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Biology & The Scientific Method

Biology & The Scientific Method

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Biology & The Scientific Method

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  1. Biology & The Scientific Method

  2. Science- an organized way of gathering and analyzing evidence about the natural world.

  3. What is Biology? Biology—a science that employs scientific methodology to study living things. It is the science, and study, of life. Bio- means life, and –ologymeans the study of

  4. Biology is a changing science Where did plants and animals come from? How did I come to be? Humans have tried to answer these questions in different ways. Some ways of explaining the world have stayed the same over time. Science, especially biology, is always changing.

  5. What Science Is and Is Not Science is not a collection of never-changing facts. Some scientific “facts” will change soon—if they haven’t changed already – and scientific ideas are open to testing, discussion, and revision.

  6. The Scientific Method

  7. Scientific Method- Precise method used by scientists that separates science from other ways of studying & learning.

  8. Observing and Asking Questions Scientific investigations usually begin with an observation, the act of noticing and describing events or processes in a careful, orderly way. For example, researchers observed that marsh grass grows taller in some places than others. This observation led to a question: Why do marsh grasses grow to different heights in different places?

  9. Inferring and Forming a Hypothesis After posing questions, scientists use further observations to make inferences, or logical interpretations based on what is already known.

  10. Observation____________________ Inference__________________

  11. Observation or Inference ?Students are working with a newly discovered organism. Is their statement an observation or an inference? ___ 1. The organism frowned to show it did not like strangers. ___ 2. The organism is green with pink spots. ___ 3. The organism lives near other organisms. ___ 4. The organism moved away from us because it was scared. ___ 5. The organism made gurgling noises. ___ 6. The organism had four spines on its back. ___ 7. The organism has one blue eye and two green eyes. ___ 8. The organism moves really slow so he must be old.

  12. Steps to the Scientific Method 1. State the problem.

  13. 2. Research / Gather Information

  14. 3. Form a Hypothesis Hypothesis- an educated guess; often based on inferences Make it short & definitive. an“if then” statement

  15. Inferring and Forming a Hypothesis Researchers inferred that something limits grass growth in some places. Based on their knowledge of salt marshes, they hypothesized that marsh grass growth is limited by available nitrogen.

  16. 4. Test the Hypothesis Develop a controlled experiment -an experiment that contains only one experimental variable.

  17. Designing Controlled Experiments Testing a scientific hypothesis often involves keeping track of many variables that should remain unchanged throughout the experiment. Examples of these controlled variables include temperature, light, time, and availability of nutrients.

  18. Designing Controlled Experiments

  19. Experimental Variable- The thing being tested Controlled Variables- All other variables in the experiment that are kept the same

  20. Controlling Variables It is important to control variables because if several variables are changed in the experiment, researchers can’t easily tell which variable is responsible for any results they observe. The variable that is deliberately changed is called the independent variable (also called the manipulated variable). The variable that is observed and that changes in response to the independent variable is called the dependent variable (also called the responding variable).

  21. Does Weight Control Food Affect Weight Loss in Dogs ? Independent Variable?______________________ Dependent Variable?________________________ Hypothesis_________________________

  22. Control and Experimental Groups Typically, an experiment is divided into control and experimental groups. A control group is exposed to the same conditions as the experimental group except for one independent variable. .

  23. Designing Controlled Experiments The researchers selected similar plots of marsh grass. All plots had similar plant density, soil type, input of freshwater, and height above average tide level. The plots were divided into control and experimental groups. The researchers added nitrogen fertilizer (the independent variable) to the experimental plots. They then observed the growth of marsh grass (the dependent variable) in both experimental and control plots.

  24. Collecting and Analyzing Data Scientists record experimental observations, gathering information called data. There are two main types of data: quantitative data and qualitative data.

  25. Quantitative Data- deals with numbers data which can be measured Ex>length, height, area, volume, weight, speed, time, temperature, humidity, cost sound levels Quantitative  Quantity

  26. Collecting and Analyzing Data In the marsh grass experiment, it could include the number of plants per plot, plant sizes, and growth rates.

  27. Qualitative Data- deals with a description data that can be OBSERVED but not measured Ex>colors, textures, smells, tastes, appearance Qualitative  Quality

  28. Collecting and Analyzing Data In the marsh grass experiment, it might include notes about foreign objects in the plots, or whether the grass was growing upright or sideways.

  29. There are 30 students in the class. Quantitative

  30. The freshman class has positive school spirit. Qualitative

  31. This coffee has a serving temperature of 150oF. Quantitative

  32. Bobby’s coffee is in an orange mug. Qualitative

  33. 5.Analyze Data & Draw Conclusions Analyze experimental results and record observations Organize data into graphs & tables

  34. Is your hypothesis supported? If a hypothesis is proven incorrect, change the hypothesis, not the data

  35. Drawing conclusions Experiments must be reproducible and produce consistent results. A hypothesis can change based on results of an experiment.

  36. In the experiment, analysis showed that marsh grasses grew taller than controls by adding nitrogen.

  37. Drawing Conclusions The original hypothesis is reevaluated and revised; new predictions are made, and new experiments are designed. Hypotheses may have to be revised and experiments redone several times before a final hypothesis is supported and conclusions can be drawn.

  38. Example 1 State the Problem: Is Raid the best insecticide on the market?

  39. Research: Find information on the topic in books, the Internet, calling a customer service rep. for the product

  40. Hypothesis: If Raid is the best insecticide on the market, then it will kill insects 30% faster than three other insecticides.

  41. Test the hypothesis in a controlled experiment Spray 4 separate containers with equal amounts of 4 different insecticides (one of which is Raid). Cover each one with the same type and size glass. Add equal amounts of the same type of insects (10) to each glass. Place them side-by-side and time the results.

  42. Data

  43. Conclusion Raid is the best insecticide on the market. It killed insects 30% faster than three other insecticides.

  44. Scenario When metals are added to an acid, a chemical change occurs and heat is released. Students decide to test which of two metals will produce more heat when added to hydrochloric acid. They place 2g of zinc and 2g of aluminum in test tubes. A third tube is empty. They take a temperature reading in all three tubes. They then add 10ml of HCl to the three tubes and take a temperature reading every two minutes for 10 minutes.

  45. Problem- Research- Hypothesis-

  46. Data

  47. Conclusion- Next step-

  48. Research Tools Scientists choose appropriate tools for collecting and analyzing data, such as a meterstick, or sophisticated equipment such as a machine that measures nitrogen content.

  49. Sources of Error Researchers must be careful to avoid errors in data collection and analysis. Data analysis and sample size must be chosen carefully. The larger the sample size, the more reliably researchers can analyze variation and evaluate differences between experimental and control groups.