Introduction to Biology

The provided text is identical to the existing notes. No changes have been made.

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

Core Principles of Biology

• Cell theory: All living organisms are composed of cells
• Genes: Heredity and genetic information are encoded in DNA
• Evolution: Life evolves through natural selection
• Homeostasis: Living organisms maintain a stable internal environment
• Thermodynamics: Life requires energy and is governed by the laws of thermodynamics

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins
• Cells: The basic unit of life, can be prokaryotic or eukaryotic
• Tissues: Groups of similar cells performing a specific function
• Organs: Structures composed of different tissues working together
• Organ Systems: Groups of organs that cooperate to perform major bodily functions
• Organisms: Individual living entities
• Populations: Groups of individuals of the same species in a given area
• Communities: Populations of different species interacting in a given area
• Ecosystems: Communities and their non-living environment
• Biosphere: All ecosystems collectively, the regions of Earth inhabited by life

Cell Structure and Function

• Cells are the fundamental units of life
• Two main types of cells: prokaryotic and eukaryotic

Prokaryotic Cells

• Lack a nucleus and other membrane-bound organelles
• Include bacteria and archaea
• Have a cell wall, plasma membrane, cytoplasm, ribosomes, and genetic material (DNA)

Eukaryotic Cells

• Possess a nucleus and other membrane-bound organelles (mitochondria, endoplasmic reticulum, Golgi apparatus)
• Found in plants, animals, fungi, and protists
• More complex structure allows for specialized functions

Key Organelles

• Nucleus: Contains the cell's DNA and controls cell activity
• Mitochondria: Site of cellular respiration, generates ATP
• Endoplasmic Reticulum (ER): involved in protein and lipid synthesis
• Golgi Apparatus: Modifies, sorts, and packages proteins
• Lysosomes: Contain enzymes for breaking down cellular waste
• Chloroplasts (plants only): Site of photosynthesis

Cell Membrane

• A selectively permeable barrier separating the cell's interior from the external environment
• Composed of a phospholipid bilayer with embedded proteins

Cell Communication

• Cells communicate through chemical signals
• Reception: Signal binds to a receptor protein
• Transduction: Signal is converted into a form that can bring about a cellular response
• Response: Cellular activity is altered

Genetics and Heredity

• Genetics is the study of heredity and variation of inherited characteristics

DNA Structure

• DNA (deoxyribonucleic acid) is the molecule that carries genetic information
• Double helix structure composed of nucleotides
• Nucleotides consist of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine)

DNA Replication

• Process by which DNA is copied
• DNA replicates semi-conservatively, each new DNA molecule consists of one original and one newly synthesized strand

Gene Expression

• Process by which information encoded in a gene is used to synthesize a functional gene product
• Transcription: DNA is transcribed into RNA
• Translation: RNA is translated into protein

Mutations

• Changes in the DNA sequence
• Can be spontaneous or induced by mutagens
• Can have harmful, beneficial, or neutral effects

Mendelian Genetics

• Gregor Mendel's laws of inheritance
• Law of Segregation: Allele pairs separate during gamete formation
• Law of Independent Assortment: Alleles of different genes assort independently of one another during gamete formation.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations

Natural Selection

• The mechanism driving evolution
• Individuals with traits better suited to their environment are more likely to survive and reproduce
• Leads to adaptation

Evidence for Evolution

• Fossil record: Provides evidence of extinct species and transitional forms
• Comparative anatomy: Similarities in anatomical structures reflect common ancestry
• Comparative embryology: Similarities in embryonic development suggest common ancestry
• Molecular biology: Similarities in DNA and protein sequences indicate evolutionary relationships
• Biogeography: The geographic distribution of species reflects their evolutionary history

Mechanisms of Evolution

• Mutation: Introduces new genetic variation
• Gene flow: Movement of genes between populations
• Genetic drift: Random changes in allele frequencies
• Natural selection: Differential survival and reproduction based on heritable traits

Speciation

• The process by which new species arise
• Allopatric speciation: Geographic separation leads to divergence
• Sympatric speciation: Speciation occurs in the same geographic area

Classification of Life

• Taxonomy is the science of classifying organisms
• Hierarchical classification system (Linnaean system): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

The Three Domains of Life

• Bacteria: Prokaryotic, unicellular organisms
• Archaea: Prokaryotic, unicellular organisms distinct from bacteria
• Eukarya: Eukaryotic organisms, including protists, fungi, plants, and animals

Ecology

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

Ecosystem Components

• Biotic factors: Living organisms
• Abiotic factors: Non-living components (temperature, water, sunlight, soil)

Trophic Levels

• Producers: Autotrophs that produce their own food (e.g., plants)
• Consumers: Heterotrophs that obtain energy by consuming other organisms
• Decomposers: Break down dead organic matter

Food Webs

• Interconnected food chains illustrating the flow of energy through an ecosystem

Population Ecology

• Study of population size, density, distribution, and dynamics

Community Ecology

• Study of interactions between different species in a community (competition, predation, mutualism, commensalism, parasitism)

Ecosystem Ecology

• Study of energy flow and nutrient cycling in ecosystems

Conservation Biology

• Focuses on preserving biodiversity and protecting ecosystems

Importance of Biodiversity

• Provides ecosystem services (pollination, water purification, climate regulation)
• Source of medicines and other valuable resources
• Ethical and aesthetic value