Introduction to Biology

• Biology constitutes the scientific study of life.
• It encompasses a vast array of subjects, ranging from the molecular processes inside cells to the ecosystems spanning the entire planet.
• Biology integrates elements of chemistry, physics, geology, and mathematics.
• Advances in biology have facilitated progress in medicine, agriculture, and environmental preservation.

Core Principles

• Cell theory: The cell serves as the fundamental structural and functional unit of life.
• Gene theory: DNA represents the basic unit of heredity.
• Evolution: All life forms have descended from a shared ancestor through natural selection.
• Homeostasis: Living organisms uphold a stable internal environment.
• Thermodynamics: Life relies on the flow of energy and matter.

Subdisciplines

• Biochemistry: Focuses on the study of chemical processes within and pertaining to living organisms.
• Molecular Biology: Centers on the molecular foundation of biological activity, encompassing interactions among DNA, RNA, and proteins.
• Cell Biology: Examines the structure, function, and behavior of cells.
• Genetics: Explores heredity and the variation of inherited traits.
• Evolutionary Biology: Investigates the evolutionary mechanisms responsible for the diversity of life on Earth.
• Ecology: Studies the interactions between organisms and their environment.
• Physiology: Investigates the mechanical, physical, and biochemical functions of living organisms.
• Anatomy: Studies the structure of living organisms.
• Microbiology: Focuses on the study of microorganisms, including bacteria, viruses, fungi, and protozoa.
• Botany: Specializes in the study of plants.
• Zoology: Dedicated to the study of animals.

Characteristics of Life

• Organization: Living beings display intricate organization, progressing from atoms to molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
• Metabolism: Living organisms execute chemical reactions to procure energy and synthesize new molecules.
• Growth: Living organisms exhibit an increase in size or cell number.
• Reproduction: Living organisms generate new individuals through either sexual or asexual means.
• Response to stimuli: Living organisms react to alterations in their environment.
• Adaptation: Living organisms acquire adaptations that enhance their suitability to their environment.
• Homeostasis: Living organisms uphold a stable internal environment.

Molecular Basis of Life

• Water: Indispensable for life owing to its characteristics as a solvent, its elevated heat capacity, and its involvement in chemical reactions.
• Carbon: Forms the backbone of organic molecules, possessing the capacity to establish stable bonds with itself and other elements.
• Carbohydrates: Furnish energy and structural support, exemplified by sugars, starches, and cellulose.
• Lipids: Function as energy storage, provide insulation, and constitute components of cell membranes, including fats, oils, phospholipids, and steroids.
• Proteins: Undertake a diverse range of functions, encompassing catalysis, transport, defense, and structure, illustrated by enzymes, antibodies, hormones, and structural proteins.
• Nucleic acids: Convey genetic information, represented by DNA and RNA.

Cell Structure and Function

• Prokaryotic Cells: Lack a nucleus and additional membrane-bound organelles, as seen in bacteria and archaea.
• Eukaryotic Cells: Possess a nucleus and other membrane-bound organelles, as observed in protists, fungi, plants, and animals.
• Nucleus: Houses DNA and regulates cell activities.
• Ribosomes: Synthesize proteins.
• Endoplasmic Reticulum (ER): Engaged in protein synthesis and lipid metabolism.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Mitochondria: Generate energy via cellular respiration.
• Chloroplasts: Facilitate photosynthesis in plant cells.
• Lysosomes: Enclose enzymes for intracellular digestion.
• Cell Membrane: Regulates the passage of substances into and out of the cell.
• Cell Wall: Offers support and protection in plant, fungi, and bacterial cells.

Genetics and Heredity

• Chromosomes: Structures composed of DNA containing genes.
• Genes: Segments of heredity that dictate specific traits.
• DNA Replication: The process by which DNA is copied.
• Transcription: The process by which RNA is synthesized from DNA.
• Translation: The process by which proteins are synthesized from RNA.
• Mutations: Alterations in the DNA sequence that can result in variations in traits.
• Mendelian Genetics: The laws of inheritance derived from the work of Gregor Mendel, including the law of segregation and the law of independent assortment.
• Gene Expression: The mechanism through which the information encoded in a gene is utilized to synthesize a functional gene product, like a protein or RNA.

Evolution and Natural Selection

• Natural Selection: Organisms with traits more advantageous for their environment tend to survive and reproduce more successfully.
• Adaptation: A characteristic that enhances an organism's survival and reproduction within a specific environment.
• Genetic Variation: Disparities in genes among individuals within a population.
• Speciation: The process through which new species emerge.
• Evidence of Evolution: Supported by the fossil record, comparative anatomy, embryology, biogeography, and molecular biology.

Ecology and Ecosystems

• Population: A group of individuals of the same species residing in the same area.
• Community: A collection of diverse species inhabiting the same region and interacting with one another.
• Ecosystem: Encompasses a community of organisms and their physical surroundings, functioning as a unified ecological entity.
• Biome: A vast geographic area distinguished by particular climate conditions, animal populations, and plant species.
• Biosphere: The entirety of all ecosystems on Earth.
• Food Chain: The transfer of energy from one organism to another.
• Food Web: A complex framework of interconnected food chains within an ecological community.
• Trophic Levels: Denotes an organism's position in a food chain, such as producers, primary consumers, secondary consumers, and decomposers.
• Nutrient Cycles: The cyclical movement of essential elements (e.g., carbon, nitrogen, phosphorus) through ecosystems.
• Ecological Succession: The process of change in the structure of an ecological community over time.

Biodiversity

• Biodiversity: The variety of life spanning all levels of biological organization, from genes to ecosystems.
• Importance of Biodiversity: Provides essential ecosystem services like pollination and water purification, supports human well-being, and holds intrinsic value.
• Threats to Biodiversity: Subject to habitat destruction, invasive species, pollution, climate change, and overexploitation.
• Conservation Biology: Dedicated to the scientific investigation of biodiversity conservation.

Biological Processes

• Photosynthesis: Plants and other organisms convert light energy into chemical energy through this process.
• Cellular Respiration: Cells break down glucose to create ATP (adenosine triphosphate) through this process, which serves as the cell's energy currency.
• Mitosis: Cell division resulting in two identical daughter cells.
• Meiosis: A type of cell division that yields four genetically distinct daughter cells, each containing half the number of chromosomes as the parent cell.
• Transport Mechanisms: Processes facilitating the movement of substances across cell membranes, including diffusion, osmosis, and active transport.
• Signal Transduction: The mechanism through which cells receive and respond to external signals.

Classification of Life

• Taxonomy: The science of categorizing and naming organisms.
• Three Domains of Life: Consisting of Bacteria, Archaea, and Eukarya.
• Taxonomic Hierarchy: Arranged as Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Viruses

• Viruses: Non-cellular entities necessitating a host cell for replication.
• Structure: Composed of genetic material (DNA or RNA) enclosed within a protein coat (capsid).
• Replication: Invade host cells and utilize the host's cellular machinery to generate additional virus particles.
• Diseases: Responsible for a wide spectrum of diseases in plants, animals, and humans, including influenza, HIV, and COVID-19.

Biotechnology

• Biotechnology: The use of biological systems, organisms, or their components to develop or create products.
• Genetic Engineering: The modification of an organism's genes to create new traits or products.
• Cloning: Creating genetically identical copies of an organism or cell.
• Applications: Used in medicine for gene therapy and drug development, in agriculture for genetically modified crops, and in environmental science for bioremediation.

Human Biology

• Anatomy and Physiology: Study of the structure and function of the human body.
• Organ Systems: Circulatory, respiratory, digestive, nervous, endocrine, skeletal, muscular, immune, excretory, reproductive.
• Human Health: Influenced by genetics, lifestyle, and environment.
• Disease: A disorder of structure or function that produces specific signs or symptoms or that affects a specific location and is not simply a direct result of physical injury.