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1. Introduction to Biology

  • What is Biology?
    • The scientific study of life and living organisms.
    • Derived from Greek words: bios (life) and logos (study).
  • Characteristics of Life
    • Order: Living things exhibit complex and highly organized structures.
    • Sensitivity or Response to Stimuli: Organisms react to changes in their environment.
    • Reproduction: Ability to produce new organisms from existing ones.
    • Adaptation: Organisms evolve over time to better suit their environment.
    • Growth and Development: Increase in size and complexity over an organism's life.
    • Regulation/Homeostasis: Maintenance of a stable internal environment.
    • Energy Processing: Acquisition and use of energy for metabolic activities.

2. Biological Organization

  • Levels of Organization
    1. Atoms: Smallest unit of matter.
    2. Molecules: Groups of atoms bonded together.
    3. Organelles: Specialized structures within cells.
    4. Cells: Basic unit of life.
    5. Tissues: Groups of similar cells performing a specific function.
    6. Organs: Structures composed of multiple tissues working together.
    7. Organ Systems: Groups of organs working together.
    8. Organisms: Individual living beings.
    9. Populations: Groups of the same species in an area.
    10. Communities: All populations in an area.
    11. Ecosystems: Communities plus the non-living environment.
    12. Biosphere: All ecosystems on Earth.
  • Prokaryotic vs. Eukaryotic Cells
    • Prokaryotic Cells (e.g., bacteria, archaea)
      • Simpler, smaller, and older.
      • Lack a true nucleus and membrane-bound organelles.
      • Genetic material (DNA) is in the cytoplasm (nucleoid region).
    • Eukaryotic Cells (e.g., plants, animals, fungi, protists)
      • Larger and more complex.
      • Possess a true nucleus enclosing genetic material.
      • Contain various membrane-bound organelles (mitochondria, ER, Golgi, etc.).

3. Cellular Processes

  • Cellular Respiration
    • The process by which organisms convert glucose into ATP (cellular energy).
    • General Equation: C6H{12}O6 + 6O2 \to 6CO2 + 6H2O + \text{ATP}
    • Aerobic Respiration: Requires oxygen.
      1. Glycolysis: Occurs in cytoplasm, breaks glucose into two pyruvate molecules. Produces 2 ATP.
      2. Krebs Cycle (Citric Acid Cycle): Occurs in mitochondrial matrix. Produces ATP, NADH, FADH_2.
      3. Oxidative Phosphorylation (Electron Transport Chain): Occurs on inner mitochondrial membrane. Produces the most ATP (approx. 28-34 ATP).
    • Anaerobic Respiration (Fermentation): Occurs without oxygen.
      • Lactic Acid Fermentation: Produces lactic acid (e.g., in muscle cells).
      • Alcoholic Fermentation: Produces ethanol and CO_2 (e.g., in yeast).
  • Photosynthesis
    • Process used by plants, algae, and some bacteria to convert light energy into chemical energy (glucose).
    • Occurs in chloroplasts.
    • General Equation: 6CO2 + 6H2O + \text{Light Energy} \to C6H{12}O6 + 6O2
    • Stages:
      1. Light-Dependent Reactions: Occur in thylakoid membranes. Light energy is captured to produce ATP and NADPH. Water is split, releasing O_2.
      2. Light-Independent Reactions (Calvin Cycle): Occur in the stroma. ATP and NADPH are used to convert CO_2 into glucose.

4. Genetics

  • DNA (Deoxyribonucleic Acid)
    • The genetic material that carries instructions for an organism's development and function.
    • Structure: Double helix, composed of nucleotides (sugar, phosphate, nitrogenous base).
    • Bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
    • Base Pairing Rules: A pairs with T, C pairs with G.
  • RNA (Ribonucleic Acid)
    • Involved in gene expression (protein synthesis).
    • Structure: Single strand, nucleotides contain ribose sugar instead of deoxyribose.
    • Bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U).
  • Central Dogma of Molecular Biology: DNA \to RNA \to Protein
    • Replication: DNA makes copies of itself.
    • Transcription: DNA is copied into mRNA.
    • Translation: mRNA sequence is used to synthesize proteins.
  • Mendelian Genetics
    • Genes: Units of heredity.
    • Alleles: Different forms of a gene.
    • Genotype: Genetic makeup of an organism.
    • Phenotype: Observable characteristics.
    • Dominant Allele: Expressed even if only one copy is present.
    • Recessive Allele: Only expressed if two copies are present.
    • Segregation: Alleles for a gene separate during gamete formation.
    • Independent Assortment: Genes for different traits assort independently of each other.

5. Evolution

  • Natural Selection (Darwin's Theory)
    • Mechanisms of change in populations over time.
    • Key Principles:
      1. Variation: Individuals in a population differ.
      2. Heritability: Traits can be passed from parents to offspring.
      3. Overproduction: More offspring are produced than can survive.
      4. Differential Survival and Reproduction: Individuals with advantageous traits are more likely to survive and reproduce.
  • Evidence of Evolution
    • Fossil Record: Preserved remains of past organisms.
    • Comparative Anatomy: Similarities in body structures (homologous structures).
    • Embryology: Similarities in embryonic development.
    • Molecular Biology: Similarities in DNA and protein sequences.
    • Biogeography: Geographic distribution of species.

6. Ecology

  • Ecosystems
    • A community of living organisms (biotic factors) and their non-living environment (abiotic factors).
    • Biotic Factors: Producers, consumers, decomposers.
    • Abiotic Factors: Water, sunlight, temperature, soil, etc.
  • Biomes: Large-scale ecosystems characterized by specific climates and vegetation types (e.g., forests, deserts, grasslands, tundra, aquatic).
  • Food Chains and Food Webs
    • Food Chain: Shows a single pathway of energy flow.
      • Producer \to Primary Consumer \to Secondary Consumer \to Tertiary Consumer
    • Food Web: Interconnected food chains, showing multiple feeding relationships in an ecosystem.
    • Trophic Levels: Position an organism occupies in a food chain.
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