Introduction to Biology

• Biology is the scientific study of life.

Core Principles of Biology

• Cell theory: all living organisms are composed of cells.
• Gene theory: traits are inherited through genes.
• Evolution: all life forms have evolved over time from a common ancestor.
• Homeostasis: maintenance of a stable internal environment.
• Thermodynamics: life processes involve energy transformations.

Characteristics of Life

• Organization: Living things exhibit complex organization.
• Metabolism: Living organisms carry out metabolic reactions.
• Reproduction: Living organisms reproduce to create new organisms.
• Growth: Increase in size or cell number.
• Response: Ability to detect and respond to stimuli.
• Adaptation: Evolving traits to suit their environment.

Levels of Biological Organization

• From smallest to largest: molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
• Each level builds upon the previous one and exhibits emergent properties.

Cell Structure and Function

• Cells are the basic units of life.
• Two main types: prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles (e.g., bacteria).
• Eukaryotic cells have a nucleus and other membrane-bound organelles (e.g., animal, plant, fungi, and protist cells).

Key Cellular Organelles and Functions

• Nucleus: Contains the cell's genetic material (DNA) and controls cell activities.
• Mitochondria: Generate energy (ATP) through cellular respiration.
• Ribosomes: Synthesize proteins.
• Endoplasmic reticulum (ER): Network of membranes involved in protein and lipid synthesis.
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Contain enzymes for breaking down cellular waste and debris.

Cell Membrane

• Selectively permeable barrier composed of a lipid bilayer with embedded proteins.
• Regulates the movement of substances into and out of the cell.

Cell Communication

• Cells communicate through chemical signals.
• Receptors receive signals and initiate cellular responses.

Metabolism and Enzymes

• Metabolism is the sum of all chemical reactions in an organism.
• Enzymes are biological catalysts that speed up chemical reactions.
• Enzymes are highly specific and bind to specific substrates.

Energy and ATP

• ATP (adenosine triphosphate) is the primary energy currency of the cell.
• Energy is released when ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate.

Photosynthesis

• Process by which plants and other organisms convert light energy into chemical energy.
• Occurs in chloroplasts.
• Involves two main stages: light-dependent reactions and the Calvin cycle.

Cellular Respiration

• Process by which cells break down glucose to generate ATP.
• Occurs in mitochondria.
• Three main stages: glycolysis, Krebs cycle (citric acid cycle), and electron transport chain.

DNA Structure and Function

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

DNA Replication

• Process by which DNA is copied.
• DNA polymerase is the main enzyme involved.
• Results in two identical DNA molecules.

RNA Structure and Function

• RNA (ribonucleic acid) is involved in protein synthesis.
• Single-stranded structure composed of nucleotides.
• Nucleotides consist of a ribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil).
• Main types of RNA: mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).

Protein Synthesis

• Two main stages: transcription and translation.
• Transcription: DNA is transcribed into mRNA in the nucleus.
• Translation: mRNA is translated into a protein by ribosomes in the cytoplasm.

Genes and Inheritance

• Genes are segments of DNA that code for proteins.
• Alleles are different versions of a gene.
• Genotype is the genetic makeup of an organism.
• Phenotype is the observable characteristics of an organism.

Mendelian Genetics

• Gregor Mendel's laws of inheritance: segregation and independent assortment.
• Punnett squares are used to predict the genotypes and phenotypes of offspring.

Chromosomes and Cell Division

• Chromosomes are structures that carry genetic information.
• Humans have 46 chromosomes (23 pairs).
• Mitosis: cell division that produces two identical daughter cells.
• Meiosis: cell division that produces four haploid gametes (sperm and egg cells).

Mutation

• Changes in the DNA sequence.
• Can be spontaneous or caused by mutagens.
• Can have no effect, a positive effect, or a negative effect on an organism.

Evolution

• Change in the genetic makeup of a population over time.
• Supported by evidence from fossils, comparative anatomy, embryology, and molecular biology.

Natural Selection

• Mechanism of evolution proposed by Charles Darwin.
• Individuals with advantageous traits are more likely to survive and reproduce.

Speciation

• Process by which new species arise.
• Can occur through geographic isolation or reproductive isolation.

Taxonomy and Classification

• Science of classifying organisms.
• Hierarchical system: domain, kingdom, phylum, class, order, family, genus, species.

Domains of Life

• Bacteria, Archaea, and Eukarya.
• Bacteria and Archaea are prokaryotic.
• Eukarya includes protists, fungi, plants, and animals.

Ecology

• Study of the interactions between organisms and their environment.

Population Ecology

• Study of the size, density, distribution, and dynamics of populations.

Community Ecology

• Study of the interactions between different species in a community.

Ecosystem Ecology

• Study of the flow of energy and cycling of nutrients in ecosystems.

Biomes

• Large geographic areas characterized by specific climate conditions and plant communities (e.g., tundra, taiga, temperate forest, grassland, desert, tropical rainforest).

Biodiversity

• Variety of life on Earth.
• Includes genetic diversity, species diversity, and ecosystem diversity.

Conservation Biology

• Study of the conservation of biodiversity.
• Addresses threats to biodiversity, such as habitat loss, pollution, and climate change.

An overview of biology, the scientific study of life, covering core principles, characteristics of life, and levels of biological organization. Topics include cell theory, gene theory, evolution and homeostasis. Also explores metabolism, reproduction, growth, and response.