SC.6.N.2.2: Explain that scientific knowledge is durable because it is open to change as new evidence or interpretations are encountered. SC.7.N.3.1: Recognize and explain the difference between theories and laws and give several examples of scientific theories and the evidence that supports them.

Bell Ringer 1. During the nineteenth century, biologists knew that South America and Africa contained similar fossils. These fossils led them to believe that a temporary land bridge between South America and Africa allowed ancient species to move between both continents. In the twentieth century, evidence showed that South America and Africa were once part of the same larger continent and that there were no land bridges between them. How should biologists respond to the new geological finding? Biologists should reject the geological finding, because it is new. Biologists should ask physicists what to do, because physics is a more exact science. Biologists should reject the belief in ancient species, because there were no land bridges. Biologists should update the history of life, because it should include the new geological finding.

Bell Ringer 3. The validity of scientific theories and laws depends on evidence. Which of the following statements of evidence supports a law rather than a theory? Electrons orbit the nucleus of an atom within a certain radius. DNA analysis reveals that a modern species is related to an extinct species. Seafloor spreading occurs at a rate of three centimeters per year in the mid-Atlantic. The amount of matter in a closed system is the same at the start of a reaction as at the end of the reaction. There are many important laws and theories in science. Which of the following is a law of science? A living thing is made of at least one cell. An atom is made of electrons orbiting a nucleus. Gravity will pull two objects toward each other. Natural selection will change species to fit their environments.

Demonstrations Item Drop and Seafloor Spreading One demonstration supports a theory, while the other can be describe by a law. Scientific laws are like legal laws. both describe events. Scientific theories are more like a legal case or defense. both are used to explain events

Law vs. Theory A law summarizes what happens A theory (model) is an attempt to explain why it happens.

LAWS A scientific law is a statement that describes what scientists expect to happen every time under a particular set of conditions. For example, the law of gravity states that all objects in the universe attract each other. Unlike a theory, a scientific law describes an observed pattern in nature without attempting to explain it. Both scientific theories and scientific laws are developed slowly through repeated observation and experimentation. Law of Universal Gravitation Law of Superposition Law of Conservation of Mass Law of Conservation of Energy

THEORIES Scientific knowledge changes as a result of new evidence or new interpretations of existing evidence. For example, thousands of years went by with people thinking the sun revolved around the Earth. To them, it made sense with information they had. The sun would rise on one side of the sky, move across the sky, and set on the opposite side. A scientific theory is a well-tested explanation for a wide range of observations or experimental results. A scientific theory connects large sets of related observations by one explanation. Examples of scientific theories include the atomic theory and the cell theory. The atomic theory states that all substances are made up of tiny particles called atoms. The cell theory states that cells are the basic units of structure and function in living things. The Theory of Evolution Cell Theory Atomic Theory Theory of Plate Tectonics

LEFT Side- Theories and Laws Fill in the table below focusing on the difference between what makes something a theory or a law. Theories and Laws Brief Description Why is it a theory or a law?  Law of Universal Gravitation  All objects in the Universe attract each other  Because it has been proven to be true every time!!!!!!!!!! Theory of Plate Tectonics  All tectonic plates were once connected in a super continent (Pangea). Now they are moving apart.  Because scientists have enough evidence to support it. Example all continents fit together like a puzzle and there are similar fossils. Law of Superposition    The oldest layer of rocks is always at the bottom!  Because it is something scientists expect to be true every time!!!! Atomic Theory   Everything is made up of tiny particles (atoms).  There has been a lot of experimentation with a lot of supporting evidence. Law of Conservation of Mass  Mass cannot be created or destroyed.  It has been proven true. Cell Theory    All living things are made up of cells. Cells the basic unit of structure & function, and they come from pre-existing cells. Law of Conservation of Energy   Energy cannot be created or destroyed. The Scientific Theory of Evolution  All living things have one common ancestor.

Exit Ticket Identify several theories and laws. Describe why each is a law or a theory. Explain the difference between a scientific theory and a scientific law. Explain why theories may be modified, but rarely discarded.