Introduction to Biology

• Biology is the scientific study of life
• It encompasses the structure, function, growth, origin, evolution, and distribution of living organisms

Core Principles

• Cell theory: All living organisms are composed of cells, and all cells arise from pre-existing cells
• Gene theory: Traits are inherited through genes, which are specific sequences of DNA
• Evolution: Life evolves over time through processes like natural selection
• Homeostasis: Living organisms maintain a stable internal environment

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins
• Cells: The basic unit of life, can be prokaryotic (lacking a nucleus) or eukaryotic (possessing a nucleus)
• Tissues: Groups of similar cells performing a specific function
• Organs: Structures composed of different tissues working together
• Organ systems: Groups of organs that cooperate to perform major bodily functions
• Organisms: Individual living entities
• Populations: Groups of individuals of the same species living in the same area
• Communities: Populations of different species interacting with each other
• Ecosystems: Communities and their non-living environment
• Biosphere: The sum of all ecosystems on Earth

Cell Structure and Function

• Cell membrane: A selectively permeable barrier that encloses the cell
• Cytoplasm: The gel-like substance within the cell, containing organelles
• Nucleus: Contains the cell's DNA and controls cellular activities (eukaryotic cells)
• Ribosomes: Synthesize proteins
• Endoplasmic reticulum (ER): Involved in protein and lipid synthesis
  • Rough ER: Contains ribosomes
  • Smooth ER: Lacks ribosomes
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids
• Mitochondria: Produce ATP through cellular respiration
• Chloroplasts: Conduct photosynthesis (plant cells)
• Lysosomes: Contain enzymes for intracellular digestion
• Cytoskeleton: Provides structural support and facilitates movement

Genetics

• DNA: The molecule that carries genetic information; a double helix structure
• Genes: Specific sequences of DNA that code for proteins
• Chromosomes: Structures made of DNA and proteins that carry genes
• DNA replication: The process of copying DNA
• Transcription: The process of synthesizing RNA from a DNA template
• Translation: The process of synthesizing proteins from an RNA template
• Mutations: Changes in DNA sequence
• Genetic engineering: Modifying an organism's genes to produce desired traits

Evolution

• Natural selection: Organisms with traits better suited to their environment 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
• Evidence for evolution: Fossil record, comparative anatomy, embryology, molecular biology, biogeography

Classification of Life

• Three domains: Bacteria, Archaea, Eukarya
• Eukarya includes:
  • Protista: A diverse group of mostly unicellular eukaryotes
  • Fungi: Heterotrophic organisms with cell walls made of chitin
  • Plantae: Autotrophic organisms with cell walls made of cellulose
  • Animalia: Heterotrophic organisms without cell walls

Ecology

• Populations: Groups of individuals of the same species living in the same area
• Communities: Populations of different species interacting with each other
• Ecosystems: Communities and their non-living environment
• Biomes: Large-scale ecosystems characterized by specific climate conditions and plant communities
• Food chains and food webs: Shows the flow of energy and nutrients through an ecosystem
• Trophic levels: The position an organism occupies in a food chain
• Ecological succession: The process of change in the species structure of an ecological community over time
• Biogeochemical cycles: The cycling of nutrients (e.g., carbon, nitrogen, water) through an ecosystem

Plant Biology

• Photosynthesis: The process by which plants convert light energy into chemical energy (sugars)
• Plant structures: Roots, stems, leaves, flowers
• Vascular tissues: Xylem (transports water) and phloem (transports sugars)
• Plant reproduction: Sexual and asexual reproduction
• Plant hormones: Regulate plant growth and development

Animal Biology

• Animal tissues: Epithelial, connective, muscle, nervous
• Organ systems: Digestive, circulatory, respiratory, excretory, nervous, endocrine, reproductive, immune, skeletal, muscular
• Homeostasis: Maintaining a stable internal environment
• Animal behavior: Responses to stimuli; can be innate or learned

Microbiology

• Bacteria: Prokaryotic organisms, some are beneficial, others are pathogenic
• Viruses: Non-cellular entities that require a host cell for replication
• Fungi: Eukaryotic organisms, includes yeasts and molds, some are pathogenic
• Protists: A diverse group of eukaryotic microorganisms
• Importance of microorganisms: Nutrient cycling, decomposition, disease, biotechnology

Human Biology

• Anatomy: The study of the structure of the human body
• Physiology: The study of the function of the human body
• Major organ systems: Skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, reproductive, immune
• Human genetics: Study of genes, heredity, and genetic variation in humans
• Human diseases: Causes, prevention, and treatment of diseases

Scientific Method

• Observation: Notice a phenomenon or ask a question
• Hypothesis: Formulate a testable explanation
• Experiment: Design and conduct a controlled experiment
• Data analysis: Analyze the results of the experiment
• Conclusion: Draw conclusions based on the data; accept or reject the hypothesis
• Communication: Share the findings with the scientific community

Biomolecules

• Carbohydrates: Energy source and structural components (e.g., sugars, starches, cellulose)
• Lipids: Energy storage, insulation, and components of cell membranes (e.g., fats, oils, phospholipids)
• Proteins: Diverse functions including enzymes, structural components, hormones, antibodies
• Nucleic acids: Carry genetic information (DNA and RNA)

Energy and Metabolism

• ATP (adenosine triphosphate): The primary energy currency of the cell
• Enzymes: Biological catalysts that speed up chemical reactions
• Cellular respiration: The process of breaking down glucose to produce ATP (occurs in mitochondria)
• Photosynthesis: The process of using light energy to synthesize sugars (occurs in chloroplasts)

Cell Division

• Mitosis: Cell division that results in two identical daughter cells (for growth and repair)
• Meiosis: Cell division that results in four genetically different daughter cells (for sexual reproduction)

Biotechnology

• Genetic engineering: Modifying an organism's genes to produce desired traits
• Cloning: Creating a genetically identical copy of an organism
• Biotechnology applications: Medicine, agriculture, industry, environmental science

Homeostasis

• Maintaining a stable internal environment
• Involves feedback mechanisms:
  • Negative feedback: Reduces the original stimulus
  • Positive feedback: Amplifies the original stimulus
• Examples include:
  • Temperature regulation
  • Blood glucose regulation
  • Water balance

Viruses

• Non-cellular infectious agents
• Contain genetic material (DNA or RNA) enclosed in a protein coat (capsid)
• Require a host cell for replication
• Can cause a variety of diseases
• Classified based on genetic material (DNA or RNA), capsid structure, and host range

Immunology

• The study of the immune system
• Immune system components:
  • White blood cells (leukocytes)
  • Antibodies
  • Cytokines
  • Lymphoid organs (e.g., thymus, spleen, lymph nodes)
• Types of immunity:
  • Innate immunity: Non-specific, rapid response
  • Adaptive immunity: Specific, slower response (humoral and cell-mediated)