Grade 10 Biology Study Guide: Biochemical Molecules, Cell Reproduction, Human Biology, and Ecology

Unit 3: Biochemical Molecules

• Nucleic Acids: These are defined as polymers of nucleotides. These molecules are critical for storing and transmitting genetic information.

• Nitrogenous Bases: The specific bases that form nucleic acids include adenine, guanine, cytosine, thymine (in DNA), and uracil (in RNA).

Unit 4: Cell Reproduction

• Cell Cycle Divisions: The cell cycle consists of organized phases that a cell undergoes to replicate. Control of the cell cycle is essential; failure to control it can lead to uncontrolled growth.

• Cell Cycle Components: Includes the cell membrane, cytoplasm, nucleus, nucleolus, mitochondria, endoplasmic reticulum (both smooth and rough with ribosomes), Golgi apparatus, vacuole, and lysosomes.

• Mitosis: A type of cell division resulting in two daughter cells with the same genetic content as the parent. It is primary for tissue renewal and growth. Phases include:

  • Prophase: Chromatin condenses into visible chromosomes.

  • Metaphase: Chromosomes align at the equatorial plane.

  • Anaphase: Sister chromatids separate towards opposite poles.

  • Telophase: Nuclear membranes reform around the new sets of chromosomes.

• Sister Chromatids: Identical copies of a chromosome connected at a centromere; the mitotic spindle emerges from centrosomes to facilitate their separation.

• Meiosis: A specialized cell division reducing the chromosome number by half, essential for sexual reproduction. It involves two rounds of division: Meiosis I and Meiosis II.

• Importance of Meiosis: It produces gametes and ensures genetic diversity through recombination.

• Ethiopian Geneticist Profile: Dr. Melaku Worede is a renowned geneticist known for his work in biodiversity and genetic conservation in Ethiopia.

Unit 5: Human Biology

• Digestive System Components: Includes the alimentary canal (mouth, esophagus, stomach, small intestine, large intestine) and accessory organs (liver, gallbladder, pancreas, salivary glands).

• Digestion in the Mouth: Involves mechanical digestion by teeth and chemical digestion by salivary amylase.

• Teeth Structure:

  • Types: Incisors (cutting), Canines (tearing), Premolars, and Molars (grinding).

  • Parts: Crown, neck, root, enamel (outer hard layer), dentine, pulp cavity (containing nerves and blood vessels), and cementum.

• The Stomach:

  • Sphincters regulate the movement of food into and out of the stomach.

  • Gastric Juice: Contains hydrochloric acid and enzymes (like pepsin) to break down proteins.

  • Chyme: The partially digested, semi-liquid food that moves from the stomach to the small intestine.

• Small Intestine and Absorption:

  • Villi: Finger-like projections that increase surface area for absorption into the blood and lacteals.

• Digestive Enzymes Summary:

  • Salivary Amylase: Starch + $H_2O$ \rightarrow Maltose.

  • Pepsin (Stomach): Protein + $H_2O$ \rightarrow Peptides.

  • Pancreatic Amylase: Starch + $H_2O$ \rightarrow Maltose.

  • Lipase: Fat droplets + $H_2O$ \rightarrow Glycerol + Fatty acids.

  • Peptidases: Peptides + $H_2O$ \rightarrow Amino acids.

  • Maltase: Maltose + $H_2O$ \rightarrow Glucose.

• The Liver: A unique organ with regard to blood circulation; it produces bile stored in the gallbladder to emulsify fats.

• Circulatory System:

  • Heart Anatomy: Consists of four chambers (Right Atrium, Left Atrium, Right Ventricle, Left Ventricle). Septum separates the right and left sides.

  • Valves: Tricuspid, bicuspid (mitral), and semilunar valves ensure one-way blood flow.

  • Circulation Types: Pulmonary circulation (heart to lungs) and Systemic circulation (heart to body).

  • Heart Sounds: The "lub-dub" sound is caused by the closing of heart valves.

• Blood Components:

  • Red Blood Cells (Erythrocytes): Biconcave cells without a nucleus, specialized for carrying oxygen via hemoglobin.

  • White Blood Cells (Leukocytes): Part of the immune system; higher counts may indicate infection.

  • Platelets: Cell fragments essential for blood clotting.

  • Plasma: The liquid portion of blood carrying nutrients, hormones, and waste.

• Blood Groups and Compatibility:

  • ABO System: Types A, B, AB, and O defined by antigens on RBCs.

  • Rh Factor: Rh+ contains the Rh antigen, Rh- does not. Incompatibility (e.g., during pregnancy) can lead to erythroblastosis fetalis causing anemia in fetuses.

• Lymphatic System: An open system containing lymph nodes, tonsils, spleen, and lymphatic vessels. It returns fluid to the circulatory system and aids immunity.

• Excretory System (Kidneys):

  • Functions: Filtration of blood, regulation of solutes, and production of urine.

  • Structure: Cortex (outer), Medulla (inner), Renal Pelvis, and Nephrons (functional units).

  • Urine Formation: Involves filtration in the glomerulus, reabsorption in the tubules, and secretion.

• Breathing System:

  • Organs: Nasal cavity (warms/filters air), Pharynx, Larynx (voice box), Trachea (windpipe), Bronchi, and Alveoli.

  • Gas Exchange: Occurs in the alveoli via diffusion between air and blood in capillaries.

  • Air Comparison:

    • Atmospheric Air: $78\%$ Nitrogen, $21\%$ Oxygen, $0.04\%$ Carbon dioxide.

    • Exhaled Air: $78\%$ Nitrogen, $16\%$ Oxygen, $4\%$ Carbon dioxide.

• Immune System:

  • Immunity: Can be innate or acquired; breastfeeding provides immediate passive immunity to infants.

  • Scientific Figures: Prof. Asrat Woldeyes and Dr. Widad Kidane Mariam are noted for their contributions to medicine and medical education in Ethiopia.

Unit 6: Ecological Interactions

• Energy Flow: The ultimate source of energy for life is the Sun. Energy is transferred from producers (plants) to consumers (herbivores and carnivores) in a unidirectional flow.

• Food Chains and Webs: Illustrate feeding relationships. Productivity begins with producers (P), followed by herbivores (H), and various levels of carnivores ($C_1$, $C_2$).

• Trophic Levels: Steps in a food chain; energy decreases as it moves up levels (roughly $10\%$ rule).

• Ecological Pyramids:

  • Pyramid of Number: Shows the count of individuals at each level.

  • Pyramid of Biomass: Represents the total organic matter at each level.

  • Pyramid of Energy: Shows the energy available at each level; always upright because energy is lost as heat.

• Nutrient Cycling:

  • Water Cycle: Involves evaporation, transpiration, condensation, and precipitation.

  • Carbon Cycle: Cycles carbon through photosynthesis ($CO_2 + H_2O \rightarrow C_6H_{12}O_6 + O_2$), respiration, and decomposition.

  • Nitrogen Cycle: Converts atmospheric nitrogen into forms usable by plants (nitrates) via nitrogen-fixing bacteria, and returns it to the atmosphere via denitrification.

Questions & Discussion

• Cell Division: Why does a cell not diminish in size through repeated division? Before division, a cell must replicate its contents to maintain its size.

• Internal Organs: What happens if food wrongly enters the trachea? The larynx/epiglottis prevents such occurrences.

• Ecology: What is the advantage of being a vegetarian? It is more energy-efficient as humans eat lower on the food chain, accessing more of the original energy stored by producers.

• Biology and Society: How does Rh factor affect a fetus? If an Rh- mother is sensitized to Rh+ blood, her antibodies can attack the Rh+ fetus's RBCs.