Methods of Biological Inquiry Lecture Notes

9/23/2024 Methods of Biological Inquiry Biol 2000H Paul Frost LHS D232 ext. 7903 [email protected] 1 2 3 4  9/...

9/23/2024 Methods of Biological Inquiry Biol 2000H Paul Frost LHS D232 ext. 7903 [email protected] 1 2 3 4  9/23/2024 5 6 PREDICTION How many versions of the scientific method are there? 7 8  9/23/2024 Somewhere between zero and many? Different versions of the scientific 1) Science often progresses without the use of the scientific method method? 2) There are many versions of the scientific method and they are all equal 9 10 11 12  9/23/2024 13 14 15 16  9/23/2024 17 18 What are the similarities and differences What are the similarities and differences among these versions of the scientific among these versions of the scientific method? method? 1) Most seek to explain some observations 2) Most invoke hypotheses and use experiments 3) Many base conclusions on comparisons between actual results and predictions 4) Differences largely cosmetic and involve jargon 5) Most are less explicit (and missing logic) compared to the ‘classic’ version presented here 19 20  9/23/2024 What are the similarities and differences Make among these versions of the scientific observations method? Scientific If they match, hypothesis is 1) Most seek to explain some observations Ask why is it method supported They aren’t really that 2) Most invoke hypotheses and use experiments like this? 3) Many base conclusions on comparisons different! between actual results and predictions 4) Differences largely cosmetic and involve Hypothesize Collect data Compare results with prediction jargon Deduce a If they differ, 5) Most are less explicit (and missing logic) Imagine a test prediction hypothesis is compared to the ‘classic’ version presented not supported here Classic version 21 22 Why use the ‘classic’ Make scientific method? observations Scientific If they match, hypothesis is (As opposed to one of these other versions) Ask why is it method supported like this? 1) It’s logical and explicit (no missing steps) Compare results 2) It’s not overly or unnecessarily Hypothesize with prediction complicated Collect data 3) It’s applicable to every branch of science Deduce a If they differ, 4) It’s been highly successful in the past prediction hypothesis is not supported 23 24  9/23/2024 25 26 Alternative Hypotheses Why are some food chains longer than others? 27 28  9/23/2024 Predictions Alternative Hypotheses 1) Productivity: More nutrients leads to more energy input into the foodweb allowing for extra trophic levels to be added at the top of the food chain 2) Ecosystem size: Big ecosystems have more space allowing for more species to be present and this leads to longer food chains 29 30 Predictions Predictions If productivity determines food chain length And we compare the food chain length in lakes of varying sizes Then big lakes should have similar food chains as small lakes If ecosystem size determines food chain length And we compare the food chain length in lakes of varying sizes Then big lakes should have longer food chains than small lakes regardless of their productivity 31 32  9/23/2024 Conclusions If productivity determines food chain length And we compare the food chain length in lakes of varying sizes Then big lakes should have similar food chains than small lakes And they don’t Therefore the productivity hypothesis is not supported If ecosystem size determines food chain length And we compare the food chain length in lakes of varying sizes Then big lakes should have longer food chains than small lakes regardless of their productivity And they do Therefore therefore the ecosystem size hypothesis is supported Post, David M., Michael L. Pace, and Nelson G. Hairston Jr. "Ecosystem size determines food-chain length in lakes." Nature 405.6790 (2000): 1047-1049. 33 34 Make observations Scientific If they match, hypothesis is Ask why is it method supported like this? Science is trying to demonstrate Compare results and determine if a particular claim Hypothesize Collect data with prediction about the natural world is true Deduce a If they differ, prediction hypothesis is not supported 35 36  9/23/2024 Logical 1. How do you convince someone? Arguments 2. How do you decide to believe something or not? + Data 37 38 Why did we see what we saw? Why did we see what we saw? If the hypothesis is “true” If the hypothesis is “true” And a test is completed And a test is completed Then I should see this thing happen Then I should see this thing happen And I saw this thing happen And I saw this thing happen Therefore the hypothesis is supported Therefore the hypothesis is supported A scientific argument 39 40  9/23/2024 An argument is when you use reasoning to Premises often use words like: provide support for a conclusion since supporting reasons also known as premises the reason being one or more premises are used for support because due to the fact that 41 42 Conclusions often use words such as: Arguments: thus must have at least one premise therefore and one conclusion consequently sometimes have multiple premises as a result 43 44  9/23/2024 Inductive argument All ducks in the pond are white, therefore all ducks are white All ducks in the pond are white, therefore all ducks are white “inductive reasoning” Use your observations of a pattern to produce a generalized pattern 45 46 Inductive argument Inductive argument Premise: My dog is brown Premise: My dog is brown Conclusion: Therefore all dogs are brown Premise: All other dogs on my street are also brown This argument is not necessarily true. My dog Conclusion: Therefore all dogs are brown might not be a typical dog. This argument is not necessarily true. The dogs on my street may not typical as well. 47 48  9/23/2024 Inductive argument Inductive reasoning Premise: My dog is brown no explicit use of a hypothesis Premise: All other dogs on my street are also creates generalizations from a sample brown not truth-preserving Conclusion: Therefore other dogs might also be brown Might work. Seems ok. 49 50 When do we use inductive reasoning in the Hypo-deductive reasoning scientific method? involves a hypothesis is used to produce a prediction If the hypothesis is “true” if well-stated, leads to a valid And a test is completed conclusion (in this case, it’s the Then I should see this thing happen prediction) And I saw this thing happen this is truth-preserving Therefore the hypothesis is supported 51 52  9/23/2024 Why did the light bulb go out? When do we use hypo-deductive reasoning in the scientific method? If the bulb burned out And I flip the switch on and off If the hypothesis is “true” Then the light should not turn back on And a test is completed Then I should see this thing happen And I saw this thing happen Therefore the hypothesis is supported 53 54 Abductive arguments (aka- inference) Abductive arguments Given all of the evidence, what consistent with the scientific method explanation is likely to be correct based on assessing evidence against predictions to judge utility of hypotheses This is used when you compare results retains a chance of incorrectness and predictions to determine whether an explanation has support or not 55 56  9/23/2024 Science Writing 10 minute break 57 58 Science Writing How to write science 1.Active voice is ok. 2.Passive voice is ok. 3.Use the one that is needed 59 60  9/23/2024 How to write science 1. First person ok. 2. Third person ok. Use depends on the situation. 1st person, active 61 62 Subject-verb separation 3rd person, passive 63 64  9/23/2024 Subject-verb separation Subject-verb separation -Readers expect subject to be immediately followed by verb. -Material in between subject and verb are interruptive -Readers give less importance to interruptive material -Scientists like to use interruptive text to provide background and context -Don’t separate subjects and verbs 65 66 How do you want me to reference my report? References Referencing for academic purposes 1. 2. Show that you aren’t plagiarizing Appropriately acknowledge Referencing for scientific purposes 1. Place current work in context of previous studies source material 2. Appropriately acknowledge 3. Demonstrate effort to identify source of idea or content and use material from outside of 3. Provide strength to your textbook or lectures scientific argument 67 68  9/23/2024 How do you want me to What do we ‘know’? reference my lab report? Rank each of the following statements 1. definitely true In this class- follow scientific conventions. 2. probably true Reference content in reports and 3. perhaps true assignments that are not you own ideas 4. may be true or false and/or thoughts 5. perhaps false References not needed for 1st 2 lab 6. probably false assignments 7. definitely false Do not reference your own ideas 69 70 All living cells contain Earth is spherical in shape DNA 71 72  9/23/2024 Plants capture sunlight An intelligent designer to produce energy containing created all life on Earth organic molecules 73 74 More species of mammals Plants grow poorly live in the oceans than in the Arctic because of the cold on land. 75 76  9/23/2024 All? How many of these were definitely true or false? Some? None? 77 78 Is this definitely true beyond all doubt? Is this true beyond most doubt? Earth is spherical in shape Earth is spherical in shape 79 80  9/23/2024 Objective view of the world Scientific Implications There are definitive properties of the Nothing is known with absolute certainty universe we live in Everything is known with varying degrees of certainty Our ability to perceive and describe Strongest conclusion: very nearly certain these properties are limited by our senses something is true or false There is always a chance that we have Words like “proven”, “fact”, “true” are usually it wrong avoided unless accompanied by a qualifier Scientific knowledge is not a cultural construct and is open to revision if we get new/better data 81 82 The Scientific Method Hypothesis tests 1. Observe/describe and ask “Why”? Objective: Provide support for or 2. Generate alternative explanations against the hypothesis of interest 3. Imagine tests for these explanations 4. Deduce a prediction 5. Complete test and compare results with prediction 6. Make a conclusion 83 84  9/23/2024 What constitutes a well-designed test? relevant to the hypothesis has a clearly defined response variable Hypotheses are tested with: controlled (isolates the effect of one variable, accounts for other variables) Observational tests produces unique predictions replicated (examines more than one test subject) practical and ethical 85 86 What affects diet What affects diet quality of gorillas? quality of gorillas? Hypothesis: Season 87 88  9/23/2024 What affects diet quality of gorillas? How would you experimentally test this? Hypothesis: Season 89 90 Observational tests Observational tests Observations are collected and Useful to study questions that have variables that are not easily manipulated. compared to predicted results. Often correlational in nature No active manipulation of the system Can be useful for historical studies is involved. A well-designed observational study often chooses subjects based on some defining characteristic. 91 92  9/23/2024 What affects undergraduate class attendance? What affects undergraduate class attendance? Hypothesis: Breakfast Hypothesis: Breakfast Observational test: Survey students about Observational test: Enroll students into study attendance tendencies and breakfast eating. and track their class attendance over the Look at relationship between two variables. semester. Have them keep a food diary. 93 94 Why did zebra mussels arrive in Lake Erie? Why affects plant diversity in northern Ontario? Hypothesis: Importation of fish Hypothesis: Glaciation Observational test: Collect samples from Observational test: ??? imported fish water and look for zebra mussel veligers 95 96  9/23/2024 Why affects plant diversity in northern Ontario? Observational tests Hypothesis: Glaciation Useful to study questions that have variables that are not easily manipulated. IF true, there should evidence of extensive Often correlational in nature glaciation in Ontario, there should be patterns of Can be useful for historical studies recolonization captured by pollen records (in Common in medical studies because less lake sediments), and there should be less ethically challenged than experiments (in diversity in Ontario compared to areas that were some cases). not glaciated (but that have similar climate and Unlikely to cause unintended effects soils). 97 98 Plant production correlates with temperature Observational tests Typically have limited control of other variables Often faced with “correlation does not equal causation” criticism 99 100  9/23/2024 Plant production correlates with temperature Observational tests Typically have limited control of other variables Often faced with “correlation does not equal causation” criticism Does this invalidate observational tests? Drier Wetter 101 102 103