/fruits. Polarly transported.
Functions: Promotes cell elongation (stem), mediates apical dominance, governs phototropism/gravitropism, stimulates vascular cambium cell division, root initiation on cuttings, fruit development. Delays/promotes abscission based on concentration.
Gibberellins (GAs): Synthesized in young leaves, developing seeds, root tips. Transported via xylem/phloem.
Functions: Promotes stem elongation (reverses dwarfism), breaks seed dormancy (germination), stimulates fruit growth (e.g., grapes), promotes flowering, induces bolting.
Cytokinins: Derivatives of adenine (e.g., zeatin, kinetin). Synthesized in root tips, developing seeds/fruits. Transported mainly in xylem.
Functions: Promotes cell division (with auxins, in tissue culture), stimulates bud/seed germination, delays leaf/flower senescence (maintains chlorophyll), promotes lateral bud growth (counteracts apical dominance).
Ethene (Ethylene, ): Gaseous hydrocarbon hormone produced by most plant tissues (ripening fruits, senescing leaves, stress).
Functions: Promotes climacteric fruit ripening (respiration burst, softening), accelerates senescence and abscission of leaves/flowers/fruits, influences flower development/root hair formation.
Abscisic acid (ABA): Inhibitory hormone, critical for stress response/dormancy. Synthesized in mature leaves (under water stress), root caps, developing seeds.
Functions: Promotes stomatal closure (water stress), induces/maintains seed/bud dormancy (inhibits growth promoters), general role in plant adaptation/stress signaling.
Artificial growth substances: Synthetic plant hormones similar to natural ones, used commercially to control plant growth.
Examples: Synthetic auxins: IAA, IBA, NAA (for rooting cuttings, fruit thinning). 2,4-D and 2,4,5-T (selective herbicides: cause uncontrolled growth/death in broadleaf weeds, sparing grasses; components of Agent Orange).
Applications: Used in agriculture to improve yields, quality, efficiency:
Rooting: Synthetic auxins (IBA, NAA) stimulate adventitious roots on cuttings for vegetative propagation.
Fruit set and development: Auxins/gibberellins improve fruit set, prevent premature drop, increase fruit size.
Weed control: High concentrations of synthetic auxins as selective herbicides kill broadleaf weeds in cereal crops.
Breaking dormancy: Gibberellins induce uniform germination/sprouting of seeds/tubers.
Delaying spoilage: Cytokinins delay senescence of leafy vegetables/cut flowers post-harvest, extending shelf life.
Ripening: Ethene gas ripens climacteric fruits uniformly after harvest for transport/storage.
Ethical considerations: Concerns include environmental impact (herbicide runoff, non-target effects), potential consumer health effects (food residues), and ecological balance. Leads to strict regulations, research into safer alternatives, and sustainable practices.
8 Support and Movements of Organisms
8.1 Movement in animals: Fundamental for navigating environment, acquiring food, escaping predators, reproduction, dispersal, adaptation.
Unicellular Organisms: Use specialized cellular structures for locomotion in aqueous environments.
Pseudopodia ('false feet'): Temporary cytoplasmic extensions for amoeboid movement (e.g., Amoeba, macrophages); crawl, engulf food.
Cilia: Numerous, short, hair-like. Coordinated rhythmic beating propels organisms (Paramecium) or moves fluids (respiratory tract).
Flagella: Longer, whip-like. Rotate/undulate for propulsion (Euglena, sperm cells).
Multicellular Animals (Humans/Vertebrates): Complex, integrated musculoskeletal systems for diverse, coordinated movements. Crucial for survival and reproduction.
Muscles and Bones: Muscles contract to generate force, transmitted by tendons to bones (skeleton) acting as levers. Muscles work in antagonistic pairs (e.g., biceps/triceps) for opposing movements. Bones provide rigid framework, support, protection, mineral storage, hematopoiesis.
Different Appendages: Specialized for specific movements:
Limbs: Paired (legs, arms) for terrestrial locomotion (walking, running, climbing) and manipulation.
Wings: Modified forelimbs (birds, bats) or outgrowths (insects) for flight.
Fins: Flattened, membranous (fish, marine mammals) for aquatic propulsion, steering, stability.
8.2 Muscles and bones: Coordinated interaction fundamental for vertebrate movement.
Muscles: Bundles of contractile fibers. Contraction generates force transmitted to bones via tendons, causing movement at joints. Often in antagonistic pairs (flexor/extensor) for opposing actions (e.g., biceps/triceps at elbow).
Bones: Rigid body framework. Structural support, posture, vital organ protection, muscle attachment sites (leverage). Mineral storage (calcium/phosphate), hematopoiesis (blood cell production).
Joints: Connections between bones allowing movement.
Hinge joints: One-plane movement (e.g., elbow, knee, ankle, finger joints); flexion/extension.
Ball-and-socket joints: Greatest range of motion (multiple planes: flexion, extension, abduction, adduction, rotation, circumduction) (e.g., shoulder, hip).
Elbow joint model: Biceps (flexor) contracts, pulls forearm (radius/ulna) upwards (flexion); triceps (extensor) relaxes. Conversely, triceps contracts, biceps relaxes to extend arm.
8.3 Plant movements: Primarily growth or turgor pressure changes. Optimize resource acquisition, reproduction, stress avoidance.
Tropic movements (Tropisms): Directional growth responses to external stimuli (slow, irreversible, differential growth).
Phototropism: Growth towards light (+ve in stems/leaves, mediated by auxin; roots often -ve/insensitive).
Gravitropism (Geotropism): Growth response to gravity (+ve in roots, -ve in shoots).
Hydrotropism: Growth towards water (+ve in roots).
Thigmotropism: Growth response to touch (e.g., tendrils coiling around support).
Nastic movements: Non-directional responses (faster, reversible, turgor-driven).
Thigmonasty: Rapid, non-directional response to touch (Mimosa pudica rapid leaf folding via turgor changes in pulvini).
Nyctinasty (Sleep movements): Daily rhythmic leaf movements (folding at night) mediated by turgor changes and circadian clock.
8.4 In-situ conservation: Preserving organisms within their natural habitats/ecosystems. Protects species, communities, ecological processes, and genetic diversity in native environments. Crucial for biodiversity and evolution.
9 The Evolutionary Process
9.1 Origin of the Earth: Estimated ~ billion years old.
Nebular Theory: Solar System formed from collapsing solar nebula (gas/dust). Sun formed centrally, planets accreted from surrounding disk.
Big Bang Theory: Cosmological model for universe origin (~ billion years ago), not specifically Earth (Earth formed later within expanding universe).
Earth's Cooling and Core Formation: Early Earth molten; denser iron/nickel sank to form core, lighter silicates formed mantle/crust. Surface cooled and solidified.
Atmospheric Changes: Early 'reducing' atmosphere (little ), likely from volcanism. Photosynthesis (cyanobacteria, ~ billion years ago) gradually oxygenated atmosphere ('Great Oxidation Event'), enabling aerobic life.
9.2 Origin of life: Hypotheses for abiogenesis (life from non-life):
Special Creation: Theological/philosophical belief, not scientific theory.
Spontaneous Generation: Discredited ancient hypothesis (life from non-living matter, e.g., maggots from meat). Disproved by Louis Pasteur (biogenesis: life from life).
Cosmozoic (Panspermia) Theory: Life originated elsewhere, transported to Earth (e.g., via meteorites); doesn't explain ultimate origin of life.
Biochemical Evolution (Oparin-Haldane Hypothesis): Most accepted scientific hypothesis. Life arose gradually from inorganic matter on early Earth through complex chemical reactions. Primitive reducing atmosphere + energy -> simple inorganics -> organic monomers (amino acids) -> macromolecules (proteins, nucleic acids) -> self-replicating systems (protobionts/protocells) -> first simple cells.
Miller-Urey Experiments (1953): Simulated early Earth conditions (reducing atmosphere, boiling water, electrical sparks). Produced various organic molecules (amino acids, sugars, lipids), supporting Oparin-Haldane hypothesis.
9.3 Evolution: Process by which organisms develop and diversify from simpler forms over generations. Changes in heritable characteristics of populations. Driven by natural selection on genetic variation.
Evidence for Evolution: Multiple independent lines of support:
Fossil Records: Chronological record of life in rock layers. Shows extinct species, gradual morphological changes, transitional forms (e.g., Archaeopteryx).
Biogeography: Geographical distribution patterns of species. Explained by common ancestry, isolation, adaptation (e.g., Australian marsupials, Darwin's finches).
Comparative Anatomy: Similarities/differences in anatomical structures.
Homologous Structures: Similar underlying structure/origin, different functions (common ancestor) (e.g., vertebrate forelimbs: human arm, bat wing, whale flipper, cat leg).
Analogous Structures: Different underlying structure/origin, similar functions (convergent evolution) (e.g., insect vs. bird wings for flight).
Comparative Embryology: Similarities in early embryonic development across diverse vertebrates suggest common ancestry (e.g., gill slits, post-anal tail).
Molecular Biology (DNA and Protein Similarities): Strongest quantifiable evidence. Universal genetic code, similarities in DNA/RNA/protein sequences (e.g., cytochrome c) demonstrate common descent. Closer species have fewer molecular differences.
Living Fossils: Existing species resembling fossil ancestors with little morphological change over millions of years (e.g., Coelacanth, Lingula indicating evolutionary stasis).
9.4 Biodiversity and evolution:
Natural Selection: Primary mechanism of evolution (Charles Darwin). Individuals with environmentally advantageous traits survive and reproduce more successfully, passing on those traits, leading to gradual genetic change in population.
Key principles: Variation (heritable traits), Inheritance (passed to offspring), Overproduction (competition for resources), Differential Survival and Reproduction (advantageous traits increase in frequency).
Speciation: Evolutionary process creating new distinct biological species from existing ones. Occurs via reproductive isolation + accumulated genetic differences.
Biodiversity: Variety of life on Earth (genetic, species, ecosystem diversity). Product of evolution. Crucial for ecosystem stability, resilience, and essential ecosystem services (food, water, pollination, climate regulation).
12 Bio-diversity
12.1 Introduction: Biodiversity = totality of life's variety on Earth (forms, levels, variation). Considered at three hierarchical levels.
Ecosystem defined: Functional unit of living organisms (biotic) interacting with non-living environment (abiotic) in a specific area. Characterized by energy flow, nutrient cycling.
Levels of Biodiversity:
Genetic Diversity: Variation in genes (alleles) within a species/population. Raw material for adaptation, resists diseases, ensures long-term survival (e.g., rice varieties, human immune genes).
Species Diversity: Variety of different species in a habitat/ecosystem/region. Includes richness (number of species) and evenness (relative abundance).
Ecosystem Diversity: Variety of different habitats, communities, and ecological processes within a geographical area (e.g., rainforests, grasslands, reefs, rivers).
12.2 Importance: Provides critical ecosystem services (natural capital) for planet health and human well-being.
Ecosystem Services: Direct/indirect benefits from healthy ecosystems.
Provisioning services: Products (food, fresh water, timber, medicinal plants, genetic resources).
Regulating services: Regulation of processes (climate regulation, disease control, water purification, pollination, waste decomposition, flood regulation).
Cultural services: Non-material benefits (recreation, aesthetic, spiritual, art, education).
Supporting services: Necessary for all other services (nutrient cycling, soil formation, primary production, habitat provision).
Ecosystem Stability and Resilience: Diverse ecosystems are more stable, productive, resilient to disturbances (drought, pests, climate change) due to wider range of species/adaptations.
Aesthetic and Intrinsic Value: Inherent beauty and right of diverse life/landscapes to exist.
Tourism and Recreation: Many activities depend on intact, biodiverse environments, creating economic opportunities.
Sri Lanka’s rich biodiversity: Global biodiversity hotspot (Indo-Burma). High endemic species (amphibians, reptiles, freshwater fish, flora). Highlights irreplaceable ecological value and urgent conservation need.
12.3 Threats: Unprecedented global biodiversity decline, primarily human-induced.
Natural Threats: Often local, less widespread than human-induced.
Volcanic eruptions: Habitat destruction, climate alteration, toxic gases, life loss.
Tsunamis and Earthquakes: Physical habitat destruction, coastal erosion, salinization, direct life loss.
Floods and Droughts: Extreme weather events impacting water, causing erosion, habitat destruction, species stress/death.
Human-induced Threats: Leading, pervasive, interconnected causes.
Habitat Destruction and Fragmentation: Conversion of natural habitats for agriculture, urbanization, industry, infrastructure, logging/mining. Single biggest threat, leading to lost living space, disrupted processes, isolated populations.
Pollution: Contamination of air/water/soil (industrial chemicals, pesticides, plastics, heavy metals, sewage, nutrient runoff). Directly harms organisms, degrades ecosystems.
Invasive Alien Species (IAS): Non-native species introduced into new ecosystems. Outcompete/prey on natives, introduce diseases, disrupt food webs, alter habitats, causing native species decline/extinction.
Climate Change: Long-term global weather pattern alterations (anthropogenic greenhouse gas). Rising temperatures, altered precipitation, sea-level rise, ocean acidification.