Core Principles of Biology

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

Core Principles of Biology

• Cell theory: All living organisms are composed of cells
• Cells are the basic units of structure and function in living organisms
• All cells arise from pre-existing cells
• Gene theory: Hereditary information is encoded in DNA and genes
• Genes are the units of inheritance and are passed from parents to offspring
• Evolution: Life evolves over time through natural selection
• Natural selection is the process by which organisms with favorable traits are more likely to survive and reproduce, leading to adaptation
• Homeostasis: Living organisms maintain a stable internal environment
• Homeostasis involves various regulatory mechanisms to keep conditions within tolerable limits
• Energy: Life requires energy and nutrients
• Energy flows through ecosystems, typically starting with sunlight and photosynthesis

Branches of Biology

• Biochemistry: The study of the chemical processes within and relating to living organisms
• Molecular Biology: The study of the structure and function of biological macromolecules, such as proteins and nucleic acids
• Cell Biology: The study of cell structure, function, and behavior
• Genetics: The study of heredity and variation in organisms
• Ecology: The study of the interactions between organisms and their environment
• Evolution: The study of the history of life and the processes that have shaped its diversity
• Physiology: The study of the functions and mechanisms in a living system
• Anatomy: The study of the structure of organisms and their parts
• Microbiology: The study of microorganisms, including bacteria, viruses, fungi, and protozoa
• Botany: The scientific study of plants
• Zoology: The scientific study of animals

Characteristics of Living Organisms

• Organization: Living things exhibit a complex and ordered organization, from the atomic and molecular levels to cells, tissues, organs, and organ systems
• Metabolism: Living organisms carry out metabolic processes, including chemical reactions that convert energy and materials
• These processes include anabolism (building up) and catabolism (breaking down)
• Growth: Living organisms increase in size and complexity
• Reproduction: Living organisms produce offspring, either sexually or asexually
• Response to Stimuli: Living organisms respond to changes in their environment
• This includes both internal and external stimuli
• Adaptation: Living organisms evolve adaptations that enable them to survive and reproduce in their environment
• Homeostasis: Living organisms maintain a stable internal environment
• Heredity: Living organisms pass on their traits to their offspring through genes

Levels of Biological Organization

• Molecular Level: Includes atoms, molecules, and macromolecules such as proteins, carbohydrates, lipids, and nucleic acids
• Cellular Level: Cells are the basic unit of life
• Includes prokaryotic and eukaryotic cells
• Tissue Level: Tissues are groups of similar cells performing a specific function
• Examples: epithelial tissue, connective tissue, muscle tissue, nervous tissue
• Organ Level: Organs are structures composed of different tissues that work together to perform a specific function
• Examples: heart, lungs, stomach, brain
• Organ System Level: Organ systems consist of multiple organs that work together to carry out a major bodily function
• Examples: digestive system, respiratory system, circulatory system, nervous system
• Organism Level: An individual living thing composed of multiple organ systems
• Population Level: A group of individuals of the same species living in the same area
• Community Level: All the different populations of organisms living in the same area
• Ecosystem Level: A community of organisms together with their physical environment
• Biosphere Level: The sum of all ecosystems on Earth

Cell Structure and Function

• Prokaryotic Cells: Simple cells lacking a nucleus and other membrane-bound organelles
• Bacteria and Archaea
• Eukaryotic Cells: Complex cells containing a nucleus and other membrane-bound organelles
• Animals, plants, fungi, and protists
• Nucleus: Contains the cell's genetic material (DNA) and controls cell activities
• Ribosomes: Synthesize proteins
• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis
• Rough ER: Contains ribosomes
• Smooth ER: Lacks ribosomes
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids
• Mitochondria: Generate energy (ATP) through cellular respiration
• Chloroplasts: Carry out photosynthesis in plant cells
• Lysosomes: Contain enzymes for breaking down cellular waste and debris
• Cell Membrane: Regulates the movement of substances into and out of the cell

Genetics and Heredity

• DNA: The hereditary material that carries genetic information
• Double helix structure composed of nucleotides
• Genes: Segments of DNA that encode for specific traits or proteins
• Chromosomes: Structures made of DNA that contain genes
• Alleles: Different versions of a gene
• Genotype: The genetic makeup of an organism
• Phenotype: The observable characteristics of an organism
• Mendelian Genetics: Principles of inheritance based on the work of Gregor Mendel
• Law of Segregation: Allele pairs separate during gamete formation
• Law of Independent Assortment: Alleles of different genes assort independently during gamete formation
• Mutations: Changes in DNA sequence that can lead to variation
• Genetic Engineering: The manipulation of genes for practical purposes

Evolution and Natural Selection

• Natural Selection: The process by which organisms with favorable traits are more likely to survive and reproduce
• Adaptation: Traits that enhance survival and reproduction in a specific environment
• Evidence for Evolution:
• Fossil Record: Provides evidence of extinct organisms and the sequence of evolutionary changes
• Comparative Anatomy: Similarities in anatomical structures suggest common ancestry
• Embryology: Similarities in embryonic development suggest common ancestry
• Molecular Biology: Similarities in DNA and protein sequences suggest common ancestry
• Biogeography: The distribution of species reflects their evolutionary history
• Mechanisms of Evolution:
• Mutation: Introduces new genetic variation
• Gene Flow: The movement of genes between populations
• Genetic Drift: Random changes in allele frequencies
• Natural Selection: Differential survival and reproduction based on traits
• Speciation: The process by which new species arise
• Allopatric Speciation: Speciation due to geographic isolation
• Sympatric Speciation: Speciation without geographic isolation

Ecology and Environment

• Ecosystem: A community of organisms interacting with their physical environment
• Population Ecology: The study of how populations interact with their environment
• Community Ecology: The study of the interactions between different species in a community
• Trophic Levels: The different levels of feeding relationships in an ecosystem
• Producers: Autotrophs that make their own food (e.g., plants)
• Consumers: Heterotrophs that eat other organisms (e.g., herbivores, carnivores, omnivores)
• Decomposers: Break down dead organisms and organic matter (e.g., bacteria, fungi)
• Food Webs: Complex networks of feeding relationships in an ecosystem
• Energy Flow: The transfer of energy through an ecosystem
• Energy is lost at each trophic level due to metabolic processes and heat
• Nutrient Cycling: The movement of nutrients through an ecosystem
• Nutrients are recycled between living organisms and the physical environment
• Biomes: Major types of ecosystems characterized by distinct climate conditions and plant communities
• Examples: forests, grasslands, deserts, tundra
• Conservation Biology: The study of how to protect and manage biodiversity
• Environmental Issues:
• Climate Change: Caused by increasing greenhouse gas emissions
• Habitat Destruction: Loss of natural habitats due to human activities
• Pollution: Contamination of air, water, and soil
• Invasive Species: Introduction of non-native species that can harm native ecosystems

Plant Biology

• Photosynthesis: The process by which plants convert light energy into chemical energy
• Occurs in chloroplasts
• Requires carbon dioxide, water, and sunlight
• Plant Structure:
• Roots: Absorb water and nutrients from the soil
• Stems: Support the plant and transport water and nutrients
• Leaves: Carry out photosynthesis
• Plant Reproduction:
• Sexual Reproduction: Involves the fusion of gametes (pollen and ovule)
• Asexual Reproduction: Vegetative propagation (e.g., cuttings, grafting)
• Plant Hormones: Regulate plant growth and development
• Examples: auxins, gibberellins, cytokinins, abscisic acid, ethylene
• Plant Adaptations:
• Adaptations to different environments (e.g., deserts, aquatic habitats)
• Adaptations for pollination and seed dispersal

Animal Biology

• Animal Classification:
• Based on evolutionary relationships and shared characteristics
• Major groups: vertebrates (animals with a backbone) and invertebrates (animals without a backbone)
• Animal Physiology: The study of animal functions, including:
• Digestion: Breaking down food into absorbable nutrients
• Respiration: Exchange of gases (oxygen and carbon dioxide)
• Circulation: Transport of blood and nutrients
• Excretion: Removal of waste products
• Nervous System: Coordination of body functions and response to stimuli
• Endocrine System: Regulation of body functions through hormones
• Animal Behavior: The study of how animals interact with their environment and each other
• Innate behavior: Genetically determined behavior
• Learned behavior: Behavior acquired through experience
• Animal Adaptations:
• Adaptations to different environments (e.g., aquatic, terrestrial, aerial)
• Adaptations for feeding, defense, and reproduction