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 of Biology

• Cell theory: All living organisms are composed of cells
• Gene theory: Heredity occurs through genes, units of inheritance
• Evolution: Populations evolve over time
• Homeostasis: Living organisms maintain a stable internal environment

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins
• Cells: Basic unit of life, consisting of organelles and other structures
• Tissues: Groups of similar cells performing a specific function
• Organs: Structures composed of different tissues working 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 specific area
• Communities: Assemblages of different populations living and interacting in an area
• Ecosystems: Communities and their physical environment
• Biosphere: All ecosystems on Earth

Cell Structure and Function

• Cells are of two types: prokaryotic and eukaryotic
• Prokaryotic cells lack a nucleus and other membrane-bound organelles
• Eukaryotic cells possess a nucleus and other membrane-bound organelles

Cell Organelles

• Nucleus: Contains the cell's genetic material (DNA) and controls cell activities
• Endoplasmic reticulum (ER): Involved in protein and lipid synthesis
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids
• Mitochondria: Powerhouse of the cell, produces ATP through cellular respiration
• Chloroplasts: Found in plant cells, site of photosynthesis
• Lysosomes: Contain enzymes for intracellular digestion
• Ribosomes: Site of protein synthesis

Cell Membrane

• Phospholipid bilayer with embedded proteins
• Regulates the movement of substances in and out of the cell
• Involved in cell signaling and communication

Cell Communication

• Cells communicate through chemical signals
• Signal transduction pathways convert signals into cellular responses

Cell Cycle and Division

• Cell cycle: Sequence of growth, DNA replication, and division
• Mitosis: Cell division that produces two identical daughter cells
• Meiosis: Cell division that produces four genetically different daughter cells (gametes)

Genetics

• Genes are units of heredity made of DNA
• DNA: Deoxyribonucleic acid, carries genetic information
• Chromosomes: Structures made of DNA and proteins that contain genes
• Genotype is the genetic makeup of an organism
• Phenotype is the observable characteristics of an organism
• Inheritance: Transmission of traits from parents to offspring

DNA Replication

• The process of copying DNA
• Helicase unwinds the DNA double helix
• DNA polymerase synthesizes new DNA strands

Transcription

• The process of synthesizing RNA from a DNA template
• RNA polymerase is the enzyme that catalyzes transcription

Translation

• The process of synthesizing proteins from RNA
• Ribosomes are the site of translation
• tRNA molecules bring amino acids to the ribosome

Mutations

• Changes in the DNA sequence
• Can be spontaneous or induced by mutagens
• Can be harmful, beneficial, or neutral

Evolution

• Change in the heritable characteristics of biological populations over successive generations
• Natural selection: Differential survival and reproduction of individuals with advantageous traits
• Adaptation: Traits that enhance survival and reproduction in a specific environment
• Speciation: The process by which new species arise

Evidence for Evolution

• Fossil record: Provides evidence of past life forms
• Comparative anatomy: Similarities in the anatomy of different species
• Embryology: Similarities in the development of different species
• Molecular biology: Similarities in the DNA and protein sequences of different species

Classification of Living Organisms

• Taxonomy: The science of classifying organisms
• Three domains of life: Bacteria, Archaea, and Eukarya
• Eukarya includes four kingdoms: Protista, Fungi, Plantae, and Animalia

Ecology

• The study of the interactions between organisms and their environment
• Populations: Groups of individuals of the same species living in a specific area
• Communities: Assemblages of different populations living and interacting in an area
• Ecosystems: Communities and their physical environment
• Biosphere: All ecosystems on Earth

Ecosystem Components

• Biotic factors: Living organisms
• Abiotic factors: Non-living components, such as temperature, light, and water

Ecological Interactions

• Competition: Organisms compete for resources
• Predation: One organism (predator) feeds on another organism (prey)
• Symbiosis: Close interactions between different species
  • Mutualism: Both species benefit
  • Commensalism: One species benefits, the other is not affected
  • Parasitism: One species benefits, the other is harmed

Energy Flow in Ecosystems

• Producers: Autotrophs that produce their own food through photosynthesis or chemosynthesis
• Consumers: Heterotrophs that obtain energy by feeding on other organisms
• Decomposers: Break down dead organisms and organic matter

Food Chains and Food Webs

• Food chain: Linear sequence of organisms through which nutrients and energy pass
• Food web: Interconnected network of food chains

Biomes

• Major regional or global biotic communities, characterized by climate and vegetation
• Examples: Tropical rainforest, desert, grassland, tundra

Human Impact on the Environment

• Pollution: Contamination of the environment with harmful substances
• Deforestation: Clearing of forests
• Climate change: Changes in global temperature and weather patterns
• Loss of biodiversity: Reduction in the variety of life on Earth