Introduction to biology

• Biology is the scientific study of life

Core Principles of Biology

• Biology recognizes cells as the basic unit of life
• Genes are the basic unit of heredity
• Evolution explains the unity and diversity of life
• Living organisms maintain homeostasis to survive

Branches of Biology

• Biochemistry: Explores the chemical processes within and relating to living organisms
• Botany: Focuses on the study of plants, including their physiology, genetics, ecology, distribution, classification, and economic importance
• Cell Biology: Studies the structure, function, and behavior of cells
• Ecology: Examines the interactions of organisms with each other and their environment
• Evolutionary Biology: Investigates the evolutionary processes that produce the diversity of life on Earth
• Genetics: Is concerned with the study of heredity and variation of inherited characteristics
• Microbiology: Studies microorganisms, including bacteria, viruses, fungi, and protozoa
• Molecular Biology: Studies the molecular basis of biological activity
• Physiology: Studies the normal functions of living organisms and their parts
• Zoology: Focuses on the study of animals, including their behavior, physiology, genetics, ecology, evolution, and classification

Basic Requirements of All Living Things

• Organization: Living things exhibit complex organization, from cells to tissues, organs, and organ systems
• Metabolism: Living organisms require energy and nutrients to carry out life processes. Metabolism includes both anabolism (building up) and catabolism (breaking down)
• Growth: Increase in size or cell number
• Reproduction: The process by which organisms produce offspring, either sexually or asexually
• Response to Stimuli: Ability to detect and respond to changes in the environment
• Adaptation: Evolve over time in response to environmental pressures

Cell Structure

• The cell is the basic unit of life. There are two main types of cells: prokaryotic and eukaryotic
• Prokaryotic Cells: Lack a nucleus and other membrane-bound organelles. Bacteria and archaea are prokaryotes
• Eukaryotic Cells: Contain a nucleus and other membrane-bound organelles. Eukaryotic cells are found in protists, fungi, plants, and animals
• Cell Membrane: A selectively permeable barrier that encloses the cell, made of a phospholipid bilayer and proteins
• Nucleus: Contains the cell's DNA and controls the cell's activities
• Cytoplasm: The region of the cell between the nucleus and the cell membrane, containing organelles suspended in cytosol
• Organelles: Structures within the cell that perform specific functions, such as mitochondria (energy production), ribosomes (protein synthesis), endoplasmic reticulum (protein and lipid synthesis), Golgi apparatus (protein processing and packaging), and lysosomes (waste disposal)

Genetics

• Genes: The basic units of heredity, composed of DNA and arranged on chromosomes
• DNA (Deoxyribonucleic Acid): The molecule that carries genetic information
• Chromosomes: Structures composed of DNA and proteins that contain genes
• DNA Replication: The process by which DNA is copied
• Transcription: The process by which RNA is synthesized from a DNA template
• Translation: The process by which proteins are synthesized from RNA
• Mutations: Changes in the DNA sequence that can lead to genetic variation
• Mendelian Genetics: Principles of inheritance described by Gregor Mendel, including segregation and independent assortment
• Gene Expression: The process by which the information encoded in a gene is used to synthesize a functional gene product, such as a protein

Evolution

• Evolution: The change in the heritable characteristics of biological populations over successive generations
• Natural Selection: The process by which individuals with certain heritable traits survive and reproduce at a higher rate than others because of those traits
• Adaptation: A trait that enhances the survival and reproduction of an organism in its environment
• Genetic Variation: The raw material for evolution, arising from mutation and sexual reproduction
• Mechanisms of Evolution: Include natural selection, genetic drift, gene flow, and mutation
• Speciation: The process by which new species arise

Ecology

• Ecology: The study of the interactions of organisms with each other and their environment
• Population Ecology: Focuses on the factors that affect population size, density, and distribution
• Community Ecology: Examines the interactions between different species in a community
• Ecosystem Ecology: Studies the flow of energy and nutrients through an ecosystem, including interactions between biotic and abiotic factors
• Biomes: Large-scale ecosystems characterized by specific climate conditions and dominant plant and animal communities
• Food Chains and Food Webs: Describe the flow of energy and nutrients from one organism to another in an ecosystem
• Trophic Levels: The position an organism occupies in a food chain

Physiology

• Physiology: The study of the normal functions of living organisms and their parts
• Homeostasis: The maintenance of a stable internal environment
• Organ Systems: Groups of organs that work together to perform specific functions, such as the circulatory system (transport), respiratory system (gas exchange), digestive system (nutrient absorption), nervous system (communication and control), and endocrine system (hormone regulation)
• Feedback Mechanisms: Processes that regulate physiological functions, such as negative feedback (dampens a stimulus) and positive feedback (amplifies a stimulus)

Biochemistry

• Biochemistry: The study of the chemical processes within and relating to living organisms
• Macromolecules: Large biological molecules, including carbohydrates, lipids, proteins, and nucleic acids
• Enzymes: Biological catalysts that speed up chemical reactions in living organisms
• Metabolism: The sum of all chemical reactions that occur in an organism, including catabolism (breaking down molecules) and anabolism (building up molecules)
• Cellular Respiration: The process by which cells generate energy (ATP) by breaking down glucose and other organic molecules
• Photosynthesis: The process by which plants and other autotrophs convert light energy into chemical energy in the form of glucose

Classification of Living Organisms

• Taxonomy: The science of classifying and naming organisms
• Taxonomic Hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
• Three Domains of Life: Bacteria, Archaea, and Eukarya
• Kingdoms within Eukarya: Protista, Fungi, Plantae, and Animalia