Introduction to Biology

• Biology is the scientific study of life
• It explores the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms

Core Principles

• Cell theory: All living organisms are composed of cells
• Gene theory: Hereditary information is encoded in DNA and passed from parents to offspring
• Evolution: Life evolves over time through processes like natural selection
• Homeostasis: Living organisms maintain a stable internal environment

Branches of Biology

• Biochemistry: Study of chemical processes within and relating to living organisms
• Molecular Biology: Study of the structure and function of macromolecules
• Cell Biology: Study of cell structure and function
• Genetics: Study of heredity and variation of inherited characteristics
• Microbiology: Study of microorganisms
• Botany: Study of plants
• Zoology: Study of animals
• Ecology: Study of the interactions of organisms with each other and their environment
• Physiology: Study of the functions and mechanisms in a living system

Chemical Basis of Life

• Living organisms are composed of organic molecules (containing carbon)
• Key organic molecules include carbohydrates, lipids, proteins, and nucleic acids
• Carbohydrates provide energy and structural support
• Lipids store energy, form cell membranes, and act as hormones
• Proteins perform a wide variety of functions, including catalysis, transport, and structure
• Nucleic acids (DNA and RNA) store and transmit genetic information

Cell Structure and Function

• Cells are the basic unit of life
• Two main types of cells: prokaryotic (lacking a nucleus) and eukaryotic (having a nucleus)
• Key cell structures include the plasma membrane, cytoplasm, nucleus (in eukaryotes), ribosomes, mitochondria, and endoplasmic reticulum
• Plasma membrane controls the movement of substances into and out of the cell
• Cytoplasm is the gel-like substance within the cell where organelles are located
• Nucleus contains the cell's DNA
• Ribosomes are responsible for protein synthesis
• Mitochondria generate energy (ATP) through cellular respiration
• Endoplasmic reticulum is involved in protein and lipid synthesis

Energy and Metabolism

• Metabolism is the sum of all chemical reactions in an organism
• Catabolism breaks down molecules to release energy
• Anabolism uses energy to build molecules
• Enzymes are biological catalysts that speed up chemical reactions
• Cellular respiration is the process by which cells break down glucose to produce ATP
• Photosynthesis is the process by which plants and some bacteria use sunlight to synthesize glucose

Genetics

• Genes are units of heredity that contain instructions for building proteins
• DNA is the molecule that carries genetic information
• Chromosomes are structures within the nucleus that contain DNA
• DNA replication is the process by which DNA is copied
• Transcription is the process by which RNA is synthesized from DNA
• Translation is the process by which proteins are synthesized from RNA
• Mutations are changes in DNA sequence that can lead to genetic variation

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations
• Natural selection is the process by which organisms with advantageous traits are more likely to survive and reproduce
• Adaptation is the process by which organisms become better suited to their environment
• Evidence for evolution comes from fossil records, comparative anatomy, embryology, and molecular biology

Classification of Life

• Taxonomy is the science of classifying organisms
• Organisms are classified into a hierarchical system of groups: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species
• Three Domains of life: Bacteria, Archaea, and Eukarya
• Kingdoms within Eukarya include Protista, Fungi, Plantae, and Animalia

Ecology

• Ecology is the study of the interactions of organisms with each other and their environment
• Key ecological concepts include populations, communities, ecosystems, and biomes
• Populations are groups of individuals of the same species living in the same area
• Communities are groups of different species living in the same area
• Ecosystems are communities of organisms interacting with their physical environment
• Biomes are large-scale ecosystems characterized by specific climate conditions and dominant plant life

Human Biology

• Human biology is the study of the human body and its functions
• Key systems of the human body include the skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, and reproductive systems
• Skeletal system provides support and protection
• Muscular system enables movement
• Nervous system controls and coordinates bodily functions
• Endocrine system produces hormones
• Cardiovascular system transports blood and nutrients
• Respiratory system exchanges gases
• Digestive system breaks down food
• Urinary system eliminates waste
• Reproductive system enables reproduction

Microbiology

• Microbiology is the study of microorganisms, including bacteria, archaea, fungi, protists, and viruses
• Microorganisms play important roles in nutrient cycling, decomposition, and disease
• Bacteria are prokaryotic organisms that can be beneficial or harmful
• Viruses are non-cellular entities that require a host cell to replicate
• Fungi are eukaryotic organisms that can be unicellular or multicellular
• Protists are a diverse group of eukaryotic organisms

Plant Biology

• Plant biology is the study of plants
• Plants are autotrophs that produce their own food through photosynthesis
• Key structures of plants include roots, stems, leaves, and flowers
• Roots anchor the plant and absorb water and nutrients
• Stems provide support and transport
• Leaves are the site of photosynthesis
• Flowers are involved in reproduction
• Plants play important roles in oxygen production, carbon sequestration, and food production

Animal Biology

• Animal biology is the study of animals
• Animals are heterotrophs that obtain their food by consuming other organisms
• Animals are multicellular eukaryotic organisms
• Key characteristics of animals include movement, reproduction, and response to stimuli
• Animal diversity is vast, ranging from simple invertebrates to complex vertebrates.

Biology is the scientific study of life, exploring the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms. Key principles include cell theory, gene theory, evolution, and homeostasis. It has branches like biochemistry, molecular biology, and ecology.