Introduction to Biology

• Biology is the scientific study of life and living organisms.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells. The cell is the basic structural and functional unit of life, and all cells arise from pre-existing cells.
• Gene theory: Traits are inherited through genes, which are specific locations on chromosomes and consist of DNA.
• Evolution: All life forms have evolved over time from a common ancestor through a process of natural selection.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow of energy; energy is converted from one form to another to sustain life.

Branches of Biology

• Biochemistry: The study of the chemical processes within and relating to living organisms.
• Molecular Biology: The study of the molecular basis of biological activity.
• Cell Biology: The study of cell structure and function.
• Genetics: The study of heredity and variation of inherited characteristics.
• Evolutionary Biology: The study of the evolutionary processes that produced the diversity of life on Earth.
• Ecology: The study of the relationships between living organisms, including humans, and their physical environment.
• Physiology: The study of the normal functions of living organisms and their parts.
• Anatomy: The study of the structure of living things.
• Microbiology: The study of microorganisms.
• Botany: The study of plants.
• Zoology: The study of animals.

Characteristics of Living Organisms

• Organization: Living things exhibit complex organization, from cellular to organismal levels.
• Metabolism: Living organisms carry out chemical reactions (metabolism), including synthesis (anabolism) and breakdown (catabolism).
• Growth: Living things grow and increase in size.
• Reproduction: Living organisms produce new individuals, either sexually or asexually.
• Response: Living organisms respond to stimuli in their environment.
• Adaptation: Living organisms adapt to their environment over time through evolutionary change.
• Homeostasis: Living organisms maintain a stable internal environment.

Basic Chemistry of Life

• Water: Essential for life due to its properties as a solvent, its high heat capacity, and its role in chemical reactions.
• Carbon: The backbone of organic molecules; it can form diverse structures.
• Macromolecules: Large organic molecules that are essential for life.
• Carbohydrates: Provide energy and structural support.
• Lipids: Include fats, oils, and steroids; involved in energy storage, insulation, and cell membrane structure.
• Proteins: Perform a wide variety of functions, including enzymes, structural components, and transport molecules.
• Nucleic Acids: DNA and RNA; carry genetic information.

Cell Structure and Function

• Prokaryotic Cells: Lack a nucleus and other membrane-bound organelles (e.g., bacteria and archaea).
• Eukaryotic Cells: Contain a nucleus and other membrane-bound organelles (e.g., plants, animals, fungi, and protists).
• Cell Membrane: A selectively permeable barrier that controls the movement of substances into and out of the cell.
• Nucleus: Contains the cell's DNA and controls cellular activities.
• Ribosomes: Synthesize proteins.
• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Mitochondria: Produce ATP through cellular respiration.
• Chloroplasts: (In plant cells) Carry out photosynthesis.
• Lysosomes: Contain enzymes for intracellular digestion.

Energy and Metabolism

• Photosynthesis: The process by which plants and other organisms convert light energy into chemical energy in the form of glucose.
• Cellular Respiration: The process by which cells break down glucose to produce ATP, the main energy currency of the cell.
• Glycolysis: Initial breakdown of glucose in the cytoplasm.
• Krebs Cycle (Citric Acid Cycle): Further oxidation of glucose derivatives in the mitochondrial matrix.
• Electron Transport Chain: Production of ATP through oxidative phosphorylation on the inner mitochondrial membrane.
• Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy.

Genetics

• DNA: Deoxyribonucleic acid, the molecule that carries genetic information.
• Structure: Double helix composed of nucleotides (adenine, guanine, cytosine, and thymine).
• Replication: The process by which DNA is copied.
• RNA: Ribonucleic acid, involved in protein synthesis.
• Types: mRNA (messenger RNA), tRNA (transfer RNA), rRNA (ribosomal RNA).
• Transcription: The process by which RNA is synthesized from a DNA template.
• Translation: The process by which proteins are synthesized from RNA.
• Genes: Segments of DNA that code for specific traits.
• Chromosomes: Structures within the nucleus that are composed of DNA and proteins.
• Genetic Mutations: Changes in the DNA sequence that can lead to variations in traits.
• Mendelian Genetics: Principles of inheritance described by Gregor Mendel.
• Law of Segregation: Allele pairs separate during gamete formation.
• Law of Independent Assortment: Alleles of different genes assort independently of one another during gamete formation.
• Gene expression: The process of converting information encoded in a gene into a protein or other functional product.

Evolution

• Natural Selection: The process by which organisms with traits that are better suited to their environment survive and reproduce more successfully than organisms with less adaptive traits.
• Adaptation: A trait that enhances an organism's survival and reproductive success in a particular environment.
• Genetic Variation: Differences in genes among individuals within a population.
• Mutation: The source of all genetic variation.
• Gene Flow: The movement of genes between populations.
• Genetic Drift: Random changes in allele frequencies within a population.
• Speciation: The process by which new species arise.
• Allopatric Speciation: Occurs when populations are geographically isolated.
• Sympatric Speciation: Occurs within the same geographic area.
• Evidence for Evolution:
• Fossil Record: Provides evidence of past life forms and their transitions.
• Comparative Anatomy: Similarities in the anatomy of different species suggest common ancestry.
• Embryology: Similarities in the embryonic development of different species suggest common ancestry.
• Molecular Biology: Similarities in DNA and protein sequences suggest common ancestry.
• Biogeography: The distribution of species on Earth reflects their evolutionary history.

Ecology

• Population Ecology: The study of populations, including their size, density, distribution, and growth rate.
• Community Ecology: The study of interactions between different species within a community.
• Competition: Occurs when two or more species require the same limited resource.
• Predation: Occurs when one species (the predator) consumes another species (the prey).
• Symbiosis: A close and long-term interaction between two or more species.
• Mutualism: Both species benefit.
• Commensalism: One species benefits, and the other is neither harmed nor helped.
• Parasitism: One species benefits, and the other is harmed.
• Ecosystem Ecology: The study of the interactions between living organisms and their physical environment.
• Food Chains and Food Webs: Describe the flow of energy and nutrients through an ecosystem.
• Trophic Levels: The position an organism occupies in a food chain (e.g., producers, primary consumers, secondary consumers).
• Biogeochemical Cycles: The movement of elements (e.g., carbon, nitrogen, phosphorus) through ecosystems.
• Biodiversity: The variety of life in a particular habitat or ecosystem.
• Conservation Biology: The study of how to protect and manage biodiversity.

Plant Biology

• Plant Anatomy: The study of the internal structure of plants.
• Roots: Anchor the plant and absorb water and nutrients from the soil.
• Stems: Support the plant and transport water and nutrients.
• Leaves: Carry out photosynthesis.
• Plant Physiology: The study of the functions of plant tissues and organs.
• Photosynthesis: Plants use light energy to convert carbon dioxide and water into glucose and oxygen.
• Transpiration: The process by which water is lost from the leaves of plants through evaporation.
• Nutrient Uptake: Plants absorb essential nutrients from the soil through their roots.
• Plant Reproduction: Plants can reproduce sexually (through the fusion of gametes) or asexually (through vegetative propagation).
• Plant Hormones: Chemical signals that regulate plant growth and development.

Animal Biology

• Animal Anatomy: The study of the internal structure of animals.
• Animal Physiology: The study of the functions of animal tissues and organs.
  • Digestive System: Breaks down food into smaller molecules that can be absorbed.
  • Respiratory System: Exchanges gases (oxygen and carbon dioxide) between the animal and its environment.
  • Circulatory System: Transports blood, nutrients, and gases throughout the body.
  • Excretory System: Removes waste products from the body.
  • Nervous System: Coordinates and controls bodily functions.
  • Endocrine System: Produces hormones that regulate bodily functions.
  • Immune System: Protects the body against pathogens.
  • Musculoskeletal System: Provides support and enables movement.
• Animal Behavior: The study of how animals interact with their environment and with each other.
  • Innate Behavior: Genetically determined behavior.
  • Learned Behavior: Behavior that is acquired through experience.
• Animal Development: The process by which an animal develops from a zygote (fertilized egg) into an adult.