Grade 10 Biology Complete Course Companion: Biology Study Guide

Unit 1: Sub-fields of Biology

  • Definition of Biology: Geography, history, and physical sciences help describe the world, but biology is the scientific study of life and living organisms, covering their structure, function, growth, origin, evolution, and distribution.

  • Major Sub-fields Based on Structure Studied:

    • Morphology: The study of the external form and structure of organisms.

    • Anatomy: The study of the internal structure of organisms, often through dissection.

    • Histology: The study of tissues using microscopes.

    • Cytology (Cell Biology): The study of individual cells.

    • Physiology: The study of the functions and processes of living organisms.

    • Taxonomy: The science of naming, describing, and classifying organisms.

    • Ecology: The study of relationships between organisms and their environment.

    • Genetics: The study of heredity and variation in organisms.

    • Evolution: The study of the origin and changes of species over time.

    • Embryology: The study of the development of an embryo from fertilization.

  • Biological Sciences in Relation to Other Fields:

    • Biophysics (Biology + Physics): Applying physical principles to biological phenomena (e.g., nerve impulses, muscle contraction).

    • Biochemistry (Biology + Chemistry): Studying chemical processes within and relating to living organisms (e.g., metabolism, enzyme action).

    • Biostatistics (Biology + Mathematics): Using mathematical tools to analyze biological data.

    • Biogeography (Biology + Geography): Studying the geographic distribution of species.

  • Pure vs. Applied Biology:

    • Pure Biology: Focuses on theoretical knowledge and understanding biological principles (e.g., Zoology, Botany, Microbiology).

    • Applied Biology: Focuses on using biological knowledge for practical purposes (e.g., Agriculture, Medicine, Biotechnology, Forestry, Pharmacy).

  • Historical Figures in Biology:

    • Aristotle: Often called the father of biology; classified animals based on their environment.

    • Galen: Early pioneer in human anatomy and medicine.

    • Antonie van Leeuwenhoek: Developed powerful single-lens microscopes and discovered microorganisms ("animalcules").

    • Carl Linnaeus: Developed binomial nomenclature (Genus and species names).

    • Charles Darwin: Proposed the theory of evolution by natural selection.

    • Gregor Mendel: Known as the father of genetics; studied inheritance in pea plants.

    • Louis Pasteur: Developed pasteurization and vaccines for rabies and anthrax; disproved spontaneous generation.

    • Robert Koch: Developed Koch's Postulates to link specific microbes to specific diseases.

    • Jane Goodall: Famous for her long-term study of wild chimpanzees in Tanzania.

    • Barbara McClintock: Discovered "jumping genes" (transposons).

    • Watson and Crick: Discovered the double-helix structure of DNA.

    • Wilmut and Campbell: Successfully cloned the first mammal, Dolly the sheep.

  • Ethiopian Biologists and Their Contributions:

    • Prof. Yalemtsehay Mekonnen: First female professor at Addis Ababa University; research focuses on human health and environmental toxicology.

    • Dr. Aklilu Lemma: Discovered that the fruit of the endod plant (Phytolacca dodecandra) acts as a molluscicide to kill snails carrying Schistosomiasis.

    • Prof. Gebissa Ejeta: Awarded the World Food Prize for his work in developing drought-tolerant and Striga-resistant sorghum hybrids.

Unit 2: Plants

  • Classification of Plants:

    • Non-flowering Plants: Includes Bryophytes (mosses), Pteridophytes (ferns), and Gymnosperms (conifers). They reproduce via spores or seeds not enclosed in fruit.

    • Flowering Plants (Angiosperms): Reproduce via flowers and seeds enclosed within fruits.

  • Structure of Angiosperms:

    • Root System: Anchors the plant and absorbs water/minerals. Types include taproots and fibrous roots.

    • Shoot System: Includes stems, leaves, and flowers.

    • Leaf Internal Structure:

      • Epidermis: Outer layer with a waxy cuticle to prevent water loss.

      • Stomata: Pores for gas exchange (CO2CO_2 and O2O_2).

      • Mesophyll: Tissue where photosynthesis occurs (palisade and spongy layers).

      • Vascular Bundles: Xylem (water transport) and Phloem (nutrient transport).

  • Photosynthesis:

    • Occurs in Chloroplasts.

    • Chemical Equation: 6CO2+6H2O→SunlightChlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow[\text{Sunlight}]{\text{Chlorophyll}} C_6H_{12}O_6 + 6O_2

    • Limiting Factors: Light intensity, CO2CO_2 concentration, and temperature.

  • Plant Reproduction:

    • Flower Structure: Sepals (protection), Petals (attraction), Stamen (male: anther and filament), Carpel/Pistil (female: stigma, style, and ovary).

    • Pollination: Transfer of pollen from anther to stigma.

    • Seed Germination: Requires water, oxygen, and suitable temperature.

    • Types of Germination:

      • Epigeal: Cotyledons emerge above ground.

      • Hypogeal: Cotyledons remain below ground.

  • Transport in Plants:

    • Xylem: Transports water and minerals from roots to leaves through transpiration pull and root pressure.

    • Phloem: Transports manufactured food (sucrose) via translocation (from source to sink).

  • Plant Tropisms (Growth responses to stimuli):

    • Phototropism: Growth toward light (positive in shoots).

    • Geotropism (Gravitropism): Growth relative to gravity (positive in roots, negative in shoots).

    • Hydrotropism: Growth toward water (roots).

    • Auxin: The hormone responsible for these growth movements; it accumulates on the shaded side of shoots, causing elongation.

  • Medicinal Plants in Ethiopia:

    • Tena Adam (Ruta chalepensis): Used for stomach aches and flavoring.

    • Endod (Phytolacca dodecandra): Molluscicide.

    • Feto (Lepidium sativum): Used for treating diarrhea.

Unit 3: Biochemical Molecules

  • Water (H2OH_2O):

    • Polarity: Partial negative charge on Oxygen and partial positive on Hydrogen.

    • Key Properties: Solvent property (dissolves polar substances), High specific heat capacity (thermal stability), Cohesion (water molecules sticking together), Adhesion (water sticking to surfaces).

  • Inorganic Ions (Minerals):

    • Macronutrients (needed in large amounts): Na+Na^+, K+K^+, Ca2+Ca^{2+}, Mg2+Mg^{2+}, Cl−Cl^-, and Phosphate (PO43−PO_4^{3-}).

    • Micronutrients (needed in trace amounts): Iron (Fe2+/3+Fe^{2+/3+}), Copper (Cu2+Cu^{2+}), Iodine (I−I^-).

    • Specific Roles:

      • Calcium: Bone/tooth formation and blood clotting.

      • Iron: Component of hemoglobin for oxygen transport.

      • Iodine: Necessary for thyroid hormone production; deficiency causes goiter.

  • Carbohydrates (Elements: C, H, O):

    • Monosaccharides: Simple sugars like Glucose, Fructose, and Galactose.

    • Disaccharides: Formed by two monosaccharides (e.g., Maltose = Glucose + Glucose, Sucrose = Glucose + Fructose).

    • Polysaccharides: Long chains of sugars (e.g., Starch [storage in plants], Glycogen [storage in animals], Cellulose [cell walls]).

  • Lipids (Elements: C, H, O):

    • Triglycerides: Glycerol + 3 Fatty acids.

    • Phospholipids: Major component of cell membranes; contain a phosphate group.

  • Proteins (Elements: C, H, O, N, sometimes S):

    • Made of Amino Acids linked by Peptide Bonds.

    • Functions: Catalysis (enzymes), Structure (collagen, keratin), Transport (hemoglobin), Defense (antibodies).

  • Nucleic Acids (Elements: C, H, O, N, P):

    • DNA (Deoxyribonucleic Acid): Stores genetic information; double-stranded; contains Deoxyribose sugar and bases A, T, C, G.

    • RNA (Ribonucleic Acid): Involved in protein synthesis; single-stranded; contains Ribose sugar and bases A, U, C, G.

    • Nucleotide Structure: Phosphate group + Five-carbon sugar + Nitrogenous base.

Unit 4: Cell Reproduction

  • The Cell Cycle:

    • Interphase: The longest phase where the cell prepares to divide (G1G_1, SS [DNA replication], G2G_2).

    • M-Phase: Mitotic phase.

  • Mitosis (Division for growth and repair):

    • Results in two identical diploid (2n2n) daughter cells.

    • Prophase: Chromosomes condense, spindle fibers form.

    • Metaphase: Chromosomes align at the equator.

    • Anaphase: Sister chromatids are pulled to opposite poles.

    • Telophase: Nuclear envelopes reform around two sets of chromosomes.

    • Cytokinesis: Division of the cytoplasm.

  • Meiosis (Division for gamete formation):

    • Results in four non-identical haploid (nn) cells.

    • Meiosis I: Homologous chromosomes separate (reduction division).

    • Meiosis II: Sister chromatids separate (similar to mitosis).

    • Crossing Over: Occurs in Prophase I, leading to genetic variation.

Unit 5: Human Biology

  • Digestive System:

    • Alimentary Canal: Mouth (physical/chemical digestion), Esophagus (peristalsis), Stomach (gastric juice, pepsin), Small Intestine (absorption via villi), Large Intestine (water absorption).

    • Accessory Organs: Liver (produces bile to emulsify fats), Gallbladder (stores bile), Pancreas (secretes enzymes).

  • Circulatory System:

    • Heart: Four chambers (Left/Right Atria and Ventricles). Left ventricle is thicker to pump blood to the whole body.

    • Vessels: Arteries (away from heart, high pressure), Veins (toward heart, valves prevent backflow), Capillaries (exchange of materials).

    • Blood: Plasma (liquid), RBCs (erythrocytes, transport O2O_2), WBCs (leukocytes, immunity), Platelets (blood clotting).

    • Blood Groups: ABO system (A, B, AB, O) and Rh factor (Rh+/Rh−Rh^+/Rh^-).

  • Respiratory System:

    • Pathway: Nasal cavity $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.

    • Gas Exchange: Occurs in the Alveoli by diffusion across the respiratory membrane.

    • Mechanism: Inspiration (Diaphragm contracts/lowers, thoracic volume increases) and Expiration (Diaphragm relaxes).

  • Excretory System:

    • Kidneys: Filter blood and maintain homeostasis.

    • Nephron: Functional unit of the kidney. Parts: Bowman's capsule, Glomerulus (filtration), Proximal convoluted tubule, Loop of Henle, Distal convoluted tubule, Collecting duct (reabsorption and secretion).

  • Immune System:

    • Defense: Includes skin (barrier), WBCs (phagocytes and lymphocytes), and Antibodies.

    • Immunity: Native (innate) and Acquired (through infection or vaccines).

Unit 6: Ecological Interactions

  • Energy Flow:

    • Unidirectional: Energy enters as sunlight and flows through producers (plants) to consumers (herbivores, carnivores).

    • Food Chains: Linear sequence of feeding relationships.

    • Food Webs: Interconnected food chains.

    • Trophic Levels: Positions in a food chain (Primary producer $\rightarrow$ Primary consumer $\rightarrow$ Secondary consumer $\rightarrow$ Tertiary consumer).

  • Ecological Pyramids:

    • Pyramid of Numbers: Shows the population size at each level.

    • Pyramid of Biomass: Shows the total mass of living material.

    • Pyramid of Energy: Always upright because energy is lost (90%90\%) at each transfer (only 10%10\% is passed on).

  • Nutrient Cycles:

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

    • Carbon Cycle: Balance of Photosynthesis (takes CO2CO_2) and Respiration/Combustion (releases CO2CO_2).

    • Nitrogen Cycle: Atmospheric Nitrogen (N2N_2) $\rightarrow$ Nitrogen fixation (by bacteria like Rhizobium) $\rightarrow$ Ammonium $\rightarrow$ Nitrification (Nitrites/Nitrates) $\rightarrow$ Denitrification (N2N_2 back to atmosphere).

    • Phosphorus Cycle: Involves weathering of rocks, absorption by plants, and decomposition.

  • Environmental Issues:

    • Eutrophication: Excessive nutrients (N and P) in water causing algal blooms and oxygen depletion.

    • Global Warming: Increase in greenhouse gases (CO2CO_2) trapping heat in the atmosphere.