Introduction to Biology

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

Key Concepts in Biology

• Cell theory states that all living organisms are composed of cells.
• Cells are the basic units of structure and function in living organisms.
• Genetics is the study of heredity and variation of inherited characteristics.
• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Homeostasis is the ability of an organism to maintain internal stability.
• Energy is the capacity to do work, and is essential for life processes, with energy flow and transformation being a central theme.
• Ecology is the study of the interactions between organisms and their environment.

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Molecular biology studies the structure and function of macromolecules essential to life.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Botany is the scientific study of plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Zoology is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct.
• Genetics studies genes, heredity, and variation in living organisms.
• Ecology studies the relationships between living organisms, including humans, and their physical environment.
• Physiology studies the functions and mechanisms in a living system.
• Anatomy studies the structure of living things.
• Evolutionary biology studies the evolutionary processes that produced the diversity of life on Earth.

The Cell

• The cell is the basic structural and functional unit of all known living organisms.
• Cell theory: All living organisms are composed of one or more cells; the cell is the basic unit of structure and organization in organisms; and cells arise from pre-existing cells.
• Two main types of cells: eukaryotic and prokaryotic.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Prokaryotic cells do not have a nucleus or other membrane-bound organelles.

Key Cellular Structures and Functions

• Nucleus: Contains the cell's genetic material (DNA) and controls cell activities.
• Cytoplasm: Gel-like substance within the cell membrane containing organelles.
• Cell membrane: Outer boundary of the cell that controls the movement of substances in and out.
• Mitochondria: Powerhouse of the cell, responsible for cellular respiration and energy production.
• Ribosomes: Site of protein synthesis.
• Endoplasmic reticulum (ER): Network of membranes involved in protein and lipid synthesis.
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids for transport.
• Lysosomes: Contain enzymes for breaking down cellular waste and debris.

Genetics

• Genes are the basic units of heredity and are composed of DNA.
• DNA (deoxyribonucleic acid) is the molecule that carries the genetic instructions for all known living organisms.
• Chromosomes are structures within the cell that contain the DNA.
• Genes code for proteins, which carry out various functions in the cell and body.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.
• Mutation: A change in the DNA sequence that can result in altered protein function.
• Inheritance: The passing on of traits from parents to offspring.
• Mendelian genetics: Describes the inheritance of traits controlled by single genes with distinct alleles.

Evolution

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

Classification of Living Things

• Taxonomy is the science of classifying and naming living organisms.
• The Linnaean system of classification uses a hierarchical system of classifying organisms into groups based on shared characteristics.
• The major taxonomic ranks, from broadest to most specific, are: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• Three domains of life: Bacteria, Archaea, and Eukarya.
• Five kingdoms: Monera (bacteria), Protista, Fungi, Plantae, and Animalia.
• Binomial nomenclature: A system of naming species using a two-part name (genus and species).

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Ecosystems are communities of living organisms (biotic factors) interacting with their physical environment (abiotic factors).
• Populations are groups of individuals of the same species living in the same area.
• Communities are groups of interacting populations of different species.
• Food chains and food webs describe the flow of energy and nutrients through an ecosystem.
• Trophic levels: The position an organism occupies in a food chain.
• Producers (autotrophs) are organisms that produce their own food through photosynthesis or chemosynthesis.
• Consumers (heterotrophs) are organisms that obtain energy by consuming other organisms.
• Decomposers are organisms that break down dead organic matter and recycle nutrients.
• Biogeochemical cycles: The movement of elements (e.g., carbon, nitrogen, water) through ecosystems.

Plants

• Plants are multicellular, eukaryotic organisms belonging to the kingdom Plantae.
• Plants are autotrophs, meaning they produce their own food through photosynthesis.
• Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce glucose (sugar) and oxygen.
• Plant cells have cell walls made of cellulose.
• Vascular plants have specialized tissues (xylem and phloem) for transporting water and nutrients.
• Non-vascular plants lack vascular tissues and include mosses, liverworts, and hornworts.
• Plant reproduction can be sexual (involving the fusion of gametes) or asexual (vegetative propagation).

Animals

• Animals are multicellular, eukaryotic organisms belonging to the kingdom Animalia.
• Animals are heterotrophs, meaning they obtain energy by consuming other organisms.
• Animal cells lack cell walls.
• Animals have diverse body plans and adaptations for various environments.
• Invertebrates lack a backbone, while vertebrates have a backbone.
• Animal reproduction is typically sexual.
• Animal behavior is influenced by both genetics and environment.

Human Biology

• Humans are complex multicellular organisms belonging to the kingdom Animalia.
• Human anatomy and physiology studies the structure and function of the human body.
• Organ systems: Groups of organs that work together to perform specific functions.
• Major organ systems: Skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, reproductive, and immune systems.
• Homeostasis: The maintenance of a stable internal environment in the human body.
• Human genetics studies the inheritance of traits and the role of genes in human health and disease.
• Human evolution traces the evolutionary history of humans from ancestral primates.