Aim: How is it possible for scientific theories to change? Do Now: Identify as many scientific theories that you have heard about.

How would you define the word “theory” Well tested explanation that is strengthened by many observations and experiments Not an absolute truth/fact Well accepted

Examples Cell Theory Theory of Natural Selection Theory of Plate Tectonics Theory of Relativity Germ Theory

Can theories be changed? Vocabulary Ulcer- a sore which can be found in the stomach or intestines.

Answer the following Describe what scientists believed to be the original theory. Explain how this theory has changed and what is believed to be true now. In your opinion, do you think this theory could still change? Explain why.

In his theory of evolution, Lamarck suggested that organisms will develop and pass on to offspring variations they need in order to survive in a particular environment. In a later theory of evolution, Darwin proposed that changing environmental conditions favor the survival of organisms. Which statement is best illustrated by this information? 1- Scientific theories that have been changed are the only ones supported by scientists 2- All scientific theories are subject to change and improvement 3- Most scientific theories are the outcome of a single event 4- Scientific theories are not subject to change

Exit Ticket In 1910, Thomas Morgan discovered a certain pattern of inheritance in fruit flies called sex linkage. The discovery extended the ideas of inheritance that Gregor Mendel had discovered while working with garden peas in 1865. Which principle of scientific inquiry does this illustrate? 1- a control group must be part of a valid experiment 2- Scientific explanations can be modified as new evidence is found 3- The same experiment must be repeated many times to validate the results 4- Values can be used to make ethical decisions about scientific discovery.