Introduction to Biology: Core Principles and Branches

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

Core Principles

• Cell theory dictates that all living organisms are composed of cells, serving as the basic units of life
• Gene theory: Traits are inherited through genes, which are located on chromosomes
• Evolution: Life evolves over time through processes like natural selection, leading to diversity
• Homeostasis: Living organisms maintain a stable internal environment despite external changes
• Thermodynamics: Life depends on the flow of energy, converting it from one form to another

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms
  • It focuses on the structure and function of biomolecules like proteins, carbohydrates, lipids, and nucleic acids
  • It examines metabolic pathways and the flow of energy within cells
• Molecular Biology examines the molecular basis of biological activity
  • It studies the interactions between DNA, RNA, and proteins
  • Focuses on processes like DNA replication, transcription, and translation
• Cell Biology studies the structure, function, and behavior of cells
  • Cell organelles, cell division, and cell signaling are examined
  • Processes like apoptosis and cell differentiation are investigated
• Genetics studies heredity and variation in organisms
  • Genes, chromosomes, and patterns of inheritance are examined
  • Genomics, epigenetics, and population genetics are included
• Evolutionary Biology studies the evolutionary processes that have shaped life on Earth
  • Natural selection, genetic drift, and speciation are the foci
  • The fossil record and phylogenetic relationships between organisms are examined
• Ecology studies the interactions between organisms and their environment
  • Populations, communities, and ecosystems are examined
  • Nutrient cycling, energy flow, and conservation biology are investigated
• Physiology studies the functions and mechanisms of living organisms and their parts
  • Organ systems, tissues, and cells are examined
  • Respiration, circulation, and digestion are the focus
• Anatomy studies the structure of organisms and their parts
  • It involves dissection and examination of tissues and organs
  • Comparative anatomy examines similarities and differences between species
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa
  • Examines their structure, function, and behavior.
  • Includes areas like bacteriology, virology, and parasitology
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance
• Zoology Studies animals, including their classification, physiology, behavior, and ecology

Key Concepts

• Cell Structure and Function: Cells are the basic units of life, with prokaryotic and eukaryotic types
  • Prokaryotic cells lack a nucleus and other membrane-bound organelles
  • Eukaryotic cells have a nucleus and other organelles like mitochondria and endoplasmic reticulum
• Genetic Material: DNA contains the genetic instructions for the development and function of all known living organisms
  • DNA is a double-stranded helix made up of nucleotides
  • Genes are segments of DNA that encode for specific proteins
• Central Dogma of Molecular Biology describes the flow of genetic information from DNA to RNA to protein
  • DNA is transcribed into RNA, which is then translated into protein
• Metabolism is the sum of all chemical reactions that occur within a living organism
  • Catabolism (breaking down molecules) and anabolism (building molecules) are included
• Energy Flow moves through ecosystems from producers to consumers
  • Producers (autotrophs) like plants convert sunlight into chemical energy through photosynthesis
  • Consumers (heterotrophs) obtain energy by feeding on other organisms
• Reproduction: The process by which organisms produce offspring
  • Asexual reproduction involves one parent and results in genetically identical offspring
  • Sexual reproduction involves two parents and results in genetically diverse offspring
• Evolution by Natural Selection: The process by which populations of organisms change over time
  • Individuals with traits that are better suited to their environment are more likely to survive and reproduce
  • This leads to the accumulation of favorable traits in a population over generations
• Biodiversity: The variety of life on Earth, including genetic diversity, species diversity, and ecosystem diversity
  • It is important for ecosystem stability and resilience
  • Threatened by habitat loss, climate change, and other human activities

Core Biological Molecules

• Carbohydrates serve as a primary source of energy and provide structural components
  • Monosaccharides, disaccharides, and polysaccharides such as glucose, sucrose, and starch
• Lipids are involved in energy storage, insulation, and cell membrane structure
  • Fats, oils, phospholipids, and steroids
• Proteins perform a wide range of functions, including enzymatic catalysis, structural support, and transport
  • Composed of amino acids linked by peptide bonds
• Nucleic Acids store and transmit genetic information
  • DNA and RNA composed of nucleotides

Genetics Basics

• Genes are the basic units of heredity, composed of DNA and arranged on chromosomes
• Alleles are different versions of a gene; homozygous refers to having two identical alleles, while heterozygous refers to having two different alleles
• Genotype describes the genetic makeup of an organism, while phenotype describes the observable characteristics
• Mendelian Genetics explains inheritance patterns based on the segregation and independent assortment of alleles
• Mutations are alterations in the DNA sequence that can lead to genetic variation

Evolution Mechanisms

• Natural Selection is the differential survival and reproduction of individuals based on heritable traits
• Genetic Drift is the random change in allele frequencies in a population
• Gene Flow is the transfer of genetic material between populations
• Mutation introduces new genetic variation into a population
• Adaptation is the process by which populations become better suited to their environment over time
• Speciation is the process by which new species arise from existing species

Ecosystems

• An ecosystem includes all living organisms in a specific area, along with their physical environment
• Populations, communities, and ecosystems are organized levels of ecological study
• Energy flows through ecosystems via food chains and food webs
• Nutrient cycling involves the movement of elements and compounds through biotic and abiotic components of ecosystems

Biological Processes

• Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy
• Cellular Respiration is the process by which cells break down glucose to release energy in the form of ATP
• Mitosis is cell division that results in two identical daughter cells
• Meiosis is cell division that results in four genetically different daughter cells (gametes)
• Homeostasis is the maintenance of a stable internal environment

Virology

• Viruses are acellular entities that contain genetic material (DNA or RNA) surrounded by a protein coat
• Viruses replicate by invading host cells and using the host's cellular machinery
• Viral infections can cause a wide range of diseases in plants, animals, and humans

Cell Communication

• Cells communicate through various signaling mechanisms, including direct contact, paracrine signaling, endocrine signaling, and synaptic signaling
• Signal transduction pathways involve a series of molecular events that relay signals from the cell surface to the cell interior
• Cell signaling plays a crucial role in regulating cell growth, differentiation, and apoptosis