3 Thinking about the Nature of Science What is science?What makes science powerful?What characteristics must something have in order for it to be science?How does one “do” science?
4 What is Science? What is biology? Science – an organized way of using evidence to learn about the natural worldBiology – the study of the living world
5 How Scientists WorkWhat are your ideas about what specifically makes science the most powerful method we have for understanding nature?
6 How Scientists Work Using Scientific Method Ask a Question Form a HypothesisTest the HypothesisAnalyze the ResultsDraw ConclusionsCommunicate Results
7 Scientific Method“The Scientific Method” = umbrella term for a variety of methods of study.All rigorous, systematic, evidence-based, and objective means of testing explanations of the natural world.Steps not the same order every time.
9 Ask a QuestionScientists form questions when they observe nature through their senses (sight, hearing, touch, smell)Examples:Some peaches are juicy and sweet. Others are spongy with very little flavor.What makes some peaches juicier than others?My neighbor has thick, green grass. Mine is brown in spots and is thin.What does grass need to be healthy?
10 Ask a Question Practice Make observations and form a scientific question about the pictures below.
11 Form a HypothesisHypothesis – a proposed explanation for a set of observations or possible answer to a questionMust be testable, or it’s not scientificWrite the hypothesis as a clear statement, do not say “I think that ….”ATTENTION - It is okay for your hypothesis to be wrong! Never change your hypothesis after an experiment to make it correct.Prediction – what you expect to observe. The data the experiment will produce if the hypothesis is correctCan be written as an “If the hypothesis is correct, then…” statement.
12 Form a Hypothesis Example Hypothesis: Apples develop thicker skins as a defense against cold temperatures.Prediction: If apples are exposed to cool temperatures, then they will have thicker skin than other apples.
13 Form A Hypothesis Practice Write a possible hypothesis and prediction for each of the following observations.The plants in Mr. Smith’s living room are large, healthy and green but the plants in Mr. Smith’s dining room are small and yellowish in color.All of the fish in the classroom fish tank are healthy except for the algae eaters that keep dying.
14 Test the Hypothesis* Whenever possible, an experiment should be designed to have only ONE variable that is changed at a time. (AKA: Controlled Experiment)Controlled Variable/s – the variable/s that are purposely kept the sameManipulated Variable – the ONE variable that is deliberately changed (also called independent)Responding Variable – the variable that is observed and that changes in response to the manipulated variable (also called dependent)Experimental Group – the group in which the manipulated variable is changedControl or Control Group – the group used as a standard for comparison for the experimental group
15 Test the Hypothesis Practice Hypothesis: Tomato plants given fertilizer will produce more tomatoes than plants that are not fertilized.Plant A Plant B* Both plants are given the same soil, amount of water and sun, temperature, pot size, and growth time.* Plant B is fertilized once a week.What are the controlled variables, the manipulated variable, and the responding variable?Which is the control and the experimental group?
16 AnswersControlled Variables – soil, amount of water and sun, temperature, pot size, and growth timeManipulated Variable – fertilizerResponding Variable – # of tomatoesControl – Plant AExperimental Group – Plant B
17 Why change only one variable? Plant A5 hours of sunlight per dayl L of water every 4 daysquart sized pot30°C for 6 weeksno fertilizationPlant B7 hours of sunlight per dayl L of water every 2 daysgallon sized pot35°C for 9 weeksfertilized once a weekCan’t tell!Why did plant B grow more tomatoes?It’s the only way to know which manipulated variable caused the responding variable to change.
18 Test the Hypothesis Practice Describe why the experiment below is poorly designed. Write a prediction for the hypothesis and then re-design the experiment to make it better. Identify all variables and groups.Hypothesis: Bacteria exposed to antibiotics will be killed.Plate BStored in incubator (35° C)Given ampicillinStored in darkGiven nutrientsPlate AStored on counter (22° C)Given penicillinStored in lightNot given nutrients
19 Analyze the ResultsAll experimental data must include units. (examples: 9cm, 20sec, 98°C)Tables and graphs are used to represent data and must be labeled with units and titles.
20 Analyze the Results Example Notice the table below has units and clear labels.Effect of Storage Temperature on Seed GerminationStorage TemperatureInside68˚FOutside25˚FGerminated Seeds0%80%85%
21 Representing Data in Graphs Effects of Storage Temperature on Seed Germination10080604020Germinated Seeds (%)- Inside 68˚F- Inside 25˚F- Outside 25˚FStorage Temperature °F
22 Analyze the Results Practice Add to the data table and graph to improve them.Hypothesis: Caffeine improves muscle performance.Prediction: Caffeinated frogs will jump farther than uncaffeinated frogs.Results: Frogs given caffeine jumped 27cm and frogs not given caffeine jumped 20 cm.Frog not given caffeineFrog given caffeineDistance of jump2027
23 Table needs units, labels, and title. Graph needs a title, labels on X and Y axis, and a key.Table needs units, labels, and title.Effect of Caffeine on Frog JumpsEffect of Caffeine on Frog JumpsAmount of CaffeineNo CaffeineCaffeineDistance of jump20cm27cmDistance of jump (cm)Amount of Caffeine
24 Table needs units, labels and a title. Graph needs a title, labels on X and Y axis, and a key.Effect of Caffeine on Frog JumpsAmount of CaffeineNo CaffeineCaffeineDistance of jump20cm27cmEffect of Caffeine on Frog JumpsDistance of jump (cm)Uniform scale: every line stands forexactly 5 cm, no “skips”Amount of Caffeine
25 Choosing Bar vs Line Graphs Bar graph = Used for groups/categories, Line graph = Comparing two number scalesManipulated variable on X-axis, responding variable on Y-axis
26 Graph ExamplesNumber of students per town… what kind of graph, bar or line?Town# of StudentsCanton9Stoughton2Norwood1Westwood4Dedham3MiltonRandolphSharonHyde Park
27 Graph ExamplesNumber of students at different heights… what kind of graph, bar or line?Height (cm)# of Students15021511523153615451551561157
28 Bar or Line Graph?Number of American Thrushes living in each of five forests100 students’ choices for their favorite lunchComparing the number of chromosomes to the number of genesThe number of mates attracted by red vs yellow vs blue-beaked parrotsThe growth of a seedling (days old vs height)
29 Draw ConclusionsConclusion – a final summation of experimental resultsA conclusion’s main purpose is to evaluate your initial ideas (hypothesis & prediction) using your dataA conclusion should do the following:
30 Draw Conclusions (Add your own notes) State the purpose in your own words.Summarize the scientific idea the lab is about, and define any vocab words.Restate the hypothesis and prediction, not copying exactly how they were already written.Summarize (1-2 sentences) the procedure.State whether the results support or refute the hypothesis/prediction.Support the evaluation you made in step 5 with specific evidence (data).“The average height in group A was 2 cm higher than group B.” = Specific “Group A grew more.” = Not specific.Give a final concluding statement.If your hypothesis was supported, summarize that.If it was refuted, give a new and improved hypothesis.
31 Draw Conclusions Example Label the paragraph with numbers, marking where each of the 7 steps occurs:The experiment was designed to test whether caffeine would increase the distance frogs could jump. Caffeine is a stimulant. Stimulants are psychoactive drugs, meaning that they affect the nervous system. Jumping involves the nervous and muscular systems, so it’s possible that caffeine could affect jumping. It was hypothesized that caffeine improves muscle action, and it was predicted that the more caffeine a frog has, the farther it will jump. To test this, some frogs were given caffeine and others were not, and the lengths of their jumps were measured.The results supported the hypothesis and prediction, showing that frogs given caffeine jumped an average of 7cm farther than frogs that were not given caffeine. Caffeine does indeed increase the distance that frogs can jump.
32 Draw Conclusions Practice Examine the hypothesis and experimental results below, and write an appropriate conclusion.Hypothesis: Carrots require high nitrogen levels for best growth.Results:Effects of Nitrogen Levels on Carrot GrowthLevel of NitrogenNoneLowHighAverage Carrot Length6 in.10 in.4 in.
33 Communicate ResultsScientists always report their results through journals and scientific papers.Allows others to repeat the investigation, skeptically evaluate the validity of the results, & can lead to further questions and investigations.
35 Scientific Language The scientific process has a language of its own. Sometimes, this language diverges from conversational English.“Science words” can be different from English words even when they look exactly the same.
36 Scientific LanguageFor example: the words for different kinds of scientific outcomes and models.In English, an observation is…In Science, an observation is…
37 Scientific LanguageObservation (Science definition): A data point gathered by one of the five senses.An example of an observation in science: “After adding solution A to solution B, the mixture has a sharp sour smell.”
43 Scientific LanguageTheory (Science Definition): A powerful explanation of numerous natural phenomena.Example: Matter is made up of atoms, properties of matter come from atomic behavior (Atomic theory)
45 Characteristics of Living Things made up of cellsreproduceDNAgrow and developneed materials and energyrespond to the environmentmaintain a stable internal environment (homeostasis)evolve (as a group, change over time)
46 Living things are… made up of cells. Cell – a collection of living matter enclosed by a barrier separating the cell from its surroundingsCells are the smallest units of life in all organisms.Unicellular organisms – single celledMulti-cellular organisms – composed of more than one cell
47 Living things… reproduce. Reproduction – process where organisms produce new organisms or offspringSexual Reproduction: two cells from different parents unite to produce first cell of new organismAsexual Reproduction: a single-celled organism divides in half to form two new organisms OR a portion of an organism splits off to form a new organism
48 Living things… contain DNA. DNA (deoxyribonucleic acid) carries directions for inheritance.DNA determines the inherited traits of every organism on Earth.
49 Living things… grow and develop. Growth – getting larger in sizeUnicellular: cell gets biggerMulticellular: create more cellsDevelopment – changes that occur during an organisms lifetime (life cycles)
50 Living things… need materials and energy. Metabolism: organism’s chemical reactions building or breaking down materialsOrganisms vary in how they obtain energy:Autotrophs: capture energy from sun and convert it into food energyHeterotrophs: must take in food for energy
51 Living things… respond to the environment. Organisms live in constantly changing environments (living and nonliving parts).Organisms respond or change to cope.
52 Living things… maintain internal balance. Organisms maintain stable internal conditions (homeostasis) despite fluctuations in environment.temp, water content and food intake
53 Living things… evolve over time. Populations of organisms evolve (change over time).Natural selection – organisms that have certain favorable traits are better able to successfully reproduce than organisms that lack these traits