Introduction to Biology

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

Key concepts in biology

• Cell theory: All living organisms are composed of cells.
• Gene theory: Traits are inherited through genes.
• Evolution: All life forms have evolved from a common ancestor through a process of natural selection.
• Homeostasis: All living organisms maintain a stable internal environment.

Subdisciplines of biology

• Biochemistry: The study of the chemical processes within living organisms.
• Molecular biology: The study of the structure and function of biological molecules.
• Cell biology: The study of the structure and function of cells.
• Genetics: The study of heredity and variation in organisms.
• Evolutionary biology: The study of the evolutionary processes that have shaped the diversity of life.
• Ecology: The study of the interactions between organisms and their environment.
• Physiology: The study of the function of living organisms and their parts.
• Anatomy: The study of the structure of living organisms.
• Microbiology: The study of microorganisms.
• Botany: The study of plants.
• Zoology: The study of animals.

Characteristics of life

• Organization: Living things exhibit a complex organization, from cells to tissues, organs, and organ systems.
• Metabolism: Living things carry out chemical reactions to obtain and utilize energy.
• Growth: Living things increase in size and complexity.
• Reproduction: Living things produce offspring, either sexually or asexually.
• Response to stimuli: Living things react to changes in their environment.
• Adaptation: Living things evolve and adapt to their environment over time.
• Homeostasis: Living things maintain a stable internal environment.

The scientific method in biology

• Observation: Scientists make observations about the natural world.
• Hypothesis: Scientists formulate a testable explanation for their observations.
• Experimentation: Scientists design and conduct experiments to test their hypotheses.
• Data analysis: Scientists analyze the data from their experiments to determine whether their hypotheses are supported.
• Conclusion: Scientists draw conclusions based on their data analysis.
• Communication: Scientists share their findings with the scientific community through publications and presentations.

Important biological molecules

• Carbohydrates: Energy source and structural components. Examples include sugars, starches, and cellulose.
• Lipids: Energy storage, insulation, and cell membrane components. Examples include fats, oils, and phospholipids.
• Proteins: Enzymes, structural components, and transporters. Examples include enzymes, antibodies, and hormones.
• Nucleic acids: Genetic information storage and transfer. Examples include DNA and RNA.

Cell structure and function

• Prokaryotic cells: Simple cells without a nucleus or other membrane-bound organelles.
• Eukaryotic cells: Complex cells with a nucleus and other membrane-bound organelles.
• Cell membrane: Regulates the passage of substances into and out of the cell.
• Cytoplasm: The fluid-filled space inside the cell.
• Nucleus: Contains the cell's genetic material (DNA).
• Ribosomes: Synthesize proteins.
• Mitochondria: Generate energy for the cell through cellular respiration.
• Chloroplasts: Carry out photosynthesis in plant cells.
• Endoplasmic reticulum: Synthesizes and transports proteins and lipids.
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Digest cellular waste and debris.

Genetics and heredity

• Genes: Units of heredity that determine traits.
• DNA: The molecule that carries genetic information.
• Chromosomes: Structures that contain DNA.
• Alleles: Different versions of a gene.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable characteristics of an organism.
• Inheritance: The passing of traits from parents to offspring.
• Mutation: A change in the DNA sequence.

Evolution and natural selection

• Evolution: The change in the genetic makeup of a population over time.
• Natural selection: The process by which organisms with traits that are better suited to their environment are more likely to survive and reproduce.
• Adaptation: A trait that helps an organism survive and reproduce in its environment.
• Speciation: The formation of new species.
• Evidence for evolution: Fossil record, comparative anatomy, embryology, biogeography, and molecular biology.

Ecology and the environment

• Ecosystem: A community of interacting organisms and their physical environment.
• Biomes: Large-scale ecosystems characterized by specific climate conditions and plant communities.
• Population: A group of individuals of the same species living in the same area.
• Community: A group of interacting populations of different species living in the same area.
• Food chain: A series of organisms in which each organism feeds on the one below it.
• Food web: A complex network of interconnected food chains.
• Trophic levels: The position an organism occupies in a food chain or food web.
• Energy flow: The movement of energy through an ecosystem.
• Nutrient cycling: The movement of nutrients through an ecosystem.
• Biodiversity: The variety of life in an ecosystem.
• Conservation biology: The study of how to protect biodiversity.
• Environmental issues: Pollution, climate change, deforestation, and overexploitation of resources.

Plant Biology

• Photosynthesis: The process by which plants convert light energy into chemical energy.
• Plant structures: Roots, stems, leaves, flowers, and fruits.
• Plant tissues: Vascular tissue (xylem and phloem), ground tissue, and epidermal tissue.
• Plant reproduction: Sexual and asexual reproduction.
• Plant hormones: Regulate plant growth and development.

Animal Biology

• Animal classification: Based on shared characteristics, such as body plan, symmetry, and development.
• Animal tissues: Epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
• Animal organ systems: Digestive system, respiratory system, circulatory system, excretory system, nervous system, endocrine system, skeletal system, and muscular system.
• Animal behavior: Instinctive and learned behaviors.
• Animal communication: Visual, auditory, chemical, and tactile signals.

Microbiology

• Bacteria: Unicellular prokaryotic organisms.
• Viruses: Noncellular infectious agents.
• Fungi: Eukaryotic organisms with cell walls made of chitin.
• Protists: Eukaryotic organisms that are not plants, animals, or fungi.
• Microorganisms: Play important roles in nutrient cycling, decomposition, and disease.

Human Biology

• Human anatomy: The study of the structure of the human body.
• Human physiology: The study of the function of the human body.
• Human genetics: The study of human heredity and variation.
• Human evolution: The study of the evolutionary history of humans.
• Human health: The study of the factors that affect human health and disease.

Biotechnology

• Genetic engineering: The manipulation of genes to modify organisms.
• Cloning: The creation of genetically identical copies of organisms.
• Gene therapy: The use of genes to treat diseases.
• Biotechnology applications: Medicine, agriculture, and industry.