Organism – a life form; a living entity made up of one or more cellsno simple definition of life endorsed by all biologists, but most agree that organisms share a suite of 5 fundamental characteristicsorganisms obtain and use energyare made up of cells (cellularity)process informationreplicate (reproduce)evolution (change over time)theory – an explanation for a very general class of phenomena or observationscell theory and theory of evolution established 2 of the 5 attributes of life: organisms are cellular and their populations change over timeRobert Hook1665 – used a crude microscope (30x) to examine the structure of cork from an oak treecork had small, pore-like compartments that were invisible to the naked eye ---- structures were called cellsAnton van LeeuwenDeveloped a much powerful microscope (300x)Inspected samples of pond water and discovered first human blood cells and sperm cellsCell – a highly organized compartment that is bounded by a thin, flexible structure called a plasma membrane and contains concentrated chemicals is a aqueous solutionScientific theories have two components:A pattern in the natural worldA mechanism or process that is responsible for creating that patternCell theory – all organisms are made up of cells, and all cells come from preexisting cellsTwo hypotheses:Hypothesis – a proposed explanationSpontaneous generation: springing to life from non-living materialsAll-cells-from-cells hypothesis: cells do not spring to life spontaneously, but are produced only when preexisting cells grow and divideExperiment to test hypothesis – Louis PasteurPrediction – something that can be measured and that must be correct if the hypothesis is valid**see figure 1.2 on page 3**experimental set up was effective because there was only one difference between the two treatments and because that difference was the factor being testing – in this case, a broth’s exposure to preexisting cellsTheory of Evolution by Natural SelectionDarwin & Wallace – papers written separately explaining thisTheory has pattern & process componentSpecies are related by common ancestrythe characteristics of species can be modified from generation to generation --- “descent with modification”natural selection – explains how evolution occursoccurs whenever 2 conditions are met:individuals within a population vary in characteristics that are heritable (traits that can be passed on to offspring)in a particular environment, certain versions of these heritage traits help individuals survive better or reproduce more than do other versionsnatural selections acts on individuals, but evolutionary change occurs in populationsartificial selection – changes in population that occur when humans select certain individuals to produce the most offspringevolution occurs when heritable variation leads to differential success in reproductionfitness – the ability of an individual to produce offspring. Individuals with high fitness produce many surviving offspringadaption – a trait that increases the fitness of an individual in a particular environmentCell theory and theory of evolution provided science of biology with two central, unifying ideas:The cell is the fundamental structural unit in all organismsAll species are related by common ancestry and have changed over time in response to natural selectionSpeciation – populations of one species to diverge and form new speciesAll species come from preexisting speciesAll species trace their ancestry back to a single common ancestorTree of life – a family tree of organismsCarl Woese – analyzed chemical components of organisms as a way to understand theory evolutionary relationshipsGoal was to understand phylogeny (actual genealogical relationships) or all organismsRNA – ribonucleotide acidRibosomal RNA (rRNA) is a trait that can change during the course of evolutionIf theory is correct, rRNA sequences should be very similar in organisms that are less closely related. Species that are part of the same evolutionary lineage, should share certain changes in rRNA that no other species haveA phylogenic tree shows relationships between species. On a phylogenic tree, branches that share a recent common ancestor represent species that are closely related; branches that don’t share a recent common ancestor represent species that are more distantly relatedTree of LifeThree fundamental groups or lineages of organismsThe Bacteria - prokaryoteThe Archaea - prokaryoteThe Eukarya - eukaryoteEukaryotesNucleusMulticellular (“many-celled”)ProkaryotesUnicellular (“one-celled”)Taxonomy – the effort to name and classify organismsAny named group is called a taxonWoese proposed domain as a new taxonomic categoryThree domains of life: Bacteria, Archaea, EukaryaPhylum – major lineages within each domainEach phylum is considered a major branch on the tree of lifeScientific NamesCarolus Linneaus established systemEach scientific name is uniqueOften descriptiveTwo-part name unique to each organismFirst part – genus (made up of closely related groups of species)Second part – organism’s speciesExample: genus – homo, species – sapiens ---> homo sapiens (humans)The Nature of ScienceScientists ask questions that can be answered by measuring thingsScience is about formulating hypotheses and finding evidence that supports or conflicts with these hypothesesHypothesis testing is a two-step processState the hypothesis as precisely as possible and list the predications it makesDesign an observation or experimental study that is capable of testing those predictionsTwo ways to test hypotheses: experimental evidence or observational evidenceExperiments are a powerful, scientific tool because they allow researchers to test the effect of a single, well-defined factor on a particular phenomenonGood scientific hypotheses make testable predictions (predictions that can be supported and rejected by collecting and analyzing dataA null hypothesis specifies what we should observe when the hypothesis being tested isn’t correctImportant Characteristics of good experimental design:Critical to include control groups (A group of outside subjects whose performance or abilities are compared with the experimental subjects.)Checks for factors other than the ones being testedThe experimental conditions must be as constant or equivalent as possibleEliminates alternative explanations for the resultsRepeating the test is essentialRepeated in large groupsAmount of