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 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 sense and respond to stimuli, maintain homeostasis, and can reproduce.
• Despite the complexity, there are unifying aspects that tie it into a single, coherent field.

Branches of Biology

• Biochemistry: Explores the chemical processes within and relating to living organisms.
• Botany: The scientific study of plants.
• Cell Biology: Studies the cell, its structure, function, and behavior.
• Ecology: Investigates the interactions of organisms with each other and their environment.
• Evolutionary Biology: Studies the evolutionary processes that produced the diversity of life on Earth.
• Genetics: The science of genes, heredity, and variation in living organisms.
• Microbiology: Studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular Biology: Studies the molecular basis of biological activity.
• Zoology: The study of animals, including their behavior, physiology, structure, and classification.

Key Concepts in Biology

• Cell Theory: All living organisms are composed of one or more cells, the cell is the basic unit of life, and cells arise from pre-existing cells.
• Gene Theory: Characteristics are inherited through genes, which are located on chromosomes and consist of DNA.
• Homeostasis: The ability of an organism to maintain internal stability in response to changing environmental conditions.
• Evolution: The change in the characteristics of a species over several generations and relies on the process of natural selection.
• Energy: All living organisms require energy to survive, grow, and reproduce.
• Organization: Living organisms exhibit a high level of organization, from cells to tissues, organs, and organ systems.

The Scientific Method

• Observation: The process of gathering information about events or processes in a careful, orderly way.
• Hypothesis: A testable explanation for a set of observations.
• Experiment: A scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact.
• Data Analysis: Interpreting the meaning of the data collected in the experiment
• Conclusion: Judgement based on the results of an experiment.
• Communication: Share the results with the scientific community through publications and presentations.

Characteristics of Life

• Organization: Living things exhibit complex organization, from atoms to the biosphere.
• Metabolism: Living organisms carry out chemical reactions to obtain and use energy (metabolism).
• Homeostasis: Maintenance of a stable internal environment.
• Growth: Increase in size or cell number.
• Reproduction: The production of new organisms.
• Response to Stimuli: Ability to react to environmental changes.
• Evolution: Adaptation to the environment through evolutionary change.

Biochemistry Basics

• Biochemistry studies the molecules of life, including carbohydrates, lipids, proteins, and nucleic acids.
• Carbohydrates – primary source of energy.
• Lipids – fats, oils, and waxes, important for energy storage, insulation, and forming cell membranes.
• Proteins – involved in virtually all cell functions, including enzymes, structural components, and transport molecules.
• Nucleic Acids – DNA and RNA, carry genetic information.
• Enzymes are biological catalysts that speed up chemical reactions.

Cell Structure and Function

• Cells are the basic units of life.
• Eukaryotic cells (plants, animals, fungi, protists) have a nucleus and other membrane-bound organelles.
• Prokaryotic cells (bacteria and archaea) do not have a nucleus or other membrane-bound organelles.
• Major organelles in eukaryotic cells include the nucleus (control center containing DNA), mitochondria (powerhouse of the cell producing ATP), endoplasmic reticulum (involved in protein and lipid synthesis), Golgi apparatus (modifies and packages proteins), lysosomes (digestion and waste removal), and ribosomes (protein synthesis).
• Cell membrane controls what enters and exits the cell.

Genetics and Heredity

• Genes are the units of heredity and are made of DNA.
• DNA (deoxyribonucleic acid) carries the genetic instructions for all living organisms.
• DNA is organized into chromosomes.
• During sexual reproduction, offspring inherit genes from both parents.
• Mutations are changes in the DNA sequence and can lead to genetic variation.
• Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product (protein or RNA).

Evolution and Natural Selection

• Evolution is the change in the characteristics of a species over time.
• Natural selection is the mechanism of evolution, where individuals with advantageous traits are more likely to survive and reproduce.
• Adaptations are traits that enhance survival and reproduction in a specific environment.
• Evidence for evolution comes from fossils, comparative anatomy, embryology, and molecular biology.
• Speciation is the process by which new species arise.

Ecology and Ecosystems

• Ecology is the study of the interactions between organisms and their environment.
• An ecosystem includes all the living organisms in an area and the non-living physical environment.
• Populations are groups of individuals of the same species living in the same area.
• Communities are assemblages of different populations that live together in a defined area.
• Food chains and food webs describe the flow of energy and nutrients through an ecosystem.
• Trophic levels represent the position of an organism in a food chain (e.g., producers, consumers, decomposers).
• Biomes are large geographic areas characterized by specific climate conditions, animal populations, and plant species.