Comprehensive University Biology Lecture Guide

Biology: The Science of Life and its Organizational Hierarchy

• Definition of Biology: Biology is formally defined as the scientific study of life.

Hierarchical Organization of Life

Life is characterized by a high degree of organization, spanning from the subatomic to the planetary scale. The hierarchy is organized as follows (from smallest to largest):

• Subatomic Component: Oxygen and Hydrogen atoms.

• Atom: The basic unit of matter.

• Molecule: For example, Water ($\text{H}_2\text{O}$).

• Macromolecule: Large molecules such as DNA or proteins.

• Organelles: Specialized structures within a cell (e.g., mitochondria).

• Cell: The fundamental unit of life.

• Tissue: A group of similar cells working together.

• Organ: A structure composed of different tissues (e.g., the heart).

• Organ System: A group of organs working towards a common goal (e.g., circulatory system).

• Organism: An individual living entity.

• Population: A group of individuals of the same species in a specific area.

• Community: Different populations interacting in an area.

• Ecosystem: Interactions between living (biotic) and non-living (abiotic) factors.

• Biosphere/Ecosphere: The global sum of all ecosystems.

• Specific Spheres: Life interacts within the Hydrosphere (water), Atmosphere (air), and Lithosphere (land).

Traits of Life

1. Genetic Basis: Traits of life are encoded in genetic information. This follows the path of DNA $\rightarrow$ RNA $\rightarrow$ Protein via transcription and translation.

2. Growth and Development: All life grows and develops.

   • Animal Development: Begins with a Zygote (fertilized egg) $\rightarrow$ Eight cells $\rightarrow$ Blastula (cross section) $\rightarrow$ Gastrula (cross section showing movement/gut cavity) $\rightarrow$ Adult animal (e.g., sea star).

   • Plant Development: Zygote $\rightarrow$ Two cells $\rightarrow$ Embryo inside seed (including seed leaves) $\rightarrow$ Plant (featuring Shoot Apical Meristem and Root Apical Meristem). This involves cell division, morphogenesis, and cell differentiation.

3. Energy Requirement: Life requires energy for biological processes, illustrated by food chains.

   • Terrestrial Food Chain: Primary Producers (plant) $\rightarrow$ Primary Consumers (herbivore) $\rightarrow$ Secondary Consumers (carnivore) $\rightarrow$ Tertiary Consumers (carnivore) $\rightarrow$ Quaternary Consumers (carnivore).

   • Marine Food Chain: Phytoplankton $\rightarrow$ Zooplankton $\rightarrow$ Carnivores.

4. Interactions: Interactions between organisms and their environment ensure smooth operation.

5. Reproduction: Life reproduces to ensure continuity.

   • Sexual: Involves Male (sperm) and Female (egg) $\rightarrow$ Zygote $\rightarrow$ Embryo $\rightarrow$ Baby.

   • Asexual: Example: Hydra budding (1 Parent $\rightarrow$ 2 Developing bud $\rightarrow$ 3 New bud $\rightarrow$ 4 New Hydra).

6. Variation and Evolution: Life varies and evolves from a common ancestor. This spans three domains: Bacteria, Archaea, and Eukarya (including Animals, Fungi, Plants, and various Protists like Ciliates and Diatoms).

Fields of Biology

• Botany: The study of plants.

• Zoology: The study of animals.

• Morphology: The study of structure and forms.

• Anatomy: The study of parts or structures of organisms.

• Cytology: The study of the structure and function of cells.

• Physiology: The study of the normal function of parts of an organism.

• Histology: The study of tissues.

• Ecology: The study of the environment and interrelationships of organisms.

• Systematics: The study of classification, nomenclature, and evolutionary histories.

• Taxonomy: A subset of systematics concerned specifically with naming and classification.

• Genetics: The study of genes, variation, and heredity.

• Evolution: The study of the origin and differentiation of different kinds of organisms.

• Molecular Biology: The study of the molecular basis of biological phenomena.

• Paleontology: The study of fossils and their distribution in time.

• Microbiology: The study of microorganisms.

• Bioinformatics: The study of methods and tools to interpret biological data.

Chemical Basis of Life: Inorganic and Organic Compounds

Inorganic Compounds

These compounds usually lack carbon/hydrocarbons and are involved in cellular function rather than structure.

• Water ($\text{H}_2\text{O}$): The biological medium of Earth; 70–95% of cell composition.

• Acids: Substances that increase the $\text{H}^+$ concentration of a solution.

• Bases: Any substance that reduces the $\text{H}^+$ concentration of a solution.

• Salts: General inorganic compounds found in organisms.

Organic Compounds

These contain hydrocarbons or carbon bonded to hydrogen, grouped into four classes of macromolecules:

• Carbohydrates: Sugars and sugar polymers.

• Lipids: Hydrophobic molecules such as fats, phospholipids, and steroids.

• Proteins: Comprise more than 50% of the dry mass of most cells; built from 20 amino acids.

• Nucleic Acids: DNA and RNA.

Properties of Water

1. Polarity: Water is a polar molecule, allowing for hydrogen bonding.

2. Cohesive Behavior:

   • Cohesion: Hydrogen bonds hold water molecules together; helps transport water against gravity in plants.

   • Adhesion: Attraction between water and different substances (e.g., plant cell walls).

3. Ability to Moderate Temperature:

   • Water absorbs heat from warmer air and releases it to cooler air.

   • Specific Heat: Amount of heat absorbed/lost for $1\,g$ to change temperature by $1\,^\circ\text{C}$. Specific heat of water = $1\,cal/g/^\circ\text{C}$.

   • Heat of Vaporization: Heat a liquid must absorb for $1\,g$ to convert to gas.

   • Evaporative Cooling: As liquid evaporates, the remaining surface cools.

4. Expansion Upon Freezing: Ice is less dense than liquid water because hydrogen bonds are more "ordered." Floating ice insulates the water below.

5. Versatility as a Solvent:

   • Solution: Homogeneous mixture of substances.

   • Solvent: Dissolving agent.

   • Solute: Substance being dissolved.

   • Aqueous solution: Solved in water.

   • Hydrophilic: Affinity for water.

   • Hydrophobic: No affinity for water (non-polar).

Detailed Organic Compounds

Carbohydrates

• Monosaccharides: Simplest sugars, formulas usually multiples of $\text{CH}_2\text{O}$.

  • Glucose ($\text{C}_6\text{H}_{12}\text{O}_6$): Most common sugar.

  • Fructose: Sweetest sugar; found in fruits.

  • Galactose: Found in milk.

• Oligosaccharides: 2–10 sugar units (e.g., lactose) joined by covalent glycosidic linkages.

• Polysaccharides: Polymers with storage and structural roles.

  • Starch: Storage in plants (Amylose and Amylopectin).

  • Glycogen: Storage in animals (found in liver and muscles).

  • Cellulose: Major component of plant cell walls.

  • Chitin: Found in the exoskeleton of arthropods and fungal cell walls; used for surgical thread.

Lipids

• Fats: Glycerol (3-carbon alcohol) + Fatty Acids (carboxyl group + carbon skeleton).

  • Saturated Fatty Acids: No double bonds, solid at room temperature.

  • Unsaturated Fatty Acids: One or more double bonds (cis bonds cause bending), liquid at room temperature.

• Phospholipids: Two fatty acids and a phosphate group attached to glycerol. They are amphipathic (hydrophilic head, hydrophobic tail).

• Steroids: Four fused rings. Cholesterol is a vital component of animal cell membranes.

Proteins

• Functions: Catalysis (enzymes), defense (antibodies), storage (ovalbumin), transport (hemoglobin), hormonal (insulin), receptor response, movement (actin/myosin), and structural support (keratin/collagen/elastin).

• Structure: Polypeptides are chains of amino acids (carboxyl group, amino group, and unique R-group).

• Levels of Protein Structure:

  • Primary: Unique sequence of amino acids.

  • Secondary: Coils (helix) and folds (pleated sheet) via hydrogen bonds.

  • Tertiary: Overall shape from R-group interactions.

  • Quaternary: Interaction of multiple polypeptide chains.

Nucleic Acids

• Nucleotide: Phosphate group + Pentose sugar + Nitrogenous base.

• DNA: Double-stranded; contains deoxyribose; bases A, G, C, and Thymine (T).

• RNA: Single-stranded; contains ribose; bases A, G, C, and Uracil (U).

• Bases: Pyrimidines (Cytosine, Thymine, Uracil) and Purines (Adenine, Guanine).

Cell Structure and Function

Comparison of Prokaryotic and Eukaryotic Cells

Key Eukaryotic Organelles

• Nucleus: Contains most DNA; enclosed by a nuclear envelope; contains chromatin/chromosomes.

• Endomembrane System:

  • Endoplasmic Reticulum (ER): Smooth ER (lipid synthesis, carb metabolism, $Ca^{2+}$ storage, detoxification); Rough ER (protein synthesis via ribosomes, glycoprotein production).

  • Golgi Apparatus: Stacks of flattened sacs (cis and trans faces) that modify, sort, and package proteins/carbohydrates.

  • Lysosome: Sac of hydrolytic enzymes for digestion and recycling.

  • Vacuole: Large vesicle for storage, waste disposal, and water balance.

• Mitochondria: Site of cellular respiration; double-membraned.

• Chloroplast: Site of photosynthesis; contains chlorophyll; double-membraned plastid.

• Cell Wall: Protection and shape maintenance. (Plant: cellulose/lignin; Fungal: chitin; Bacterial: peptidoglycan; Archaea: pseudopeptidoglycan; Animal: absent).

• Others: Peroxisome (ROS conversion, fatty acid breakdown), Centrosomes (MTOC in animals), Cytoskeleton (fibers for support and motility).

Cell Membrane and Transport

Fluid Mosaic Model

• Composed of a phospholipid bilayer, cholesterol, and proteins.

• Phospholipids: Amphipathic with a phosphate head and fatty acid tails.

• Selective Permeability: Regulates passage of substances.

Types of Transport

• Passive Transport: No energy required; movement down a concentration gradient.

  • Diffusion: High to low concentration.

  • Osmosis: Diffusion of water from low solute concentration to high solute concentration.

    • Isotonic: Equal solute; normal for animals, flaccid for plants.

    • Hypotonic: Low solute outside; lysed for animals, turgid (normal) for plants.

    • Hypertonic: High solute outside; shriveled for animals, plasmolyzed for plants.

  • Facilitated Diffusion: Uses transport proteins.

• Active Transport: Requires energy (ATP) via hydrolysis; moves solutes against the gradient using carrier proteins.

  • Exocytosis: Exporting material via vesicles.

  • Endocytosis: Importing material into the cell.

Energy Transformation

Photosynthesis

• Formula: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Sunlight} \xrightarrow{\text{Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

• Stages:

  1. Light-dependent Reactions: Occur in the Thylakoid/Granum; use light and $\text{H}_2\text{O}$ to produce $\text{O}_2$, ATP, and NADPH.

  2. The Calvin Cycle: Occurs in the Stroma; uses $\text{CO}_2$, ATP, and NADPH to produce G3P (which leads to glucose).

• Calvin Cycle Specifics: $3\,\text{CO}_2$ molecules produce $6\,\text{G3P}$. $1\,\text{G3P}$ exits while 5 are recycled to regenerate RuBP.

• Requirement for 1 Glucose: To produce one molecule of glucose, it requires $6\,\text{CO}_2$, $18\,\text{ATP}$, and $12\,\text{NADPH}$.

Cellular Respiration

• Formula: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP (Energy)}$

• Aerobic Respiration Steps:

  1. Glycolysis: In cytosol; breaks glucose into 2 Pyruvate ($+2\,\text{ATP}$, $2\,\text{NADH}$).

  2. Pyruvate Oxidation: Moves into mitochondria; produces $2\,\text{Acetyl CoA}$ ($2\,\text{NADH}$).

  3. Citric Acid Cycle (Krebs): Produces $2\,\text{ATP}$, $6\,\text{NADH}$, $2\,\text{FADH}_2$.

  4. Oxidative Phosphorylation: Electron transport and chemiosmosis; produces approx. $26-28\,\text{ATP}$.

• Total ATP Yield: Approx. $30$ to $32\,\text{ATP}$ per glucose molecule.

• Anaerobic Respiration (Fermentation):

  • Alcoholic Fermentation: Glucose $\rightarrow$ Pyruvate $\rightarrow$ Ethyl Alcohol + $\text{CO}_2$.

  • Lactic Acid Fermentation: Glucose $\rightarrow$ Pyruvate $\rightarrow$ Lactate.

Organismal Biology: Plants

Plant Cells and Tissues

• Cell Types:

  • Parenchyma: Primary cell wall; for photosynthesis and storage.

  • Collenchyma: Uneven primary wall; for structural support.

  • Sclerenchyma: Secondary wall, lacks nucleus at maturity; for support and water transport.

• Meristems: Rapidly dividing cells for growth.

  • Apical Meristems: Found at shoot (SAM) and root (RAM) tips; enable primary growth.

  • Lateral Meristems: Vascular and cork cambium for secondary growth.

• Tissue Systems:

  • Dermal: Epidermis (protection), Root hair (surface area), Stomatal complex (gas exchange).

  • Ground: Cortex and Pith (photosynthesis, storage).

  • Vascular:

    • Phloem: Transports sugars; composed of Sieve elements and Companion cells.

    • Xylem: Transports water; composed of Tracheids (tapered) and Vessel elements (wider).

Plant Form and Hormones

• Organs: Roots, Stem, Leaves, Flowers.

• Flower Parts: Petals, Sepals, Stamens (Anther, Filament), Pistils (Stigma, Style, Ovary).

• Hormones:

  • Auxin: Cell elongation, organ bending.

  • Cytokinins: Cell division, slows organ death.

  • Gibberellins: Stem elongation, seed dormancy breaking.

  • Abscisic Acid (ABA): Stomatal closure, promotes seed dormancy.

  • Ethylene: Fruit ripening, triple response.

Organismal Biology: Animals

Animal Tissues

1. Epithelial: Simple squamous (linings), Stratified squamous (skin/vagina), Columnar (absorptive surfaces), Cuboidal (ducts).

2. Connective: Connects structures.

   • Fibrous: Tendons and ligaments.

   • Loose: Holding organs in place.

   • Adipose: Insulation and fuel storage.

   • Cartilage: Hyaline (joints), Fibrocartilage (disks), Elastic (ears).

   • Bone: Osteoblasts; hydroxyapatite ECM.

   • Blood: RBCs (oxygen transport), WBCs (immune defense: Nutrophil, Eosinophil, Basophil, Lymphocyte, Monocyte), Platelets (clotting), Plasma.

3. Muscular: Smooth (involuntary, spindle-shaped), Cardiac (involuntary, striated, branched), Skeletal (voluntary, striated, multinucleated).

4. Nervous: Neurons (sensory, motor, interneurons) sense stimuli and transmit signals.

Animal Organ Systems

• Digestive: Liver (bile, energy cleaning), Stomach (protein digestion), Pancreas (enzymes, insulin), Small Intestine (main digestion), Large Intestine (water absorption).

• Circulatory:

  • Open: Hemolymph bathing organs.

  • Closed: Heart pumping blood through vessels (e.g., human circulation).

• Respiratory: Spiracles/Tracheae (insects), Gills (fish), Lungs/Alveoli (mammals).

• Excretory: Kidney/Nephron steps: 1. Glomerulus (filtration), 2. Proximal tubule (reabsorption), 3. Descending loop (water removal), 4. Ascending loop ($\text{NaCl}$ removal), 5. Distal tubule (ion balance), 6. Collecting duct.

• Endocrine: Glands like Thyroid (metabolism), Adrenal (stress), Pancreas (glucose), Pituitary (master gland), Ovaries/Testes.

• Reproductive:

  • Male: Testes (sperm), Epididymis (maturation), Seminal vesicles/prostate (fluid).

  • Female: Ovaries (eggs), Fallopian tubes (fertilization), Uterus (fetal development), Vagina.

Cell Cycle

1. Interphase:

   • G1 (Gap 1): Cell growth, new organelles.

   • S (Synthesis): DNA replication.

   • G2 (Gap 2): Growth, protein synthesis for mitosis.

2. M Phase (Mitosis): Division of nucleus.

   • Prophase: Chromosomes condense, spindle forms.

   • Prometaphase: Nuclear envelope fragments.

   • Metaphase: Chromosomes align at equator.

   • Anaphase: Sister chromatids separate.

   • Telophase: Nuclear envelopes reform.

3. Cytokinesis: Division of cytoplasm via cleavage furrow.

4. Meiosis: Reduction division (diploid to haploid).

   • Meiosis I: Prophase I (Crossing over at chiasmata), Metaphase I (homologous pairs), Anaphase I (homologous pairs separate).

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

Genetics

• Central Dogma: DNA (Replication) $\rightarrow$ Transcription (RNA) $\rightarrow$ Translation (Protein).

• Terminology:

  • Genotype: Allele pair present.

  • Phenotype: Observable characteristic.

  • Homozygous: Same alleles (YY).

  • Heterozygous: Different alleles (Yy).

• Mendel’s Laws:

  • Law of Segregation: Alleles separate during gamete formation.

  • Law of Independent Assortment: Non-homologous chromosomes assort independently.

  • Law of Dominance: Dominant trait masks recessive.

• Non-Mendelian Inheritance:

  • Incomplete Dominance: Intermediate phenotype (e.g., pink flowers).

  • Codominance: Both phenotypes expressed (e.g., AB blood).

  • Multiple Alleles: More than two alleles (e.g., Blood types $I^A$, $I^B$, $i$).

  • Pleiotropy: One gene affecting multiple characters (e.g., Sickle-cell).

Genetics Sample Problems

Sample 1: Genotype AaBbccDDEe

1. Possible gametes: $2^n$ (where n = heterozygous loci). n = 3 (A, B, E). $2^3 = 8\,\text{gametes}$.

2. Probability of ABcDeFgHIj: $\text{N/A}$ based on genomic input; typically calculated as $\frac{1}{2^n}$.

Sample 2: AB blood woman marries A blood man (whose father was O).

• Woman: $I^A I^B$; Man: $I^A i$.

• Cross: $I^A I^B \times I^A i \rightarrow I^A I^A, I^A i, I^A I^B, I^B i$.

• Probability child is group A: $\frac{1}{2}$. Probability child is group O: $0$.

• Probability first child is girl ($\frac{1}{2}$) and type AB ($\frac{1}{4}$): $\frac{1}{2} \times \frac{1}{4} = \frac{1}{8}$.

Evolution and Systematics

• Evolution: Descent with modification; change in genotype/phenotype due to isolation.

• Natural Selection: Based on overproduction, variation, selection (survival), and adaptation.

• Structural Evidence:

  • Homologous: Common ancestry, divergent evolution (e.g., pentadactyl limbs in humans vs. cats).

  • Analogous: Common selection pressures, convergent evolution (e.g., wings in insects vs. birds).

• Convergent Evolution Example: Streamlined shape in sharks (fish) and dolphins (mammals) due to aquatic environment.

• Taxonomy Domains: Eubacteria, Archaea, Eukarya.

• Evolutionary Origins: Plants (approx. $470\,\text{mya}$ from green algae); Animals (Metazoa approx. $770\,\text{mya}$).