Introduction to Biology

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

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: maintenance of a stable internal environment
• Thermodynamics: life depends on energy flow and transformation

Branches of Biology

• Zoology: study of animals
• Botany: study of plants
• Microbiology: study of microorganisms
• Genetics: study of heredity and variation
• Ecology: study of the interactions between organisms and their environment
• Anatomy: study of the structure of organisms
• Physiology: study of the function of organisms

Chemical Basis of Life

• Living organisms are composed of organic molecules (carbohydrates, lipids, proteins, nucleic acids)
• Water is essential for life due to its properties as a solvent, its high heat capacity, and its role in various biochemical reactions
• Carbon's ability to form diverse structures is fundamental to the complexity of organic molecules

Cell Structure and Function

• Cells are the basic structural and functional units of life
• Prokaryotic cells (bacteria and archaea) lack a nucleus and other membrane-bound organelles
• Eukaryotic cells (protists, fungi, plants, and animals) have a nucleus and other membrane-bound organelles
• Key organelles in eukaryotic cells include the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, and chloroplasts (in plant cells)
• Cell membrane regulates the movement of substances in and out of the cell, maintaining cell integrity and communication

Metabolism

• Metabolism is the sum of all chemical reactions that occur within an organism
• Catabolism: break down complex molecules into simpler ones, releasing energy
• Anabolism: use energy to build complex molecules from simpler ones
• Enzymes are biological catalysts that speed up biochemical reactions by lowering the activation energy

Energy and Life

• Photosynthesis converts light energy, water, and carbon dioxide into glucose and oxygen (occurs in plants, algae, and some bacteria)
• Cellular respiration breaks down glucose in the presence of oxygen to produce ATP (energy currency of the cell), water, and carbon dioxide (occurs in most organisms)
• ATP powers cellular activities, such as muscle contraction, nerve impulse transmission, and biosynthesis

Genetics

• DNA (deoxyribonucleic acid) carries the genetic information in cells
• Genes are specific sequences of DNA that encode for proteins or functional RNA molecules
• DNA replication is the process of copying DNA molecules
• Transcription converts DNA into RNA
• Translation converts RNA into protein
• Mutations are changes in the DNA sequence that can lead to variation
• Genetic engineering allows scientists to manipulate genes and genomes for various purposes

Cell Cycle and Cell Division

• Cell cycle include growth, DNA replication, and cell division
• Mitosis is the process of cell division that produces two identical daughter cells (for growth, repair, and asexual reproduction)
• Meiosis is the process of cell division that produces four genetically different daughter cells (for sexual reproduction)
• Chromosomes are structures made of DNA and proteins that carry genetic information

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations
• Natural selection is the mechanism 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 fossils, comparative anatomy, embryology, and molecular biology
• Speciation is the process by which new species arise

Classification of Living Organisms

• Taxonomy is the science of classifying organisms based on their evolutionary relationships
• The hierarchical classification system includes domain, kingdom, phylum, class, order, family, genus, and species
• Three domains of life: Bacteria, Archaea, and Eukarya
• Six kingdoms of life: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia

Ecology

• Ecology is the study of the interactions between organisms and their environment
• Populations are groups of individuals of the same species living in the same area
• Communities are groups of different populations living in the same area
• Ecosystems consist of communities and their physical environment
• Biomes are large geographic areas characterized by specific climate and vegetation
• Biosphere encompasses all ecosystems on Earth

Ecosystem Dynamics

• Energy flows through ecosystems from producers (autotrophs) to consumers (heterotrophs)
• Food chains and food webs illustrate the feeding relationships among organisms in an ecosystem
• Trophic levels represent the position of an organism in a food chain
• Nutrient cycles (carbon, nitrogen, phosphorus, water) are essential for maintaining ecosystem health
• Ecological succession is the process of change in the species structure of an ecological community over time

Human Impact on the Environment

• Deforestation leads to habitat loss, soil erosion, and climate change
• Pollution contaminates air, water, and soil, harming organisms and ecosystems
• Climate change is caused by the increase in greenhouse gases, leading to global warming and altered weather patterns
• Conservation biology aims to protect and restore biodiversity
• Sustainable practices promote the use of resources in a way that meets the needs of the present without compromising the ability of future generations to meet their own needs

Plant Biology

• Plants are autotrophic organisms that obtain energy through photosynthesis
• Vascular tissues (xylem and phloem) transport water and nutrients throughout the plant
• Roots anchor the plant, absorb water and nutrients, and store food
• Stems support the plant and transport substances
• Leaves are the primary site of photosynthesis
• Flowers are the reproductive structures of plants

Animal Biology

• Animals are heterotrophic organisms that obtain energy by consuming other organisms
• Major animal phyla include Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata, and Chordata
• Vertebrates have a backbone and belong to the phylum Chordata
• Organ systems in animals include the digestive, circulatory, respiratory, nervous, endocrine, excretory, skeletal, muscular, and reproductive systems

Microbiology

• Microorganisms include bacteria, archaea, viruses, fungi, and protists
• Bacteria are prokaryotic cells that play important roles in nutrient cycling, decomposition, and disease
• Viruses are acellular entities that require a host cell to replicate
• Fungi are eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds and mushrooms)
• Protists are a diverse group of eukaryotic organisms that are not plants, animals, or fungi