Transcript Biology
David Sadava, David M. Hillis, H. Craig Heller, May R. Berenbaum La nuova biologia.blu Le cellule e i viventi Studying Life What Is Biology? Biology is the scientific study of living things (organisms). What Is Biology? Genome: the sum total of all the DNA in a cell. DNA consists of repeating subunits called nucleotides. Gene: a specific segment of DNA that contains information for making a protein. All the cells of a multicellular organism have the same genome, yet different cells have different functions and structures. Different cells are expressing different parts of the genome. DNA Is Life’s Blueprint The Hierarchy of Life (part 1) Cells became specialized in multicellular organisms; a biological hierarchy emerged: • differentiated cells are organized into tissues; • different tissue types form organs (e.g., a heart); • organs are grouped into organ systems. The Hierarchy of Life (part 2) A group of individuals of the same species is a population. Populations of all the species that live and interact in a defined area are called a community. Communities together with their abiotic (nonliving) environment constitute an ecosystem. Characteristics of living organisms (part 1) Characteristics of living organisms: • Made of a common set of chemical components: carbohydrates, fatty acids, nucleic acids, amino acids • Most are made of cells enclosed by plasma membranes • Convert molecules from their environment into new biological molecules • Extract energy from the environment and use it to do biological work Characteristics of living organisms (part 2) • Contain genetic information that uses a universal code to specify proteins • Share similarities among a fundamental set of genes, and replicate this genetic information when reproducing • Exist in populations that evolve through changes in frequencies of genetic variants over time • Self-regulate their internal environment, maintaining conditions that allow them to survive Organisms need of nutrients Organisms acquire nutrients from their environment. Nutrients supply energy and materials for biochemical reactions. Some reactions break nutrient molecules into smaller units, releasing energy for work. Energy can be used immediately or stored. The Mechanism of Homeostasis Organisms must regulate their internal environment, made up of extracellular fluids. Maintenance of the narrow range of conditions that support survival is known as homeostasis. The Natural Selection of Life Evolution is the major unifying principle of biology. Charles Darwin compiled factual evidence for evolution. He argued that differential survival and reproduction among individuals in a population (natural selection) could account for much of the evolution of life. The Many Faces of Life (Part 1) Three domains of life: •Bacteria (prokaryotes) •Archaea (prokaryotes) •Eukarya (eukaryotes) Eukaryotic cells have internal membranes that enclose specialized organelles within their cells, including the nucleus, which contains the genetic material. The Many Faces of Life (Part 2) How Do Biologists Investigate Life? Scientific investigations are based on observation, data, experimentation, and logic. Observation has been improved by new technologies. Information, or data, must be quantified using mathematical and statistical methods. Scientific Methodology How Do Biologists Investigate Life? Model systems: using one type of organism to understand others. This is possible because all life is related by descent from a common ancestor, shares a genetic code, and consists of similar building blocks—cells. Adapted from Life: The Science of Biology, Tenth Edition, Sinauer Associates, Sunderland, MA, 2014 Inc. All rights reserved