APEX Life Sciences Grade 10 Comprehensive Study Guide
General Biology: Levels of Organization and Definitions
Levels of Biological Organization: An organism is a complex structure composed of a hierarchy of levels: - Atom: The fundamental unit of matter. - Molecule: A group of atoms bonded together. - Cell: The basic structural and functional unit of life. - Tissue: A group of cells that have the same structure and are specialized to carry out a certain function. - Organ: A group of different tissues with a similar function. - Organ System: A group of organs working together for the same purpose. - Organism: The individual living being formed by the integration of all systems.
Crucial Vocabulary: - Differentiation/Differentiate: The process of becoming specialized for a particular function. - Intercellular Spaces: Gaps between cells, which mostly contain gases like or . - Waxy Cuticle: A waxy layer covering the surface of the plant to prevent water loss (desiccation). - Stomata (Stoma): Small openings in the leaf epidermis used for gaseous exchange and transpiration. - Guard Cells: Bean-shaped cells surrounding the stomata that control their opening and closing.
Plant Systems: Meristematic and Permanent Tissues
Meristematic Tissue: This tissue is defined by cells that are actively dividing through mitosis to form new cells. - Apical Meristems (Primary Meristem): Typically found at the root and shoot tips; responsible for growth in length. - Lateral Meristems (Secondary Meristem): Responsible for the increase in girth (thickness) of roots and stems.
Permanent Tissue: Cells that have finished actively dividing for growth and have become structurally specialized for specific functions. These cells only divide for repair and are found throughout the plant except in meristematic regions.
Simple Permanent Tissue: - Parenchyma Tissue: - Structure: Thin cell walls, large vacuoles, round to oval shape, and presence of intercellular air spaces. - Functions: Acts as packaging tissue, stores water, sugar, and starch. Intercellular spaces facilitate the passage of water and gases. Photosynthesis occurs here. - Collenchyma Tissue: - Structure: Similar to parenchyma but with cell walls that are unevenly thickened; no intercellular spaces. - Functions: Acts as supporting tissue, particularly in young stems and leaves. - Sclerenchyma Tissue: - Structure: Evenly thickened cell walls containing lignin. These are dead cells with no internal contents and a narrow lumen (inner space). - Cell Types: Sclerenchyma fibres (long with thickened walls) and stone cells (small, round, and hard). - Functions: Provides mechanical support and strength.
Complex Permanent Tissue: - Epidermal Tissue: - Structure: A single layer of thin-walled, closely packed cells covering the entire plant. It often features a waxy cuticle on the outer layer. - Root Hairs: Unicellular elongated extensions of the root epidermis. They lack a cuticle to facilitate water absorption and increase the surface area for the uptake of water and mineral salts from the soil. - Conducting (Vascular) Tissue: - Xylem: Transports water and dissolved mineral salts from roots to leaves and providing strength. - Vessels: Dead cells with no cross-walls, elongated and hollow, joined end-to-end. Walls are lignified and perforated with pits. Thickenings may be spiral or annular. - Tracheids: Dead cells, long and tapered at both ends with lignified walls and pits. - Phloem: Transports manufactured food (glucose) from leaves to the rest of the plant. - Sieve Tubes: Elongated, hollow cells filled with cytoplasm, joined end-to-end. End-walls are perforated (pits) to form sieve plates. They contain no nucleus. - Companion Cells: Small cells found adjacent to sieve tubes; they possess a large nucleus and control the function of the sieve tubes.
Plant Organs: The Leaf
Primary Purpose: To increase surface area for the manufacturing of food via photosynthesis and provide surface area for transpiration and gaseous exchange.
Leaf Internal Structure and Functions: - Waxy Cuticle: Reduces water loss to prevent drying out (desiccation). - Upper Epidermis: Tightly packed for protection; transparent to allow light penetration for photosynthesis. - Palisade Mesophyll: Closely packed cells filled with chloroplasts; the primary site of photosynthesis. - Spongy Mesophyll: Contains fewer chloroplasts; large intercellular air spaces enable the gaseous exchange of and into and out of cells. - Lower Epidermis: Contains stomata for gaseous exchange and transpiration; transparent and protects inner tissues. - Vascular Bundle: Consists of Xylem (transporting water/minerals), Phloem (transporting glucose), and Cambium (unspecialized cells promoting growth/secondary thickening). - Guard Cells: Control the size of the stomatal pore to regulate the rate of photosynthesis and transpiration.
Support and Transport Systems in Dicotyledonous Plants
Dicotyledonous Root: - External Regions: Root Cap (protects growing point), Meristematic region (cell formation), Region of elongation, Root hair region (absorption), and Mature region (lateral root development). - Internal Tissues: - Epidermis: Outer layer, brick-shaped cells, no cuticle. - Cortex: Parenchyma tissue between the epidermis and vascular tissue; allows passage of minerals and stores starch. - Endodermis: Surrounds vascular tissue. Contains Casparian strips (waxy, waterproof bands) to regulate water passage. - Pericycle: Layer of parenchyma cells that forms lateral roots. - Vascular Tissue: Centrally located Xylem and Phloem.
Dicotyledonous Stem: - External Structure: Nodes (where leaves/branches develop), Internodes (space between nodes), Terminal bud (apical meristem for primary growth), and Axillary buds (lateral branches/flowers). - Internal Tissues: - Pith: Spongy central tissue made of parenchyma for storage. - Sclerenchyma Fibers: Protect the vascular bundle and strengthen the stem. - Secondary Thickening: Growth in thickness caused by cambium. Cambium divides to form secondary xylem on the inside and secondary phloem on the outside, creating annual rings.
Movement of Water and Substances in Plants
Uptake of Water: Occurs in root hairs via Osmosis (movement from high water potential in soil to low water potential in the root hair through a selectively permeable membrane).
Uptake of Mineral Salts: Occurs via Active Transport (moving salts from low concentration in soil to high concentration in root hair), requiring energy.
Pathways to Xylem: - Cell-to-cell via osmosis (slow). - Through cell walls and intercellular spaces via diffusion (fast). - Water must pass through "passage cells" in the endodermis because Casparian strips block the cell-wall route.
Upward Movement Forces: - Capillarity: Spontaneous movement in narrow tubes (Xylem). Involves Cohesion (attraction between water molecules) and Adhesion (attraction between water and xylem walls). - Root Pressure: Upward force resulting from the continuous influx of water from soil to roots via osmosis. - Transpiration Pull (Suction Force): The main force drawing water up. As water vapour leaves stomata, water potential in mesophyll decreases, creating a suction that pulls water from the root xylem upward.
Translocation: The active, energy-requiring movement of sugars (manufactured in leaves) via Phloem to the rest of the plant.
Transpiration, Guttation, and Environmental Factors
Transpiration: The loss of water vapour through aerial parts of the plant, primarily stomata. It facilitates water/mineral transport and cools the plant.
Guttation: The forced release of water droplets through small openings when high humidity slows transpiration and high root pressure exists.
External Factors Increasing Transpiration: High temperature, high light intensity, and wind.
External Factors Decreasing Transpiration: High humidity.
Wilting: Occurs when water loss via transpiration exceeds absorption, causing cells to lose turgor pressure (: a cell with a full vacuole pushing against the wall).
Leaf Adaptations to Limit Transpiration: - Reduced leaf size/thorns (smaller surface area). - Stomata located on the bottom (shaded) side. - Sunken stomata (traps moist air). - Epidermal hairs (traps water vapour). - Thickened cuticle.
Animal Systems: Tissues
Epithelial Tissue: Tightly packed cells with no intercellular spaces, lining internal and external surfaces. - Squamous Epithelium: Thin, flat cells; lines blood vessels, heart, and alveoli; facilitates diffusion and prevents friction. - Cuboidal Epithelium: Cube-shaped; lines glands (sweat/salivary); functions in secretion and absorption. - Columnar Epithelium: Elongated cells with nuclei at the base; lines the digestive tract; functions in absorption, secretion (via Goblet cells), and sensation. - Ciliated Columnar Epithelium: Features cilia (hair-like structures); lines the trachea and nasal cavities to trap and expel dust.
Connective Tissue: Binds, supports, and surrounds other tissues. - Areolar: Jelly-like matrix with yellow elastic and white collagen fibres; insulates and protects organs. - Dense Connective: Parallel fibres; includes Inelastic Tendons (muscle to bone) and Elastic Ligaments (bone to bone). - Cartilage: Tough matrix of chondrin; acts as a shock absorber and prevents friction in joints. - Bone: Hard matrix of calcium phosphate/carbonate; contains Haversian canals for blood vessels. - Blood: Liquid matrix (plasma); contains Erythrocytes (transfer /), Leucocytes (fight infection), and Thrombocytes (clotting).
Muscle Tissue: Contracts and relaxes for movement. - Striated (Skeletal): Long, striped fibres; voluntary; moves the skeleton. - Smooth: Unstriped; involuntary; found in internal organ walls (peristalsis). - Cardiac: Branched, cross-striated fibres with myocardial bridges; involuntary; heart pumping.
Nerve Tissue (Neurons): Conducts impulses. - Structure: Cell body (metabolism), Dendrites (receive impulses), Axon (carries impulses away, often insulated by a Myelin sheath). - Types: Sensory (receptors to CNS), Motor (CNS to effectors/muscles), and Interneuron (connects sensory to motor within the CNS/Brain/Spinal Cord). - Synapse: A microscopic gap between neurons across which impulses must jump.
Support Systems in Animals
Types of Skeletons: - Hydroskeleton: Fluid-filled cavity (e.g., jellyfish). Flexible but lacks fast movement. - Exoskeleton: Chitinous outer shell (e.g., insects). Protects and prevents dehydration but limits growth (requires molting). - Endoskeleton: Internal bone/cartilage (e.g., humans). Allows large growth and flexibility but leaves skin/muscle vulnerable to external damage.
Structure of a Long Bone: - Periosteum: Tough outer membrane. - Diaphysis (Shaft): Compact bone surrounding the marrow cavity (linked with endosteum). - Epiphysis (Head): Spongy bone covered in hyaline cartilage. - Marrow: Yellow marrow (fat/white cells) in the shaft; Red marrow (blood cell production) in the heads.
The Human Skeleton
Total Bones: 206.
Axial Skeleton: - Skull: Includes Cranium (protects brain, features foramen magnum) and Facial bones (mandible is the only movable bone). Permanent dental formula: . - Vertebral Column: Supports skull via the Atlas (nodding) and Axis (rotation) vertebrae. Cervical, thoracic, lumbar, sacrum, and coccyx regions. - Rib Cage: 12 pairs of ribs. True ribs (1-7), False ribs (8-10), Floating ribs (11-12). Sternum and thoracic vertebrae protect the heart and lungs.
Appendicular Skeleton: Pectoral girdle (scapula/clavicle), Pelvic girdle, Upper limbs (Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges), and Lower limbs (Femur, Tibia, Fibula, Patella, Tarsals, Metatarsals, Phalanges).
Joints: - Immovable: Sutures in the skull. - Semi-movable: Between vertebrae. - Synovial (Freely movable): Ball and socket (shoulder), Hinge (elbow), Pivot (atlas/axis), Gliding (wrist).
Skeletal Muscle and Movement
Muscle Structure: Enclosed by sarcolemma; contains sarcoplasm and myofibrils. Myofibrils consist of actin (thin) and myosin (thick) filaments.
Contraction: The Sarcomere (region between Z-lines) shortens as actin slides past myosin.
Antagonistic Muscles: Muscles arranged in pairs to produce coordinated movement. When the Biceps contract (flexor), the Triceps relax (extensor), and vice versa.
Skeletal Diseases: - Rickets: Vitamin D or calcium deficiency; bone softening. - Osteoporosis: Decreased bone density/porosity; higher risk in postmenopausal women. - Arthritis: Joint inflammation. Osteoarthritis (cartilage disintegration) and Rheumatoid Arthritis (autoimmune thickening of synovial membranes).
Transport Systems in Animals
Types of Circulation: - Open: Blood fills spaces (haemocoels) and submerges organs (e.g., invertebrates). - Closed: Blood stays in vessels (arteries, veins, capillaries). - Double Circulatory System: Pulmonary circuit (Heart to Lungs) and Systemic circuit (Heart to Body).
The Heart: - Structure: Pear-shaped, cardiac muscle, enclosed in the pericardium, divided by the septum. - Chambers: Right Atrium (receives deoxygenated blood via Vena Cava), Right Ventricle (pumps to lungs), Left Atrium (receives oxygenated blood via Pulmonary Veins), Left Ventricle (thickest walls, pumps to the whole body via Aorta).
Cardiac Cycle: - Atrial Systole: Atria contract, forcing tricuspid/bicuspid valves open; blood enters ventricles. - Ventricular Systole: Ventricles contract, tricuspid/bicuspid valves close, semi-lunar valves open; blood moves to lungs/body. - General Diastole: Atria and ventricles relax; heart fills with blood.
Blood Vessels: - Arteries: Thick walls, muscular/elastic, carry blood away from heart (usually oxygenated). - Veins: Thin walls, large lumen, valves to prevent backflow, carry blood to heart (usually deoxygenated). - Capillaries: One-cell thick (endothelial), allow for diffusion between blood and cells.
Cardiovascular Health
Diseases: - Hypertension: High blood pressure; can lead to stroke. - Hypotension: Low blood pressure; causes dizziness. - Stroke: Brain function loss due to blood supply disturbance (clot or burst vessel). - Heart Attack (Myocardial Infarction): Interrupted blood flow to cardiac muscle via coronary arteries, often due to fat/cholesterol deposits.
Treatments: Medication (clot-dissolving), Angioplasty (stretching blocked arteries), Bypass surgery, and Heart transplants.
Questions & Discussion
Activity: Mitosis importancia: Why is mitosis biologically important? Mitosis is necessary for growth, repair of damaged tissues, and asexual reproduction.
Activity: Plant Cell vs. Animal Cell: What are the main differences? Plant cells have a cell wall, large central vacuole, and chloroplasts; animal cells lack these and usually have smaller vacuoles.
Activity: Transpiration Practical: How is the rate of transpiration measured? Using a Potometer, which tracks the movement of an air bubble representing water uptake to replace what was transpired.
Activity: Skeleton Functions: What does the skeleton do besides support? It protects organs, stores minerals (Calcium/Phosphate), produces blood cells in the marrow, and assists in hearing (ear bones).