Introduction to Biology

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

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell biology studies the structure and function of cells, the basic units of life.
• Ecology studies the interactions of living organisms with each other and their environment.
• Evolutionary biology studies the processes that have led to the diversity of life on Earth.
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular biology studies the structure and function of biological molecules.
• Physiology studies the functions and mechanisms of living organisms and their parts.
• Zoology studies animals, including their physiology, anatomy, behavior, genetics, ecology, evolution, and classification.

Characteristics of Life

• Living organisms exhibit several key characteristics that distinguish them from non-living matter.
• Organization: Living things are highly organized, from the molecular level to ecosystems; complexity is a hallmark of life.
• Metabolism: Living organisms carry out metabolic processes, including energy conversion and the synthesis of new molecules.
• Growth: Living organisms can grow and increase in size, often involving cell division and differentiation.
• Reproduction: Living organisms can reproduce, creating new organisms similar to themselves.
• Response to Stimuli: Living things respond to stimuli from their environment, enabling them to adapt and survive.
• Adaptation: Populations of living organisms can evolve and adapt to their environment over time.
• Homeostasis: Living organisms maintain a stable internal environment, despite external changes.

Cell Structure and Function

• The cell is the basic structural and functional unit of all known living organisms.
• Cell Theory: All living organisms are composed of one or more cells; the cell is the basic unit of structure and organization in organisms; cells arise from pre-existing cells.
• Prokaryotic Cells: Lack a nucleus and other membrane-bound organelles; Bacteria and Archaea.
• Eukaryotic Cells: Have a nucleus and other membrane-bound organelles; protists, fungi, plants, and animals.
• Key Organelles:
  • Nucleus: Contains the cell's DNA and controls cell activities.
  • Mitochondria: Powerhouse of the cell; generate ATP through cellular respiration.
  • Ribosomes: Synthesize proteins.
  • Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  • Lysosomes: Contain enzymes for breaking down cellular waste and debris.
  • Chloroplasts (in plant cells): Conduct photosynthesis.
  • Cell Membrane: Encloses the cell and regulates the movement of substances in and out.
  • Cell Wall (in plant cells): Provides support and protection.

Genetics

• Genetics is the study of heredity and variation in organisms.
• Genes: Units of heredity made up of DNA, which encode specific traits.
• DNA: Deoxyribonucleic acid; the molecule that carries genetic information.
• Chromosomes: Structures within the nucleus that contain DNA organized into genes.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.
• Mendelian Genetics: Basic principles of inheritance, including segregation and independent assortment.
• Mutation: Changes in the DNA sequence that can lead to variations in traits.
• Gene Expression: The process by which the information encoded in a gene is used to synthesize a functional gene product (protein or RNA).

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural Selection: The process by which organisms better adapted to their environment tend to survive and reproduce more successfully.
• Adaptation: A trait that enhances an organism's survival and reproduction in a specific environment.
• Speciation: The process by which new species arise.
• Evidence for Evolution: Fossil record, comparative anatomy, embryology, biogeography, and molecular biology.
• Mechanisms of Evolution: Mutation, gene flow, genetic drift, and natural selection.
• Phylogeny: The evolutionary history of a species or group of species.

Ecology

• Ecology is the study of the interactions of living organisms with each other and their environment.
• Ecosystem: A community of living organisms and their physical environment interacting as a system.
• Population: A group of individuals of the same species living in the same area.
• Community: An interacting group of various species in a common location.
• Food Webs: Interconnected food chains that illustrate the flow of energy and nutrients through an ecosystem.
• Trophic Levels: The position an organism occupies in a food web (e.g., producer, primary consumer, secondary consumer).
• Biomes: Large geographic areas characterized by specific climate conditions, animal populations, and plant populations
• Ecological Succession: The process of change in the species structure of an ecological community over time.
• Conservation Biology: Concerned with preserving and protecting biodiversity and ecosystems.

Biology is the scientific study of life, covering structure, function, evolution, and taxonomy. It recognizes the cell as the basic unit of life and genes as the unit of heredity. Living organisms are open systems, transforming energy and reducing entropy to survive.