Biology 1000 Lecture #1-2.pdf

Lecture #1 What is Science? Textbook Chapter 1  What is Science? Defined as knowledge that is obtained through study Either by accidental observation or as a result of experimentation Science also refers to the body of knowledge gained as a result of these...

Lecture #1 What is Science? Textbook Chapter 1  What is Science? Defined as knowledge that is obtained through study Either by accidental observation or as a result of experimentation Science also refers to the body of knowledge gained as a result of these studies Dependent on direct observation  What is Science? Biology makes use of two primary scientific approaches: 1. Discovery Science 2. Hypothesis-Based Science 1. Discovery Science: The result of verifiable observations and measurements Conclusions made from discovery science are a result of inductive reasoning This refers to conclusions drawn because of a large number of observations Example: Conclude that all living things are made of cells because of the observation that all biological specimens over thousands of years all contained cells  What is Science? 2. Hypothesis-Based Science: Observations from discovery science cause us to ask questions about causes and explanations leading to the development of a hypothesis A hypothesis is a suggested explanation for a given set of observations Hypotheses are then tested by further observations and by specially designed experiments This form of science makes use of deductive reasoning Deductive reasoning moves from a general statement down to a specific conclusion Example: Premise #1: all living things are composed of cells Premise #2: human beings are living Deductive reasoning leads to the conclusion that human beings must then be composed of cells  Theory vs Hypothesis A theory is very broad and explains many different observations Theories are also supported by a large and growing body of evidence Theories continually give way to new hypotheses Hypotheses are much more specific  Hypothesis-Based Science Example: You observe that your flashlight is not working You then ask yourself why the flashlight is not working and come up with two explanations or hypotheses Hypothesis #1: the batteries may be dead Hypothesis #2: the bulb may be burnt out  Hypothesis-Based Science Deductive reasoning is then used to come up with predictions based on previous observations (referred to as if-then logic) Hypothesis #1: dead batteries Prediction: replacement of batteries will allow the flashlight to work Hypothesis #2: burnt out bulb Prediction: replacing the bulb will allow the flashlight to work  Hypothesis-Based Science To be a true hypothesis it must be both: Testable: there must be some way of testing whether or not it is correct Falsifiable: experimentation must be able to show that it is not true Testing supports a particular hypothesis not by showing that it is correct but by not eliminating it by finding evidence that it is false Hypotheses can never be proven without a doubt but if it survives various attempts to disprove it than it becomes increasingly likely to be the valid explanation for the observation in study  Hypothesis-Based Science Case Study Uses actual scientific research Begins with an observation: Most poisonous animals are brightly colored in order to alert predators to the potential danger, saving the poisonous animal from predation There also exist mimics who avoid predation in the same way as the poisonous animals however they do not harbor any poison Hypothesis: the mimicry functions to reduce the likelihood that the harmless animal will be eaten Experiments are then designed to test the above hypothesis Hypothesis-Based Science Case Study Both snake types (brightly colored and poisonous) and (brightly colored and non-poisonous) are found in North and South Carolina The non-poisonous variety is also found in areas where the poisonous variety is not If the hypothesis is true and predators avoid brightly colored snakes because of the association with poison then predators will attack the non-poisonous snakes more frequently in areas where the poisonous variety is not found Due to the fact that predators in these areas are not accustomed to brightly colored snakes being poisonous This prediction was tested by creating two different versions of a fake snake constructed out of plasticine: Experimental group: brightly colored fake snakes Control group: plain brown fake snakes Hypothesis-Based Science Case Study Equal numbers of both snake types were placed in areas where both poisonous and non-poisonous snakes are found as well as in areas where only the non-poisonous variety is found After an elapsed time of one month the snakes were removed and tested for signs of attack If the hypothesis is true one would expect the brightly colored snakes to be attacked in the areas where poisonous snakes are absent Results: Hypothesis-Based Science Case Study **The inclusion of a control group allowed for the analysis of the effects of color alone on the rate of predation