Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• Broadly, biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms are open systems that survive by transforming energy and decreasing their local entropy.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells.
• Gene theory: Hereditary information is encoded in DNA and genes.
• Evolution: All life has evolved and diversified through natural selection.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow of energy and matter.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA, proteins, and carbohydrates.
• Cells: The basic unit of life, consisting of organelles and other structures enclosed by a membrane.
• Tissues: Groups of similar cells performing a specific function.
• Organs: Structures composed of different tissues that work 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 a particular area.
• Communities: Assemblages of different populations of species interacting with each other.
• Ecosystems: Communities of organisms and their physical environment.
• Biosphere: The global sum of all ecosystems.

Branches of Biology

• Biochemistry: The study of the chemical substances and vital processes occurring in living organisms.
• Molecular Biology: The study of the molecular basis of biological activity.
• Cell Biology: The study of cell structure and function.
• Genetics: The study of heredity and variation in organisms.
• Evolutionary Biology: The study of the evolutionary processes that have produced the diversity of life on Earth.
• Ecology: The study of the interactions of organisms with each other and their environment.
• Physiology: The study of the functions and mechanisms of living organisms.
• Anatomy: The study of the structure of living organisms.
• Microbiology: The study of microorganisms.
• Botany: The study of plants.
• Zoology: The study of animals.

Cell Structure and Function

• Cells are the fundamental units of life.
• Two main types of cells exist: prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells possess a nucleus and membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.
• Key cell structures include the plasma membrane, cytoplasm, nucleus, ribosomes, and organelles.
• The plasma membrane controls the movement of substances in and out of the cell.
• The cytoplasm houses the organelles and is the site of many cellular processes.
• The nucleus contains the cell's DNA and controls cell activities.
• Ribosomes are responsible for protein synthesis.
• Mitochondria generate energy through cellular respiration.
• The endoplasmic reticulum is involved in protein and lipid synthesis.
• The Golgi apparatus processes and packages proteins.

Genetics and Heredity

• Genes are the units of heredity, consisting of DNA sequences that encode proteins or RNA molecules.
• DNA (deoxyribonucleic acid) is the genetic material that carries instructions for the development and functioning of all living organisms.
• Chromosomes are structures within the nucleus that are made of DNA and proteins.
• Genes are located on chromosomes.
• 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 RNA.
• Mutations are changes in the DNA sequence that can result in altered protein function.
• Mendelian genetics describes the principles of inheritance based on the work of Gregor Mendel.
• Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable characteristics.

Evolution and Natural Selection

• Evolution is the process of change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the mechanism of evolution, in which individuals with advantageous traits are more likely to survive and reproduce.
• Evidence for evolution includes the fossil record, comparative anatomy, comparative embryology, and molecular biology.
• Adaptation is the process by which organisms become better suited to their environment.
• Speciation is the process by which new species arise.
• Phylogenetic trees illustrate the evolutionary relationships between different organisms.

Ecology and Ecosystems

• Ecology is the study of the interactions between organisms and their environment.
• Ecosystems consist of communities of organisms and their physical environment.
• Populations are groups of individuals of the same species living in a particular area.
• Communities are assemblages of different populations of species interacting with each other.
• Food chains and food webs describe the flow of energy and nutrients through an ecosystem.
• Trophic levels represent the position of an organism in a food chain.
• Energy transfer between trophic levels is inefficient, with only about 10% of the energy being transferred.
• Biogeochemical cycles describe the movement of elements, such as carbon, nitrogen, and phosphorus, through ecosystems.
• Biodiversity refers to the variety of life in an ecosystem.

Biological Processes

• Photosynthesis: Conversion of light energy into chemical energy by plants and other organisms.
• Cellular Respiration: Process by which cells break down organic molecules to release energy.
• Osmosis: Movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.
• Diffusion: Movement of molecules from an area of high concentration to an area of low concentration.
• Active Transport: Movement of molecules across a membrane against their concentration gradient, requiring energy.
• Mitosis: Cell division that results in two identical daughter cells.
• Meiosis: Cell division that results in four daughter cells with half the number of chromosomes as the parent cell.

Classification of Living Organisms

• Taxonomy is the science of classifying and naming living organisms.
• The Linnaean system of classification uses a hierarchical system with the following ranks: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• The three domains of life are Bacteria, Archaea, and Eukarya.
• The Eukarya domain includes the kingdoms Protista, Fungi, Plantae, and Animalia.
• Binomial nomenclature is the system of naming species using a two-part name consisting of the genus and species.

Viruses

• Viruses are acellular infectious agents.
• They contain genetic material (DNA or RNA) enclosed in a protein coat called a capsid.
• Viruses require a host cell to replicate.
• The viral replication cycle includes attachment, penetration, replication, assembly, and release.
• Viruses can cause a variety of diseases in plants and animals.

Human Biology

• Human biology encompasses the study of the human body, its structure, function, and its interactions with the environment.
• Anatomy focuses on the structure of the human body, including organs, tissues, and cells.
• Physiology explores how the human body functions, including processes such as respiration, circulation, digestion, and reproduction.
• The human body consists of various organ systems, including the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems.
• Human health depends on the proper functioning of all organ systems, as well as factors such as nutrition, exercise, and hygiene.

Overview of biology, the study of life, including cell theory, genes, evolution, homeostasis and thermodynamics. Exploration of biological organization levels: molecules, cells.