Introduction to Biology

• Biology is the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy.

Key Concepts in Biology

• Cell Theory: All living organisms are composed of cells, the basic units of life.
• Gene Theory: Traits are inherited through genes.
• Evolution: All life forms have evolved over time from a common ancestor.
• Homeostasis: All living organisms maintain a stable internal environment.

Chemical Basis of Life

• Matter consists of chemical elements in pure form and in combinations called compounds.
• Essential elements for life include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (CHNOPS).
• Atoms are the smallest unit of an element that retains its chemical properties, comprising protons, neutrons, and electrons.
• Molecules are formed by atoms held together through chemical bonds.
• Covalent bonds involve the sharing of electrons between atoms.
• Ionic bonds involve the transfer of electrons between atoms creatin ions.
• Hydrogen bonds are weak bonds formed by the attraction between a hydrogen atom and an electronegative atom.
• Water's unique properties, such as cohesion, adhesion, high specific heat, and being a versatile solvent, are essential for life.
• pH is a measure of hydrogen ion concentration; acids have a high concentration of hydrogen ions, while bases have a low concentration.
• Buffers minimize changes in pH.

Biological Macromolecules

• Large organic molecules are essential for life.
• Carbohydrates include monosaccharides (e.g., glucose), disaccharides (e.g., sucrose), and polysaccharides (e.g., starch, cellulose).
• Lipids include fats, phospholipids, and steroids; they are hydrophobic molecules.
• Proteins are composed of amino acids; they have diverse functions.
• Nucleic acids (DNA and RNA) store and transmit genetic information; they are composed of nucleotides.

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 include the nucleus (containing DNA), endoplasmic reticulum (involved in protein and lipid synthesis), Golgi apparatus (modifies and packages proteins), mitochondria (energy production), lysosomes (digestive enzymes), and chloroplasts (photosynthesis in plants).
• The plasma membrane controls the movement of substances into and out of the cell; it is a phospholipid bilayer with embedded proteins.

Cellular Processes

• Enzymes are biological catalysts that speed up chemical reactions.
• Factors affecting enzyme activity include temperature, pH, and substrate concentration.
• Cellular respiration is the process by which cells generate energy in the form of ATP; it includes glycolysis, the Krebs cycle, and oxidative phosphorylation.
• Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy; it occurs in chloroplasts and involves the light-dependent and light-independent reactions (Calvin cycle).
• DNA replication is the process by which DNA is copied; it occurs during cell division.
• Transcription is the process by which RNA is synthesized from a DNA template.
• Translation is the process by which proteins are synthesized from RNA.

Genetics

• Genes are units of heredity made of DNA.
• Chromosomes are structures containing DNA.
• Genotype is the genetic makeup of an organism; phenotype is the physical expression of the genotype.
• Mendel's laws of inheritance include the law of segregation and the law of independent assortment.
• Genetic mutations can result in changes in DNA sequence and can be harmful, beneficial, or neutral.
• Genetic engineering involves manipulating genes for practical purposes.

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.
• Evidence for evolution includes fossils, comparative anatomy, embryology, and molecular biology.
• Mechanisms of evolution include mutation, gene flow, genetic drift, and natural selection.
• Speciation is the process by which new species arise.

Classification of Living Organisms

• Taxonomy is the science of classifying organisms, the taxonomic ranks are: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• The three domains of life are Bacteria, Archaea, and Eukarya.
• Kingdoms include 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 assemblages of different populations living in the same area.
• Ecosystems include all the living and nonliving components of an area.
• Biomes are large-scale ecosystems characterized by specific climate conditions and vegetation types.
• Food chains and food webs describe the flow of energy and nutrients through an ecosystem.
• Biogeochemical cycles (e.g., carbon, nitrogen, water) describe the movement of elements and compounds through an ecosystem.