Introduction to Biology

• Biology is the scientific study of life and living organisms.
• It explores the structure, function, growth, origin, evolution, distribution, and taxonomy of living things.
• Biology encompasses a wide range of fields, including botany, zoology, microbiology, genetics, and ecology.

Key Concepts in Biology

• Cell Theory: All living organisms are composed of cells, which are the basic units of structure and function.
• Genetic Information: DNA serves as the blueprint of life, containing the instructions for building and maintaining an organism.
• Evolution: The process by which populations of organisms change over time.

Levels of Biological Organization

• Atoms: The basic building blocks of matter.
• Molecules: Groups of atoms held together by chemical bonds.
• Organelles: Structures within cells that perform specific functions.
• Cells: The basic unit of life.
• Tissues: Groups of similar cells performing a specific function.
• Organs: Structures composed of different tissues working together.
• Organ Systems: Groups of organs working together.
• Organisms: Individual living beings.
• Population: A group of individuals of the same species living in the same area.
• Community: Populations of different species living in the same area.
• Ecosystem: A community of organisms and their physical environment.
• Biosphere: The part of Earth where life exists.

Cell Structure and Function

• Cells are the fundamental units of life, categorized as prokaryotic (lacking a nucleus) or eukaryotic (possessing a nucleus).
• Key cell structures include the plasma membrane, cytoplasm, nucleus (in eukaryotes), ribosomes, and organelles.
• The plasma membrane controls the movement of substances in and out of the cell.
• The cytoplasm is the gel-like substance within the cell where organelles are located.
• The nucleus contains the cell's genetic material (DNA) and controls cell activities in eukaryotes.
• Ribosomes are responsible for protein synthesis.
• Organelles, such as mitochondria, chloroplasts, endoplasmic reticulum, and Golgi apparatus, perform specific functions within the cell.

Genetics and Heredity

• Genes are the units of heredity, composed of DNA and located on chromosomes.
• DNA (deoxyribonucleic acid) carries the genetic instructions for all known living organisms.
• DNA structure: a double helix composed of nucleotides containing a sugar, phosphate group, and nitrogenous base (adenine, guanine, cytosine, or thymine).
• RNA (ribonucleic acid) is involved in protein synthesis and gene regulation.
• Genetic information is passed from parents to offspring.
• Inheritance patterns follow the principles of Mendelian genetics.
• Mutations are changes in the DNA sequence that can lead to genetic variation.
• Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product (protein or RNA).

Evolution and Natural Selection

• Evolution is the process of change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the mechanism driving evolution, where individuals with advantageous traits are more likely to survive and reproduce.
• Evidence for evolution includes the fossil record, comparative anatomy, embryology, and molecular biology.
• Adaptation is the process by which organisms become better suited to their environment through natural selection.
• Speciation is the process by which new species arise from existing ones.

Ecology and Ecosystems

• Ecology is the study of the interactions between organisms and their environment.
• Ecosystems consist of communities of organisms and their physical environment.

Key ecological concepts include:

• Food chains and food webs describe the flow of energy and nutrients through an ecosystem.
• Trophic levels represent the different feeding positions in a food chain or food web (producers, consumers, decomposers).
• Energy flow is the transfer of energy from one trophic level to another, with energy loss at each level.
• Nutrient cycling involves the movement of essential nutrients (carbon, nitrogen, phosphorus) through an ecosystem.
• Biodiversity is the variety of life in an ecosystem, important for ecosystem stability and resilience.
• Human impact on ecosystems includes pollution, deforestation, climate change, and habitat destruction.

Biological Processes

• Homeostasis is the ability of an organism to maintain a stable internal environment.
• Reproduction is the process by which organisms produce offspring, either sexually or asexually.
• Metabolism is the sum of all chemical reactions that occur within an organism.
• 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.

Classification of Living Things

• Taxonomy is the science of classifying and naming organisms.
• Linnaean system: Hierarchical classification system including:
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Three domains of life: Bacteria, Archaea, and Eukarya.
• Five kingdoms: Monera (Prokaryotes), Protista, Fungi, Plantae, and Animalia.
• Binomial nomenclature is a system of naming species with a two-part name (genus and species).

Important Biological Molecules

• Carbohydrates: Provide energy and structural support (e.g., sugars, starches, cellulose).
• Lipids: Store energy, form cell membranes, and act as hormones (e.g., fats, oils, phospholipids, steroids).
• Proteins: Perform a wide variety of functions, including enzymes, structural components, and transport molecules (e.g., enzymes, antibodies, collagen).
• Nucleic acids: Carry genetic information (DNA and RNA).