21-1 What is Science? Goal of science Observations vs. inferences What is a hypothesis?
3Goal of science To investigate and understand nature To explain events in natureUse those explanations to make useful predictionsScience- organized way of using evidence to learn about the natural worldIt’s a process!Term can also refer to the body of knowledge scientists have built up after years using this process
4Observations vs. Inferences Observation- gather information using one or more of the sensesInformation gathered is called evidence or dataTwo types of observationsQualitative- involves characteristics that cannot be easily measured or countedQuantitative- involves numbers like when measuring or counting objects
5Observations vs. Inferences Inference-logical interpretation based on prior knowledge and experience
6Observations vs. Inferences Statement Observation InferenceObject A is round and orange.XObject A is a basketball.Object C is round and black and white.Object C is larger than Object B.Object B is smooth.Object B is a table-tennis ball.Each object is used in a different sport.
7Explaining the Evidence A hypothesis is a possible explanation for a set of observations or an answer to a scientific questionMust be testable!
8Formulating a Hypothesis Mystery WormsA teacher collected some beetles from a rotting log and placed them in a container of dry oatmeal in her classroom. She kept the box covered with a light cloth so that the beetles could not escape. She also asked one of her students to add potato and apple pieces once a week to provide food and moisture for the beetles. After several weeks, the student reported that there were some strange-looking, wormlike organisms in the container.1. Formulate a hypothesis that might explain the presence of the “worms” in the container.2. How could you test your hypothesis?
91-2 How Scientists Work Designing an Experiment Publishing and Repeating InvestigationsWhen Experiments are Not PossibleHow a Theory Develops
10Designing an Experiment State the ProblemAnalyze ResultsForm a HypothesisDraw a ConclusionSet Up a Controlled ExperimentPublish ResultsRecord Results
11Controlled Experiment Only one variable must be changed at a timeAll other variables should be kept unchanged or controlledManipulated (independent) variable- variable that is deliberately changedResponding (dependent) variable- variable that is observed and changes in response to the manipulated variable
12Redi’s Experiment, designed to refute Spontaneous Generation- the idea that life could arise from nonliving matterOBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.HYPOTHESIS: Flies produce maggots.PROCEDUREUncovered jarsCovered jarsControlled Variables:jars, type of meat,location, temperature,timeSeveraldays passManipulated Variables:gauze covering thatkeeps flies away frommeatResponding Variable:whether maggotsappearMaggots appearNo maggots appearCONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.
13Recording and Analyzing Results Lab reportsScientific drawingsOnline storage
14Drawing a Conclusion After testing your hypothesis… Option 1: Data supports it“data supports the hypothesis”Never proves itOption 2: Data proves it wrong“hypothesis is refuted”Rewrite and test again
15Repeating RediKey assumption in science- experimental results can be reproduced because nature acts in a consistent mannerRedi’s work followed byNeedham-used an experiment with “animalcules” to attack Redi’s workSpallanzani- improved upon Needham’s experimentPasteur-allowed broth to come into contact with the air
16Spallanzani’s Experiment Gravy is boiled.Flask isopen.Flask issealed.Gravy is free ofmicroorganisms.Gravy is boiled.
17Pasteur’s ExperimentBroth is boiled.Broth is free ofmicroorganismsfor a year.Curved neckis removed.Broth isteeming with microorganisms.Showed that all living things come from other living things
18When Experiments are Not Possible Examples:Observing animalsProhibited by ethical considerationsAttempting to maintain a controlled experimentStudy large groups of subjectsID as many relevant variables as possible
19Developing a TheoryTheory- well-tested explanation that unifies a wide range of observationsHappens when a hypothesis is so well supported by the scientific communityNo theory is considered absolute truthMay be revised or replaced by a more useful explanation
201-3 Studying Life Characteristics of living things Branches of biology Biology in everyday life
21Characteristics of Living Things 1. Made Up of Cells2. Reproduce3. Based on a Genetic Code4. Grow and Develop5. Need Materials and Energy6. Respond to the Environment7. Maintain Internal Balance8. Evolve
22Characteristic Examples Living things are made up of units called cells.Many microorganisms consist of only a single cell. Animals and trees are multicellular.Living things reproduce.Maple trees reproduce sexually. A hydra can reproduce asexually by budding.Living things are based on a universal genetic code.Flies produce flies. Dogs produce dogs. Seeds from maple trees produce maple trees.Living things grow and develop.Flies begin life as eggs, then become maggots, and then become adult flies.Living things obtain and use materials and energy.Plants obtain their energy from sunlight. Animals obtain their energy from the food they eat.Living things respond to their environment.Leaves and stems of plants grow toward light.Living things maintain a stable internal environment.Despite changes in the temperature of the environment, a robin maintains a constant body temperature.Taken as a group, living things change over time.Plants that live in the desert survive because they have become adapted to the conditions of the desert.