Introduction to Biology

• Biology is the scientific study of life, encompassing a wide range of topics from the molecular mechanisms within cells to the complex interactions of ecosystems
• Explores the structure, function, growth, origin, evolution, and distribution of living organisms

Core Principles

• Cell theory states all living organisms are composed of cells, the basic units of structure and function
• Gene theory states hereditary information is encoded in DNA and passed from parents to offspring
• Evolution is the process where life on Earth has evolved over time through natural selection
• Homeostasis describes how living organisms maintain a stable internal environment

Branches of Biology

• Biochemistry is the study of the chemical processes within and relating to living organisms
• Molecular Biology focuses on the structure and function of biological macromolecules, like proteins and nucleic acids
• Cell Biology studies cell structure, function, and behavior
• Genetics explores heredity and the variation of inherited characteristics
• Evolutionary Biology studies the evolutionary processes that have shaped the diversity of life
• Ecology studies the interactions between organisms and their environment
• Physiology studies the normal functions of living organisms and their parts
• Anatomy studies the structure of living organisms
• Microbiology studies microorganisms like bacteria, viruses, and fungi
• Botany is the study of plants
• Zoology is the study of animals

Chemical Basis of Life

• Living organisms are composed of organic molecules containing carbon
• Key organic molecules: carbohydrates, lipids, proteins, and nucleic acids
• Carbohydrates provide energy and structural support, examples include sugars, starches, and cellulose
• Lipids store energy, form cell membranes, and act as hormones, examples include fats, oils, and phospholipids
• Proteins perform varied functions like catalyzing reactions, transporting molecules, and providing structural support, examples include enzymes, antibodies, and collagen
• Nucleic acids store and transmit genetic information (DNA and RNA)

Cell Structure and Function

• Cells are fundamental units of life; organisms are made of one or more
• Eukaryotic Cells contain membrane-bound organelles, including a nucleus, mitochondria, and endoplasmic reticulum; found in plants, animals, fungi, and protists
• Prokaryotic Cells lack membrane-bound organelles; found in bacteria and archaea
• Cell Membrane encloses the cell and regulates the movement of substances in and out
• Nucleus contains the cell's DNA and controls cellular activities
• Mitochondria generate energy through cellular respiration
• Endoplasmic Reticulum synthesizes and transports proteins and lipids
• Golgi Apparatus modifies, sorts, and packages proteins and lipids
• Lysosomes contain enzymes that break down cellular waste and debris

Genetics and Heredity

• Genes are units of heredity that contain instructions for building proteins
• DNA (Deoxyribonucleic Acid) carries the genetic information in cells
• Chromosomes are structures made of DNA that contain genes; humans have 46 chromosomes arranged in 23 pairs
• DNA Replication is the process by which DNA is copied
• Transcription is the process by which RNA is synthesized from a DNA template
• Translation is the process by which proteins are synthesized from an RNA template
• Mutations are changes in the DNA sequence that can lead to genetic variation
• Mendelian Genetics: Principles of inheritance based on the work of Gregor Mendel, including the laws of segregation and independent assortment

Evolution and Natural Selection

• Evolution is the process by which populations of organisms change over time
• Natural Selection is the differential survival and reproduction of individuals based on their traits
• Adaptation refers to traits that enhance an organism's survival and reproduction in a particular environment
• Genetic Variation is the differences among individuals in their genes, which is the raw material for evolution
• Evidence for Evolution: Fossil record, comparative anatomy, embryology, and molecular biology
• Speciation is the process by which new species arise

Ecology and Ecosystems

• Ecology is the study of the interactions between organisms and their environment
• Ecosystem is a community of interacting organisms and their physical environment
• Population is a group of individuals of the same species living in the same area
• Community is an assemblage of different populations that live together in the same area
• Food Chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another
• Food Web is an interconnected network of food chains
• Trophic Levels are the position an organism occupies in a food chain (e.g., producers, consumers, decomposers)
• Biomes are large geographic areas characterized by specific climate conditions and plant and animal communities (e.g., forests, grasslands, deserts)
• Biodiversity is the variety of life in a particular habitat or ecosystem

Plant Biology

• Plants are multicellular, eukaryotic organisms that produce their own food through photosynthesis
• Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose
• Plant Structures: Roots (absorb water and nutrients), stems (support the plant), and leaves (site of photosynthesis)
• Plant Reproduction: Sexual (involving pollination and fertilization) and asexual (vegetative propagation)
• Plant Transport: Xylem (transports water and minerals) and phloem (transports sugars)
• Plant Hormones regulate growth, development, and responses to the environment, examples include auxins, gibberellins, cytokinins

Animal Biology

• Animals are multicellular, eukaryotic organisms that obtain nutrients by consuming other organisms
• Animal Tissues: Epithelial (covers surfaces), connective (supports and connects tissues), muscle (enables movement), and nervous (transmits signals)
• Animal Organ Systems: Integumentary (skin), skeletal (support), muscular (movement), nervous (control and coordination), endocrine (hormone regulation), cardiovascular (circulation), respiratory (gas exchange), digestive (nutrient absorption), urinary (waste elimination), and reproductive (procreation)
• Animal Behavior consists of responses to stimuli, including innate (instinctive) and learned behaviors
• Animal Development: Embryonic development, including fertilization, cleavage, gastrulation, and organogenesis

Microbiology

• Microorganisms are microscopic organisms, including bacteria, viruses, fungi, and protists
• Bacteria are prokaryotic organisms that play important roles in nutrient cycling, decomposition, and disease
• Viruses are non-cellular entities that require a host cell to replicate; can cause a variety of diseases
• Fungi are eukaryotic organisms that obtain nutrients by absorbing organic matter; include yeasts, molds, and mushrooms
• Protists are a diverse group of eukaryotic organisms, including algae and protozoa
• Microbial Ecology studies the interactions between microorganisms and their environment
• Microbiology is the study of microorganisms, including their structure, function, genetics, and interactions with other organisms

Important Biological Processes

• Photosynthesis is the conversion of light energy to chemical energy by plants and other organisms
• Cellular Respiration is the process by which cells break down glucose to release energy in the form of ATP
• Mitosis is cell division that results in two identical daughter cells; used for growth and repair
• Meiosis is cell division that results in four genetically different daughter cells; used for sexual reproduction
• Osmosis is the movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration
• Diffusion is the movement of molecules from an area of high concentration to an area of low concentration
• Active Transport is the movement of molecules across a cell membrane against their concentration gradient, requiring energy
• Enzyme Catalysis: Enzymes speed up chemical reactions in cells by lowering the activation energy

Biology is the scientific study of life, exploring everything from molecular mechanisms to ecosystems. It covers structure, function, growth, origin, evolution, and distribution of living organisms. Key principles include cell theory, gene theory, evolution, and homeostasis.