Introduction to Biology

• Biology explores the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms

Core Principles of Biology

• Cell theory states all living organisms consist of cells
• Gene theory states hereditary information is encoded in DNA and passed from parents to offspring
• Evolution occurs over time through natural selection
• Homeostasis is the maintenance of a stable internal environment in living organisms

Levels of Biological Organization

• Molecules consist of combined atoms, such as DNA and proteins
• Cells, the basic unit of life, are the smallest entity exhibiting life's characteristics
• Tissues are groups of similar cells performing a specific function
• Organs are structures composed of different tissues working together for a common purpose
• Organ Systems are groups of organs cooperating to perform bodily functions
• Organisms are individual living entities
• Populations are groups of individuals of the same species in a specific area
• Communities are populations of different species interacting within a specific area
• Ecosystems are communities together with their physical environment
• The Biosphere is all ecosystems combined; the regions of Earth inhabited by life

Key Concepts in Biology

• Genetics covers heredity and genes
• Evolution is the change in the traits of a species over generations
• Ecology examines interactions between organisms and their environment
• Physiology studies the functions and mechanisms in living systems
• Anatomy studies the structure of living things

Cell Biology

• Cells are classified as either prokaryotic or eukaryotic
• Prokaryotic cells lack a nucleus and complex organelles
• Eukaryotic cells possess a nucleus and membrane-bound organelles
• The plasma membrane surrounds cells, regulating substance movement
• Cytoplasm, a gel-like substance within cells, contains organelles
• Organelles include mitochondria for energy production, ribosomes for protein synthesis, endoplasmic reticulum for protein and lipid synthesis, Golgi apparatus for processing and packaging, and lysosomes for waste disposal

Genetics and Heredity

• Genes are units of heredity made of DNA
• DNA has two strands forming a double helix with nucleotides that contain a sugar, phosphate group, and one of four nitrogenous bases: adenine, guanine, cytosine, thymine
• DNA replication is the process where DNA copies itself
• Transcription is the process of creating RNA from a DNA template
• Translation is the process of synthesizing proteins from RNA
• Mutations are changes in DNA sequence that can be harmful, beneficial, or neutral
• Mendelian genetics describes the principles of inheritance
• Chromosomes are structures containing DNA; humans have 46 chromosomes in 23 pairs

Evolution and Natural Selection

• Evolution is the change in heritable traits of biological populations across generations
• Natural selection is the mechanism by which evolution occurs, favoring traits enhancing survival and reproduction
• Adaptation refers to inherited traits that enhance survival and reproduction
• Speciation is the process by which new species arise
• Evidence for evolution includes the fossil record, comparative anatomy, embryology, biogeography, and molecular biology

Ecology and Ecosystems

• Ecology studies interactions between organisms and their environment
• Ecosystems are communities of organisms interacting with their physical environment
• Populations are groups of individuals of the same species living in a specific area
• Communities are populations of different species interacting within a specific area
• Trophic levels represent an organism's position in a food chain: producers, consumers, and decomposers
• Food webs are interconnected food chains within an ecosystem
• Biomes are large geographic areas with similar climate and ecosystems like forests, grasslands, deserts, and tundra

Plant Biology

• Plants are autotrophs, producing their own food through photosynthesis
• Photosynthesis converts light energy into chemical energy (glucose), using carbon dioxide and water
• Plant structures include roots for absorbing water and nutrients, stems for support and transport, leaves for photosynthesis, and flowers for reproduction
• Plant reproduction occurs sexually (pollination and fertilization) and asexually (vegetative propagation)
• Plant hormones regulate growth, development, and environmental responses, including auxins, gibberellins, and cytokinins
• The vascular system includes xylem for water transport and phloem for sugar transport

Animal Biology

• Animals are heterotrophs, obtaining nutrients by consuming other organisms
• Animal classification is based on body plan, symmetry, and developmental patterns
• Animal tissues include epithelial, connective, muscle, and nervous
• Animal organ systems are digestive, circulatory, respiratory, excretory, nervous, endocrine, reproductive, and immune
• Animal behavior includes responses to stimuli, both innate (instinctive) and learned
• Homeostasis is the maintenance of a stable internal environment balancing temperature, pH, and blood glucose

Microbiology

• Microbiology studies microorganisms, namely bacteria, archaea, viruses, fungi, protozoa
• Bacteria and archaea are prokaryotic organisms with varied metabolic capabilities
• Viruses are non-cellular entities requiring a host to replicate
• Fungi are eukaryotic organisms obtaining nutrients by absorption
• Protozoa are single-celled eukaryotic organisms with various modes of nutrition
• Microorganisms play crucial roles in nutrient cycling, decomposition, and disease

Human Biology

• Human anatomy studies the structure of the human body
• Human physiology studies the function of the human body
• Interactions between organ systems maintain homeostasis
• Genetics and heredity covers inheritance of traits and genetic disorders
• Human evolution covers the evolutionary history of humans
• Disease and immunity covers mechanisms of disease and immune system responses

Scientific Method in Biology

• Observation involves noting phenomena or asking a question
• A hypothesis is a tentative explanation for an observation
• Experimentation tests the hypothesis through controlled experiments
• Data collection gathers evidence to support or refute the hypothesis
• Analysis interprets data and draws conclusions
• Communication shares results through publications and presentations

Important Biological Molecules

• Carbohydrates: Source of energy and structural components (e.g., glucose, starch, cellulose)
• Lipids: Energy storage, insulation, and structural components (e.g., fats, oils, phospholipids)
• Proteins: Diverse functions, including enzymes, structural proteins, and transport proteins (e.g., enzymes, antibodies, collagen)
• Nucleic acids: Store and transmit genetic information (DNA, RNA)

Energy and Metabolism

• Metabolism is the sum of all chemical reactions in an organism
• Enzymes are proteins that catalyze (speed up) biochemical reactions
• Cellular respiration is the process by which cells break down glucose to produce ATP (energy)
• ATP (adenosine triphosphate) is the main energy currency of cells
• Photosynthesis is the conversion of light energy into chemical energy (glucose)

Reproduction and Development

• Sexual reproduction involves the fusion of gametes (egg and sperm)
• Asexual reproduction does not involve gametes and produces genetically identical offspring
• Animal development involves fertilization, cleavage, gastrulation, and organogenesis
• Plant development involves seed germination, growth, and differentiation

Taxonomy and Classification

• Taxonomy is the science of naming and classifying organisms
• The Linnaean system is a hierarchical classification system with kingdom, phylum, class, order, family, genus, and species
• Binomial nomenclature is a two-part naming system including genus and species
• Phylogeny describes evolutionary history and relationships among organisms

Biotechnology

• Biotechnology uses biological systems or organisms for industrial or technological purposes
• Genetic engineering modifies an organism's DNA to introduce new traits
• Cloning creates genetically identical copies of organisms
• Applications are found in medicine, agriculture, and environmental science

Biology is the scientific study of living organisms, encompassing their structure, function, and evolution. Key principles include cell theory, gene theory, evolution, and homeostasis. Biological organization ranges from molecules and cells to organisms and populations.