Introduction to Biology: Core Principles and Organization

• Biology is the scientific study of life
• Explores the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms
• Encompasses botany, zoology, microbiology, genetics, and ecology, among others
• Aims to understand the fundamental principles governing living systems

Core Principles of Biology

• Cell theory: the cell is the basic unit of life
• All living organisms are composed of cells
• Cells arise from pre-existing cells
• Genes are the basic units of heredity
• Composed of DNA and encode necessary information
• Evolution: change in species characteristics over time
• Driven by natural selection and other mechanisms
• Homeostasis: maintaining a stable internal environment, essential for survival
• Energy is required for all life processes
• Obtained through photosynthesis, respiration, or other metabolic pathways

Levels of Biological Organization

• Atoms are the basic units of matter
• Molecules are two or more atoms held by chemical bonds
• Organelles are structures within cells with specific functions
• Cells are the basic units of life
• Tissues are groups of similar cells performing specific functions
• Organs are structures of two or more tissues working together
• Organ systems are groups of organs performing specific functions
• Organisms are individual living things
• Populations are groups of individuals of the same species in the same area
• Communities are groups of different populations in the same area
• Ecosystems are communities of organisms and their physical environment
• Biosphere is the sum of all ecosystems on Earth

Major Fields of Biology

• Biochemistry explores chemical processes within/related to living organisms
• Botany studies plants: physiology, structure, genetics, ecology, distribution, classification, and economic importance
• Cell biology studies the structure, function, and behavior of cells
• Ecology studies interactions between organisms and their environment
• Evolutionary biology studies processes that diversified life on Earth
• Genetics studies heredity and variation in organisms
• Microbiology studies microorganisms: bacteria, viruses, fungi, and protozoa
• Molecular biology studies structure/function of biological macromolecules
• Zoology studies animals: physiology, structure, genetics, ecology, evolution, classification, and behavior

Key Concepts in Biology

• Adaptation is a trait enhancing survival and reproduction
• Biodiversity is the variety of life on Earth
• Includes genetic, species, and ecosystem diversity
• Classification organizes organisms by evolutionary relationships
• Development is the process of organismal growth and change
• Disease is any condition impairing normal function
• Ecology studies interactions between organisms and their environment
• Evolution is the process of change in species characteristics
• Metabolism is the sum of all chemical reactions in an organism
• Reproduction is the process by which organisms produce offspring

Scientific Method in Biology

• Observation involves data gathering about a phenomenon
• Hypothesis is a testable explanation for a phenomenon
• Experimentation is a controlled test of a hypothesis
• Data analysis involves the interpretation of experimental results
• Conclusion states whether the hypothesis was supported or refuted
• Scientific theory is a well-substantiated explanation incorporating facts, laws, inferences, and tested hypotheses

The Cell

• The cell is the basic structural and functional unit of all known living organisms
• It is the smallest unit of an organism that is considered living
• Cells can exist as single entities (like bacteria and protozoa) or integrated into multicellular organisms (like animals and plants)

Cell Structure

• Cell membrane: outer boundary, controlling entry/exit
• Cytoplasm: gel-like substance containing organelles
• Nucleus: control center with DNA

Cell Types

• Prokaryotic cells lack a nucleus and other membrane-bound organelles
• Eukaryotic cells have a nucleus and other membrane-bound organelles

Cell Membrane

• Phospholipid bilayer: main structure of phospholipids
• Proteins: embedded, with various functions like transport/signaling
• Cholesterol: maintains membrane fluidity

Cell Organelles

• Nucleus: contains DNA, controls activities
• Mitochondria: generates energy (ATP) through respiration
• Ribosomes: synthesize proteins
• Endoplasmic reticulum (ER): synthesizes and transports proteins/lipids
• Golgi apparatus: processes and packages proteins
• Lysosomes: break down waste materials
• Vacuoles: store water, nutrients, and waste
• Chloroplasts (plant cells): carry out photosynthesis
• Cell wall (plant cells): provides support and protection

Cell Processes

• Cell division: a cell divides into two new cells
• Mitosis: cell division for growth and repair
• Meiosis: cell division for sexual reproduction
• Photosynthesis: converts light energy into chemical energy
• Cellular respiration: breakdown of glucose to release energy (ATP)

Genetics

• Genetics is the study of heredity and variation

Basic Genetic Concepts

• Gene: a unit of heredity, segment of DNA coding for a protein
• Allele: different forms of a gene
• Genotype: genetic makeup of an organism
• Phenotype: observable characteristics of an organism

DNA and Chromosomes

• DNA: deoxyribonucleic acid, the genetic material
• Double helix: the structure of DNA
• Nucleotides: building blocks of DNA (A, G, C, T)
• Chromosomes: structures containing DNA, found in the nucleus
• Humans have 46 chromosomes (23 pairs)

Genetic Inheritance

• Mendelian genetics: principles of inheritance discovered by Gregor Mendel
• Dominant allele: masks the effect of a recessive allele
• Recessive allele: only expressed when two copies are present
• Homozygous: having two identical alleles for a gene
• Heterozygous: having two different alleles for a gene

Genetic Variation

• Mutation: a change in DNA sequence
• Recombination: exchange of genetic material during meiosis

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations
• Evolutionary processes give rise to diversity at every level of biological organization, including species, individual organisms, and molecules.

Mechanisms of Evolution

• Natural selection: differential survival/reproduction based on traits
• Mutation: creates new genetic variation
• Genetic drift: random changes in allele frequencies
• Gene flow: movement of genes between populations

Evidence for Evolution

• Fossil record: shows changes in organisms over time
• Comparative anatomy: similarities/differences in anatomy
• Embryology: similarities in development
• Molecular biology: similarities in DNA/protein sequences
• Biogeography: the distribution of species

Ecology

• Ecology is the study of the interactions between organisms and their environment

Levels of Ecological Study

• Individuals: study of individual organisms and their behavior
• Populations: study of groups of individuals of the same species
• Communities: study of groups of different species living together
• Ecosystems: study of the interactions between communities and their physical environment
• Biosphere: the global ecosystem

Key Ecological Concepts

• Biotic factors: living components of the environment
• Abiotic factors: non-living components (temperature, water, sunlight)
• Food chains/webs: flow of energy
• Trophic levels: organism's position in a food chain
• Producers: organisms that make their own food (plants)
• Consumers: organisms that eat other organisms (animals)
• Decomposers: organisms that break down dead organisms
• Nutrient cycles: movement of nutrients (carbon, nitrogen)
• Biomes: large-scale ecosystems with specific climate and vegetation

Biological Classification

• Biological classification is the process by which scientists group living organisms
• Organisms are classified based on shared characteristics

Taxonomic Hierarchy

• Domain: broadest category (Archaea, Bacteria, Eukarya)
• Kingdom: e.g., Animalia, Plantae, Fungi, Protista
• Phylum
• Class
• Order
• Family
• Genus
• Species: most specific category

Binomial Nomenclature

• Two-part naming system: Genus species (e.g., Homo sapiens)
• Genus is capitalized, species is not
• Both are italicized or underlined