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UT Knoxville BIOL 140 - Chapter 1

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Chapter 1What Does It Mean to Say That Something Is Alive?TheoriesThe Cell TheoryLouis Pasteur’s ExperimentSlide 6Slide 7Slide 8Implications of the Cell TheoryThe Theory of Evolution by Natural SelectionSlide 11Evolution and Natural SelectionNatural Selection and PopulationsEvolutionary ChangeArtificial SelectionDifferential Reproductive SuccessFitness and AdaptationThe Tree of LifeUsing Molecules to Understand the Tree of LifeSlide 20The Phylogenic Tree of LifeSlide 22Interpreting the Tree of LifeTaxonomyLinnaeus’ Taxonomic System of ClassificationRules of NomenclatureDoing Biology: The Nature of ScienceHypothesis TestingElements of a Well-Designed ExperimentThe Principles of Experimental Design© 2011 Pearson Education, Inc.Chapter 1© 2011 Pearson Education, Inc.What Does It Mean to Say That Something Is Alive?All living organisms share five fundamental characteristics–Energy –All organisms acquire and use energy.–Cells–All organisms are made up of membrane-bound cells.–Information –All organisms process hereditary information encoded in genes as well as information from the environment.–Replication–All organisms are capable of reproduction.–Evolution–Populations of organisms are continually evolving.© 2011 Pearson Education, Inc.Theories•A theory is an explanation for a very general class of phenomena or observations. •Theories have two components.–Pattern–Something that occurs in the natural world–Process –Responsible for creating the pattern•Two theories form the framework for modern biological science.–The cell theory–The theory of evolution by natural selection© 2011 Pearson Education, Inc.The Cell Theory•In the late 1660s, Robert Hooke and Anton van Leeuwenhoek were the first to observe cells.•A cell is a highly organized compartment bounded by a plasma membrane that contains concentrated chemicals in an aqueous solution.The cell theory states that –All organisms are made of cells (pattern).–All cells come from preexisting cells (process).© 2011 Pearson Education, Inc.Louis Pasteur’s Experiment•A hypothesis is a proposed explanation. •A prediction is something that can be measured and must be correct if a hypothesis is valid. •Louis Pasteur proved that cells arise from cells and not by spontaneous generation.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Implications of the Cell Theory•Because all cells come from preexisting cells, all individuals in a population of single-celled organisms are related by common ancestry.•All of the cells present in a multicellular organism have descended from preexisting cells and are connected by common ancestry.© 2011 Pearson Education, Inc.The Theory of Evolution by Natural Selection •In 1858, Charles Darwin and Alfred Russel Wallace made two claims regarding the natural world:–All species are related by common ancestry (pattern). –Characteristics of species can be modified from generation to generation. –Descent with modification (process)© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Evolution and Natural Selection •Evolution is a change in the characteristics of a population over time. It means that species are related to one another and can change through time.•Natural selection explains how evolution occurs.© 2011 Pearson Education, Inc.Natural Selection and Populations•A group of individuals of the same species living in the same area at the same time constitute a population. •Two conditions must be met for natural selection to occur in a population:1. Individuals in the population vary in characteristics that are heritable.2. In a particular environment, certain versions of these heritable traits help individuals survive better or reproduce more than do other versions.© 2011 Pearson Education, Inc.Evolutionary ChangeIf certain heritable traits lead to increased success in producing offspring, these traits become more common in the population over time. In this way, the population’s characteristics change as a result of natural selection acting on individuals.–Natural selection acts on individuals, but evolutionary change occurs in populations.© 2011 Pearson Education, Inc.Artificial Selection•In artificial selection, changes in populations occur when humans select which individuals will produce the most offspring. •Repeating this process over generations results in changes in the characteristics of a domesticated population over time.© 2011 Pearson Education, Inc.Differential Reproductive Success•Evolution occurs when heritable variation leads to differential success in reproduction.•This can occur via:–Artificial selection – humans select desirable traits within a domestic population –Natural selection – traits beneficial to the current environment are “selected” within a natural population© 2011 Pearson Education, Inc.Fitness and Adaptation•Fitness is the ability of an individual to produce offspring. –Individuals with high fitness produce many surviving offspring.•Adaptation is a trait that increases the fitness of an individual in a particular environment.© 2011 Pearson Education, Inc.The Tree of Life•The cell theory and the theory of evolution by natural selection imply that all species come from preexisting species and that all species, past and present, trace their ancestry back to a single common ancestor. •Speciation is a divergence process in which natural selection has caused populations of one species to diverge to form new species.•The tree of life is a family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base. •Phylogeny is the actual genealogical relationships among all organisms.© 2011 Pearson Education, Inc.Using Molecules to Understand the Tree of Life•Carl Woese and colleagues studied small subunit ribosomal RNA (rRNA), a molecule found in all organisms, to understand evolutionary relationships.•rRNA is comprised of four chemical units called ribonucleotides.–Symbolized by letters A, U, C, & G•The sequence of ribonucleotides can change during evolution. •Based on the theory of evolution, rRNA sequences should be very similar in closely related organisms but less similar in less closely related organisms.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The Phylogenic Tree of LifeA phylogenetic tree


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