BIOLOGY 1408 What is Biology?

Transcription

1 BIOLOGY 1408 Lecture 2 Chris Doumen, Ph.D. Collin College, 2014 What is Biology? The scientific study of life Contains two important elements Scientific study Life 1

2 The Process Of Science The word science is derived from a Latin verb meaning to know. Science is a way of knowing. Science requires vision, and the ability to observe the implications of results. Collecting data is part of the process, and it also needs to be analyzed and interpreted. There are two major ways of obtaining data, through measurement (= quantitative) through observation (= qualitative) The Process Of Science Generally, qualitative measurements are arbitrary, uses a scale designed to measure abstract responses and constructs. Measuring animal behavior such as anxiety, preference, pain and aggression are some examples of concepts measured qualitatively Quantitative measurements are generally associated with what are known as data crunching, collection of numbered data A quantitative measurement has an actual counted number or usually a unit of measurement after it such as %, kg, meters,. For example how many people lost weight during a diet regime, or how much was lost when comparing two different diets, 2

3 The Process Of Science Scientists use two main approaches to learn about nature Discovery science Primarily describes nature through verifiable observations and qualitative measurements. Example : discovery of new species, discovery of new chemicals, discovery of new proteins, discovery of new.. Hypothesis- driven science Attempts to explain nature by studying questions drawn from observations made during "discovery science" It relies on collecting quantitative data from experiments created to support or reject a hypothesis The Process Of Science A hypothesis is a tentative prediction to a problem or question that is being asked. It is a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation. 3

4 The Process Of Science A hypotheses is thus a starting point. It needs to be tested in order to expand on it. The scientific process includes these two aspects inductive reasoning to draw general conclusions from many observations ( = hypotheses forming process) deductive reasoning to come up with ways to test a hypothesis, a proposed explanation for a set of observations. It all depends on a logic flows of thinking : what do we expect to happen if the hypotheses is true, and how do we design an experiment to test this (sometimes we refer to that as an educated guess of what we expect to happen). The Process Of Science An Initial Example : Let us assume you have limited knowledge of the world around you and observation tells you that every bird you have ever seen has wings. Inductive reasoning tells you : Jee-wiz, all birds have wings Deductive reasoning and possible hypothesis: IF all birds have wings, and if someone hands me a critter with wings, THEN it must be a bird.. This is a good hypothesis to start with. But it needs experimentation and/ or better observations. A hypothesis provides room for rejection of the initial educated guess! Experimentation will provide evidence for a hypothesis or will reject the initial premise. 4

5 The Process Of Science Here are some additional observations! So what would happen to your hypothesis? Birds? The Process Of Science Obviously the hypothesis was wrong, flawed and hence becomes rejected. Why was it wrong? In this case, a lack of information, a lack of our generalized knowledge about the world. Thus, the more knowledge we have, the better informed we become, the better our educated guesses. A refined hypothesis would then look like : If the animal is a bird, then it must have wings. 5

6 Some other examples Inductive reasoning from observations : All flies have one pair of wings and flies are insects Deductive reasoning: If a fly is an insect and a fly has wings, then all insects have one pair of wings. Good or bad reasoning (Hypothesis)? Inductive reasoning : All insects have a head, a thorax with six legs and an abdomen Deductive reasoning : If I see these characteristics in a critter, then I am dealing with an insect. Good or bad reasoning (Hypothesis)? Generalized Knowledge Observations and research that provides layers of evidence in support for a hypothesis eventually become what we know as generalized knowledge in science. Tons of information tells us indeed that all insects have six legs and a body divided into head, thorax and abdomen Insect or not? 6

7 Hypothesis- based Science Hypothesis-based science applies the five steps of the scientific method: (1) Observations from others or results of earlier tests (2) Questions about unclear aspects of the observations: How? Why? When? (3) Hypotheses or tentative explanations of a phenomenon Must be testable Must be falsifiable (4) Predictions developed by the use of deductive reasoning (if...then) (5) Tests of predictions (experiments) to determine if the predictions are supported or falsified. ScienBfic Method 7

8 An EveryDay Example The reasoning used in the scientific method is something we use everyday we to figure out problems. For example. Why doesn t my flashlight work? Inductive reasoning (the experiences you gained growing up in a modern household) tells you flashlights use batteries and a lightbulb. Using deductive reasoning we realize therefore that the problem is either (1) the bulb or (2) the batteries. Further, a hypothesis must be testable and Falsifiable (the outcome is not predetermined) In this case, we can approach the problem via two possible hypotheses Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb 8

9 Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test prediction Test prediction Test falsifies hypothesis Test does not falsify hypothesis 9

10 ScienBfic Method The scientific method thus allows to gain educated answers to problems, backed up with experimental data. The experimental data are the proof to support our claims Every hypothesis and subsequent experimentation will provide clues. Sometimes these clues will support our way of thinking (positive data) ; sometimes the clues will eliminate a certain thought process clues that tell us we have to approach the problem differently (negative data) Negative data are NOT useless; they help a scientists back on the right track by reformulating a certain hypothesis. In the flashlight example, what other outcome would have been possible? And what would that tell you about the problem? A Case Study An example of an actual research project demonstrates the process of science. Scientists began with a set of observations and generalizations that Many poisonous animals are brightly colored Some related species resemble the poisonous species but are actually harmless. The hypothesis put forward : mimicry benefits these animals because a predator may confuse them with the actual poisonous species. (what is mimicry in biology?) 10

11 8/25/14 The animals of the study Coral snake Very poisonous We recognize this snake by the banding pattern Red touches yellow! King snake Not poisonous Banding pattern Red touches black 11

12 8/25/14 Possible snake predators Who is a natural predator of snakes? Which animal likes snakes as a food source? Large birds, bears, wild boars, mongooses, raccoons, foxes, coyotes, other snakes The question in the study is thus : if I look dangerous while being in fact harmless, will that protect me against my enemies, those that like to eat me? Overly ambitious frog eating snake or trying to. 12

13 The experiment The scientists conducted a controlled experiment, comparing an experimental group consisting of artificial king snakes and a control group consisting of artificial brown snakes. the groups differed only by only one factor, the coloration of the artificial snakes. Two regions were compared: one where poisonous coral snakes are common - one where coral snakes are normally not found Data were collected with respect to how many snakes were attacked by predators. The experiment An artificial King snake Artificial brown snake after being attacked and mauled by a bear. 13

14 Percent of total attacks on artificial snakes % The Experiment Data 17% 16% 84% Artificial king snakes Artificial brown snakes 0 Coral snakes absent Coral snakes present What the Data tell us Where coral snakes are normally not present, the attacks on artificial king snakes is higher. The brown snakes seem to have an advantage as their fake counterparts are not being attacked. What is a possible explanation? In those regions where there are no deadly coral snakes, the predators do not learn that it is dangerous to mess with such a snake. Thus the color pattern of the king snakes does NOT present a warning sign; it actually makes them easier to notice in the brush. The brown snakes have an advantage since they don t stand out, blend in better with the surroundings 14

15 What the Data tell us Where coral snakes are normally present, the attacks on artificial king snakes is much lower than brown snakes. Animals in this region learned not to mess with dangerous snakes; the king snake look dangerous and they are left alone more often. The brown snakes, although blending in with the environment, become the favorite food and suffer higher attack rates The data fit the key prediction of the mimicry hypothesis. Hypothesis based Science The strength of hypothesis based science is that certain outcomes can be predicted IF the hypothesis is correct So, good observations result in predictable hypothesis that provide us with certain predictable outcomes of that thought process This is part of the so- called IF THEN statements (for example, IF this drug lowers cholesterol, THEN patient test subjects will show lower cholesterol levels over time compared to control subjects) 15

16 Hypothesis based Science Hypothesis based Science This thus implies that we can generate testable, controlled experiments! If the hypothesis is un-testable, it is bad science. How do you test if a plant is thinking? How do you test the existence of ghosts? A lot of such pseudo-science is based on providing convoluted arguments that the others are wrong, but without ever providing experimental evidence that their hypothesis is right. 16

17 Hypothesis based Science When experiments provide support for a hypothesis, it generates new ways, new experiments to strengthen the hypothesis It involves creation of multiple hypotheses on a particular phenomena, many experiments and researchers. A hypothesis becomes eventually credible when repeated attempts to disprove it fail. Hypothesis becomes THEORY In non-scientific language a THEORY is just a guess or an idea about some process. A Scientific THEORY is the best possible explanation of a natural phenomenon, supported by experimental and empirical data. It is the result of generalization about the observed phenomena after years of testing and experimentation. Theory a general set of principles, supported by evidence, that provide a reliable, systematic and rigorous account of an aspect of nature. 17

18 Biology and our Life Science is a multi-disciplinary endaveour where new discoveries are shared and used. Scientists constantly evaluate each others work critically. It keeps science honest! Dishonest scientists / fake data do not last long. Many scientific outcomes will affect our daily lifes as technology is applied scientific knowledge Examples include environmental issues, medical breakthroughs, molecular and genetic engineering. Biology and our Life 18

19 Things you Should Know 1. Describe seven properties common to all life. 2. Describe the levels of biological organization from molecules to the biosphere, noting the interrelationships between levels. 3. Define the concept of emergent properties and describe an example of it. 4. Explain why cells are a special level in biological organization. Compare prokaryotic and eukaryotic cells. 5. Know that DNA encodes a cell s information. Things you Should Know 6. Compare the three domains of life. 7. Distinguish between quantitative and qualitative data. 8. Know the steps in the Scientific Process 9. Compare the definitions and use of inductive and deductive reasoning in scientific investigations. 10. Distinguish between a scientific theory and a hypothesis. 19