The Science of Biology: Understanding the Scientific Method

1. CHAPTER 1 – THE SCIENCE OF BIOLOGY What Is Science? (A) Organized way of using evidence to learn about the natural world. (B) Collection of knowledge that scientists have built up after years of using this process.

2. Steps in the Scientific Method: Step 1 – Observations – gathering data (information) This can be Quantitative – expressed in #’s. Or Qualitative – expressed other than #’s. 1. Inference – logical interpretation based on prior knowledge or experience. 2. Inferences can lead to a hypothesis, or a scientific explanation for a set of observations that can be tested in ways that support or reject it. Step 2 – Hypothesis (Prediction) 1. Proposed explanation for a set of observations. 2. Based on prior knowledge or imagination. 3. Represents a possible solution to a problem. Step 3 – Test Hypothesis – with a controlled experiment.

3. 1. When doing an experiment… a. Test one variable at a time!!!! (Variable – is something that causes the changes observed in an experiment) b. Have a controlled variable –the one that you don’t change • Independent Variable– what you are changing (manipulating) • Dependent Variable – the response to the change, or outcome Step 4 - Recording & Organizing Data – the more data the better! 1. Tables; Graphs; Averages etc. 2. Can also be qualitative and/or quantitative. Step 5 – Draw a Conclusion: use experimental data to support, refute, or revise the hypothesis

4. Example of Famous Experiments: Redi’s Experiment on Spontaneous Generation Observations: Flies land on meat that is left uncovered. Later, maggots appear on the meat. Hypothesis: Flies produce maggots. Procedure Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time. Several days pass Manipulated Variable: lid Responding Variable: Whether maggots appear Maggots appear No maggots appear Conclusion: Maggots form only when flies come in contact with meat. Spontaneous Generation of maggots did not occur.

5. Spallanzani’s Experiment This experiment showed that microorganisms will not grow in boiled and sealed gravy that is left open to the air. Gravy is teeming with organisms Questions: 1. What variables were controlled in this experiment? Flask is open Gravy is boiled 2. What variable is the experimental (manipulated) variable? Gravy is free of organisms. Flask is sealed

6. Louis Pasteur’s Experiment Broth is free of organisms for a year. Curved neck is removed Broth is teeming with microorganisms. Broth is boiled Questions: 1. Why did microorganisms not grow in the flask before the neck was removed? 2. Why did the microorganisms grow after the neck was removed?

7. Step 6 – Peer Review: Scientists share their work with others. Scientists also try to duplicate the results to confirm that the experiment was successful Step 7 – Theories: well tested explanations that unifies a broad range of observations. 1. Example: Theory of Evolution. Law – Generalizes a body of observations. It explains things, but does not describe them. 1. Example: Newton’s Laws, Principle – a concept based on scientific laws (rules assumed to be true) 1. Example: Bernoulli’s Principle (explains aerodynamics)

8. What makes a good scientist? • share scientific attitudes, or habits of mind, that lead them to exploration and discovery. • Are curious about what goes on around them • are skeptics, which means that they question existing ideas and hypotheses, and they refuse to accept explanations without evidence. • Are open-minded, meaning that they are willing to accept different ideas that may not agree with their hypothesis. • Are creative

9. 1-3 Studying Life (A) Biology – Study of living organisms; study of the living world. (B) Biosphere – The part of the Earth that contains all ecosystems (C) Pg 21 record the levels of organization

10. Characteristics of Living Things. 1. Made of units called cells. a. Unicellular – one-celled. b. Multicellular – many celled. • Reproduction • Asexual – creates offspring by iteself, 1 parent • Sexual – creates offspring by sharing DNA, 2 parents 3. Based on a universal genetic code. (DNA)

11. 4. Growth & development. • Obtain & use materials and energy. • The combination of chemical reactions through which an organism builds up or breaks down materials is called metabolism. 6. Respond to their environment. (Respond to a stimuli) • Maintain a stable internal environment. (Homeostasis) • Taken as a group, living things change over time. (Evolution) • Evidence of this shared history is found in all aspects of living and fossil organisms, from physical features to structures of proteins to sequences of information in DNA.

12. Scientific Measurement: Common Metric Units

13. Different Types of Microscopes • Simple Microscopes – magnifying glass (use 1 lens) • Compound Microscopes – use more than 1 lens (ex. Light microscope that we use in class) • Electron Microscopes (SEM and TEM) • Large, and expensive

14. Cell Culture A single cell is grown on a Petri dish, reproduces, creating a group of cells Can be used to test cell responses Cell Fractionation Cells are put into a blender and mixed Then they are placed in a centrifuge The centrifuge spins the cell parts and liquid The parts separate out by their density Laboratory Techniques