Introduction to Biology

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

Core Principles

• Cell theory: All living organisms are composed of cells.
• Gene theory: Inheritance occurs through genes passed from parents to offspring.
• Evolution: All life forms have evolved over time from a common ancestor through natural selection and genetic drift.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow of energy.

Branches

• Biochemistry: Study of the chemical processes within and relating to living organisms.
• Molecular Biology: Study of the structure and function of biological macromolecules.
• Cell Biology: Study of cell structure and function.
• Genetics: Study of heredity and variation of inherited characteristics.
• Microbiology: Study of microorganisms.
• Botany: Study of plants.
• Zoology: Study of animals.
• Ecology: Study of the interactions of organisms with each other and their environment.
• Evolutionary Biology: Study of the evolutionary processes that produced the diversity of life on Earth.

Chemical Basis of Life

• Living organisms are composed of organic molecules: carbohydrates, lipids, proteins, and nucleic acids.
• Carbon is the backbone of organic molecules due to its ability to form stable covalent bonds with itself and other elements.
• Water is essential for life because of its properties as a solvent, its high heat capacity, and its role in many biochemical reactions.

Cell Structure and Function

• Cells are the basic unit of life and are either prokaryotic (lacking a nucleus) or eukaryotic (possessing a nucleus).
• Prokaryotic cells include bacteria and archaea.
• Eukaryotic cells include protists, fungi, plants, and animals.
• Key cell structures include the plasma membrane, cytoplasm, nucleus, ribosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and cytoskeleton.
• The plasma membrane controls the movement of substances into and out of the cell.
• Ribosomes are responsible for protein synthesis.
• Mitochondria generate energy (ATP) through cellular respiration.
• The endoplasmic reticulum (ER) is involved in protein and lipid synthesis.
• The Golgi apparatus modifies, sorts, and packages proteins.
• Lysosomes contain enzymes for intracellular digestion.
• The cytoskeleton provides structural support and facilitates cell movement.

Energy and Metabolism

• Metabolism is the sum of all chemical reactions that occur in an organism.
• Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.
• ATP (adenosine triphosphate) is the primary energy currency of cells.
• Cellular respiration is the process by which cells break down glucose to produce ATP.
• Photosynthesis is the process by which plants and other organisms use sunlight to synthesize glucose from carbon dioxide and water.
• Key metabolic pathways include glycolysis, the Krebs cycle, and the electron transport chain.

Genetics

• Genes are units of heredity made of DNA (deoxyribonucleic acid).
• DNA is a double-stranded helix that carries genetic information.
• DNA replication is the process by which DNA is copied.
• Transcription is the process by which RNA (ribonucleic acid) is synthesized from DNA.
• Translation is the process by which proteins are synthesized from RNA.
• The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins by living cells.
• Mutations are changes in the DNA sequence that can lead to genetic variation.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the process by which organisms with traits that enhance survival and reproduction are more likely to pass on their genes to future generations.
• Genetic drift is the random change in the frequency of alleles in a population.
• Evidence for evolution includes the fossil record, comparative anatomy, embryology, and molecular biology.
• Speciation is the process by which new species arise.

Ecology

• Ecology is the study of the interactions of organisms with each other 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 interacting with their physical environment.
• Biomes are large-scale ecosystems characterized by specific climate conditions and vegetation types.
• Key ecological concepts include food webs, energy flow, nutrient cycling, and population dynamics.

Diversity of Life

• Life is classified into three domains: Bacteria, Archaea, and Eukarya.
• Bacteria and Archaea are prokaryotic organisms.
• Eukarya includes protists, fungi, plants, and animals.
• Viruses are non-cellular entities that require a host cell to replicate.
• Protists are a diverse group of eukaryotic organisms that are not plants, animals, or fungi.
• Fungi are heterotrophic organisms that obtain nutrients by absorption.
• Plants are autotrophic organisms that produce their own food through photosynthesis.
• Animals are heterotrophic organisms that obtain nutrients by ingestion.