Comprehensive Biology Study Notes: From Cellular Basis to Human Physiology

THE LIVING WORLD

  • Biology Definition: The science of life forms and living processes.
  • Life Characteristics:
    • Growth: Defined by increase in mass and number. Non-living objects (mountains, boulders) grow by external accumulation; living organisms grow from the inside.
    • Reproduction: Production of progeny. In unicellular organisms, growth and reproduction are synonymous. Mules and sterile worker bees are examples of living things that do not reproduce.
    • Metabolism: Sum total of all chemical reactions. Purely a defining feature of life. Isolated metabolic reactions in vitro are not living things but are "living reactions."
    • Consciousness: Ability to sense surroundings and respond to stimuli. Human beings have self-consciousness.
  • Biodiversity: Range of organisms on earth, approximately 1.7-1.8 million species known and described.
  • Taxonomy Essentials:
    • Nomenclature: Standardizing names. Binomial nomenclature (by Carolus Linnaeus) uses a Generic name and a specific epithet.
    • Binomial Rules: Latin origin; italics in print, separately underlined if handwritten. Genus starts with a capital letter; species with small.
    • Taxonomic Hierarchy: Kingdom > Phylum/Division > Class > Order > Family > Genus > Species.
  • Taxonomical Aids: Herbaria (dried plant specimens), Botanical gardens (living plants), Museums (preserved specimens), Zoological parks, and Keys (analytical tools with contrasting characters called couplets).

BIOLOGICAL CLASSIFICATION

  • Historical Systems:
    • Aristotle: First scientific basis. Plants (trees, shrubs, herbs) and Animals (red blood vs. non-red blood).
    • Linnaeus: Two Kingdom system (Plantae and Animalia).
    • R.H. Whittaker (1969): Five Kingdom Classification based on cell structure, body organization, mode of nutrition, reproduction, and phylogenetic relationships.
  • The Five Kingdoms:
    • Monera: Prokaryotes. Bacteria occur everywhere. Shapes: Coccus (spherical), Bacillus (rod), Vibrio (comma), Spirillum (spiral). Includes Archaebacteria (extreme habitats) and Eubacteria (true bacteria, including Cyanobacteria/Blue-green algae).
    • Protista: Single-celled eukaryotes. Includes Chrysophytes (diatoms), Dinoflagellates, Euglenoids, Slime moulds, and Protozoans (Amoeboid, Flagellated, Ciliated, and Sporozoans like Plasmodium).
    • Fungi: Heterotrophic. Cell walls made of chitin and polysaccharides. Classes: Phycomycetes, Ascomycetes (sac-fungi), Basidiomycetes (mushrooms), and Deuteromycetes (imperfect fungi).
    • Plantae: Eukaryotic chlorophyll-bearing organisms. Alternation of generations occurs between diploid sporophyte and haploid gametophyte.
    • Animalia: Multicellular heterotrophs lacking cell walls. Holozoic nutrition.
  • Viruses, Viroids, Prions, and Lichens:
    • Viruses: Non-cellular, genetic material (DNA or RNA) in a protein coat (capsid).
    • Viroids: Free RNA, smaller than viruses, no protein coat.
    • Prions: Infectious abnormally folded proteins (e.g., Mad Cow Disease).
    • Lichens: Symbiotic association between phycobiont (algae) and mycobiont (fungi).

PLANT KINGDOM

  • Classification Systems: Artificial (gross morphology), Natural (internal features), Phylogenetic (evolutionary relationships), Numerical Taxonomy (computational), Cytotaxonomy (chromosomes), and Chemotaxonomy (chemicals).
  • Groups:
    • Algae: Thalloid, autotrophic. Classes: Chlorophyceae (Green), Phaeophyceae (Brown), Rhodophyceae (Red). Reproduction: Isogamous, anisogamous, or oogamous.
    • Bryophytes: "Amphibians of the plant kingdom." Thallus-like, no true roots. Includes Liverworts and Mosses. Dominant phase is haploid gametophyte.
    • Pteridophytes: First terrestrial plants with vascular tissues (xylem and phloem). Includes horsetails and ferns. Sporophyte is dominant.
    • Gymnosperms: "Naked seeds." Ovules are not enclosed in ovary walls. Includes Sequoia, Pinus, Cycas.
    • Angiosperms: Flowering plants. Seeds enclosed in fruits. Divided into Monocotyledons and Dicotyledons. Unique event: Double fertilization (syngamy + triple fusion).
  • Life Cycles: Haplontic, Diplontic, or Haplo-diplontic.

ANIMAL KINGDOM

  • Basis of Classification: Levels of organization (cellular, tissue, organ, organ-system), Symmetry (radial or bilateral), Diploblastic/Triploblastic structure, Coelom (body cavity), Segmentation (metamerism), and Notochord.
  • Invertebrate Phyla:
    • Porifera: Sponges; water canal system.
    • Coelenterata: Cnidoblasts; Polyp and Medusa forms.
    • Ctenophora: Comb jellies; bioluminescence.
    • Platyhelminthes: Flatworms; flame cells for excretion.
    • Aschelminthes: Roundworms; pseudocoelomates.
    • Annelida: Segmented; nephridia for excretion.
    • Arthropoda: Largest phylum; jointed appendages; chitinous exoskeleton.
    • Mollusca: Second largest; shell present; radula for feeding.
    • Echinodermata: Spiny skinned; water vascular system.
    • Hemichordata: Worm-like; proboscis, collar, and trunk.
  • Phylum Chordata: Notochord, dorsal hollow nerve cord, gill slits, post-anal tail.
    • Vertebrata Subdivisions: Agnatha (jawless) and Gnathostomata (with jaws).
    • Classes: Cyclostomata, Chondrichthyes (cartilaginous fish), Osteichthyes (bony fish), Amphibia, Reptilia, Aves (birds), and Mammalia (mammary glands, hair).

MORPHOLOGY AND ANATOMY OF FLOWERING PLANTS

  • Roots: Tap root (dicots), Fibrous root (monocots), Adventitious roots. Regions: Root cap, meristematic, elongation, maturation.
  • Stem: Develops from plumule; nodes and internodes. Modifications: Tendrils, thorns, phylloclades.
  • Leaf: Parts include leaf base, petiole, lamina. Venation: Reticulate (dicot) or Parallel (monocot). Phyllotaxy: Alternate, opposite, whorled.
  • Inflorescence: Racemose (unlimited growth) or Cymose (limited).
  • Flower: Whorls include Calyx (sepals), Corolla (petals), Androecium (stamens), Gynoecium (carpels). Symmetry: Actinomorphic (radial) or Zygomorphic (bilateral). Placentation types: Marginal, axile, parietal, basal, central, free central.
  • Seed: Dicotyledonous (two cotyledons) or Monocotyledonous (one cotyledon/scutellum).
  • Anatomy:
    • Tissues: Meristematic (apical, intercalary, lateral) and Permanent (Simple: parenchyma, collenchyma, sclerenchyma; Complex: xylem, phloem).
    • Vascular Bundles: Radial (roots), Conjoint (stem/leaves). Open (with cambium) or Closed (no cambium).
    • Secondary Growth: Increase in girth due to vascular cambium and cork cambium (phellogen). Forms heartwood and sapwood.

STRUCTURAL ORGANISATION IN ANIMALS

  • Tissues:
    • Epithelial: Simple (Squamous, Cuboidal, Columnar) or Compound (multi-layered).
    • Connective: Loose (Areolar, Adipose), Dense (Tendons, Ligaments), or Specialized (Cartilage, Bone, Blood).
    • Muscular: Skeletal (voluntary/striated), Visceral (involuntary/smooth), and Cardiac (heart).
    • Neural: Neurons and neuroglia.
  • Organisms Study:
    • Earthworm (Pheretima): Segmented; hermaphrodite; closed circulation.
    • Cockroach (Periplaneta americana): Chitinous exoskeleton; open circulation; Malpighian tubules.
    • Frog (Rana tigrina): Amphibian; cutaneous and pulmonary respiration; 3-chambered heart.

CELL: THE UNIT OF LIFE

  • Cell Theory: All living organisms are composed of cells; cells arise from pre-existing cells (Virchow).
  • Prokaryotic Cells: No well-defined nucleus. Plasmids (circular DNA). Cell envelope (Glycocalyx, cell wall, plasma membrane). 70S ribosomes.
  • Eukaryotic Cells: Organelles like ER, Golgi, Lysosomes (suicide bags), Vacuoles, Mitochondria (ATP production), Plastids (Chloroplasts), and Nucleus (Chromatin, nucleolus).
  • Cell Membrane: Fluid Mosaic Model (Singer & Nicolson). Lipid bilayer with proteins. Passive and Active transport (Na^+/K^+ pump).
  • Cytoskeleton: Cilia and Flagella (9+2 array), Centrosome and Centrioles.

BIOMOLECULES

  • Metabolites: Primary (necessary for physiological processes) and Secondary (alkaloids, rubber, toxins).
  • Macromolecules:
    • Proteins: Polymers of amino acids linked by peptide bonds. Collagen is most abundant in animals; RuBisCO in the biosphere.
    • Polysaccharides: Cellulose, Starch (amylose), Glycogen, Chitin.
    • Nucleic Acids: DNA and RNA. Polynucleotides linked by phosphodiester bonds. DNA structure (Watson-Crick model).
  • Enzymes: Biological catalysts. Lower activation energy. Factors: Temperature, pH, substrate concentration. Competitive inhibitors mimic substrate structure.

CELL CYCLE AND DIVISION

  • Phases: Interphase (G1, S, G2 phases) and M Phase (Mitosis).
    • S phase: DNA replication occurs.
  • Mitosis: Prophase, Metaphase, Anaphase, Telophase. Results in diploid daughter cells.
  • Meiosis: Reduction division. Meiosis I (Prophase I: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis) and Meiosis II. Crossing over occurs in Pachytene.

PLANT PHYSIOLOGY

  • Transport: Diffusion, Facilitated diffusion, Active transport. Water potential (\Psiw = \Psis + \Psi_p). Plasmolysis, Imbibition. Transpiration pull (cohesion-tension model).
  • Mineral Nutrition: 17 essential elements (9 macro, 8 micronutrients). Nitrogen cycle: Nitrogen fixation by Nitrogenase (sensitive to O_2, protected by leghaemoglobin).
  • Photosynthesis: Light reaction (Z-scheme, ATP/NADPH formation via chemiosmosis) and Dark reaction (Calvin/C3 cycle). C4 plants (Kranz anatomy) avoid photorespiration.
  • Respiration: Glycolysis (EMP pathway), Krebs cycle (TCA), and ETS. RQ = \frac{\text{vol } CO2}{\text{vol } O2}.
  • Growth and Development: Auxins (apical dominance), Gibberellins (bolting), Cytokinins (cell division), Ethylene (ripening), Abscisic acid (stress hormone). Photoperiodism and Vernalisation.

HUMAN PHYSIOLOGY

  • Digestion: Mechanical and chemical breakdown. Pepsin (stomach), Trypsin (pancreas), Bile (liver - emulsification). Absorption in small intestine.
  • Breathing: Inspiration/Expiration. Oxygen transport via Haemoglobin (Oxyhaemoglobin). CO_2 transport as Bicarbonate (70\%).
  • Circulation: Blood (A, B, AB, O groups and Rh factor). Heart (Double circulation). Cardiac cycle (0.8 seconds). ECG parts (P, QRS, T waves).
  • Excretion: Nephron processes (Glomerular filtration, Reabsorption, Secretion). Counter-current mechanism concentrates urine.
  • Locomotion: Sliding filament theory (Actin and Myosin). Girdles (Pectoral and Pelvic). Joints: Fibrous, Cartilaginous, Synovial.
  • Neural Control: Nerve impulse generation (Na^+ influx) and transmission. Brain parts (Forebrain, Midbrain, Hindbrain). Reflex arc. Eye and Ear anatomy.
  • Chemical Coordination: Endocrine glands. Hypothalamus, Pituitary, Thyroid, Adrenal, Pancreas. Hormones: Steroids, Peptides, Amino-acid derivatives. Mechanism via Second messengers (cAMP) or Gene expression.