Introduction to Biology

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

• Cell theory: All living organisms are composed of cells, and all cells arise from pre-existing cells
• Gene theory: Traits are inherited through genes, which are located on chromosomes and composed of DNA
• Evolution: Life evolves over time through processes like natural selection, genetic drift, and mutation
• Homeostasis: Living organisms maintain a stable internal environment
• Thermodynamics: Life operates according to the laws of thermodynamics, involving energy transfer and transformation

Subdisciplines

• Biochemistry studies the chemical processes within and relating to living organisms
• Molecular biology studies the structure and function of biological macromolecules (e.g., proteins, nucleic acids)
• Cell biology studies the structure, function, and behavior of cells
• Genetics studies heredity and variation in organisms
• Evolutionary biology studies the evolutionary processes that produce the diversity of life on Earth
• Ecology studies the interactions of organisms with each other and their environment
• Physiology studies the functions and mechanisms operating within living organisms
• Anatomy studies the structure of organisms and their parts
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa
• Botany studies plants, including their physiology, structure, genetics, and ecology
• Zoology studies animals, including their physiology, structure, genetics, and ecology

Characteristics of Life

• Organization: Living things exhibit complex organization, from atoms to ecosystems
• Metabolism: Living things acquire and use energy through chemical reactions
• Homeostasis: Living things maintain a stable internal environment
• Growth: Living things increase in size or cell number
• Reproduction: Living things produce offspring, either sexually or asexually
• Response: Living things respond to stimuli from their environment
• Evolution: Living things evolve over time, adapting to their environment

Cell Structure and Function

• Cells are the basic units of life
• Eukaryotic cells have a nucleus and other membrane-bound organelles; examples include animal and plant cells
• Prokaryotic cells lack a nucleus and other membrane-bound organelles; examples include bacteria and archaea
• The plasma membrane controls the movement of substances into and out of the cell
• The nucleus contains the cell's genetic material (DNA)
• Ribosomes synthesize proteins
• The endoplasmic reticulum (ER) synthesizes and transports proteins and lipids
• The Golgi apparatus processes and packages proteins and lipids
• Mitochondria generate energy (ATP) through cellular respiration
• Chloroplasts (in plant cells) perform photosynthesis
• Lysosomes contain enzymes that break down cellular waste

Genetics

• Genes are segments of DNA that code for specific traits
• DNA is a double-stranded helix composed of nucleotides (adenine, guanine, cytosine, and thymine)
• RNA is a single-stranded nucleic acid that plays a role in protein synthesis
• 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 the DNA sequence that can lead to genetic variation
• Meiosis is a type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes as the parent cell
• Mitosis is a type of cell division that produces two identical daughter cells

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 a trait that increases an organism's fitness (ability to survive and reproduce)
• Genetic drift is the random change in the frequency of alleles in a population
• Mutation is a source of new genetic variation
• Gene flow is the movement of genes between populations
• Speciation is the process by which new species arise
• Phylogeny is the evolutionary history of a group of organisms

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 populations of different species living in the same area
• Ecosystems are communities of organisms and their physical environment
• The biosphere is the sum of all ecosystems on Earth
• Trophic levels describe the position of an organism in a food chain or food web
• Energy flows through ecosystems from producers (autotrophs) to consumers (heterotrophs)
• Nutrient cycles describe the movement of nutrients through ecosystems
• Biodiversity is the variety of life in an ecosystem or on Earth

Plant Biology

• Plants are multicellular, eukaryotic organisms that perform photosynthesis
• Vascular plants have specialized tissues (xylem and phloem) for transporting water and nutrients
• Non-vascular plants lack these specialized tissues
• The roots anchor the plant and absorb water and nutrients
• The stem supports the plant and transports water and nutrients
• The leaves perform photosynthesis
• Flowers are the reproductive structures of angiosperms (flowering plants)
• Fruits develop from flowers and contain seeds

Animal Biology

• Animals are multicellular, eukaryotic organisms that are heterotrophic
• Invertebrates lack a backbone, while vertebrates have a backbone
• Animals have specialized tissues and organs for various functions, such as digestion, circulation, respiration, and reproduction
• Nervous systems coordinate the activities of the body
• Endocrine systems regulate hormone production
• Immune systems protect the body from disease

Microbiology

• Microorganisms are microscopic organisms, including bacteria, viruses, fungi, and protozoa
• Bacteria are prokaryotic cells 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
• Protozoa are unicellular, eukaryotic organisms
• Microorganisms play important roles in nutrient cycling, decomposition, and disease

Biochemistry

• Biochemistry is the study of the chemical processes within and relating to living organisms
• Biomolecules are organic molecules that are essential for life, including carbohydrates, lipids, proteins, and nucleic acids
• Enzymes are proteins that catalyze biochemical reactions
• Metabolism is the sum of all chemical reactions that occur in a living organism
• Cellular respiration is the process by which cells break down glucose to produce energy (ATP)
• Photosynthesis is the process by which plants convert light energy into chemical energy (glucose)

Important Biological Processes

• Photosynthesis: Conversion of light energy into chemical energy by plants and other photosynthetic organisms
• Cellular Respiration: Process by which cells break down glucose to release energy in the form of ATP
• Protein Synthesis: Creation of proteins from amino acids based on genetic information encoded in DNA and RNA
• DNA Replication: Process of copying DNA, ensuring genetic information is passed on during cell division
• Cell Division (Mitosis and Meiosis): Processes by which cells divide for growth, repair, and reproduction, ensuring genetic continuity or diversity