Introduction to Biology

• Biology is the scientific study of life.

Core Principles of Biology

• Biology recognizes that cells are the basic unit of life.
• Genes are the basic unit of heredity.
• Evolution explains the unity and diversity of life.
• Living organisms maintain homeostasis to survive.

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Microbiology studies microorganisms, such as bacteria, viruses, fungi, and protozoa.
• Botany examines plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Zoology involves the study of animals, including their physiology, anatomy, behavior, genetics, ecology, evolution, and classification.
• Genetics explores heredity and variation of inherited characteristics.
• Ecology studies the interactions of organisms with each other and their environment.
• Evolutionary biology studies the evolutionary processes that produced the diversity of life on Earth.
• Physiology examines the functions and mechanisms in a living system.
• Anatomy studies the structure of organisms and their parts.
• Molecular biology studies the molecular basis of biological activity between biomolecules in a cell.
• Marine biology studies marine organisms and marine life.

Characteristics of Life

• Living organisms exhibit organization, meaning they contain complex structural arrangements.
• Living organisms maintain homeostasis, which involves regulating internal conditions to keep them relatively stable.
• Living organisms reproduce, creating new organisms either sexually or asexually.
• Living organisms grow and develop, increasing in size and complexity.
• Living organisms use energy for various processes, such as metabolism and movement.
• Living organisms respond to stimuli from their environment.
• Living organisms adapt and evolve to better suit their environment over time.

Cell Biology

• The cell theory states that all living organisms are composed of cells, the cell is the basic unit of life, and cells arise from pre-existing cells.
• Cells are broadly classified as prokaryotic or eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells possess a nucleus and other membrane-bound organelles.
• Key cell structures include the plasma membrane, nucleus, cytoplasm, ribosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
• The plasma membrane controls the movement of substances into and out of the cell.
• The nucleus contains the cell's genetic material (DNA) and controls cell activities.
• Ribosomes are responsible for protein synthesis.
• Mitochondria are the powerhouses of the cell, carrying out cellular respiration to produce energy (ATP).
• The endoplasmic reticulum (ER) is involved in protein and lipid synthesis.
• The Golgi apparatus processes and packages proteins and lipids.
• Lysosomes contain enzymes for breaking down cellular waste and debris.

Genetics

• Genes are segments of DNA that code for specific traits and are passed from parents to offspring.
• DNA (deoxyribonucleic acid) is the genetic material that contains the instructions for building and maintaining organisms.
• DNA is a double-stranded helix made of nucleotides, each containing a sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).
• RNA (ribonucleic acid) is a single-stranded molecule involved in protein synthesis.
• The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein.
• Transcription is the process of copying DNA into RNA.
• Translation is the process of using RNA to synthesize proteins.
• Mutations are changes in the DNA sequence that can result in altered traits.
• Mendelian genetics studies the inheritance of traits through generations.
• Genomics is the study of entire genomes, including genes and their functions.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is a mechanism of evolution in which organisms with traits better suited to their environment are more likely to survive and reproduce.
• Adaptation is the process by which organisms evolve traits that enhance their survival and reproduction in a specific environment.
• Evidence for evolution includes the fossil record, comparative anatomy, comparative embryology, molecular biology, and biogeography.
• The fossil record provides evidence of past life forms and their transitions over time.
• Homologous structures are similar structures in different organisms that share a common ancestry.
• Analogous structures are structures in different organisms that have similar functions but different evolutionary origins.
• Comparative embryology reveals similarities in the development of different organisms.
• Molecular biology provides evidence for evolution through the similarities and differences in DNA and protein sequences.
• 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.
• An ecosystem is a community of living organisms (biotic factors) interacting with their physical environment (abiotic factors).
• 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.
• Biomes are large geographic areas characterized by specific climate conditions, animal populations, and plant populations.
• The biosphere is the global sum of all ecosystems.
• Trophic levels describe the position of an organism in a food chain or food web.
• Producers (autotrophs) are organisms that produce their own food through photosynthesis or chemosynthesis.
• Consumers (heterotrophs) are organisms that obtain energy by consuming other organisms.
• Decomposers break down dead organic matter, returning nutrients to the ecosystem.
• Food chains illustrate the flow of energy from one organism to another.
• Food webs are interconnected food chains that represent the complex feeding relationships in an ecosystem.
• Biogeochemical cycles describe the movement of essential elements (e.g., carbon, nitrogen, water) through ecosystems.
• Population ecology studies the factors that influence population size, density, and distribution.
• Community ecology examines the interactions between different species in a community.

Physiology

• Physiology is the study of the functions and mechanisms in a living system.
• Homeostasis is the maintenance of a stable internal environment in the body.
• The major organ systems in animals include the nervous system, endocrine system, cardiovascular system, respiratory system, digestive system, excretory system, immune system, skeletal system, and muscular system.
• The nervous system controls and coordinates body functions through electrical and chemical signals.
• The endocrine system regulates body functions through hormones.
• The cardiovascular system transports blood, oxygen, and nutrients throughout the body.
• The respiratory system facilitates gas exchange (oxygen and carbon dioxide).
• The digestive system breaks down food and absorbs nutrients.
• The excretory system removes waste products from the body.
• The immune system defends the body against pathogens and diseases.
• The skeletal system provides support and structure to the body.
• The muscular system enables movement.
• Plant physiology studies the functions and processes in plants, including photosynthesis, transpiration, and nutrient uptake.