Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• It recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms must maintain homeostasis to survive.

Key Concepts in Biology

• Evolution: The process by which populations of organisms change over time.
  • Natural Selection: The mechanism driving evolution, where organisms with advantageous traits are more likely to survive and reproduce.
  • Adaptation: Traits that enhance survival and reproduction in a specific environment.
• Genetics: The study of heredity and the variation of inherited characteristics.
  • Genes: Units of heredity made of DNA that encode proteins or regulate gene expression.
  • DNA: Deoxyribonucleic acid; the molecule that carries the genetic instructions for all known living organisms.
  • Mutation: Changes in the DNA sequence that can lead to variations.
• Cell Biology: The study of cell structure, function, and behavior.
  • Cell Theory: All living organisms are composed of cells, cells are the basic units of structure and function in living organisms, and all cells arise from pre-existing cells.
  • Organelles: Specialized structures within cells that perform specific functions (e.g., mitochondria, chloroplasts, nucleus).
  • Cell Membrane: The outer boundary of the cell that controls the movement of substances in and out.
• Biochemistry: The study of the chemical processes within living organisms.
  • Metabolism: The sum of all chemical reactions that occur within an organism.
  • Enzymes: Proteins that catalyze biochemical reactions.
  • ATP: Adenosine triphosphate; the primary energy currency of the cell.
• Ecology: The study of the interactions between organisms and their environment.
  • Ecosystem: A community of living organisms (biotic factors) interacting with their physical environment (abiotic factors).
  • Food Web: A complex network of feeding relationships in an ecosystem.
  • Biodiversity: The variety of life in a particular habitat or ecosystem.

Branches of Biology

• Zoology: The study of animals.
• Botany: The study of plants.
• Microbiology: The study of microorganisms.
• Marine Biology: The study of marine organisms and ecosystems.
• Immunology: The study of the immune system.
• Physiology: The study of the function of living organisms and their parts.
• Anatomy: The study of the structure of living organisms.

The Organization of Life

• Biosphere: The part of Earth where life exists.
• Ecosystem: A community of living organisms and their physical environment.
• Community: Populations of different species living in the same area.
• Population: A group of individuals of the same species living in the same area.
• Organism: An individual living being.
• Organ System: A group of organs that work together to perform a specific function.
• Organ: A structure composed of different tissues that work together to perform a specific function.
• Tissue: A group of similar cells that perform a specific function.
• Cell: The basic unit of structure and function in living organisms.
• Organelle: A specialized structure within a cell that performs a specific function.
• Molecule: A group of atoms bonded together.
• Atom: The basic unit of matter.

Basic Chemistry for Biology

• Atoms: The smallest unit of matter that retains the chemical properties of an element.
  • Protons: Positively charged particles in the nucleus.
  • Neutrons: Neutrally charged particles in the nucleus.
  • Electrons: Negatively charged particles orbiting the nucleus.
• Molecules: Two or more atoms held together by chemical bonds.
  • Covalent Bonds: Sharing of electrons between atoms.
  • Ionic Bonds: Transfer of electrons between atoms, creating ions.
  • Hydrogen Bonds: Weak attractions between hydrogen atoms and other electronegative atoms.
• Water: Essential for life due to its properties.
  • Cohesion: Water molecules stick together.
  • Adhesion: Water molecules stick to other surfaces.
  • High Heat Capacity: Water resists changes in temperature.
  • Solvent: Water dissolves many substances.
• pH: A measure of the acidity or alkalinity of a solution.
  • Acids: Substances that release hydrogen ions (H+) in solution (pH < 7).
  • Bases: Substances that accept hydrogen ions (H+) in solution (pH > 7).
  • Neutral: pH = 7.
• Organic Molecules: Molecules that contain carbon.
  • Carbohydrates: Provide energy and structural support.
    • Monosaccharides: Simple sugars (e.g., glucose, fructose).
    • Disaccharides: Two monosaccharides joined together (e.g., sucrose, lactose).
    • Polysaccharides: Many monosaccharides joined together (e.g., starch, cellulose).
  • Lipids: Fats, oils, and waxes; provide energy storage, insulation, and protection.
    • Saturated Fats: Solid at room temperature, single bonds between carbons.
    • Unsaturated Fats: Liquid at room temperature, double bonds between carbons.
  • Proteins: Perform a wide variety of functions, including enzymes, structural support, and transport.
    • Amino Acids: The building blocks of proteins.
    • Peptide Bonds: Bonds between amino acids.
  • Nucleic Acids: Store and transmit genetic information.
    • DNA: Deoxyribonucleic acid; contains the genetic code.
    • RNA: Ribonucleic acid; involved in protein synthesis.
    • Nucleotides: The building blocks of nucleic acids.

Cell Structure and Function

• Prokaryotic Cells: Cells that do not have a nucleus or other membrane-bound organelles.
  • Bacteria: A domain of prokaryotic organisms.
  • Archaea: A domain of prokaryotic organisms that are often found in extreme environments.
• Eukaryotic Cells: Cells that have a nucleus and other membrane-bound organelles.
  • Nucleus: Contains the cell's DNA and controls cell activities.
  • Mitochondria: Powerhouse of the cell; produces ATP through cellular respiration.
  • Chloroplasts: Found in plant cells; site of photosynthesis.
  • Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.
    • Rough ER: Contains ribosomes for protein synthesis.
    • Smooth ER: Involved in lipid synthesis and detoxification.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  • Lysosomes: Contain enzymes for breaking down waste materials and cellular debris.
  • Vacuoles: Storage of water, nutrients, and waste products.
  • Cell Wall: Provides support and protection; found in plant cells, bacteria, and fungi.
• Cell Membrane: A selectively permeable barrier that controls the movement of substances in and out of the cell.
  • Phospholipid Bilayer: The basic structure of the cell membrane.
  • Membrane Proteins: Perform various functions, including transport, signaling, and cell recognition.
• Transport Across Membranes:
  • Passive Transport: Movement of substances across the membrane without the use of energy.
    • Diffusion: Movement of molecules from an area of high concentration to an area of low concentration.
    • Osmosis: Movement of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.
    • Facilitated Diffusion: Movement of molecules across the membrane with the help of transport proteins.
  • Active Transport: Movement of substances across the membrane with the use of energy (ATP).
    • Pumps: Transport proteins that use ATP to move molecules against their concentration gradient.
    • Vesicular Transport: Movement of large molecules or bulk quantities of substances across the membrane.
      • Endocytosis: Movement of substances into the cell.
      • Exocytosis: Movement of substances out of the cell.

Energy and Metabolism

• Photosynthesis: The process by which plants and other organisms convert light energy into chemical energy in the form of glucose.
  • Light-Dependent Reactions: Convert light energy into chemical energy (ATP and NADPH).
  • Light-Independent Reactions (Calvin Cycle): Use ATP and NADPH to convert carbon dioxide into glucose.
• Cellular Respiration: The process by which organisms break down glucose to release energy in the form of ATP.
  • Glycolysis: Breakdown of glucose into pyruvate.
  • Krebs Cycle (Citric Acid Cycle): Oxidation of pyruvate to produce ATP, NADH, and FADH2.
  • Electron Transport Chain: Uses NADH and FADH2 to generate a large amount of ATP.
• Enzymes: Biological catalysts that speed up chemical reactions.
  • Substrate: The molecule upon which an enzyme acts.
  • Active Site: The region of an enzyme where the substrate binds.
  • Factors Affecting Enzyme Activity: Temperature, pH, substrate concentration, enzyme concentration.

Genetics and Heredity

• Chromosomes: Structures that contain DNA.
• Genes: Segments of DNA that code for specific traits.
• Alleles: Different versions of a gene.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable characteristics of an organism.
• Mendelian Genetics:
  • Law of Segregation: Each individual has two alleles for each gene, and these alleles separate during gamete formation.
  • Law of Independent Assortment: Alleles for different genes assort independently of one another during gamete formation.
• DNA Replication: The process by which DNA is copied.
  • DNA Polymerase: The enzyme that adds nucleotides to the growing DNA strand.
• Transcription: The process by which RNA is synthesized from a DNA template.
  • RNA Polymerase: The enzyme that synthesizes RNA.
• Translation: The process by which proteins are synthesized from RNA.
  • Ribosomes: Site of protein synthesis.
  • mRNA: Messenger RNA; carries the genetic code from DNA to ribosomes.
  • tRNA: Transfer RNA; brings amino acids to ribosomes during protein synthesis.
• Mutations: Changes in the DNA sequence.
  • Point Mutations: Changes in a single nucleotide.
  • Frameshift Mutations: Insertions or deletions of nucleotides that shift the reading frame.
• Genetic Engineering: The manipulation of an organism's genes.
  • Recombinant DNA: DNA that has been altered by combining DNA from different sources.
  • Gene Therapy: The use of genes to treat or prevent disease.

Evolution and Diversity

• Natural Selection: The process by which organisms with advantageous traits are more likely to survive and reproduce.
• Adaptation: Traits that enhance survival and reproduction in a specific environment.
• Speciation: The process by which new species arise.
  • Allopatric Speciation: Speciation that occurs when populations are geographically isolated.
  • Sympatric Speciation: Speciation that occurs without geographic isolation.
• Evidence for Evolution:
  • Fossil Record: Provides evidence of extinct species and the changes that have occurred over time.
  • Comparative Anatomy: Similarities in the anatomy of different species.
  • Comparative Embryology: Similarities in the embryonic development of different species.
  • Molecular Biology: Similarities in the DNA and protein sequences of different species.
• Classification of Living Organisms:
  • Domains: Bacteria, Archaea, Eukarya.
  • Kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia.

Ecology and Environment

• Ecosystems: A community of living organisms and their physical environment.
• Biomes: Large geographic areas with similar climate and vegetation.
• Trophic Levels: The position an organism occupies in a food chain.
  • Producers: Organisms that produce their own food through photosynthesis.
  • Consumers: Organisms that eat other organisms.
  • Decomposers: Organisms that break down dead organic matter.
• Food Webs: Complex networks of feeding relationships in an ecosystem.
• Energy Flow: The movement of energy through an ecosystem.
• Nutrient Cycling: The movement of nutrients through an ecosystem.
• Population Ecology:
  • Population Growth: The change in the size of a population over time.
  • Carrying Capacity: The maximum population size that an environment can support.
• Community Ecology:
  • Competition: Interaction between organisms that require the same resources.
  • Predation: Interaction in which one organism (the predator) eats another organism (the prey).
  • Symbiosis: A close relationship between two or more species.
    • Mutualism: Both species benefit.
    • Commensalism: One species benefits and the other is neither harmed nor benefited.
    • Parasitism: One species benefits and the other is harmed.
• Environmental Issues:
  • Pollution: The introduction of harmful substances into the environment.
  • Climate Change: Changes in the Earth's climate caused by human activities.
  • Deforestation: The clearing of forests.
  • Habitat Loss: The destruction of habitats.
  • Biodiversity Loss: The decline in the variety of life on Earth.